(European Society for Human Reproduction and Embryology) -- Italian scientists have confirmed that the Pill appears to affect a woman's sensitivity to smells.

In a study involving 60 non-Pill using women aged 18 to 40 they measured their ability to detect six distinctive substances - anise, musk-ketone, clove, pyridine, citral and ammonia - at three defined times in the menstrual cycle. The testing was done were during the follicular phase (day 5-8), the periovular phase (day 13-16) and the luteal phase (day18-23). The women's sense of smell was most sensitive at the time around ovulation. The research is published today in Human Reproduction.

The volunteers were then prescribed oral contraceptives - half taking a combination of ethiniloestradiol and gestodene and half taking ethiniloestradiol and desogestrel. After three months' use the women's sensitivity to smell was tested again on days 7, 14 and 21 of the 28-day month.

This time there was no difference in the women's sensitivity to smell between any of the days and the level of sensitivity most nearly matched that of the luteal (pre-menstrual) phase when the women were not taking oral contraceptives.

"This could emphasise the particular nature of the monophasic pills whose hormones are mainly progestative, which is similar to the natural clime of the luteal phase of the menstrual cycle," said Professor Salvatore Caruso of the Department of Gynaecological Science at the Ospedale S. Bambino in Catania.

"Our data seem to show that iatrogenic steroids, such as those contained in oral contraceptives, may affect changes in smell sensitivity. Biologically, odours probably influence reproductive processes in humans and perhaps the notion of concealed ovulation in humans needs rethinking. But, although our data have confirmed the existence of changes in olfactory sensitivity during oral contraceptive use with respect to non-using time, we need to carry out further studies to investigate ways in which smell variations could vary a woman's sexual life."