MATERNAL ANTHROPOMETRY AND IDIOPATHIC PRETERM LABOR

Objective: To assess the etiologic role of maternal short stature, low pre-pregnancy body mass index (BIMI), and low rate of gestational wei ght gain in idiopathic preterm labor. Methods: We carried out a three- center case-control study of 555 women with idiopathic onset of preter m labor (before 37 completed weeks), including two overlapping tie, no n-mutually exclusive) subsamples: cases with early preterm labor (befo re 34 completed weeks) and cases with recurrent preterm labor (before 37 completed weeks plus a history of prior preterm delivery or second- trimester miscarriage). Controls were matched to cases by race and smo king history. All subjects responded in person to questions about heig ht, pre-pregnancy weight, gestational weight gain, and obstetric and s ociodemographic histories. Results: Maternal height, pre-pregnancy wei ght, and gestational weight gain demonstrated excellent test-retest re liability, with intra-class correlation coefficients of 0.97, 0.99, an d 0.91, respectively. Based on matched analyses, women with a height o f 157.5 cm or less had an increased risk of idiopathic preterm labor ( odds ratio [OR] 1.85, 95% confidence interval [CI] 1.25-2.74), as did those with a prepregnancy BMI less than 19.8 kg/m(2) (OR 1.63, 95% CI 1.09-2.44) or a gestational weight gain rate less than 0.27 kg/week (O R 1.74, 95% CI 1.16-2.62). Conditional logistic regression models cont aining all three anthropometric variables and controlling for parity, marital status, language, age, and education yielded virtually identic al point estimates and CIs. Conclusion: Maternal short stature, low pr e-pregnancy BMI, and low rate of gestational weight gain may lead to s hortened gestation by increasing the risk of idiopathic preterm labor.