Abstract. Somatostatin (SRIF) was infused (500 μg over 30 min) into 68 pregnant women during labour. As a control, saline was infused into 26 pregnant women. Maternal blood was obtained prior to the infusion and at delivery and cord blood was obtained at delivery. The subjects were divided into 4 groups based upon the interval of time from the termination of SRIF infusion and delivery. There was a marked decrease in cord blood thyrotrophin (TSH) from 0 to 180 min and in cord blood growth hormone (GH) from 0 to 120 min following SRIF infusion. SRIF infusion did not affect cord blood iodothyronine and thyroglobulin concentrations. SRIF administration induced a small but significant (P < 0.05) decrease in serum GH concentration but had no other effect on maternal hormone values. These studies strongly suggest that SRIF crosses the human placenta and transiently suppresses foetal anterior pituitary TSH and GH secretion.