Intrauterine growth curves of twins: effects of socioeconomic level Curvas de crescimento intra-uterino de gêmeos: efeitos do nível socioeconômico

Objective: To study the influence of different socioeconomic level on intrauterine growth curves of singletons and twins. Methods: Data referring to the birth weight and gestational age of singletons and twins were obtained from neonatal records from three different hospitals so called A, B and C, from lower to higher socioeconomic level, in the 90s. Intrauterine growth curves were constructed for each population and then compared. Statistical methods included mean and standard deviation estimates, Students t test, analysis of variance followed by multiple comparison tests, non parametric tests and regression analysis. Results: At hospital A, 370 singletons and 370 twins were studied; at hospital B, 306 twins and 306 singletons; and at hospital, C 562 twins and 562 singletons. Intrauterine growth curves for singletons depict that at approximately 39 weeks, the higher socioeconomic hospital (C) has its curve above those of hospitals A and B. Considering twins born at 36 weeks gestational age there were significant differences among the three hospital, beeing the lowest weights those of hospital A. Conclusions: Birth weight of twins born at 36 weeks gestational age was dependent of their socioeconomic level and the intrauterine growth curves of twins begin to show such an influence later in pregnancy.