Fetal Timeline      Maternal Timeline      News     News Archive    Sep 3, 2015 

The rate of stillbirth per 1,000 births at Magee-Womens Hospital UPMC
ranged from 7.7 for lean women to 17.3 for severely obese women.

Obesity and stillbirth

Obese women are nearly twice as likely as lean women to have stillborn babies. There are several preventable medical reasons why, revealed in an analysis by the University of Pittsburgh Graduate School of Public Health.

Placental diseases and hypertension are the most common causes of stillbirth among obese women, according to a study to be published in the October issue of the American Journal of Clinical Nutrition. The research was supported by the National Institutes of Health (NIH).

According to Lisa Bodnar PhD, MPH, RD, lead author and associate professor at Pitt Public Health's Department of Epidemiology: "We've known for some time that obese women are more likely to have stillbirths, but this is one of the first and most comprehensive efforts to figure out why. Our hope is that this work can be used to better counsel women on the importance of a healthy pre-pregnancy weight and monitor them for complications that may threaten the survival of their fetus. If we can reduce pre-pregnancy obesity through environmental or policy changes by even a small amount, we could significantly reduce the burden of stillbirth."

There are 3.2 million stillbirths annually worldwide, and the United States has the highest number of stillbirths among high-income countries. Research shows obesity is likely responsible for more stillbirths than smoking or advanced maternal age.

658 stillbirths were reviewed between 2003 and 2010 by Dr. Bodnar and her colleagues at Magee-Womens Hospital at the University of Pennsylvania Medical Center (UPMC), one of the largest labor and delivery units in the United States. Stillbirths were defined as cases where the baby had reached at least 16 weeks gestation, but with no evidence of life after delivery. Mothers were classified as lean, overweight, obese or severely obese based on their pre-pregnancy body mass index - a measure calculated by weight versus height.

The rate of stillbirth per every 1,000 births ranged from 7.7 in lean to 17.3 in severely obese women.

Maternal hypertension (high blood pressure), placental diseases/disorders where the placenta does not properly sustain the baby, fetal abnormalities where a baby would be unlikely to live if born, and umbilical cord abnormalities were more common in obese women.

"Obstetricians should monitor obese patients for these complications and quickly treat conditions like hypertension if they arise in order to reduce risk of stillbirth. However, we'd like to see these women before they even become pregnant. When a doctor has an obese patient who is considering pregnancy, she should be referred to a maternal-fetal medicine specialist who can counsel her on the benefits of losing weight before pregnancy, as well as safe approaches to weight loss."

Hyagriv N. Simhan MD, senior author, professor, Division Chief of maternal-fetal medicine, and Medical Director of obstetrical services at Magee-Womens Hospital UPMC.

Abstract
Background: In high-income countries, maternal obesity is one of the most important modifiable causes of stillbirth, yet the pathways underpinning this association remain unclear.

Objective: We estimated the association between maternal prepregnancy body mass index (BMI) and the risk of stillbirth defined by pathophysiologic contributors or causes.

Design: Using a case-cohort design, we randomly sampled 1829 singleton deliveries from a cohort of 68,437 eligible deliveries at Magee-Womens Hospital in Pittsburgh, Pennsylvania (2003–2010), and augmented it with all remaining cases of stillbirth for a total of 658 cases. Stillbirths were classified based on probable cause(s) of death (maternal medical conditions, obstetric complications, fetal abnormalities, placental diseases, and infection). A panel of clinical experts reviewed medical records, placental tissue slides and pathology reports, and fetal postmortem reports of all stillbirths. Causes of fetal death were assigned by using the Stillbirth Collaborative Research Network Initial Causes of Fetal Death protocol from the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Proportional hazards models were used to estimate the BMI-stillbirth association after adjustment for confounders.

Results: The rate of stillbirth among lean, overweight, obese, and severely obese women was 7.7, 10.6, 13.9, and 17.3 per 1000 live-born and stillborn infants, respectively. Adjusted stillbirth HRs (95% CIs) were 1.4 (1.1, 1.8) for overweight, 1.8 (1.3, 2.4) for obese, and 2.0 (1.5, 2.8) for severely obese women, respectively, compared with lean women; associations strengthened when limited to antepartum stillbirths. Obesity and severe obesity were associated with stillbirth resulting from placental diseases, hypertension, fetal anomalies, and umbilical cord abnormalities. BMI was not related to stillbirth caused by placental abruption, obstetric conditions, or infection.

Conclusions: Multiple mechanisms appear to link obesity to stillbirth. Interventions to reduce stillbirth among obese mothers should consider targeting stillbirth due to hypertension and placental diseases—the most common causes of fetal death in this at-risk group.

Additional authors on this research are W. Tony Parks, M.D., Kiran Perkins, M.D., Sarah J. Pugh, M.P.H., Maisa Feghali, M.D., Karen Florio, D.O., Omar Young, M.D., and Sarah Bernstein, M.D., all of Pitt; and Robert W. Platt, Ph.D., of McGill University.

This research was funded by NIH grant R21 HD067851.

Return to top of page