BMI Greater Than 25 May Increase Risk of Miscarriage of a Normal Fetus

SAN FRANCISCO — The risk of miscarriage of a genetically normal fetus is significantly increased in overweight women, compared with normal weight women, the findings of a retrospective case-control study of 204 miscarriages suggest.

The rate of euploid miscarriage among 204 first trimester missed abortions that occurred between 1999 and 2008 in women at a single center was 53% in those with a body mass index of 25 or greater, compared with 37% in those with a BMI of less than 25. The difference was statistically significant, Dr. Innes V. Landres reported at the annual meeting of the American Society for Reproductive Medicine.

The mean age of the women in both groups was the same (34 years). Those over age 39 years were excluded because of the increased risk of miscarriage in women with advanced maternal age, noted Dr. Landres, a chief resident in obstetrics and gynecology at Stanford (Calif.) University.

The groups also were similar in types of assisted reproductive technologies used and in pregnancy history.

The study was undertaken to explore the cytogenetic results of miscarriages in relation to maternal weight and insulin resistance, Dr. Landres explained.

Both obesity and insulin resistance have been linked with spontaneous abortion and recurrent pregnancy loss. Most spontaneous abortions are a result of fetal aneuploidy, as was the case in 59% of patients overall in this study—67% in those over age 34 years, and 50% in those 34 years and younger. There is some evidence, however, that obesity predisposes women to euploid miscarriage, and that there is an increased rate of spontaneous abortion even among obese women with ovum donation.

For the current study, the medical records of women with first trimester missed abortion, subsequent dilation and curettage, and karyotype analysis of the products of conception were reviewed. Among the patients excluded—other than those older than 39 years—were those patients with a history of diabetes, those using steroids or narcotics, and those with donor eggs or preimplantation genetic diagnosis.

In addition to an increase in euploid miscarriage risk based on BMI, a trend toward increased risk among women with polycystic ovary syndrome, compared with those without PCOS, was observed (48% vs. 39%, respectively), but the difference did not reach statistical significance. Also, no significant differences in euploid miscarriage were seen based on insulin resistance status. However, because all but one of the women with insulin resistance were on insulin-lowering therapy at the time of conception, the conclusions in these populations are limited, Dr. Landres noted.

The findings, which suggest that BMI over 25 is a risk factor for euploid miscarriage, are important, given the fact that BMI (unlike age) is a modifiable risk factor. Although the study is limited by its retrospective nature, lack of power, and multiple confounders for which the investigators could not control, it is nonetheless important that elevated BMI be identified as a risk factor for euploid miscarriage, and that women with elevated BMI be counseled about the importance of lifestyle modification. Also, although more study is needed on the effects of insulin-lowering medications in this population, treatment should be considered.

Additional study of the effects of BMI on endometrial dysfunction and miscarriage rates, as well as on the effects of lifestyle modification, is needed, Dr. Landres concluded.

Elevated BMI should be seen as a risk factor for euploid miscarriage, said Dr. Innes V. Landres. Roman Sivion