This chapter should be cited as follows: This chapter was last updated:
Henshaw, S, Glob. libr. women's med.,
(ISSN: 1756-2228) 2008; DOI 10.3843/GLOWM.10437
March 2008

Pregnancy termination

Induced Abortion: Epidemiologic Aspects

Stanley K. Henshaw, PhD
Senior Fellow, Guttmacher Institute, 7th Floor, 125 Maiden Lane, New York, New York 10038, USA


Induced abortion occurs at least occasionally in all societies and is common in those with low fertility. Even during the 19th century when abortion was illegal, its incidence in the United States and parts of Europe was high enough to be a factor in the declining fertility rates. It is only within the past 50 years, however, that abortion in Western countries has changed from being predominantly illegal and unsafe to being one of the most commonly performed and intensely studied surgical procedures in obstetric and gynecologic practice.

The two sources of national epidemiologic data on legal abortions in the United States are the Centers for Disease Control and Prevention (CDC) in Atlanta, and the Guttmacher Institute in New York City. The CDC publishes an annual survey on abortion based mainly on reports by state health authorities.1 This publication contains information on the characteristics of women obtaining abortions, including age, race, Hispanic ethnicity, parity, marital status, number of previous induced abortions, weeks of gestation, and method of abortion. The CDC has also monitored abortion-related deaths since 1972. The Guttmacher Institute has conducted periodic surveys of providers of abortion services that have identified larger numbers of abortions than the CDC and have provided information about abortion providers.2 To obtain a complete picture of legal abortion in the United States, it is necessary to generate estimates based on a combination of CDC and Guttmacher Institute data. Such estimates have been used throughout this chapter.


Among the countries of the world, the legal status of induced abortion ranges from complete prohibition to elective abortion at the request of the pregnant woman.3 The situation as of the end of 2007 can be summarized as follows. Approximately one fourth of the world's 7 billion people lived in countries where abortion was prohibited without exception or where it was permitted only to save the life of the pregnant woman. These included most of the Muslim countries of Asia, almost two thirds of the countries of Latin America, a majority of the countries of Africa, and one country in Europe (Ireland). Approximately one tenth lived under statutes authorizing abortion on broader medical grounds, such as to avert a threat to the woman's physical health rather than to her life, and sometimes on eugenic, or fetal, indication (known genetic or other impairment of the fetus or increased risk of such impairment) or juridical indication (e.g. rape, incest) as well.

A fourth of the world's population resided in countries where abortion is permitted to protect a woman's mental health as well as her physical health; where social factors, such as inadequate income, substandard housing, and unmarried status, could be taken into consideration in the evaluation of the threat to the woman's health (social-medical indication); or where adverse social conditions alone, without reference to health, could justify termination of pregnancy. Important countries in this group were Great Britain, India, and Japan.

Countries allowing abortion on request without specifying reasons—sometimes limited to the first trimester of pregnancy—accounted for two fifths of the world's people. Abortions on medical grounds are usually permitted beyond the gestational limit prescribed for elective abortions, and parental consent may be required if the pregnant woman is a minor. This category includes a heterogeneous list of countries: Austria, Canada, the People's Republic of China, Cuba, Denmark, France, Germany, Italy, The Netherlands, Norway, Singapore, South Africa, the republics of the former Soviet Union, Sweden, Tunisia, Turkey, the United States, Vietnam, and most of the formerly socialist republics of Eastern and Central Europe.

Several of the categories in the preceding paragraphs cover a range of situations. A statute authorizing abortion to avert a threat to the pregnant woman's mental health may be interpreted strictly or may allow most women to obtain abortions. Social indications are usually defined or interpreted broadly to allow almost any woman to terminate a pregnancy within gestation limits, as in Great Britain, India, and Japan.

The abortion statutes of many countries are not strictly enforced, and occasional abortions on medical grounds are probably tolerated in almost all countries. It is well known that in some countries with restrictive laws, abortions can be obtained openly and without interference from the authorities when performed by private physicians, as in Korea and parts of South America. Abortions may even be performed in public hospitals, as in Cuba before their legalization in 1979. Conversely, legal authorization of abortion does not guarantee that the procedure is actually available to all women who may want their pregnancies terminated. Lack of medical personnel and facilities and conservative attitudes among physicians may effectively curtail access to abortion, especially for economically or socially deprived women, as in parts of Ghana, India, Italy, and the United States.

The worldwide trend toward liberalization of abortion laws that was evident in the 1960s and 1970s has continued in recent years, although at a much slower pace. From 1998 through 2007, laws were liberalized in the following countries with populations of 1 million or more: Benin, Bhutan, Chad, Colombia, Ethiopia, Guinea, Mali, Nepal, Niger, Portugal, Swaziland, Switzerland, Thailand, and Togo. In addition, the law in Mexico City was changed to allow abortion on request. During this period, new restrictions were imposed in El Salvador and Nicaragua.

Major reasons advanced by advocates of less-restrictive legislation in matters of abortion, and especially of abortion on request, have been considerations of public health (to combat illegal abortion with its associated morbidity and mortality); social justice (to give poor women access to abortion previously available only to the well-to-do); and women's rights (to secure a postulated right of all women to control their own bodies and reproduction). A desire to curb population growth, in the interest of economic and social development, has been an explicit reason for the adoption of nonrestrictive abortion policies in a few countries, such as Singapore, Tunisia, and China, and may have been an underlying reason for policy changes in some other countries, including India and Bangladesh. The majority of countries permitting abortion at the request of the pregnant woman or on broadly interpreted social indications, however, have low birth rates, and some of them actively pursue pronatalist population policies.

Opposition to the liberalization of abortion laws has come traditionally from conservative groups, mainly on moral and religious grounds, with the Roman Catholic Church the most vigorous and articulate but by no means the only opponent. The desire for higher birth rates has led to restrictive legislation in a few instances, especially in Eastern and Central Europe during the 1960s and 1970s. Abortion has become one of the most emotional and divisive political issues in a number of countries in recent years.


In the United States, the tradition of the British common law that abortion was not a crime before the fetus quickened, and that the aborted woman was immune from prosecution, prevailed into the mid-19th century. Connecticut was the first state to deal with the subject by legislation by including it in its revised criminal code in 1821. In 1845, Massachusetts was the first state to enact a law dealing separately and exclusively with abortion. Of the 20 states with statutory provisions on abortion in 1860, all but three retained the common law immunity of women and approximately half incorporated the common law principle that abortion was a crime only after quickening. The other 13 states had no abortion statutes at that time.

After 1860, the medical profession began well-organized anti-abortion campaigns. These campaigns, as well as public reaction to explicit and flamboyant advertisements by abortionists and apothecaries and to sensationally reported abortion cases in the courts, caused legislatures to review the subject and to enact restrictive laws, which remained in force with little change for the next 100 years. In most states, a threat to the life of the pregnant woman was the sole legal ground on which abortion could be performed; in a few states, a serious threat to the woman's health was included.

A more liberal type of legislation was proposed by the American Law Institute in 1962. Following the example set by the countries of northern Europe, the relevant paragraph of the Institute's Model Penal Code would have permitted abortion if a licensed physician “believes there is substantial risk that continuance of the pregnancy would gravely impair the physical or mental health of the mother or that the child would be born with grave physical or mental defect” or if the pregnancy resulted from rape, forcible or statutory, or incest. Beginning with Colorado in 1967, approximately a dozen states adopted legislation based on the Model Penal Code.

In 1970, the legislatures of three states—Alaska, Hawaii, and New York—enacted laws authorizing abortion on request. In the state of Washington, the same result was achieved by popular referendum and in the District of Columbia as a result of a court decision.

On January 22, 1973, two landmark decisions invalidating the abortion laws of most states were handed down by the Supreme Court. In one of these, Roe v. Wade, the Court ruled seven to two that during the first trimester, “... the abortion decision and its effectuation must be left to the medical judgment of the pregnant woman's attending physician,” in consultation with the pregnant woman. After the first trimester, “... the State … may, if it chooses, regulate the abortion procedure in ways that are reasonably related to maternal health.” After the fetus has reached viability, “... the State … may, if it chooses … proscribe abortion except where necessary … for the preservation of the life or health of the mother.” In the other case, Doe v. Bolton, the Supreme Court struck down a number of procedural provisions, such as the requirements that the termination of pregnancy be authorized by an abortion committee and that the woman seeking abortion must be a resident of the state in which the operation is to be performed. The Court also stressed that the attending physician's “... medical judgment may be exercised in the light of all factors—physical, emotional, psychological, familial, and the woman's age—relevant to the well-being of this patient.” This statement echoes the World Health Organization's definition of health as “... a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity”.

The reception of these decisions ranged from enthusiastic support by those committed to women's 'right to choose', to emphatic rejection by an increasingly well-organized 'right-to-life' movement. In response to anti-abortion sentiment, most states have attempted to institute some form of restriction on abortion services. Possibly the most severe of the restrictions that have been found constitutional is the exclusion of abortion coverage from Medicaid and other governmental health-funding programs. As of 2008, the federal government and all but 17 states provide no public funding of abortions except in cases in which the woman's life would be endangered by continuation of the pregnancy, or if the pregnancy resulted from rape or incest. One study found that approximately one third of women who would have had publicly funded abortions instead carried their pregnancies to term when public funding was unavailable.4

The Supreme Court found that parents could not exercise a veto over a minor daughter's decision to terminate her pregnancy, but approved parental consent requirements for minors provided that a court or other mechanism is available in which a young woman can show that she is sufficiently mature to make an informed decision or that an abortion would be in her best interest. Parental consent or notification requirements are in effect in many states, and in others they are enjoined because they do not meet the Supreme Court's requirements or provisions of the state constitution.

The Supreme Court found several other restrictions unconstitutional until 1989, when it changed direction in Webster v. Reproductive Health Services. In this decision and in Casey v. Planned Parenthood of SE Pennsylvania, the court, although reaffirming that the state may not place an “undue” burden on a woman's right to abortion, indicated that restrictions such as waiting periods and required specific content of preabortion counseling are permissible. Laws requiring waiting periods, usually 24 hours, and specific counseling, are now in effect in many states. The information required to be provided generally includes the gestational age of the fetus; characteristics of the fetus at that point in development; risks of the abortion procedure; risks of continuing the pregnancy; and assistance that may be available if the woman were to have the baby and keep it or place it for adoption. Although laws in Guam and Louisiana that would have prohibited almost all abortions were not allowed to stand, the Court has not yet clarified the extent of restrictions that would be permitted under the “undue burden” standard. Restrictions on abortion providers such as requiring licensing as surgicenters have been increasingly permitted.


The number of pregnancies terminated each year by induced abortion throughout the world cannot be known exactly. A recent estimate is that approximately 20 million illegal and 22 million legal abortions take place annually, for a worldwide total of 42 million.5 Because there are approximately 134 million live births a year, there is approximately one induced abortion for each four known pregnancies (pregnancies ending in birth or induced abortion).

In the United States, relatively few legal abortions were performed before 1960. After 1960, the attitude of the medical profession began to change; mental health gained acceptance as a valid reason for the termination of pregnancy and more legal abortions were performed. This trend was greatly accelerated after the passage of more liberal abortion laws in a number of states and continued after the legalization of abortion by the Supreme Court (Table 1). Many of the legal abortions replaced abortions that would have been performed illegally if the law had not changed.

Table 1. Legal abortions in the United States (1970–2005)


Number of abortions

Abortion rate per 1000 women aged 15–44

Abortion ratio per 100 known pregnancies





































20001,313,000 21.324.5





*1970–1972: Abortions reported to the Centers for Disease Control and Prevention.
1973–2005: Abortions reported to the Guttmacher Institute.2

After 1973, the number of abortions rose to 1.6 million in 1980, remained at that level until 1990, and then began a steady decline. Both the abortion rate (abortions per 1000 women aged 15–44 years) and the abortion ratio (abortions per 100 births and abortions) peaked around 1981 and have declined since 1985. In 2005, the abortion rate was 19.4 per 1000, and 22% of pregnancies (excluding miscarriages) ended in abortion. At 2004 age-specific rates, a cohort of 100 women would have 61 abortions by the time they reach menopause and about one-third would have at least one abortion. The relatively large number of abortions reflects an even larger number of unintended pregnancies. In 2001, an estimated 49% of all pregnancies were unintended; of these, 42% ended in induced abortion, 44% in birth, and the rest in spontaneous abortion or stillbirth.6 The decline in the abortion rate since the early 1990s was concentrated among teenagers and women aged 20–24. Teenagers experienced fewer abortions largely because of improved contraceptive use and secondarily because of delayed initiation of sexual activity7 and a trend toward continuing rather than terminating unintended pregnancies.6

Compared with Western European countries where abortion is available either at the request of the pregnant woman or on broadly interpreted social or social-medical indications and where reasonably complete statistics have been published for recent years, the United States is at the high end of the range (Table 2).8 The abortion rate in the United States is three times as high as in Germany, and is also higher than in Britain and Canada. However, it is comparable to the rates in Sweden and Australia, and lower than in some of the countries of Eastern and Central Europe and the former Soviet Union. The high US abortion rate is attributable to the elevated rate among racial minorities and Hispanic women. Legal abortion rates in developing countries range from much lower than in the United States (Tunisia) to much higher (Cuba). Rates are also estimated to be higher in many developing countries where abortion is illegal under most circumstances.5

Table 2. Legal abortions per 1000 women aged 15–44 years (selected countries)



Abortion Rate







The Netherlands*



Czech Republic  2003                   13










England & Wales*









United States















*Residents only
Reporting incomplete


Abortion occurs among women in all population subgroups, as shown in Table 3. A majority of abortion patients are aged 18–29 years (67%), not currently married (83%), and have children (59%). Minorities are over-represented: 45% are nonwhite and approximately 22%, most of whom are classified as white, are Hispanic. Approximately 34% are non-Hispanic white women.

Table 3. Percentage distribution, rate and ratio of abortions by selected characteristics (United States, 2004)


Percentage distribution





Age of woman (yr)






























    40 or older




Marital status






    Not currently married




Prior births


















    4 or more










    Non-Hispanic white34.1    10.5    15.4





    Other                 7.8   22.9    25.7

Hispanic ethnicity










Prior induced abortions











    3 or more



Weeks of gestation§























    21 or more



Abortion procedure


    Instrumental evacuation



    Medical (nonsurgical) 



    Intrauterine instillation






*For age <15, denominator is women age 14; for 40+, denominator is women aged 40–44
Denominator is abortions plus live births 6 months later (to match time of conception with abortions)
Separated women are included with married
§ Weeks since onset of last menstrual period
#Includes hysterotomy, hysterectomy, some combination procedures, and procedures reported as 'other'


Table 3 illustrates the differences between the two major approaches to the statistical evaluation of pregnancy termination: abortion rates (per 1000 women of reproductive age) and abortion ratios (per 100 pregnancies, excluding spontaneous abortions). Age-specific abortion rates start at a low level in the youngest age group, rise to a peak at 20–24 years (when most women are still unmarried but are sexually active), then decline steadily to a low level among women in their 40s. The pattern of abortion ratios per 100 pregnancies is quite different. Ratios are fairly high among the youngest women, decline progressively to 30–34 years of age, when most women are married and many are building their families, then rise to a higher level among the relatively few pregnancies occurring after age 40.

Whether measured by rates or ratios, abortion is more common among unmarried women than among married women, even when age is taken into account. Rates are highest among unmarried cohabiting women.9 Because many women having abortions are nulliparous and a majority intend to have children in the future, it is of highest priority in providing abortion services to minimize risk to the woman's subsequent reproductive potential.9, 10

Although white women, including Hispanics, made up a majority of women having abortions in 2004, the abortion rate for black women (50 per 1000) was more than three times as high as the rate for white women (14 per 1000), and almost five times the rate of non-Hispanic white women (11 per 1000). This difference reflects a high percentage of unwanted and mistimed pregnancies among economically and socially disadvantaged women rather than a greater propensity to terminate such pregnancies by abortion. Compared with white women, black and Hispanic women have a higher rate of unintended pregnancies; these result in more unplanned births as well as in more abortions.6

Among other demographic characteristics associated with abortion incidence are income (in 2000, the abortion rate of women with family income under the federal poverty level was four times that of women whose family income was at least three times the poverty level); Hispanic origin (the abortion rate of Hispanic women is between that of white and black women); place of residence (incidence is relatively low among residents of nonmetropolitan counties); and religion (abortion rates are below average among Protestant women, close to average among Catholics, and above average among women of other religions or no religious identification).9

The issue of repeat abortion is a matter of concern, especially for those who feel that abortion is unacceptable as a primary method of fertility regulation and should be used only as a backup measure when contraception has failed. Others fear that even minor adverse effects on the outcome of later pregnancies would be cumulated by multiple abortion experiences. The percentage of repeat abortions increased for 25 years after legalization and has begun to decline as the abortion rate has declined. Forty-seven percent of abortions are now repeat procedures; 20% are third or higher order abortions. The increase did not reflect a progressive change from contraception to abortion as the primary method of fertility regulation. Rather, it reflected the growing number of women who have had a first legal abortion and, therefore, are at high risk of having a repeat abortion. Most women who have had an abortion are at risk of a repeat unintended pregnancy and abortion because they are sexually active, able to become pregnant, have difficulty using contraceptives effectively, are willing to end an unwanted pregnancy by abortion, and are concentrated in subgroups with high rates of unintended pregnancy. It is therefore important for clinicians to pay special attention to the contraceptive needs of patients with a history of abortion.

Women usually have a number of reasons for seeking abortions, more than four reasons on average according to one study. The reasons most commonly reported were that a baby would interfere with work, school, or family responsibilities (74%); lack of financial resources to support a child (73%); and problems in the relationship with her partner or desire to avoid single parenthood (48%). Health reasons were reported by 12% and fear of a possible fetal defect by 13% (although it is likely that few were advised by a physician of such a risk). One percent of the respondents said the pregnancy was the result of rape or incest.11 A major concern of many women is the wellbeing of their present and future children.12 More than half of women having abortions practice contraception during the month they become pregnant, although not necessarily correctly and consistently.13


One of the most important factors affecting the risk of morbidity and mortality associated with induced abortion is the period of gestation at which the pregnancy is terminated. Although the traditional division has been between abortions in the first trimester and those in the second trimester, experience indicates that this dichotomy is not sufficient because morbidity and mortality increase with the progress of gestation, even within each trimester.

In the United States, more than half (62%) of the abortions take place at eight weeks from the last menstrual period or earlier, and an increasing proportion (28% in 2004) are performed before seven weeks. Medical methods of early abortion by use of mifepristone or methotrexate in combination with the prostaglandin misoprostol are now commonly available, and early vacuum aspiration, either manual or electric, is sometimes used as early as pregnancy can be detected. Contributing to these developments is the availability in clinics and physicians' offices of sensitive vaginal ultrasound equipment for assessing pregnancy and ensuring that the uterus is empty after the procedure.

In 2004, 12% of abortions occurred after 12 weeks, including 1% after 20 weeks. Under extraordinary circumstances, abortions may be performed after 24 weeks; a reasonable estimate is that there are on the order of 2000–3000 such abortions a year. Many of these follow the discovery of fetal abnormalities.

Abortions past 12 weeks occur most frequently among the youngest women, as shown in Fig. 1. The strong inverse association of period of gestation and a woman's age probably reflects the inexperience of the very young in recognizing the symptoms of pregnancy, their unwillingness to accept the reality of their situation, their ignorance about where to seek advice and help, and their hesitation to confide in adults. Economic considerations and, in many states, regulations prohibiting abortions for minors without parental consent or notification or a court order, also contribute to delays.

Fig. 1. Legal abortions by woman's age and weeks of gestation, United States, 2004





Approximately 88% of abortions are performed by instrumental evacuation. During the first trimester, vacuum aspiration with or without subsequent check curettage is the most frequently used method, but use of medication (mifepristone or methotrexate followed by misoprostol) is increasing and in 2005 accounted for 22% of abortions before nine weeks.2 Between 16 and 20 weeks, dilation and evacuation was used in 96% of abortions in 2004, and after 20 weeks in 87%.1 Prostaglandins are often used for cervical preparation with dilation and evacuation. Intrauterine saline instillation and uterine surgery (hysterectomy and hysterotomy) are rarely used.

Experience has shown that both first- and second-trimester abortions can be performed safely in clinics and physicians' offices. The proportion of abortions performed in hospitals has declined from more than half in 1973 to 5% in 2005. In that year, only approximately 1% of all abortions were hospital inpatient procedures, the remainder being performed on an outpatient basis or in a nonhospital facility.2 The number of hospitals where abortions are known to be performed has dropped from a peak of 1687 in 1976 to 604 in 2005, and among hospitals offering abortion services, the number of abortions per hospital has fallen. An important factor in the shift of abortion services to nonhospital settings is the greater cost of using hospital facilities to provide the service.

Abortion services are increasingly concentrated in high-volume facilities. In 2005, 80% of abortions took place in the 393 clinics and 7 hospitals that performed 1000 or more of the procedures during the year, and 69% took place in clinics where half or more of patient visits were for abortion services.2 Such facilities are generally located in large metropolitan areas, with the result that many women in small cities and rural areas must travel long distances for services. The concentration of abortions in high-volume clinics probably increases the experience and competence of the professionals involved and, thereby, the quality of the services. Conversely, follow-up care is fragmented, with possible unfavorable effects on the patient.

Although a majority of clinicians performing abortions are obstetrician/gynecologists, specialty training is unnecessary for this simple procedure. In 1997, 32% of clinicians in National Abortion Federation member clinics were family physicians, other physicians who were not obstetrician/gynecologists, or midlevel practitioners.14 Studies have shown that first-trimester vacuum aspiration abortions can safely be performed by midlevel practitioners such as physician assistants, who are providing abortion services in several states.15, 16


Complication rates for abortion are difficult to define and to measure. For example, blood loss that would be considered unproblematic to one investigator might be considered hemorrhage by another. Complications recorded on state-mandated abortion-reporting forms may be underreported in part because infection and other problems may appear after the day the procedure was performed and the reporting form completed. Because fewer than one-third of abortion patients on average return for routine follow-up examination, delayed complications are not always known to the abortion facility.

A large case series of low-risk U.S. abortion patients covered 170,000 consecutive first-trimester abortions performed by vacuum aspiration between 1971 and 1987. Follow-up information was obtained either at the clinic or by return of a physician's note on all but 8%. Only 121 patients had complications requiring hospitalization, a rate of 0.07%. Minor complications were reported for 0.85%; the most common of these were mild infection and need for resuctioning.17

The largest database of abortion complications in the United States is maintained by the National Abortion Federation, an association of abortion providers. In 2005, members reported information on 223,800 abortions at all gestational ages; follow-up information was available for 29%. Complications requiring hospitalization were reported for 139 patients for a rate of 0.06% of all patients and 0.21% of those with follow-up, and transfusion was required for 0.01% (0.05% of those with follow-up). Assuming all complications were known to the providers, the complication rates of first-trimester surgical patients were as follows: retained tissue, 0.32%; continuing pregnancy, 0.12%; infection, 0.06%; hemorrhage 0.01%; and unrecognized ectopic pregnancy and uterine injury, each 0.006%. Complication rates for early medication abortion were: retained tissue, 1.0%; continuing pregnancy, 0.6%; hemorrhage, 0.06%; infection, 0.06%; and unrecognized ectopic pregnancy, 0.01%. The true rates are likely to be higher because not all complications may have been known to providers and reported.

There have been no other large-scale compilations of abortion complications in recent years in the United States, only smaller studies from individual providers.  Complication rates are described further in the chapters on abortion procedures.

Because abortions are often obtained by young, nulliparous women, the effect of induced abortion on future reproductive capacity is an important concern. A series of reviews have examined the literature for studies that estimate the relative risk of adverse reproductive outcomes for women who have had an abortion compared with those who have not. Only studies that met basic criteria for methodologic adequacy were included. Following are some of the conclusions.18, 19, 20 Of nine studies identified, eight found no elevated risk of secondary infertility that was statistically significant. The one study that did find an elevated risk took place in Greece, where abortion was illegal and was often performed by dilation and curettage rather than vacuum aspiration.

None of 10 studies reviewed found a statistically significant association between induced abortion and subsequent ectopic pregnancy. Of seven studies of midtrimester spontaneous abortion, none found a significantly higher risk among women who have had one prior pregnancy that was terminated by vacuum aspiration compared with women pregnant for the first time. Three of four studies, however, found an association between dilation and curettage and subsequent midtrimester spontaneous abortion. Studies published since the reviews have generally confirmed these findings.

None of the seven studies examined found prematurity to be more common among women who had had an induced abortion than among women with no prior pregnancies, and none of nine studies reviewed showed an increased risk of low birthweight after vacuum aspiration. Three more recent large European studies, however, found elevated odds ratios for preterm birth of 1.3,211.4,22and 1.5,23 while one found no effect on mean length of gestation.24  These studies included women with more than one prior abortion and included second-trimester abortions. The authors suggest that the results are consistent with infectious processes. Latent upper genital tract infection could result from behavioral factors associated with unintended pregnancy and abortion rather than from the abortion itself. 

Overall, although infection occasionally occurs after induced abortion and can undoubtedly impair fecundity in some women, the studies as a group suggest that the true relative risk of reproductive impairment could be close to one.

Two studies have compared pregnancy outcomes of women who had a prior abortion by mifepristone followed by misoprostol, with those of women who had a prior first-trimester vacuum aspiration abortion.25, 26  Both found no significant difference in the rate of preterm birth or low birthweight between the two groups.  One of the studies also compared rates of ectopic pregnancy and spontaneous abortion, and found no differences.  

Studies of abortions performed by dilation and curettage have had less clear results. The effects of second-trimester abortions and multiple abortions have not been adequately studied for definite conclusions to be drawn, but if the effects were large, they would have been noted.

Many studies have examined the relation of induced abortion to subsequent breast cancer with varying results.  Some relied on abortion histories reported retrospectively by women with cancer and controls, a methodology that may result in more complete reporting of past abortions by women with cancer than by those without cancer.  An exhaustive meta-analysis of 53 studies found that the ones that relied on women's retrospective reports of abortion found a cancer risk, while the studies that relied on medical records or prospective data, including several large studies, collectively found no such risk.  The relative risk in the studies using prospective data, including a total of 44,000 women with breast cancer, was 0.93 (0.89–0.96, p=0.0002).27 The meta-analysis and subsequent studies provide conclusive evidence that induced abortion causes no increase in risk of breast cancer.


High levels of mortality from legal abortion prevailed in the United States as elsewhere during the period of restrictive legislation, when a significant proportion of the women undergoing abortion experienced pre-existing complications that made them poor risks for any type of surgery. In 1972, the mortality rate was 4 per 100,000 legal terminations. The rate fell to 2 in 1973–1977, when elective abortion became more easily available to most women (Table 4). As abortion services improved with increasing experience and technical advances, mortality fell to 0.8 in 1978–1982 and to 0.7 in 1983–1992. Since 1992, mortality has leveled off at about 0.6 per 100,000. Mortality from illegal abortion fell from 39 recorded deaths in 1972 to 2 in 1976. In recent years there has continued to be a death every few years from illegal abortions (i.e. abortions performed by someone other than a licensed physician or someone acting under the supervision of a licensed physician).

Table 4. Number of legal abortions, number of associated deaths, and mortality per 100,000 abortions (United States)

Years or characteristics

 Number of abortions

 Number of deaths

 Deaths per 100,000 abortions



















    1993–2003 14,729,000             87              0.6

Gestation, 1988–1997 (weeks)*

    8  7,700,000          11.1              0.1





















Age, 1988–1997










    30 and older




Race, 1988–1997






    Black and other




*Twenty-six deaths with unknown gestation were distributed proportionately.

Note: Number of abortions as estimated by the Guttmacher Institute.

Information on abortion mortality is provided by the CDC, which investigates all reports of abortion-related deaths, whether or not abortion is recorded as a cause of death on the death certificate.1 The CDC reports include all deaths associated with abortion, including those with another primary cause, usually a pre-existing medical condition. The main causes of death associated with legal abortion are infection,  hemorrhage, embolism, and complications of anesthesia. Since the early 1970s, the number of deaths has dropped sharply from all causes.28 One of the main risk factors for abortion mortality is the period of gestation when pregnancies are terminated. In the United States between 1988 and 1997, mortality ranged from 0.1 per 100,000 abortions at 8 weeks or less to 13.0 per 100,000 for abortions at 21 weeks or more. Mortality increased by approximately 30–40% with each week of gestation past 8 weeks.29

Age has little relation to abortion mortality, but mortality is distinctly higher among women of minority races than among white women. Mortality was higher during 1974–1977 for first-trimester abortions performed in hospitals than for abortions in nonhospital facilities. The difference disappeared when women with pre-existing complications or concurrent sterilization were excluded from the hospital data.30 Similar results were found for abortions performed at 13–15 weeks by dilation and evacuation between 1972 and 1978.31 These analyses have not been repeated for more recent years.

Abortion-related mortality may be compared appropriately with the risk to life associated with carrying a pregnancy to term. In the United States, maternal mortality attributed to complications of pregnancy and childbirth, excluding induced abortion, was 8.7 deaths per 100,000 live births in 1993–2003, based on data recorded on death certificates. Excluding deaths from spontaneous abortion and ectopic pregnancy, some of which may have resulted from pregnancies that would have ended in induced abortion if they had been normal, mortality was 7.9 per 100,000 live births. These statistics exclude deaths associated with but not attributed to pregnancy and childbirth. Thus, mortality from induced abortion before around 20 weeks of gestation is lower than maternal mortality attributed to childbirth, and mortality from abortion is not statistically significantly higher at any gestation. Overall, the mortality risk associated with continuing a pregnancy (at least 7.9) is more than 10 times the risk associated with induced abortion (0.6).

The safety of abortion in the United States is comparable to that in other developed countries, even though most other countries have a smaller proportion of second-trimester abortions and count only the deaths attributed to abortion. As listed in Table 5, abortion mortality ranges from 0.11.0 death per 100,000 procedures. Because of the small numbers of deaths on which the rates are based, the differences among the countries are not statistically significant.

Table 5. Number of legal abortions, associated deaths, and mortality rate per 100,000 legal abortions by country


Abortions (1000s)


Mortality Rate

Belarus (19911996)



0.8 (0.3–1.3)

Bulgaria (19841996)



0.1 (0.0–0.5)

Canada (19761994)



0.1 (0.0–0.5)

Czech Republic (19841996)



0.4 (0.0–0.7)

Denmark (19761995)



0.5 (0.1–1.7)

England & Wales (19911993)



1.0 (0.3–2.2)

Finland (19761995)



0.7 (0.1–2.7)

Hungary (19841996)



0.2 (0.0–0.7)

The Netherlands (19761997)



0.1 (0.0–0.6)

Sweden (19771995)



0.3 (0.0–1.1)

United States (19881992



0.7 (0.5–0.9)

United States (19932003)      14,729.4     87   0.6 (0.5-0.7)

*Deaths were attributed to legal abortion on death certificates, except for England and Wales, where deaths are recorded on the abortion notification form, and the United States, where deaths include all those associated with abortion after investigation by the Centers for Disease Control and Prevention.
95% confidence intervals in parentheses

In all countries for which we have data, there were sharp declines in the abortion mortality rates between the 1970s and the 1980s. Factors that appear to account for the declines include increasing skill of abortion practitioners as a result of having more years of experience; the nearly universal adoption of vacuum aspiration; improved treatment of complications; advances in abortion technology; and, in some countries, a reduction in the proportion of procedures performed during the second trimester. There may also have been improvements in the underlying health condition of patients.


Portions of this chapter were reproduced from Tietze C: Induced Abortion: Epidemiological Aspects.  In Sciarra JJ (ed): Gynecology and Obstetrics.  Philadelphia, Harper & Row, 1982.



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