‘Escape’ ovulation in women due to the missing of low dose combination oral contraceptive pills

It is generally believed that in women taking anti-conceptional combined pills, the risk of pregnancy increases if a pill is missed. A study was undertaken in healthy, normally menstruating women who were given low dose combination contraceptive pills containing norethisterone acetate (NET Ac) 1 mg and ethinyl estradiol (EE 2) 30 g. In the control group, 10 women were asked to take the pills regularly daily for 21 days starting from the day 5 of the menstrual cycle. Whereas in the study group, consisting of similar women but who were sterilized, they were asked to ‘miss the pills’ on two consecutive days anywhere between day 5 to day 17 of the menstrual cycle. Thirty-five women were ‘made to miss’ the pills in the first treatment cycle and another 19 women were asked to ‘miss the pills’ in the fourth treatment cycle. Cervical mucus and lateral vaginal wall smears were studied thrice a week. Endometrial biopsy was done on day 23 ± 2. Two serum progesterone (R) levels were determined between day 22 to day 25 of the cycle.