Objective: In pregnancy, important changes occur in the body weight of the mother, caused by sodium and water retention and by an increase in body fat tissue, but the mechanisms that regulate maternal and foetal changes in fat mass are poorly understood. Leptin is a hormone produced by adipocytes in order to regulate food intake and energy expenditure at the hypothalamic level in man. In order to verify whether leptin participates in the changes in body composition during pregnancy and postpartum, 630 healthy women were studied at specific time periods and leptin and auxological parameters were determined.
Design: A cross-sectional study in which leptin levels were measured in women at specific time periods related to pregnancy. Each woman was assessed only once.
Patients: 630 women participated in the study, and were divided into categories as follows: Group A, 29 internal controls, with no previous or current pregnancy; Group B, 73 women in the first trimester of pregnancy; Group C, 60 women in the 24 h before delivery; Group D, 212 women in the 24 h postpartum; Group E, 93 women in the eightH postpartum week (2 months group); Group F, 71 women in the sixteenth postpartum week (4 months group); Group G, 20 women in the sixth month postpartum; Group H, 23 women one year postpartum; Group I, 20 women two years postpartum; finally Group J, of 29 women who had suffered spontaneous abortion in the first trimester of pregnancy and were studied in the 24 h after the stillborn delivery.
Measurements: Serum leptin levels were measured in duplicate by radioimmunoassay using commercial kits. Height and weight was measured and BMI (kg/m2) calculated.
Results: Compared with serum leptin in the control group (11.7 +/- 1.0 micrograms/l), a non significant (NS) increase was observed in the first trimester of pregnancy (14.3 +/- 1.4 micrograms/l), with no parallel changes in body weight. A reduction in leptin occurred in the 24 h after delivery (9.4 +/- 1.4 micrograms/l, P = 0.02). After delivery a progressive increase in leptin concentrations was observed, 13.3 +/- 1.5 micrograms/l at two months (NS) and 17.4 +/- 2.6 micrograms/l at four months (P = 0.035 vs controls). Afterwards leptin values decreased towards normal values at 6, 12 and 24 months after delivery 14.4 +/- 1.8 micrograms/l; 12.9 +/- 1.6 micrograms/l; and 10.1 +/- 1.1 micrograms/l respectively (all NS). With the exception of the postpartum group, a significant correlation was observed between leptin concentrations and body weight or BMI in each group of women studied. In the women who suffered spontaneous abortion in the first trimester of pregnancy a reduction in leptin levels occurred (8.8 +/- 1.0 micrograms/l, P = 0.001 vs first trimester group).
Conclusion: Serum leptin concentrations rose slightly during pregnancy, fell following delivery and subsequently increased during the first six months postpartum. These variations were unrelated to changes in body composition, and may be responsible for the postpartum weight gain observed in some women. Abnormally low serum leptin levels were observed in women suffering spontaneous abortion in the first trimester of pregnancy.