DIRECT CHEMILUMINESCENCE IMMUNOASSAY OF ESTRIOL AND PROGESTERONE AND THEIR RATIO DURING PREGNANCY

Estriol (E3) and progesterone (P) concentrations in saliva were determ ined by direct chemiluminescence immunoassays, using solid-phase monoc lonal antibodies bound to the wells of microtitre plates, and isolumin ol-labelled steroid conjugates. Saliva samples were obtained from wome n during pregnancy, from 34 to 1 weeks before delivery. The smoothed m edian and mean salivary E3:P ratios in normal pregnancy rose gradually from 0.45 at -34 weeks to 1.5 at -1 week. In twin pregnancy a similar rise was observed. However, in preterm delivery the smoothed mean rat io rose more slowly, from 0.6 at -30 weeks to 1.1 at -1 week. In pregn ancy associated with intra-uterine growth retardation, the smoothed me an ratio did not reach a value of 1 towards the end of pregnancy. In a ll instances high and low E3:P ratios were observed shortly before spo ntaneous delivery. This raises the question of whether the E3:P ratio could be used as a predictor providing useful information in relation to the onset of labour.