PRENATAL WEIGHT-GAIN PATTERNS AND SPONTANEOUS PRETERM BIRTH AMONG NONOBESE BLACK-AND-WHITE WOMEN

Objective: To examine the relationship between prenatal weight gain an d spontaneous preterm delivery, using the Institute of Medicine (IOM) guidelines. Methods: Nonobese low-income black (677 subjects) and whit e (338) women were grouped by ethnicity and prepregnancy body mass ind ex (BMI) as low (less than 19.8) or normal (19.8-26.0). The relationsh ip of total gain (first trimester) and weekly rate of gain (second and third trimester) to spontaneous preterm delivery was determined while controlling for sociodemographic and reproductive variables as well a s for time between last weight observation and delivery. Results: For all women combined, the mean (+/- standard deviation) weight gain duri ng the first trimester was 2.48 +/- 3.36 kg, and the mean rate of gain during the second and third trimesters was 0.49 +/- 0.21 and 0.45 +/- 0.28 kg/week, respectively. Low first- or second-trimester weight gai n was not associated with increased adjusted odds ratios (OR) for spon taneous preterm delivery. Third-trimester rates of gain below the lowe r limit of the IOM-recommended range (less than 0.38 kg/week with low BMI, less than 0.37 kg/week with normal BMI) were associated with incr eased preterm delivery among all women (OR 2.46, 95% confidence interv al [CI] 1.53-3.92), all black women (OR 1.98, 95% CI 1.16-3.41), and a ll white women (OR 4.05, 95% CI 1.41-11.66). Conclusion: These observa tions suggest that a low third-trimester rate of weight gain, defined using IOM guidelines, is associated with an increased risk of spontane ous preterm delivery among nonobese black and white women.