The association of pattern of maternal weight gain with length of gestation and risk of spontaneous preterm delivery.

Monitoring weight gain during pregnancy may be useful in detecting pregnancies that are at increased risk of early delivery. This study examines 7259 deliveries that occurred at the University of California, San Francisco's Moffitt Hospital from 1980 to 1990. Obese women, women with diabetes or hypertension during pregnancy, deliveries with congenital malformations and non-spontaneous preterm deliveries were excluded. Pattern of gain was assessed by fitting a quadratic curve to each woman's series of weight and date measurements, using simple regression techniques. The parameters from this curve were used to develop a variable for pattern of gain that reflects how much an individual's pattern of gain differs from a linear pattern of gain. Multivariable linear and logistic regression analyses indicate that patterns of gain that deviate greatly from the average pattern of gain (i.e. patterns that show a marked speeding up or slowing down of gain towards the end of pregnancy) are associated with significantly shorter gestational age and confer a significantly increased risk of spontaneous preterm delivery. The results suggest that monitoring weight gain during pregnancy is important, although more specific studies are needed to understand the mechanisms by which weight gain pattern relates to preterm delivery before appropriate interventions can be developed.