How effective is the STM for contraception? And what is its use for conception?
This question is often asked. However, it is misleading since after ovulation the contraceptive effectiveness is total, meaning 100 % (Pearl index 0,0). That is to say, it is more effective than any kind of “pill”. During the first 5 cycle days, the Pearl index is 0,2. During the infertile days after day 5 and before ovulation (some 2 to 5 days), the Pearl index is 0,8. Even in this zone, the STM is as efficient as hormonal contraception. There is no simple answer to this question. It is up to you and your partner to achieve contraceptive effectiveness, depending on how you manage your fertile days: you can remain abstinent during this time or use a condom (which will decrease contraceptive effectiveness).
