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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.

This study presents information on the course and rates of weight gain and the associations among weight gain, prepregnancy weight-for-height, and infant birth weight, based on a total sample of 1419 uncomplicated term deliveries to adolescents. The distribution of cumulative weight gain indicates that for adolescents not only is the median gain at term (14.2-15.5 kg) significantly in excess of that reported for adults, but also weight-gain velocity is greater from the beginning of pregnancy. Although the contributions of prepregnancy weight-for-height and weight gain to birth weight may be independent, they are not necessarily additive. Birth weight does not appear improved for the infants of overweight adolescents except when weight gain is low (less than 11.1-12.3 kg at term), and, for Puerto Rican and black adolescents, birth weight is not further improved at any maternal prepregnancy body mass index (weight-for-height) with excessive weight gains (greater than 17.9-19.3 kg at term).

We examined the influence of two measures of maternal nutritional status: prepregnant body mass (kilograms/meter ) and Weight gain during pregnancy (adjusted for duration of gestation) on spontaneous preterm delivery (<37 completed Weeks' gestation) and duration of gestation, as well as on low birthweight (<2,500 grams) and small-for-gestational-age (SGA) in pregnant adolescents. Inadequate Weight gain for gestation increased the risk of spontaneous preterm delivery when prematurity was reckoned by the obstetric estimate (Adjusted Odds Ratio, AOR = 1.75 95% CI 1.22-2.50) or from the mother's LMP (AOR = 1.49 95% CI 1.10-2.02). In linear models, gestation duration was significantly reduced, by more than half a week, when reckoned from eiter estimate of gestation. However, the association between preterm birth or gestation duration and prepregnancy body mass was not consistent and depended on the method of estimating gestation. Low birthweight and SGA were each significantly associated with inadequate weight gain during pregnancy as well as with prepregnant body mass. These results suggest that current maternal nutritional status, as measured by weight gain during pregnancy, may influence preterm delivery and gestation duration. The inconsistent results obtained with prepregnancy body mass may reflect a size bias inherent in the obstetric estimate of gestation, rather than effects of prepregnant maternal nutritional status on gestation.

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