Association between low gynaecological age and preterm birth.

Low gynaecological age, defined as conception within 2 completed years of menarche, was examined for its association with preterm birth, using data from a geographically based cohort of over 1700 young primigravidae aged 18 or younger at start of prenatal care. After stratifying by chronological age and controlling for confounding variables, low gynaecological age was associated with almost double the risk of preterm delivery whether estimated from the mother's last menstrual period (adjusted odds ratio (AOR) = 1.77, 95% CI 1.19-2.64) or using the obstetric estimate of gestation (AOR = 2.10, 95% CI 1.36-3.25). Low gynaecological age was also associated with an increase in risk of low birthweight (LBW) (AOR = 1.70, 95% CI 1.01-2.88), but not of small-for-gestational-age babies (AOR = 0.94, 95% CI 0.49-1.81). Thus low gynaecological age may be an important addition to assessment systems to detect women at risk of preterm labour and delivery.