Menstrual Cycle Disturbances Observed for up to nine months following discontinuation of oral contraceptive
Menstrual Cycles

Richard J. Fehring
Reprint from Current Medical Research
Vol 15, No 1-2, Winter/Spring 2004
Washington, DC
Reproduced with Permission

Very few studies have been published on the effects of oral contraception on menstrual cycle parameters. Researchers from the University of Dusseldorf have been collecting charts of Sympto-Thermal users for over 15 years.1 As of July 1, 1998, 22% of the 1,426 women in their data set had previously used oral contraceptives (OCs). From this data set, 175 post-pill women were compared to a similar (according to age and socioeconomic characteristics) group of 284 women who never used OCs. The post-pill women generated 3,048 cycles of data and the control group of women 6,251 cycles. The mean age of the post-pill women was 26.25 years and for the control group 25.29 years.

The results showed that the post-pill group had significantly longer (length) cycles than the control group for up to 9 cycles. Further, with regard to frequency, the post-pill group had significantly longer cycles greater than 35 days for up to 6 cycles.

The follicular phase length (based on the day of the temperature shift minus one day) was significantly longer for up to 8 cycles in the post-pill group. The differences might be as long as 15 cycles, but the number of cycles produced by the post-pill group decreased due to anovulatory cycles or "difficult to interpret" temperature graphs. The biggest difference in the follicular length occurred in the first cycle - with an average prolonged difference of 4 days. There was a significant difference in the first two cycles in the length of the luteal phase, with the post-pill group being shorter, due mostly to insufficient luteal phase lengths (< 10 days). The onset of cervical mucus did not differ between the two groups, but the peak in cervical mucus differed for up to 9 cycles. In the first cycle the average day of peak was 23.19 for the post-pill group and 18.09 for the control group.

The researchers considered major "cycle disturbances" to be those cycles with either a monophasic BBT, a cycle length over 35 days, or a luteal phase of less than 10 days. Although none of these disturbances were found in 51.4% in the first cycle of the post-pill group, there were significantly more of these disturbances among the post-pill group than the control group for up to cycle 7 due primarily to cycles longer than 35 days. The researchers defined the beginning of regular cycling to be the first of 3 subsequent cycles with a luteal phase of at least 10 days. Based on this definition, over 70% of the post-pill group returned to a regular, ovulatory cycle pattern by the 7th cycle.


The researchers concluded that although cycle disturbances after discontinuation of OCs are reversible, the time of regeneration takes up to 9 months or longer. They theorized that the delayed regeneration is due to the time it takes for the hypothalamic-pituitary-ovarian axis to normalize and not be influenced by the circulating hormones from the OCs. Although the cycle disturbances, as described by the German researchers, are certainly similar to those observed by NFP teachers, I would urge some caution in interpreting the results. First of all, although the control group was matched by age and socio-economics, it is not a true randomized control and hence the differences could be a result of other factors, e.g., the postpill group might have had a propensity to cycle disturbances before taking the pill. Secondly, the biological indicators of ovulation used in the study (BBT and cervical mucus) are somewhat imprecise indicators of ovulation, they vary considerably around the actual day of ovulation and just because there is no BBT shift does not mean that the women did not ovulate. Of interest is that 14% of the subjects in the post-pill group and about 9% of the control group were unable to interpret a cervical mucus pattern. (Richard J Fehring)

1 Gnoth, C., Frank-Hermann, P., & Sclunoll, A., et al. Cycle characteristics after discontinuation of oral contraceptives. Gynecological Endocrinology. 2002;16:307-317. [Back]