Maternal prepregnancy body mass index and risk of spontaneous preterm birth.

Abstract

BACKGROUND:

Findings from studies examining risk of preterm birth associated with elevated prepregnancy body mass index (BMI) have been inconsistent.

METHODS:

Within a large population-based cohort, we explored associations between prepregnancy BMI and spontaneous preterm birth across a spectrum of BMI, gestational age, and racial/ethnic categories. We analysed data for 989,687 singleton births in California, 2007-09. Preterm birth was grouped as 20-23, 24-27, 28-31, or 32-36 weeks gestation (compared with 37-41 weeks). BMI was categorised as <18.5 (underweight); 18.5-24.9 (normal); 25.0-29.9 (overweight); 30.0-34.9 (obese I); 35.0-39.9 (obese II); and ≥ 40.0 (obese III). We assessed associations between BMI and spontaneous preterm birth of varying severity among non-Hispanic White, Hispanic, and non-Hispanic Black women.

RESULTS:

Analyses of mothers without hypertension and diabetes, adjusted for age, education, height, and prenatal care initiation, showed obesity categories I-III to be associated with increased risk of spontaneous preterm birth at 20-23 and 24-27 weeks among those of parity 1 in each race/ethnic group. Relative risks for obese III and preterm birth at 20-23 weeks were 6.29 [95% confidence interval (CI) 3.06, 12.9], 4.34 [95% CI 2.30, 8.16], and 4.45 [95% CI 2.53, 7.82] for non-Hispanic Whites, non-Hispanic Blacks, and Hispanics, respectively. A similar, but lower risk, pattern was observed for women of parity ≥ 2 and preterm birth at 20-23 weeks. Underweight was associated with modest risks for preterm birth at ≥ 24 weeks among women in each racial/ethnic group regardless of parity.

CONCLUSIONS:

The association between women's prepregnancy BMI and risk of spontaneous preterm birth is complex and is influenced by race/ethnicity, gestational age, and parity.

• Authors: Gary M Shaw, Paul H Wise, Jonathan Mayo, Suzan L Carmichael, Catherine Ley, Deirdre J Lyell, Bat Zion Shachar, Kathryn Melsop, Ciaran S Phibbs, David K Stevenson, Julie Parsonnet, Jeffrey B Gould, March of Dimes Prematurity Research Center at Stanford University School of Medicine
• Journal: Paediatric and perinatal epidemiology (Paediatr Perinat Epidemiol) Vol. 28 Issue 4 Pg. 302-11 (Jul 2014) ISSN: 1365-3016 [Electronic] England
• PMID: 24810721 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2014 John Wiley & Sons Ltd.

Topics

• Adult
• Black or African American (statistics & numerical data)
• Body Mass Index
• California
• Cohort Studies
• Female
• Gestational Age
• Hispanic or Latino (statistics & numerical data)
• Humans
• Obesity (complications)
• Obstetric Labor, Premature (epidemiology, etiology)
• Parity
• Pregnancy
• Pregnancy Complications (epidemiology, etiology)
• Premature Birth (epidemiology, ethnology, etiology)
• White People (statistics & numerical data)