Related Experiment Video
Updated: Sep 20, 2025

A Novel Method for Involving Women of Color at High Risk for Preterm Birth in Research Priority Setting
Published on: January 12, 2018
Population-based associations between maternal pre-pregnancy body mass index and spontaneous and medically indicated
Jonathan A Mayo1, David K Stevenson1, Gary M Shaw1
1Department of Pediatrics, Division of Neonatal and Developmental Medicine, March of Dimes Prematurity Research Center at Stanford University School of Medicine, Stanford University School of Medicine, Stanford, CA.
Background:
The literature pertaining to risk of spontaneous preterm birth (sPTB) as related to body mass index (BMI), specifically high BMI, is conflicting.
Objective:
To assess the relationships between maternal prepregnancy BMI and sPTB separately for non-Hispanic Whites, non-Hispanic Blacks, Hispanics, and Asians.
Methods:
Population-based cohort study of mothers who delivered a singleton livebirth in California from 2007 to 2012. Associations between BMI and sPTB were estimated from Cox proportional hazard models. BMI was modelled with restricted cubic splines to account for nonlinear relationships.
Results:
A total of 2,645,950 births were included in the analysis, 135,357 (5.12%) in which the mother had a sPTB. Compared to mothers within the same race/ethnicity and a BMI of 26 kg/m2, all mothers with a BMI 28 kg/m2 or higher had significantly elevated adjusted hazard ratios for sPTB. Asian mothers with a BMI between 16 and 25 kg/m2 had significantly decreased hazard ratios for sPTB while a of BMI 20 kg/m2 or less among non-Hispanic White, non-Hispanic Black, and Hispanic mothers showed increased hazard ratios.
Conclusion:
This study observed that mothers with high prepregnancy BMIs were more likely to experience sPTB across all race/ethnicities.
Related Concept Videos
Regression Toward the Mean
z Scores and Area Under the Curve
Normal Distribution
Parametric Survival Analysis: Weibull and Exponential Methods
Weibull Distribution
The Weibull distribution is a flexible model used in parametric survival analysis. It can handle both increasing and decreasing hazard rates, depending on its shape parameter...
Distributions to Estimate Population Parameter
Teratogenicity

