Modern methods of abortion are not linked with an increased risk of preterm birth

July 9, 2013

The link between previous termination of pregnancy (abortion) and preterm delivery in a subsequent pregnancy has disappeared over the last 20-30 years, according to a study of data from Scotland published in this week's PLOS Medicine. The study, led by Gordon Smith from the University of Cambridge, found that abortion was a strong risk factor for subsequent preterm birth in the 1980s but over the next 20 years, the link progressively weakened and was no longer present among women giving birth from 2000 onwards.

These findings are important as the current recommendations to discuss a possible increased risk of if a woman has an abortion were based on studies before 2000. The current analysis indicates that there is no link between abortion and the subsequent risk of preterm birth in modern practice and so current guidelines may have to be revised.

By using a large from Scotland, the authors found that out of 757,060 live first births (excluding ) between 1980 and 2008, 56,816 women reported one previous termination, 5,790 women reported two previous terminations, and 822 women reported three or more previous terminations. After adjusting for maternal characteristics, the authors found that there was a strong link between spontaneous preterm birth and previous abortion in 1980-1983, with a >30% increase in the risk of preterm birth with each previous procedure. However, this link progressively weakened, with a 10-20% increase in risk for preterm births in the 1990s, and no link at all from 2000 onwards.

The likely explanation for these findings is changes in methods of abortion. Over the period 1992 to 2008, the authors found that the procedure thought most likely to be lead to an increased risk of preterm birth (purely without the use of any drugs) decreased from 31% in 1992 to 0.4% in 2008. Furthermore, the proportion of medical terminations (procedures that avoided the use of surgery altogether) increased from 18% to 68%.

These findings suggest that use of purely surgical termination may have been responsible for the increased risk of spontaneous preterm birth and so, the phasing out of this procedure in Scotland in the 1980s and 1990s may have led to the subsequent disappearance of the established link between previous termination and preterm delivery from 2000 onwards. However, the authors could not directly test whether the two trends were related because they did not have information on the method of previous termination linked to subsequent birth outcome for individual women.

The authors say: "We have shown that previous abortion was a risk factor for preterm birth among nulliparous women in Scotland prior to 2000. However, increased use of medical methods of abortion and of cervical pre-treatment prior to surgical has been paralleled by a disappearance in the association."

The authors add: "We believe that it is plausible that modernising methods of termination of pregnancy worldwide may be an effective long-term strategy to reduce future rates of preterm birth."

Explore further: Research gives insights into abortion

More information: Oliver-Williams C, Fleming M, Monteath K, Wood AM, Smith GCS (2013) Changes in Association between Previous Therapeutic Abortion and Preterm Birth in Scotland, 1980 to 2008: A Historical Cohort Study. PLoS Med 10(7): e1001481. doi:10.1371/journal.pmed.1001481

Related Stories

Research gives insights into abortion

September 5, 2012
(Medical Xpress)—Women whose first pregnancy ends in abortion are more at risk of having a premature baby in a second pregnancy than women in their first pregnancy. However, the risk is not as high as that of women who ...

Obesity increases the risk of preterm delivery

June 11, 2013
The risk of preterm delivery increases with maternal overweight and obesity, according to a new Swedish study published in Journal of the American Medical Association (JAMA). Women with the highest Body Mass Index (BMI) also ...

Study finds residence in US a risk factor for preterm birth

February 9, 2012
In a study to be presented today at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in Dallas, Texas, researchers will report findings that indicate that duration of stay in the United States ...

Increased risk of prematurity and low birth weight in babies born after three or more abortions

August 29, 2012
One of the largest studies to look at the effect of induced abortions on a subsequent first birth has found that women who have had three or more abortions have a higher risk of some adverse birth outcomes, such as delivering ...

Daily iron during pregnancy linked to improved birth weight

June 20, 2013
Taking iron daily during pregnancy is associated with a significant increase in birth weight and a reduction in risk of low birth weight, finds a study published in BMJ today.

Presence of intra-amniotic debris a risk for early preterm birth in first pregnancy

February 11, 2013
In a study to be presented on February 14 at the Society for Maternal-Fetal Medicine's annual meeting, The Pregnancy Meeting, in San Francisco, California, researchers will report findings suggesting an increased risk of ...

Recommended for you

Population health impact of infants born small for gestational age in low- and middle-income countries

August 18, 2017
In low-and middle-income countries, it is common for babies to be born of low birth weight, due to either inadequate growth in utero (fetal growth restriction) and/or preterm birth, (birth before 37 weeks gestation). Maternal ...

Hormone from fat tissue can give protection against polycystic ovary syndrome

August 10, 2017
Obesity and reduced insulin sensitivity are common in polycystic ovary syndrome, PCOS. New research based on animal studies, and to be published in the journal PNAS, reveals that the hormone adiponectin can protect against ...

Study in mice may reveal insights into causes of miscarriages for some women

August 9, 2017
Researchers at St. Michael's Hospital have identified how natural killer cells in the mouse placenta can cause a fetus to fail to grow in the womb or cause miscarriages.

Insomnia, sleep apnea nearly double the risk of preterm delivery before 34 weeks

August 9, 2017
Pregnant women who are diagnosed with sleep disorders such as sleep apnea and insomnia appear to be at risk of delivering their babies before reaching full term, according to an analysis of California births by researchers ...

Elective freezing of IVF embryos linked to higher pregnancy rates in some cases

August 1, 2017
A delay in transferring embryos to the mother improves the success of in vitro fertilization in certain cases, according to a study by scientists at the Stanford University School of Medicine, Celmatix Inc. and several other ...

Negative birth outcomes linked to air pollution exposure early in pregnancy, study finds

July 27, 2017
Exposure to air pollution early in a pregnancy could increase risk for preterm birth and low birth weight, according to a study led by researchers at NYU School of Medicine, and published on July 27 in Environmental Health ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (3) Jul 09, 2013
So it's safe for a woman after killing her first child to have another.

To those that have killed a child before he/she was born and then went on to have another child, how do you say to your living child "you love them" as your love is conditional only on you wanting them?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.