Once hormone replacement therapy (HRT) has been commenced, it becomes extremely difficult to advise women approaching the menopause on the need for contraception. In this study of twenty women, neither the regularity of their pre-existing menstrual cycle nor a random FSH concentration predicted the likelihood of subsequent ovulation whilst taking HRT. HRT is not reliably contraceptive and women commencing HRT whilst still menstruating spontaneously must be advised on the need for additional contraception.
PIP: In Scotland, providers determined the incidence of ovulation before and during use of oral hormone replacement therapy (HRT) among 20 women aged 42-52 attending the Family Planning and Well Woman Services menopause clinic in Edinburgh and their need for contraception. Ovulation was defined as a pregnanediol concentration of more than 0.5 mmol/g creatine. HRT consisted of 1.25 mg/day of conjugated estrogens with 150 ug cyclical norgestrel for 12 of 28 days (Prempak-C). Women with irregular cycles were older than those with regular cycles (47.3 vs. 45.5 years; p 0.02). They also had considerably higher mean follicle stimulating hormone (FSH) levels (26 vs. 14.2 IU/l; p 0.001). One woman had a very high FSH level (67 IU/l) before HRT use and ovulated in the subsequent cycle with urinary pregnanediol levels indicating normal ovarian function. All 10 women who had regular cycles ovulated before HRT use. Six still ovulated during HRT use. Among women with irregular cycles, 4 of the 10 women ovulated before HRT use. Three of these women had anovulatory cycles during HRT use while 3 of the 6 who did not ovulate before HRT use ovulated during HRT use. These findings reveal that HRT with the higher dose Prempak-C does not suppress ovulation and that an elevated FSH does not always indicate the absence of ovulation. They also show that neither age nor regularity of menstrual cycles can be used to predict the need for contraception in perimenopausal women using HRT.