Does use of progestins cause early abortions, and if so could this be playing a role?
Progestin use appears to cause more early abortions than use of combination OCPs (ie, those that contain both an estrogen and a progestin), primarily because they allow such a high rate of breakthrough ovulation. William’s Obstetrics comments specifically on Norplant: “Up to one third of cycles may be ovulatory based upon serum progesterone determinations.” 7 (ie, a woman may be having three or four abortions per year while on Norplant if she conceives during those cycles). (For details concerning how Norplant or OCPs work, see Appendix 5 of book). Although the studies regarding breakthrough ovulation have been done on Norplant, the same phenomenon probably occurs with all of the other progestins in addition to Depo–Provera. It was noted earlier in Chapter 6 (“Breast Cancer, Its link to Abortion and the Birth Control Pill” by Chris Kahlenborn) that the effect of a very early abortion (ie, within the first week of gestation) regarding breast cancer is difficult to know, but that a very
