Growth and sexual maturation of low birth weight infants at early adolescence.

OBJECTIVE: To assess the growth and sexual maturity of non-handicapped children with birth weight less than 2000 g at 12 years. DESIGN: Prospective cohort study. SETTING: Infants discharged from a Neonatal Special Care Unit of a referral hospital with birth weight less than 2000 g between 1987-1989 and followed up till the age of 12 years. METHODS: The height, weight and head circumference was measured. Sexual maturity was determined by Tanners score and age of menarche in girls was reported by parents. Parental height and weight was recorded. Intelligence quotient was determined by Weschslers Intelligence Scale. RESULTS: The cohort of 180 low birth weight (LBW) infants (birth weight less than 2000 g) was divided into 3 groups according to their gestation - preterm SGA (n=73), full term SGA (n=33) and preterm AGA (n=74). Ninety full term AGA infants served as controls. Preterm SGA children had significantly less height (mean deficit 5.8 cm), weight and head circumference (P<0.001). There was no significant difference in sexual maturity and onset of menarche between the study group and controls. There was a correlation between head circumference and IQ and preterm SGA children had the lowest mean IQ (85.4 +/- 17.7). Mothers height contributed 14% variance to a total variance of 25.3% for Z score of height at 12 years. Mothers weight contributed a variance 21.1% to a total variance of 29.4% for Z score of weight. CONCLUSION: Preterm SGA children were shorter, lighter and had the smallest head circumference, and also had the lowest IQ. Mothers height and weight was an important determinant of height and weight at 12 years.

Biology versus environment in low birth weight children.

OBJECTIVE: To explore the contribution of biologic risk factors versus socio-demographic and environmental risk factors in cognitive development of children with birth weight less than 2000 g, at the age of 12 years. DESIGN: Prospective cohort study. SETTING: Infants discharged from a NICU of a referral hospital, with birth weight less than 2000 g between 1987-89 and followed up in the High Risk Clinic. METHODS: The children were assessed at the age of 12 years, with the Weschler's Intelligence Scale for IQ and by Wide Range Achievement Test for mathematics skills. Mother's education, father's education, socio-economic status, family structure, spaciousness of the house, the locality in which the child lived and the type of school the child attended, were all recorded. A stimulation score was determined at 6 and 12 months and 3 years. Family environment score was used at 12 years. RESULTS: The cohort consisted of 180 children, with 90 controls. The mean IQ of the study group was 89.5 +- 16.9, which was significantly lower than that of controls (97.2 +- 14.1) (P < 0.05). The mathematical skills of the study group were significantly poorer (P < 0.05) than that of controls. A multiple linear regression analysis was done using IQ as the dependent variable and all risk factors at birth, stimulation scores and socio-environmental factors as independent variables. Mothers education was the most important factor contributing to the total IQ, a variance of 25.2 % of the total variance 44.2 PERCENT. Fathers education emerged as an important factor for mathematics skills. School was the next important factor for IQ as well as academics. Controlling for all other background factors, birth weight was the only biologic factor of significance, and this had a very small contribution. CONCLUSION: Parental education and the type of school attended by the child were the most important factors influencing cognitive development. The only biologic factor of importance was birth weight, but this too had a very small contribution.