ABSTRACT
The etiology of higher rates of premature labor in multiple pregnancy is unknown. Some argue, rather simplistically, that it is primarily due to overdistension of the uterus and this in itself is the major cause. However, this is an observation, which is unfounded in any credible scientific basis. Sociologic and epidemiologic factors are also thought to be implicated in the etiology of premature labor, but the vast majority of studies concern singleton pregnancies, and it is widely assumed that such factors also apply to multiple gestation. Numerous epidemiologic studies show that socioeconomic deprivation, smoking, low body mass index (BMI <19kg/m2) before pregnancy and young maternal age are associated with preterm delivery. Each of these variables carries a relative risk of 1.5-2.0, and attempts to predict risk of premature labor based on such factors alone yield low sensitivity and specificity1. The single most effective predictor of preterm delivery is previous preterm delivery (relative risk 2.3), but this is unhelpful in primigravidae.
