IVF Might Increase Risk Of Pregnancy Complication Placenta Previa, Study Says

Main Category: Fertility
Article Date: 27 May 2006 - 3:00 PDT

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Women who undergo in vitro fertilization are about six times as likely as women who conceive naturally to experience a pregnancy complication called placenta previa, in which the placenta partially or completely covers the cervix, obstructing the fetus' delivery through the birth canal, according to a study published in the current issue of Human Reproduction, BBC News reports (BBC News, 5/24). Placenta previa, which occurs in about 12,000 to 15,000 deliveries annually in the U.S., is the leading cause of hemorrhaging in the second and third trimesters and raises the risk of preterm delivery, according to USA Today. For the study, Liv Bente Romundstad and colleagues at St. Olav's University Hospital in Trondheim, Norway, examined about 845,000 single-fetus pregnancies reported to the Norwegian Medical Birth Registry from 1988 to 2002, about 7,600 of which were a result of IVF. By identifying 1,349 women who had conceived both naturally and using IVF, researchers were able to adjust for risk factors, such as whether the women were older than age 30, smokers or previously had delivered several infants (Rubin, USA Today, 5/25). Conceiving through IVF -- whether before or after naturally conceiving -- raises the risk of developing placenta previa from three in 1,000 deliveries to 16 per 1,000 deliveries, according to the study (Reaney, Reuters, 5/24). Bente Romundstad said that the complication might occur because the embryo often is positioned low in the uterus when it is transferred through the cervix during the IVF process. "The procedure may induce uterine contractions due to the release of prostaglandins [hormone-like substances] after stimulation of the cervix, leading to more embryos implanting low-down in the uterus," she wrote (Martin, Daily Telegraph, 5/25). Previous research has shown that positioning the embryo lower in the uterus can increase implantation rates, so fertility clinics might intentionally do so, Reuters reports.

Recommendations, Reaction
Researchers urged fertility doctors to monitor and track where the embryo is positioned during the transfer to determine the risk of placenta previa. "We now routinely do this, but we need other centers worldwide to do this as well," Romundstad said (Reuters, 5/24). Mark Hamilton, chair of the British Fertility Society, said, "Patients who are considering IVF treatment should discuss concerns with their gynecologist in advance of treatment and those who are pregnant might want to discuss this with their obstetrician" (BBC News, 5/24). William Gibbons, president of the Society for Assisted Reproductive Technology, called the authors' theories as to why IVF might increase the risk of placenta previa "reasonable." Further studies on infertility's role in some of the differences between IVF and naturally conceived pregnancies are necessary, Gibbons added (USA Today, 5/25).

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