Umbilical serum DHAS and total oestriol in relation to gestational age and mode of delivery

Abstract

The concentrations of mixed umbilical cord serum dehvdroepiandrosterone sulphate (DHAS) and total oestriol, were determined by radioimmunoassay in 301 infants. Of 280 infants born between 36 and 42 weeks of gestation, 260 were born by vaginal delivery and 20 were delivered by Caesarean (C-section). We found that there was a significant elevation of serum total oestriol (P < 0.005) after 35 weeks with no concomitant gestational change of DHAS. Within the vaginal delivery group steroid values were similar among infants born following spontaneous, oxytocin augmented, and oxytocin induced labour. Within the C-section delivery group, steroid values were similar in infants who experienced spontaneous labour and those who did not. However, DHAS level was significantly higher (P < 0.005) in the vaginal delivery group than in the C-section group. We postulate that the higher DHAS levels in the vaginal delivery group are the result of stress during the late first stage of labour or later.The endocrine activity of the foeto-placental unit change remarkably in the last several weeks of normal pregnancy. These late gestation foetal adrenal functional changes have been postulated to play a role in the onset of labour in the human (Murphy 1973;Turnbull et al. 1974). Foetal adrenal weight increases rapidly after 34 weeks (Spector 1956) and corticosteroid in foetal blood (Smith et al. 1975) as well as free and conjugated cortisol in the amniotic fluid (Montserrat & Tulchinsky 1975) increase progressively after 36 weeks. In the maternal circulation, oestradiol-17ß (Turnbull et al. 1974; Shutt et al. 1974) and oestriol (Shutt et al. 1974;Buster et al. 1976) levels increase at about 36 weeks and this oestrogen surge has been attributed to increased production of dehydroepiandrosterone sulphate (DHAS) by the foetal adrenal gland. To further assess this change of oestrogen levels in the third trimester, and to relate the change to oestrogen precursor levels, we measured DHAS and total (conjugated and unconjugated) oestriol in cord blood samples from a large number of patients. In addition, we examin¬ ed the relationship of these two steroids to the presence or absence of labour.Patients and Methods I hreehundred and ten umbilical cord blood samples were obtained at 308 consecutive deliveries at St. Paul Ramsey Countv Hospital. At delivery, foetal and placen¬ tal sides of the cord were clamped and the blood was allowed to drain into the tubes from the placental end. This procedure vielded mainly umbilical venous blood.The blood was centrifuged after clotted and the serum was kept frozen until the time of assay. The gestational age of the infants was determined from the date of the Reprint requests to: