The WHO multicentre trial of the vasopressor effects of combined oral contraceptives: 1. Comparisons with IUD. Task force on oral contraceptives

Abstract

Changes in blood pressure were measured at three-monthly intervals over one year in a prospective study of 704 women using an oral contraceptive (OC) containing levonorgestrel 250 μg with ethinyl estradiol 50 μg and 703 women using an intrauterine device (IUD). The study was conducted in 11 centres in seven developing and three developed countries. Women using OC developed systolic blood pressures which were 3.6-5.0 mmHg higher than those using IUDs; their diastolic pressures became 1.9-2.7 mm higher. The OC-induced change was not affected by climate, age, a family history of hypertension, stroke or heart disease or by a history of hypertension in pregnancy. The life-table rate of hypertension (BP 140/90 or more) in the first year of OC treatment was 0.6 ± 0.4 in the developing countries and 1.1 ± 0.8 in the developed ones, per 100 woman-years of use. The vasopressor response to OC varied widely between centres but was not obviously related to the economic development of the country.