Association of Maternal Obesity With Longitudinal Ultrasonographic Measures of Fetal Growth: Findings From the NICHD Fetal Growth Studies–Singletons | Obesity | JAMA Pediatrics | JAMA Network
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Original Investigation
January 2018

Association of Maternal Obesity With Longitudinal Ultrasonographic Measures of Fetal Growth: Findings From the NICHD Fetal Growth Studies–Singletons

Author Affiliations
  • 1Division of Intramural Population Health Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland
  • 2Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
  • 3Christiana Care Health System, Newark, Delaware
  • 4Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
  • 5Division of Maternal-Fetal Medicine, Department of Obstetrics-Gynecology, University of California School of Medicine, Irvine
  • 6Fountain Valley Regional Hospital and Medical Center, Fountain Valley, California
  • 7Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston
  • 8Department of Obstetrics and Gynecology, Columbia University Medical Center, New York, New York
  • 9Department of Obstetrics and Gynecology, New York-Presbyterian Hospital/Queens, Queens
  • 10Department of Obstetrics and Gynecology, Miller Children’s Hospital/Long Beach Memorial Medical Center, Long Beach, California
  • 11Division of Maternal and Fetal Medicine, Department of Obstetrics and Gynecology, St Peter’s University Hospital, New Brunswick, New Jersey
  • 12Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology University of Alabama School of Medicine, Birmingham
  • 13Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Women and Infants Hospital of Rhode Island, Providence
  • 14Department of Obstetrics and Gynecology, Tufts Medical Center, Boston, Massachusetts
JAMA Pediatr. 2018;172(1):24-31. doi:10.1001/jamapediatrics.2017.3785
Key Points

Question  What are the associations of maternal obesity with fetal growth, and when do these associations start emerging?

Findings  In a longitudinal cohort study that included 468 obese and 2334 nonobese pregnant women, the femur length, humerus length, head circumference, and estimated weight of fetuses were significantly greater in the fetuses of obese women compared with fetuses of nonobese women. Differences commenced as early as 21 weeks’ gestation.

Meaning  Fetal growth differs in obese and nonobese pregnant women; the mechanisms of these findings and their long-term implications for child and adult health remain to be established.

Abstract

Importance  Despite the increasing prevalence of pregravid obesity, systematic evaluation of the association of maternal obesity with fetal growth trajectories is lacking.

Objective  To characterize differences in fetal growth trajectories between obese and nonobese pregnant women, and to identify the timing of any observed differences.

Design, Setting, and Participants  The Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies–Singletons study enrolled cohorts of pregnant women at 12 US health care institutions. Obese women (with prepregnancy body mass index > 30) and nonobese women (prepregnancy body mass indexes, 19-29.9) without major chronic diseases were recruited between 8 weeks and 0 days’ gestation and 13 weeks and 6 days’ gestation. A mixed longitudinal randomization scheme randomized participants into 1 of 4 schedules for 2-dimensional and 3-dimensional ultrasonograms to capture weekly fetal growth data throughout the remainder of their pregnancies.

Main Outcomes and Measures  On each ultrasonogram, fetal humerus length, femur length, biparietal diameter, head circumference, and abdominal circumference were measured. Fetal growth curves were estimated using linear mixed models with cubic splines. Median differences in the fetal measures at each gestational week of the obese and nonobese participants were examined using the likelihood ratio and Wald tests after adjustment for maternal characteristics.

Results  The study enrolled 468 obese and 2334 nonobese women between 8 weeks and 0 days’ gestation and 13 weeks and 6 days’ gestation. After a priori exclusion criteria, 443 obese and 2320 nonobese women composed the final cohort. Commencing at 21 weeks’ gestation, femur length and humerus length were significantly longer for fetuses of obese woman than those of nonobese women. Differences persisted in obese and nonobese groups through 38 weeks’ gestation (median femur length, 71.0 vs 70.2 mm; P = .01; median humerus length, 62.2 vs 61.6 mm; P = .03). Averaged across gestation, head circumference was significantly larger in fetuses of obese women than those of nonobese women (P = .02). Fetal abdominal circumference was not greater in the obese cohort than in the nonobese cohort but was significantly larger than in fetuses of normal-weight women (with body mass indexes between 19.0-24.9) commencing at 32 weeks (median, 282.1 vs 280.2 mm; P = .04). Starting from 30 weeks’ gestation, estimated fetal weight was significantly larger for the fetuses of obese women (median, 1512 g [95% CI, 1494-1530 g] vs 1492 g [95% CI, 1484-1499 g]) and the difference grew as gestational age increased. Birth weight was higher by almost 100 g in neonates born to obese women than to nonobese women (mean, 3373.2 vs 3279.5 g).

Conclusions and Relevance  As early as 32 weeks’ gestation, fetuses of obese women had higher weights than fetuses of nonobese women. The mechanisms and long-term health implications of these findings are not yet established.

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