Studies - PreTerm Delivery / Premature Birth / Prematurity Complications

UNC Study: Negative Abortion Effect on Prematurity & Placenta Previa (OGS,1/2003)

[Abstract follows at end of this summary]

Abortion increases risks of premature delivery (risk ratio elevation of 1.3 to 2.0), maternal depression and suicide, and other serious health consequences, such as placenta previa (RR of 1.7), reports a new medical study by prominent medical researchers.

"Preterm delivery and depression are important conditions in women's health and avoidance of induced abortion has potential as a strategy to reduce their prevalence."

The authors further conclude that more research is required, and that women need to be informed of these and other major long-term health risks of abortion: "…we conclude that informed consent before induced abortion should include information about the subsequent risk of preterm delivery and depression.

Although it remains uncertain whether elective abortion increases subsequent breast cancer, it is clear that a decision to abort and delay pregnancy culminates in a loss of protection with the net effect being an increased risk."

The "'loss of protection' effect is most pronounced in women under 20 years of age who elect to undergo abortion rather than continue their pregnancy. We think, now, that clinicians are obliged to inform pregnant women that a decision to abort her first pregnancy may almost double her lifetime risk of breast cancer through loss of the protective effect of a completed first full-term pregnancy earlier in life."

Placenta previa effects 0.3% to 0.8% of pregnancies and is the leading cause of uterine bleeding in the third trimester and of medically indicated preterm birth. Pregnancies complicated by placenta previa result in high rates of preterm birth. low birth weight, and perinatal death.


The study, published in the January 2003 issue of the Obstetric & Gynecological Survey (OGS), assesses the long-term physical and psychological health consequences of abortion. The researchers, professors of medicine at the University of North Carolina at Chapel Hill and the University of Michigan, reviewed and analyzed 30 years of medical studies on the long-term medical risks of abortion.

Their research reveals a critical need for "a detailed study of the health effects of this common procedure." Acknowledging that current data is sparse, and that current studies are flawed, the researchers recommend further studies to meet "the clear need for women to have accurate information" about the risks and potential complications of abortion.

"Follow-up across participants' life-times with careful measurement of other pertinent exposures would dramatically advance knowledge.

Until such an investigation is invested in, women are making important health decisions with incomplete information.

A commitment to such research would seem to us to be morally neutral common ground upon which both sides of the abortion/choice debate would agree is critical."

Denise Burke, staff counsel for Americans United for Life (AUL), notes, "The current lack of comprehensive and trustworthy studies revealing the long-term effects of abortion is reminiscent of the lack of information we had about the dangers of smoking 30 years ago. Women deserve to know how abortion will affect their lives and health."

The study notes that 26 of every 100 known pregnancies end in abortion. Dorinda Bordlee, AUL staff counsel, says, "Twenty-eight states currently require some level of informed consent for abortion. Given the prevalence of this procedure, we are hopeful that this new study will encourage the remaining states to enact laws that give women considering abortion complete and accurate medical information."

Bordlee continues, "Women have been at the center of a 30-year social and medical experiment, and we should unapologetically insist on mandatory reporting of abortion complications for the sake of women’s health, and in the interest of preventing a public health crisis."

The abstract, study, and extensive references (100+) are published in Obstetrical & Gynecological Survey 2003; 58(1):67-79 and may be found at (subscription may be needed)

The study’s authors: John Thorp, Jr., M.D., Mcallister Distinguished Professor, Obstetrics/ Gynecology, Department of Epidemiology, School of Public Health, and Department of Obstetrics and Gynecology, School of Medicine, Univ of North Carolina, Chapel Hill. Katherine Hartmann, M.D., Ph.D., Assist Professor, Department of Epidemiology, School of Public Health, and Department of Obstetrics and Gynecology, School of Medicine, Univ of North Carolina, Chapel Hill. Elizabeth Shadigian, M.D., Assoc Professor, Dept Obstetrics/ Gynecology, School of Medicine, Univ of Michigan, Ann Arbor. Thorp and Hartmann are Co-Directors of the Women’s Health Research Project at the Univ of North Carolina, Chapel Hill. Obstetric & Gynecological Survey reprint requests: John M. Thorp, Jr., M.D., Department of Epidemiology, School of Public Health, Univ of North Carolina, Dept of Obstetrics and Gynecology, School of Medicine, Chapel Hill, NC 27599. [email protected] [AUL, 15Jan03, [email protected]]



John M. Thorp, Jr., MD
Department of Epidemiology
School of Public Health
University of North Carolina
Department of Obstetrics and Gynecology
School of Medicine
University of North Carolina
Chapel Hill, NC 27599

Katherine E. Hartmann, MD, PhD
Department of Epidemiology
School of Public Health
University of North Carolina
Department of Obstetrics and Gynecology
School of Medicine
University of North Carolina
Chapel Hill, NC 27599

Elizabeth Shadigian, MD
Department of Obstetrics & Gynecology
F4864 Mott, Box 0264
School of Medicine
University of Michigan
Ann Arbor, MI 48109-0264

In the late 1960’s and early 1970’s, abortion was legalized in most of the western world. Legalization culminated in more women choosing termination than had been expected, (1,2) with young, socially deprived,
and childless women making up the largest proportion.(3) Initially, research focused on early complications, immediate maternal mortality, and optimization of abortion technique.(4)

Subsequent interest in the potential longterm health consequences entered scientific discussion later, not primarily driven by specific hypotheses, but rather by those with conflicting viewpoints, vis a vis, the moral status of the embryo or fetus, and desire to either limit or
expand access to abortion.(5) As profound sociologic changes in reproductive behavior were documented in the form of rising abortion rates, political pressures motivated governments to appoint special study commissions charged with the task of reporting on the long-term health implications of induced abortion.(6,7)

The resulting reports lament the lack of long-term follow-up and call for detailed study of the health effects of this common procedure.

Despite strong recommendations for substantive research, and the clear need for women to have accurate information as they execute their autonomy, current data remain sparse, studies are small and
methodologically flawed, and the conclusions are often intertwined with the political agendas of their authors and publishers.(8)

Epidemiologic data exists on abortion from most countries in which it is legal. However, the completeness of these data is subject to local statutes and their enforcement.(3) Sources of information include legally mandated registers, hospital administrative data and clinic statistics, and voluntary reporting or surveys of abortion providers.
With these limitations in mind, we nonetheless can calculate abortion incidence. Both abortion rates and ratios are important measures in understanding the epidemiology of legal abortion. Rates reflect abortions per 1000 reproductive-age women, and ratios are the number of abortions per 100 live births or pregnancies. Readers should
note that abortion ratios increase as the number of births diminish, and increases in abortion ratios can reflect not only the incidence of women deciding to terminate a pregnancy, but also the incidence of women deciding to conceive.

From the early 1970’s the annual number of abortions performed in the United States peaked at 1.61 million in 1990. Abortions have declined over the last decade with 1.37 million in 1996; this drop is attributed in
part to aging of the population(9,10) and a fall in unintended pregnancies amongst adolescent women.(11,12)

In 1996, the U.S. abortion rate per 1,000 women aged 15-44 was 23/1000, the lowest reported rate since 1975. The abortion ratio in 1996 was 26 abortions per 100 live births and abortions.

Thus, 26% of all recognized pregnancies were terminated.(6,7) Overall, the United States abortion rate (23/1000 in 1996) is high compared with similarly developed countries. In 1995 the abortion rates were 16/1000 in Canada, 15/1000 in England, 6/1000 in the
Netherlands, and 18/1000 in Sweden.(13)

One can presume that abortion is most often chosen as a response to a crisis or unintended pregnancy. The high prevalence of a history of induced abortion means that even small positive or negative effects on long-term health could influence the lives of many women and their families.

The long-term health effects of elective abortion are difficult to study and thus poorly understood. This lack of knowledge stems from a variety of causes. First and foremost, exposure to abortion cannot be assigned on an experimental basis, restricting researchers to rely on observational studies and precluding randomized trials.

Thus all research in this realm is prone to an array of different sources of bias that complicate the process of drawing conclusions. Second, it is not clear what group of women constitutes an appropriate comparison group for these observational studies.

Third, the decision to terminate a pregnancy is emotionally difficult for many women. Hence, regret, remorse, or shame may cause them to not disclose having made such a decision when queried about their reproductive histories.

Fourth, the long-term health consequences of elective abortion have been highly politicized. Those who would grant a moral status to an embryo or fetus and thus limit elective abortion, often use adverse health consequence claims as a tool to further their moral agenda, while those who support no restrictions on abortion access are at times unwilling to consider that pregnancy interruption could affect future mental and physical health. Finally, the effect sizes are small with risk ratios when present falling in the range of a doubling or
less of risk for comparatively rare outcomes. The potential for modest influence on events that are unlikely and distant for an individual woman hinders the ability of clinicians or patients to use their experience and judgment to employ such information in decision-making.

One might then reasonably ask why study such a complicated, politically treacherous, and difficult to understand phenomena. Studies would have to be large and thus expensive to have adequate power to detect small effects and control for the biases described and might not directly influence clinical care.

We would point to cigarette smoking and its health consequences as an answer. In the 1950’s and 60’s each point delineated in the
preceding paragraph could have been and were applied to the dilemma of studying whether tobacco consumption has adverse health consequences. While no individual clinician or patient could discern the harms of cigarette smoking and all studies had to be observational with their inherent biases, well-done epidemiologic research was able to document adverse consequences and ultimately inform public opinion and policy.

Elective abortion must be studied in the same fashion with similar vigor, given the frequency with which women choose to terminate a
pregnancy and the important and prevalent health conditions that some of the data gathered heretofore have linked to elective abortion, eg, preterm birth and breast cancer. Women deserve to be fully and accurately informed about potential health effects of elective abortion, preferably in a health education context separate and distinct from the
timeframe of actually being faced with making difficult decisions about whether to continue or end a pregnancy.

Until further research and meta-analyses are forthcoming, we are faced with the uncertainties outlined in this review. We find little evidence to support the claims that elective abortions increase the risk of subsequent subfertility, ectopic pregnancy, and spontaneous abortion. Of more concern are the possibility of links to preterm
birth, placenta previa, breast carcinoma, and serious mental health problems.

Abortion is a procedure most used by women at the outset of their reproductive life. The majority of women having an induced abortion are under 30 years old.(72) Preterm birth is common, affecting around 10% of deliveries in the Western World, and is the leading cause of infant morbidity and mortality.(73) Despite substantial
investigative effort, primary preventive measures to lower the rate of preterm births have proven futile and rates have been steady or increased over the past two decades.(73)

The population-based studies we reviewed suggest that induced abortion increases the risk of preterm birth in subsequent pregnancies.

Moreover, these reports suggest that a dose response effect is present with increasing numbers of abortions associated with increasing risk, and that the linkage is most strong with extremely premature deliveries (<32 weeks), which is the population of
newborns that experiences the bulk of the morbidity and mortality that occur from being born prematurely.

Readers should note that the increased risk of early childbirth associated with induced abortion occurs over and above the background risk of preterm birth (estimated to be 10%) inherent with any pregnancy. The respective roles of various surgical and medical techniques used for induced abortion and their impact on preterm birth remain unexplored and may mitigate these consequences.

In light of these data, we believe that women in general, including those considering abortion, need to be informed that surgical abortion procedures may increase the likelihood of subsequent preterm births, and that the risk associated with other methods is unknown.

For those women who choose abortion, techniques that in theory protect the cervix from trauma, such as laminaria or preabortion
cervical ripening, should be utilized.

Placenta previa effects 0.3-0.8% of pregnancies and is the leading cause of uterine bleeding in the third trimester and of medically indicated preterm birth. Pregnancies complicated by placenta previa result in high rates of preterm birth, low birth weight, and perinatal death.(27) Both the observational studies included in our review
and Ananth et al’s meta-analysis show a link between placenta previa and previous induced abortion. The metaanalysis (27) incorporated articles outside the scope of our search and exemplifies how review of other papers on topics such as smoking and placenta previa can inform the search for linkages between abortions and reproductive health.

Ananth et al speculate that a 50% reduction in induced abortion would be required to avert 1.5% of placenta previa cases. Placenta previa is rare enough and the impact of this change is so small that we would not feel obliged to mention this to women contemplating their first abortion. Our advice might change if a woman had had a
previous cesarean section, an independent risk factor for placenta previa; or if she were contemplating undergoing a
second elective pregnancy termination.(27)

In other venues, information about the existence and magnitude of risk
may be appropriate for health education summaries of the reproductive correlates of elective abortion.

Potential links between breast cancer and abortion are the most controversial long-term health consequence explored in our review. Findings are mixed with reviewers and authors of original manuscripts drawing different conclusions. The one meta-analysis done to date points to a small but significant link between abortion and breast
carcinoma. The current literature is insufficient to be informative for counseling. Nonetheless the topic is worthy of well-designed and conducted research and of careful meta-analyses using the hand-search techniques employed by Ananth et al(27) to explore sources of published data not focused on the direct link between abortion and breast cancer.

In the interim, should we, and how do we inform patients? We would argue that given the undisputed protective effect of a full-term delivery early in one’s reproductive life on subsequent breast cancer development that a young woman facing an unwanted or crisis pregnancy can and should be informed of the loss of that
protection that would derive from a decision to terminate her pregnancy and delay having a baby

To illustrate, Figure 1 utilizes the Gail Equation to predict five-year and lifetime risk of breast carcinoma for an 18-
year-old woman with an unintended or crisis pregnancy. The Gail model(99) is considered the best available
measure for estimating an individual woman’s risk of developing breast cancer. It was used to calculate risk
estimates for the National Cancer Institute’s breast cancer chemoprevention trial and is specifically designed to be
useful in decision making by women.(100)

In the first scenario, she decides to terminate and then has her first term delivery at age 32, where in the second she has a live-born infant. We then assess her individual risk at age 50 when the risk of breast cancer begins to peak. For both black and white women her decision at age 18 and subsequent reproductive choices can almost double her five-year and lifetime risk of breast neoplasia at age 50.
Tables 5, 8, and 9 demonstrate that the “loss of protection” effect is most pronounced in women under twenty years of age who elect to undergo abortion rather than continue their pregnancy.

We believe at the present time that clinicians are obliged to inform pregnant women that a decision to abort her first pregnancy may almost double her lifetime risk of breast cancer through loss of the protective effect of a completed first full-term pregnancy earlier in life.

Additionally, we believe that women should be aware of the studies that support induced abortion as an independent risk factor for breast cancer, with the only quantitative analysis showing a small but
statistically significant odds ratio of 1.3, while the other three reviews (which are non-quantitative) refute this.

The effects of elective abortion on mental health are challenging to interpret for the reasons outlined.
While earlier studies focusing on secondary outcomes were reassuring, more recent, large cohort studies linking
abortion to the “hard” outcomes of either suicide, psychiatric admission, or deliberate self harm are concerning. (90,93,97)

A major question remains unanswered because of the lack of a proper control group. Is the observed phenomena a correlate of the circumstance that may lead to a crisis or unintended pregnancy regardless of a woman’s decision to choose abortion, or is this a function of both? Until that question can be answered it wi

ll be
hard to inform women as to what if any additional risk a decision to terminate will produce.

Likewise, the uncertainty limits a clinician’s ability to reassure such a woman that her decision will not have long-term mental health effects. The observation of the association, regardless of the lack of causal linkage, suggests careful screening and follow-up for depression and anticipatory guidance/precautions for women who choose elective abortion.

Informed consent is a bioethical tool used in medical practice to protect an individual’s autonomy as he or she makes a healthcare decision.

Clinicians are obliged by law to inform patients prior to a medical decision of the benefits and risks of the treatment being pondered. The goal is not to confuse a patient nor direct her decision making process but to provide patients with the information that a reasonable person would want to know. Thus not every possible good or bad consequence or consequences that are uncertain are obliged to be shared.

In light of our review we believe that any woman contemplating an induced abortion should be cautioned about the mental health correlates of an increased risk of suicide or self-harm attempts as well as depression and a possible increased risk of death from all causes.

Analagous to the clinical practice with puerperal depression, women undergoing abortion should be screened for depression at follow-up visits, warned of the signs and symptoms of depression and
suicidal ideation, and provided easy access to mental health evaluation and treatment.

The reader should keep in mind that the informed consent process is an interaction between two
individuals, clinician and patient, with the intent to respect the patient’s autonomy. Individual patients will weigh
the importance of these potential risks differently based on their life experiences and values. Furthermore, we
anticipate the outcry arising from this approach from both sides of the abortion debate. Those who would ascribe a
moral status to an embryo or fetus will view calculation of risk as a cruel calculus compared to the loss of an
individual life. Their opponents who view maternal autonomy as paramount and fear that an unwanted pregnancy
limits a woman’s capacity for fulfillment will view information about remote risk from abortion as an attempt to
limit access to the procedure. Nevertheless, we think abortion decision-making should include the protection of
informed consent and women who wish to know the long-term physical and mental consequences of their decision
should be informed.
Furthermore, women contemplating their first induced abortion early in their reproductive life should be
informed of two major long-term health consequences. First, their risk of subsequent preterm birth, particularly of
a very low birth weight infant, will be elevated above their baseline risk in the current pregnancy. Second, they
will lose the protective effect of a full-term delivery on their lifetime risk of breast carcinoma. This loss of
protection will be in proportion to the length of time that elapses before they experience their first delivery.
Increased rates of placenta previa and the disputed independent risk of induced abortion on breast cancer risk
warrant mention as well. Failure to provide this information is a direct threat to maternal autonomy, diminishing a
woman’s ability to give informed consent. We believe a reasonable person is entitled to know these conclusions
and their limitations, and having been informed will find herself in a better place to personally evaluate the longterm
health consequences of an induced abortion.
We acknowledge that the setting of informed consent at the time of counseling about an undesired or crisis
pregnancy is suboptimal as an opportunity to be first introducing the potential risks of elective abortion. Women
would be better served by having pre-existing knowledge about the scope and nature of potential risks. That being
the case suggests that reproductive health education opportunities in clinical settings, schools, and the media, would
serve the interests of women best by featuring currently available information about potentially associated risks.
Such knowledge could hypothetically reduce behaviors that place individuals at risk of an undesired pregnancy,
and certainly would protect against the undesirable but necessary circumstance of being provided with such
information for the first time in the setting of a crisis pregnancy.
Given the central role that abortion has played in the life of women over the past thirty years, we are
distressed by the lack of term-term, well-done research designed to understand the sequelae. A clear and
overwhelming need exists for a large epidemiologic, cohort study of women with an unintended or crisis
pregnancy. Follow-up across participants’ lifetimes with careful measurement of other pertinent exposures would
dramatically advance knowledge. Until such an investigation is invested in, women are making important health
decisions with incomplete information. A commitment to such research would seem to us to be morally neutral
common ground upon which both sides of the abortion/choice debate would agree is critical.

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