Melatonin plasma levels in maternal and neonatal sheep. Melatonin treatment was given to the pregnant ewes in the last third of gestation. (A) Maternal samples were obtained at term gestation and (B) neonatal samples were obtained and averaged at 3, 7 and 12 days old. Values are means ± SEM, determined in blood samples taken at 10:00 and 22:00. Groups are control (CN, open circles, n = 6) and antenatal melatonin treated (MM, grey squares, n = 6). Significant differences (P ≤ 0.05): * vs. CN.