Effect on low implantation of the placenta on maternal blood pressure and placental function.

Low implantation of the placenta may protect against the development of pregnancy-induced hypertension (PIH) and is associated with improved values in tests of placental function. PIH occurred in six of 201 (3%) consecutive patients with placenta praevia managed at the City Hospital, Nottingham, from 1 April 1973 to 30 June 1981. None of the six patients developed associated proteinuria. Of the total number of 24,549 patients delivered in the same hospital for the years 1974-1978, 3744 (15%) developed PIH. Of the patients with placenta praevia, 52% had serum levels of human placental lactogen above the 95th centile and 25% had 24-h urinary oestriol levels above the 95th centile. The birthweight distribution was not different from that of the total live births at the City Hospital, Nottingham (based on 1975-1976 deliveries).