The WHO multicentre trial of the vasopressor effects of combined oral contraceptives: 2. Lack of effect of estrogen. Task Force on Oral Contraceptives. WHO Special Programme of Research, Development and Research Training in Human Reproduction.
Changes in blood pressure were measured in a randomized double-blind trial of 680 women using oral contraceptives containing either 50 or 30 ug of ethinyl estradiol combined with 250 mg levonorgestrel. The trial was done in 6 centres in Thailand, India, Zambia, Cuba, The Philippines, and Hungary. There were no significant differences between the two pills at any of 4 follow-up visits at approximately 3, 6, 9 and 12 months, nor in the life-table probability of developing hypertension within one year. These findings are evidence against the hypothesis that it is the estrogen in oral contraceptives which causes their vasopressor effect.
D000293:Adolescent; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects*; D003277:Contraceptives, Oral, Combined / Q000009:adverse effects*; D004997:Ethinyl Estradiol / Q000009:adverse effects*; D005260:Female; D006801:Humans; D016912:Levonorgestrel; D015337:Multicenter Studies as Topic; D009644:Norgestrel / Q000009:adverse effects*; D013997:Time Factors; D014944:World Health Organization
D003277:Contraceptives, Oral, Combined; D009644:Norgestrel; D004997:Ethinyl Estradiol; D016912:Levonorgestrel