All other things being equal, the heaviness of a menstrual flow depends on the thickness of the lining of the uterus just before the onset of menses.

The thicker the lining, the heavier the flow. In women using low-dose BCPs, there is a tendency for the uterine lining to become very thin, over the course of many months.

This is because the progestin half of the pill suppresses ovarian function, lowering secretion of estrogen. Estrogen is what drives the uterine lining to grow thick and proliferate. While the estrogen half of the BCP will do the same thing, there is not very much of it, usually a lot less than what the woman herself would have produced, were she not on the pill.

The other way that progestins in BCPs impact the uterine lining is by creating a structural matrix within the lining that supports the estrogen stimulated tissue, but also interferes to some extent with the proliferation itself.

Clinically, this is reflected as lighter and lighter periods which may even stop completely over the course of many months.

This is not a dangerous condition and will resolve if the BCPs are stopped. Stopping the BCPs is not necessary, however, because there are other safe alternatives, including ignoring the issue because this situation poses no threat to the patient.

The complexities are these:

• Pregnancy also causes a complete stoppage of periods, but is usually accompanied by other symptoms, such as breast tenderness, nausea, extreme fatigue.
• Most women, once the physiology of this amenorrhea is explained, and they are reassured that this is strictly temporary and due to the pill, are happy to avoid menstrual periods. But some are not, and for those women, alternatives should be explored.

You may change to a different BCP with different hormone in it. This will often lead to recognizable periods because the different hormone is metabolized differently.

You may add estrogen (Premarin.625 mg or Estrace 1 mg) to each BCP to increase the estrogen stimulation of the uterine lining, increasing its’ thickness and leading to heavier periods. After the desired effect has been achieved (recognizable periods), the extra estrogen can be stopped.

This extra estrogen poses little risk as these women are hypoestrogenic to begin with.