The body weight of women before pregnancy and its correct increase during the pregnancy are important factors for an optimum development of the fetus and successful outcome of the pregnancy. Both the women who were too thin before becoming pregnant and those with excessive body weight are classified as pregnant women with an increased pregnancy risk (1-4). Low body weight is connected with increased risk of low birth weight and premature birth (5-7). Overweight and obesity before the pregnancy increase the probability of pregnancy-induced hypertension, pre-eclampsia condition, gestational diabetes, cesarean delivery, as well as macrosomy and lower Apgar scores of the newborns (3, 8-14). Children of mothers with excessive body weights are burdened with the risk of becoming overweight already in the first year of their lives (8, 15, 16).

Apart from pre-pregnancy body weight, an equally important factor is the appropriate weight gain during pregnancy. This gain is considered as the best measure of the correct nutrition of a pregnant woman (15, 17). In the US, where the number of pregnant women with obesity established during the first obstetrical consultation is dramatically increasing, the experts stress that the body weight gain during pregnancy should be dependent on the body weight in the period before the pregnancy (8, 11, 18-22). The recommendations regarding gestational weight gain elaborated by the Institute of Medicine in the US are closely related to the women’s BMI before the pregnancy. The above recommendations were updated in 2009 by introducing, among others, an upper limit on the body weight gain for women who were obese before the pregnancy. However, as emphasized by experts, due to the lack of sufficient scientific data, the recommendations do not include yet the body weight gain in the various degrees of obesity (tab. 1) (23, 24). The recommended body weight gain decreases with increasing pre-pregnancy BMI of the women. The strictest values apply to women with obesity. The experts are of the opinion that energetic stocks of obese women ensure correct development of the fetus, and there is no need to increase them during the pregnancy (4). Hence the gestational weight gain among this group of women should cover mainly the mass of the fetus body, the placenta and the amniotic liquid (16, 20-21).

A separate problem connected with excessive weight gain during pregnancy are difficulties in returning to the original body weight after birth, and development of future obesity (8, 14, 18, 21, 22, 25).

The aim of the study was to assess the gestational weight gain compared to the body weight of the women before pregnancy, and its impact on the course of pregnancy.

The study was carried out among 511 pregnant women who had reported for birth at the Department Clinic of Obstetrics, Gynaecology and Oncology, 2^nd Faculty of Medicine, Medical University of Warsaw, in the period from April 2005 until March 2007. The data on the patients’ characteristics, their health status before pregnancy, body weight gain during pregnancy and pregnancy course were collected using a survey questionnaire. The data on pregnancy duration and type of birth, as well as newborns’ data, was collected from the hospital documentation. The analysis of results excluded women in multiple pregnancies, women with premature births, women who had suffered from diabetes before pregnancy, women with hypertension diagnosed before pregnancy, and women with anemia before pregnancy. Eventually, the study covered 471 patients aged 16-48. Pre-pregnancy body weights of women and gestational weight gains were determined according to American criteria, elaborated by the Institute of Medicine of the National Academy of Sciences (tab. 1) (23). The body weight gain during pregnancy represented the difference between the body weight of a woman before the pregnancy (body weight declared by the women) and the body weight measured during the last medical consultation, which was adopted as the body weight around birth. Due to the survey-based character of the study, the pre-pregnancy body weights of the patients and the body weight gains during pregnancy were determined with the accuracy up to full kilograms. Because of the small number of obese women, for the purpose of analyzing the results, they were joined together in one group, including women with excessive body weight (BMI ≥ 25). The recommendations concerning body weight gain adopted for the women in this group were the same as for overweight women. The statistical analysis of the results was carried out using the χ² test. The results recognized as statistically significant were those with p < 0.05.