Date of Award

2015

Document Type

Open Access Thesis

Department

Epidemiology and Biostatistics

Sub-Department

The Norman J. Arnold School of Public Health

First Advisor

Nansi Boghossian

Abstract

Obesity during pregnancy is associated with a high risk of adverse maternal outcomes. Little is known about how weight change between consecutive pregnancies impacts subsequent pregnancy complications and newborn outcomes. This study aimed to explore the association between interpregnancy BMI change and adverse maternal outcomes, specifically, gestational diabetes mellitus (GDM), gestational hypertension, pre-eclampsia, non-repeat cesarean delivery (C-section), and vaginal birth after cesarean delivery (VBAC). The study sample was derived from the Eunice Kennedy Shriver National Institute of Child Health and Human Development Consecutive Pregnancy Study, which collected data from 20 hospitals in Utah utilizing electronic medical records and International Classification of Diseases ninth revision codes. The study collected extensive information on maternal demographic, reproductive and medical history, pregnancy complications, and labor and delivery information. Women with at least two pregnancies during the study period who delivered between 2002-2010 were included (n=51,086 women yielding 114,679 pregnancies). After data exclusions, the study sample included 46,521 women and the outcomes of their first two pregnancies. Between their first two consecutive pregnancies, these women gained an average of 0.81 BMI units (interquartile range (IQR) -0.34 to 1.77) over an average interpregnancy interval of 634 days (IQR 373 to 814). Poisson regression with robust variance estimators was utilized to estimate the relative risks of the outcomes. After adjusting for potential confounders, every one unit increase in BMI between consecutive pregnancies increased the risk of GDM (relative risk (RR): 1.09 (95% confidence interval (CI): 1.07 – 1.11)), preeclampsia (RR: 1.06 (95% CI: 1.04 – 1.09)), and gestational hypertension in the second pregnancy increased (RR: 1.08 (95% CI: 1.06 – 1.10). For every one unit increase in BMI, the risk of having a successful VBAC decreased (RR: 0.95 (95% CI: 0.93 – 0.98)). There was no significant association seen between interpregnancy BMI change and a non-repeat C-section. Women with a BMI ≥ 3 units increase were also at a significantly increased risk of GDM (RR: 1.72 (95% CI: 1.52 – 1.93)), pre-eclampsia (RR: 1.61 (95% CI: 1.33 – 1.94)), and gestational hypertension (RR: 1.66 (95% CI: 1.42 – 1.93)) in the second pregnancy when compared to women who maintained their BMI between pregnancies (- 1 unit ≤ BMI change < 1 unit). The risk of having a successful VBAC decreased (RR: 0.72 (95% CI: 0.58 – 0.88) for women who gained ≥ 3 units, compared to women who maintained their BMI (- 1 unit ≤ BMI change < 1 unit). GDM was also increased among those who increased their BMI by at least 2 units but not more than 3 units (RR: 1.40 (95% CI: 1.22 – 1.61)) and among those who gained at least 1 unit but no more than 2 BMI units (RR: 1.23 (95% CI: 1.08 – 1.40)). These findings have public health implications for the importance of weight management between pregnancies.

Rights

© 2015, Chelsea Lynes

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