Longitudinal analysis of maternal serum leptin levels during pregnancy, atbirth and up to six weeks after birth: Relation to body mass index, skinfolds, sex steroids and umbilical cord blood leptin levels

Leptin is an important regulator of body fat mass and energy expenditure du ring adult life. The mechanisms by which maternal and fetal weight are regu lated during pregnancy are poorly understood. In order to gain more insight into a potential role of leptin during gestation, a prospective, longitudi nal study was carried out to measure leptin concentrations in maternal seru m of 29 healthy women during pregnancy up to 6 weeks after birth and also i n umbilical cord blood of their newborns. Leptin concentrations were measur ed using a specific RIA. In addition, estradiol, testosterone, and sex horm one binding globulin were determined using commercially available RIAs. The mothers' skinfolds were determined at four sites using a Holtain caliper. Leptin levels increased continuously during pregnancy and reached 25.8 +/- 14.7 ng/ml at 38-40 weeks. At birth, leptin concentrations were 23.5 +/- 15 .4 ng/ml. Three days after delivery a significant decrease of leptin levels to 10.6 +/- 6.0 ng/ml was observed. Six weeks after birth the leptin conce ntration in maternal serum was 13.8 +/- 8.6 ng/ml. At birth, maternal serum levels were significantly higher than levels in cord blood and did not cor relate with leptin levels in cord blood or neonatal weight. Furthermore, le ptin levels did not correlate with maternal sex steroids and sex hormone bi nding globulin levels. At 6-8 weeks of pregnancy, maternal leptin serum lev els correlated significantly with BMI (r = 0.81). The correlation coefficie nts (leptin vs. BMI) dropped with increasing gestational age and at birth o nly a poor correlation persisted (r = 0.50). Six weeks after birth there wa s again a high correlation between leptin levels in maternal serum and BMI (r = 0.76). Subscapular skinfold thickness was correlated to leptin concent rations in maternal serum during the whole period of the investigation. In conclusion, maternal leptin levels continuously increased from 6-8 weeks up to 38-40 weeks of pregnancy. Maternal leptin levels decreased dramatica lly after birth. Six weeks after delivery, leptin levels were comparable to the values measured at the beginning of pregnancy. We hypothesize that lep tin might play an important role during pregnancy and fetal development.