Natural Family Planning
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Efficacy of the TwoDay Method

Scientific Basis of the TwoDay Method

Secretions are a reliable indicator of fertility. When the woman does not have cervical secretions, she cannot be fertile and cannot become pregnant.

Secretions have several key functions:

Secretions make it possible for sperm to live up to 5 days in a woman's body. Without secretions, the acidic environment of the vagina will cause the sperm to deteriorate quickly.

When cervical secretions are very fluid (more watery, around the day of ovulation), they serve as a medium for the sperm to navigate into the uterus. This fluidity allows the secretions to flow down the vaginal walls making them easily noticeable for the woman at the opening of her vagina or vulva.

When secretions have little water content (on the infertile days), they form a sticky plug at the opening of the cervix, which is impenetrable by sperm. With less water content, secretions do not flow down and are not noticeable to the woman.

Therefore, if secretions are present, a woman is very likely fertile and can get pregnant. If there are no noticeable secretions, pregnancy is unlikely.

Efficacy of the TwoDay Method

An efficacy trial found the TwoDay Method® was more than 96% effective in preventing pregnancy with correct use and more than 86% with typical use among women. These efficacy rates are similar to those of other user-dependent methods. The efficacy trial followed 450 women, aged 18–39 years, wishing to use a fertility awareness–based method to prevent or delay pregnancy, for 13 cycles of method use. Click to read more about the TwoDay Method efficacy study.