The antinidatory activity of the oral contraception is generally unkno
wn: the contraceptive pill mainly prevents the gamets from meeting. Ho
wever, pregnancies under pill indicate conception of embryos. Besides,
missed pills protocols sometimes record ovulatory escape. We suggest
the computation of an Embryo Destruction Index (EDI), in order to meas
ure the antinidatory effect of two categories of oral contraceptives:
combined estroprogestatives and microprogestatives.