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Maternal obesity tied to fetal loss after amniocentesis

NEW YORK (Reuters Health) – Extremely obese women are at increased risk of fetal loss following amniocentesis, according to a report this month in Obstetrics and Gynecology.

The risk was seen in women with a body mass index (BMI) of 40 or higher – which might be reassuring for those who may be obese but not morbidly so. As lead author Dr. Lorie Harper told Reuters Health by email, “The loss rates for amniocentesis in women with BMI 30 to 40 appear similar to women with a BMI less than 30.”

Dr. Harper and colleagues at Washington University in St. Louis, Missouri note that because maternal obesity makes it hard to detect fetal anomalies with ultrasound, some have suggested that amniocentesis could aid detection in these women.

To gain more information on fetal loss rates associated with such invasive diagnostic procedures, the researchers reviewed data on more than 10,000 women who underwent amniocentesis and chorionic villus sampling (CVS).

The risk of pregnancy loss was similar in the 855 obese and the 4,125 non-obese women undergoing CVS (6.4% vs 6.3%).

There was also no overall difference in the risk of fetal loss before 24 weeks in the 2,742 obese and 8,037 non-obese women who had amniocentesis. However, compared with women not undergoing a procedure, the attributable risk for obese women was 0.3% for amniocentesis.

When pregnancies ending in termination were excluded, there was a statistically significant link between rising loss rates and rising BMI. The greatest difference was between women with a BMI of 25.0 or less and those with a BMI of over 40 (adjusted odds ratio 2.2).

“When women with a BMI greater than 40 are considering amniocentesis for fetal diagnosis, it may be appropriate to counsel them about their risk of pregnancy loss using BMI-specific risks,” Dr. Harper said.


Obstet Gynecol 2012;119:745-751.