SummaryIf endogenous prolactin secretion is important in normal development of fetal lung surfactant, the inhibition of its secretion should be associated with delayed maturation of fetal lung.We therefore studied the effect of bromoergocriptine administration to pregnant rabbits upon lecithin content of fetal lung washes.The does were treated since the 27th day of gestation with either Mesilate of 2‐Bromo‐&agr;‐ergocriptine (C32H40BrN5O5, CH3SO3H) (Bromocriptine) (Parlodel, Sandoz) (1 mg/kg/day) or solvent twice daily until delivery.The newborns were killed immediately by intraperitoneal administration of sodium penthobarbital and tracheostomized; then lung washes were performed.The extracted lipids were plated and run on heat‐activated thin layers of silica gel H. Lecithin was eluted, and phosphorus determination was performed.The level of lecithin phosphorus in the lung washes of the fetuses whose mothers received Bromocriptine was &OV0398; = 2.24 ± 0.39 &mgr;g/g dry lung weight, whereas that of fetuses of control does was &OV0398; = 6.93 ± 2.64 &mgr;g/g dry lung weight (P< 0.001).The mean body weight of the fetuses from treated mothers was 38.22 ± 6.39 g whereas that of fetuses from control rabbits was 47.63 ± 6.94 g (P< 0.001).The mother's body weight gain from days 26 to 30 in Bromo‐criptine‐treated rabbits was 156.11 ± 99.4 g, whereas that of controls was 374.38 ± 166.21 g (P< 0.01).SpeculationProlactin could be involved in the normal biochemical development of the lung and also be necessary for a normal weight gain of mother and fetuses during the last stage of gestation.