Health Informer - Medical News: Risk of Preterm Birth Rises with Abortions

Friday, August 31, 2012

Risk of Preterm Birth Rises with Abortions - MedPage Today

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ByÂ Charles Bankhead, Staff Writer, MedPage Today

Published: August 30, 2012

ReviewedÂ byÂ Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco

Action Points

The odds for a first birth before 28 weeks gestation increased significantly in women who had had one or more prior induced abortions.
Note that the risk for preterm birth before 37 weeks was increased only among women who reported three or more prior abortions.

The odds for a first birth before 28 weeks gestation increased significantly in women who had had one or more prior induced abortions, a large Finnish study showed.

The odds ratio for very preterm birth (less than 28 weeks) increased from 1.19 with one induced abortion (95% CI 0.98 to 1.44) to 2.78 for women who had had three or more abortions (95% CI 1.48 to 5.24) before giving birth for the first time.

The risk for preterm birth before 37 weeks was increased only among women who reported three or more prior abortions, as reported online in Human Reproduction.

"In terms of public health and practical implications, health education should contain information of the potential health hazards of repeat induced abortions, including very preterm birth and low birthweight in subsequent pregnancies," Reija Klemetti, PhD, of the National Institute for Health and Welfare in Helsinki, and co-authors wrote in conclusion.

"Healthcare professionals should be informed about the potential risks of repeat induced abortions on infant outcomes in subsequent pregnancy."

The authors cautioned that "observational studies like ours, however large and well controlled, will not prove causality."

Numerous studies have shown an association between induced abortion and risk of preterm birth, including a "dose-response" effect. Other studies did not find such associations, and the association disappeared altogether in adjusted analyses of some investigations.

Less is known about the relationship of induced abortion to low birthweight. Additionally, studies have yielded variable findings about the type of abortion procedure, gestational age at abortion, and number of abortions prior to giving birth.

Klemetti and colleagues sought to inform on areas of uncertainty by examining the impact of prior induced abortion on birth outcomes among first-time mothers in Finland, which maintains good records on birth outcomes and induced abortions.

They hypothesized that one induced abortion does not affect birth outcomes but several prior abortions might have an adverse impact on birth outcomes.

Finland has a low rate of legal abortions (8.9 per 1,000 women ages 15 to 49) compared with European countries, and illegal abortion is rare, as is legal abortion outside the country, the authors noted in their introduction.

The investigators searched the Finnish birth registry for 1996 to 2008, identified all first-time mothers, and linked the results to the national abortion registry for procedures performed from 1983 to 2008.

The search identified 300,858 first-time mothers. Of those, 10.3% had had one prior abortion, 1.5% had two, and 0.3% had three or more prior abortions. Of the abortion procedures, 88% were surgical, 91% were performed before 12 weeks gestation, and 97% were performed for "social reasons."

An adjusted analysis showed that prior induced abortion (versus none) increased the odds for birth before 28 weeks gestation to:

1.19 after one (NS)
1.69 after two (95% CI 1.14 to 2.51)
2.78 after three (95% CI 1.48 to 5.24)

Only with three or more prior induced abortions were the odds increased for:

Preterm birth (<37 weeks) -- OR 1.35 95% CI 1.07 to 1.17
Low birthweight (<2,500 g) -- OR 1.43 95% CI 1.12 to 1.84
Very low birthweight (<1,500 g) -- OR 2.25 95% CI 1.43 to 3.52

"With the exception of low Apgar scores, the studied adverse birth outcomes were more common among mothers having had three or more induced abortions," the authors wrote in their discussion. "Taking into account previous miscarriages and ectopic pregnancies did not notably change the results."

The study was supported by the National Institute for Health and Welfare and the Academy of Finland.

The authors had no disclosures.

Primary source: Human Reproduction
Source reference:
Klemetti R, et al "Birth outcomes after induced abortion: A nationwide register-based study of first births in Finland" Hum Reprod 2012; DOI: 10.1093/humrep/des294.