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Low Gestational Weight Gain and Risk of Adverse Perinatal Outcomes in Obese and Severely Obese Women

Bodnar, Lisa M.; Pugh, Sarah J.; Lash, Timothy L.; Hutcheon, Jennifer A.; Himes, Katherine P.; Parisi, Sara M.; Abrams, Barbara

doi: 10.1097/EDE.0000000000000535
Perinatal Epidemiology

Background: Our objective was to estimate associations between gestational weight gain z scores and preterm birth, neonatal intensive care unit admission, large- and small-for-gestational age birth, and cesarean delivery among grades 1, 2, and 3 obese women.

Methods: We included singleton infants born in Pennsylvania (2003–2011) to grade 1 (body mass index 30–34.9 kg/m2, n = 148,335), grade 2 (35–39.9 kg/m2, n = 72,032), or grade 3 (≥40 kg/m2, n = 47,494) obese mothers. Total pregnancy weight gain (kg) was converted to gestational age-standardized z scores. Multivariable Poisson regression models stratified by obesity grade were used to estimate associations between z scores and outcomes. A probabilistic bias analysis, informed by an internal validation study, evaluated the impact of body mass index and weight gain misclassification.

Results: Risks of adverse outcomes did not substantially vary within the range of z scores equivalent to 40-week weight gains of −4.3 to 9 kg for grade 1 obese, −8.2 to 5.6 kg for grade 2 obese, and −12 to −2.3 kg for grade 3 obese women. As gestational weight gain increased beyond these z score ranges, there were slight declines in risk of small-for-gestational age birth but rapid rises in cesarean delivery and large-for-gestational age birth. Risks of preterm birth and neonatal intensive care unit admission were weakly associated with weight gain. The bias analysis supported the validity of the conventional analysis.

Conclusions: Gestational weight gain below national recommendations for obese mothers (5–9 kg) may not be adversely associated with fetal growth, gestational age at delivery, or mode of delivery.

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From the aDepartment of Epidemiology, Graduate School of Public Health, bDepartment of Obstetrics, Gynecology, and Reproductive Sciences, School of Medicine, University of Pittsburgh, Pittsburgh, PA; cMagee-Womens Research Institute, Pittsburgh, PA; dDepartment of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA; eDepartment of Obstetrics and Gynaecology, University of British Columbia, Vancouver, British Columbia, Canada; and fDivision of Epidemiology, University of California at Berkeley School of Public Health, Berkeley, CA.

Submitted 14 July 2015; accepted 8 July 2016.

Supported by Thrasher Research Fund (#9181) and NIH Grants R21 HD065807 and R01 HD072008.

The authors report no conflicts of interest.

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Correspondence: Lisa M. Bodnar, Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, A742 Crabtree Hall, 130 DeSoto Street, Pittsburgh, PA 15261. E-mail:

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