Curva nacional de distribución de peso al nacer según edad gestacional. Chile, 1993 a 2000 / A national birth weight distribution curve according to gestational age in Chile from 1993 to 2000

BACKGROUND: The World Health Organization recently defined the criteria for constructing birth weight curves using population based data. AIM: To construct a national curve of weight, size and ponderal index at birth for Chile, following the criteria suggested by the World Health Organization (WHO) expert committee report from 1995. MATERIAL AND METHODS: A national database from the Chilean Istitute for Statistics was used. All alive singleton deliveries during tbe period from 1993 to 2000 were included. A birth weight curve for the total population as well as for size and ponderal index at birth was construted, including percentile distribution, mean and standard deviation of values for gestational age. Stratification by sex was performed. RESULTS: A total of 2,049,446 singleton deliveries were analyzed. The 10 percentiles (raw data) for birth weight throughout gestation from 22 to 42 weeks were: 470, 520, 560, 630, 660, 749, 810, 926, 1,031, 1,160, 1,320, 1,480, 1,680, 1,920, 2,190, 2,500, 2, 750, 2,910, 3,010, 3,080 and 3,090 g, respectively. CONCLUSIONS: A national birth weight for Chilean population (a predominant Hispanic population) was constructed. There are not differences between this curve and the standard proposed by WHO (population from California, USA) suggesting that under comparable perinatal indices, ethnicity is not a relevant factor deterimining birth weight.

Obesidad materna y riesgo reproductivo / Maternal obesity and reproductive risk

Background:The prevalence of obesity in school children and pregnant women, a known risk factor of the reproductive cycle, has increased significantly over the last few years. Aim: To analyze the association between maternal obesity and the outcome of pregnancy and newborn health. To quantify the attributable population risk of obesity in relation to negative events of pregnancy. Material and methods: A prospective study in 883 pregnant women of 6 public health centers in Santiago. Weight, height, arm circumference, skinfold thicknesses, body mass index (BMI) and fat mass were determined in each trimester. Maternal socio demographic history, smoking habits, incidence of diseases during pregnancy, labor and newborn characteristics were analyzed. Logistic regressions of multiple factors were used to determine nutritional and non-nutritional variables associated to negative events, to determine the population attributable risk of each variable that the model retained. Results: Controlling the effect of other variables, a BMI ×30 or initial body fat mass ×35 percent determined a greater risk for assisted labor with an odds ratio (OR) of 1.9 (95 percent confidence interval (CI) 1.3-2.9), gestational diabetes with an OR of 6.4 (95 percent CI 2.1-19.6), hypertension with an OR of 7.8 (95 percent CI 3.0-20.4), late fetal mortality with an OR of 3.4 (95 percent CI 1.2-10.0), p <0.001. The risk was mostly associated with the initial maternal nutritional status and in a lesser degree, with the weight gained during pregnancy. Conclusions: Maternal obesity is an important risk factor during pregnancy. The prenatal control obesity could reduce approximately 10 percent of the cesarean sections and late fetal deaths and half of the hypertension and gestational diabetes cases (Rev Méd Chile 2004; 132: 923-30).