Summary Total plasma oestriol in pregnancy was estimated by a competitive protein binding method. The advantages of the measurement of plasma oestriol levels over the 24‐ or 48‐hour urinary oestriol assays are discussed. The pattern of plasma oestriol levels in the third trimester of pregnancy was investigated in over 400 healthy women and in general a uniform increase was found from the 28th week until term. Diurnal variation was found to be present, but this did not preclude the use of the method for assessing the feto‐placental unit. Exercise and meals had a minimal effect on the oestriol levels. Following delivery the level decreased sharply to reach, within four hours, one‐half that found just prior to delivery.

A new syndrome of neonatal convulsions is described. Ninety cases were documented from one maternity hospital between 1973 and 1977. The appearance of this syndrome increased the annual incidence of neonatal convulsions from fewer than 3 to more than 16 per 1000 live births. Fits began on about the fifth day in apparently healthy babies. Investigations and therapeutic trials have not shown the cause. There were no deaths and all babies were discharged from hospital apparently well. The term fifth day fits is suggested with criteria for this diagnosis.

Serum gonadotropin, estradiol, prolactin and alpha-1-antitrypsin levels were measured in the first four days of the menstrual cycle in 14 women who were cycling normally. FSH, and to a lesser extent LH levels, were significantly higher in a group of 8 women who had at least one set of DZ twins (6 of whom had 2 sets) than in a control group of 6 women with no DZ twins. Estradiol levels also tended to be higher in mothers of twins but there were no significant differences in prolactin or alpha-1-antitrypsin concentrations. There were no differences between the means of the two groups in age, height, weight or number of pregnancies.

1,000 multiple births were examined in relation to maternal exposure to an oral contraceptive before conception. There was a significantly higher rate of monozygotic twinning among pregnancies which took place within 6 months of cessation of the contraceptive. In the monozygotic group there was a significant increase in the incidence of congenital abnormalities (P less than 0.01) when conception occurred within 3 months of cessation of the contraceptive.