[Contraceptive effectiveness of sequential preparations].
D003276:Contraceptives, Oral; D003279:Contraceptives, Oral, Sequential; D005260:Female; D006801:Humans; D011247:Pregnancy
D003276:Contraceptives, Oral; D003279:Contraceptives, Oral, Sequential
Contraceptieve betrouwbaarheid van sequentiepreparaten