Association of maternal obesity with preterm birth phenotype and
mediation effects of gestational diabetes mellitus and preeclampsia:a
prospective cohort study
Abstract
Objectives: To clarify the relationship between prepregnancy body mass
index (BMI) and the phenotypes of preterm birth and evaluate the
mediation effects of gestational diabetes mellitus (GDM) and
preeclampsia (PE) on the relationship between prepregnancy BMI and
preterm birth. Design: Prospective cohort study Setting: Shenzhen
Maternity & Child Healthcare Hospital Population or Sample: 42196
singleton livebirths Methods: Prospective cohort study using the Birth
Cohort in Shenzhen (BiCoS) dataset. Main Outcome Measures: Preterm birth
was defined as gestational age less than 37 weeks. Results: Risks of
extremely, very, and moderately preterm birth increased with BMI, and
the highest risk was observed for obese women with extremely preterm
birth (OR 3.43, 95% CI 1.07 –10.97). Maternal obesity was
significantly associated with spontaneous preterm labor (OR 1.98; 95%
CI 1.13–3.47), premature rupture of the membranes (OR 2.04; 95% CI
1.08–3.86) and medically indicated preterm birth (OR 2.05; 95% CI
1.25–3.37). GDM and PE mediated 13.41% and 36.66% of the effect of
obesity on preterm birth, respectively. GDM mediated 32.80% of the
effect of obesity on spontaneous preterm labor and PE mediated 64.31%
of the effect of obesity on medically indicated preterm birth.
Conclusions: Maternal prepregnancy obesity was associated with all
phenotypes of preterm birth, and the highest risks were extremely
preterm birth and medically indicated preterm birth. GDM and PE
partially mediated the association between obesity and preterm birth.
Funding: NSFC(81830041, 81771611); Shenzhen Science and Technology
Project (JCYJ20170412140326739) KEYWORDS: obesity, prepregnancy BMI,
preterm birth, phenotype, gestational diabetes mellitus, preeclampsia