Effects of race/ethnicity and BMI on the association between height and risk for spontaneous preterm birth

Abstract

OBJECTIVE Short height and obesity have each been associated with increased risk for preterm birth (PTB). However, the effect of short height on PTB risk, across different race/ethnicities and BMI categories, has not been studied. Our objective was to determine the influence of maternal height on the risk for PTB within race/ethnic groups, BMI groups, or adjusted for weight. STUDY DESIGN All California singleton, live births between 2007–2010 were included from birth certificate data (vital statistics) linked to hospital discharge data. Pre-pregnancy BMI (kg/m2) was categorized as underweight (< 18.5); normal (18.5–24.9); overweight (25.0–29.9) or obese (≥30.0). Maternal race/ethnicity was categorized as: Non-Hispanic White, Non-Hispanic Black, Hispanic and Asian. Maternal height was classified into 5 categories (shortest, short, middle, tall, tallest) based on racial/ethnic-specific height distributions, with the middle category serving as reference. Poisson regression models were used to estimate relative risks (RR) for the association between maternal height and risk of spontaneous PTB (< 37 weeks and < 32 weeks). Models were stratified on race/ethnicity and BMI. Generalized additive regression models (GAM) were used to detect nonlinearity of the association. Covariates considered were: maternal age, weight, parity, prenatal care, education, medical payment, previous PTB, gestational and pre-gestational diabetes, pre-gestational hypertension, preeclampsia/eclampsia, and smoking. RESULTS Among 1,655,385 California singleton live births, 5.2% were spontaneous preterm births < 37 weeks. Short stature (1st height category) was associated with increased risk for PTB for Non-Hispanic Whites and Hispanics across all BMI categories. Among obese women, tall stature (5th category) was associated with reduced risk for spontaneous PTB for Non-Hispanic Whites, Asians and Hispanics. Same pattern of association was seen for height and risk for spontaneous PTB < 32 weeks. In the GAM plots, short stature was associated with increased risk for spontaneous PTB of < 32 and <37 weeks of gestation among Whites and Asians. However, this association was not observed for Blacks and Hispanics. CONCLUSION Maternal shorter height is associated with a modest increased risk for spontaneous PTB regardless of BMI. Our results suggest that PTB risk assessment should consider race/ethnicity specific height with respect to the norm in addition to BMI assessment.

Effect of maternal origin on the association between maternal height and risk of preterm birth in Belgium: a retrospective observational cohort study

“…Our findings are consistent with those of a recent study conducted in California, which showed that patterns of association between height and risk of spontaneous PTB varied according to the maternal ethnicity. 11 In the present study, an inverse significant association between height and risk of PTB was found for Belgians, Italians and Polish. However, this association was not observed for women from Congo, France, Morocco, Romania or Turkey.…”

“… 6 9 10 These mixed results could be partly due to varying definitions of short stature or height cut-offs, variation in quality of studies, heterogeneous populations and small sample sizes in the subgroups. 11 17 …”

“… 5–9 A recent study demonstrated that the association between height and the risk of PTB varied across various ethnic groups in USA. 11 …”

Maternal Height and Risk of Preeclampsia among Race/Ethnic Groups

“…21 Height, impacted by the genetic, intrauterine, childhood, and environmental factors, is known to be associated with several diseases and conditions. [22][23][24][25][26][27][28] In pregnancy, height is inversely related to a modestly increased risk of spontaneous preterm birth, 27 gestational diabetes, 24 low infant birth weight, 25,26 length, 23 and possibly neural tube defects. 28 Height (inverse) has also been associated with the overall risk of cardiovascular disease, coronary heart disease, stroke, and heart failure, whereas it is directly related to the risk of pulmonary embolism and ruptured aortic aneurysm.…”

Maternal Characteristics, Short Mid-Trimester Cervical Length, and Preterm Delivery

“…Previous studies have demonstrated that maternal characteristics such as an obstetric history, prior cervical excisional procedure, and maternal weight and height, confer a high risk of preterm birth ( 10 11 12 13 14 15 ). However, the causality between these maternal characteristics and preterm birth remains unclear because most of the prior studies explained the relationship by using other confounders such as an obstetric history, weight, height, and a history of alcohol or substance abuse; but not included short CL.…”