除了月(yue)(yue)經(jing)(jing)期(qi)和排卵(luan)期(qi)，其余時間均為(wei)(wei)安(an)(an)全(quan)期(qi)。女性安(an)(an)全(quan)期(qi)又分(fen)為(wei)(wei)排卵(luan)前安(an)(an)全(quan)期(qi)和排卵(luan)后(hou)安(an)(an)全(quan)期(qi)。從月(yue)(yue)經(jing)(jing)干凈那(nei)天到排卵(luan)期(qi)開(kai)始(shi)的(de)(de)(de)前一(yi)天的(de)(de)(de)那(nei)段日期(qi)為(wei)(wei)排卵(luan)前安(an)(an)全(quan)期(qi)。從排卵(luan)期(qi)結束后(hou)的(de)(de)(de)第一(yi)天到下次月(yue)(yue)經(jing)(jing)來潮的(de)(de)(de)前一(yi)天為(wei)(wei)排卵(luan)后(hou)安(an)(an)全(quan)期(qi)。

女性(xing)的(de)排(pai)(pai)卵期(qi)一(yi)般在(zai)下次月經來潮前(qian)的(de)14天(tian)(tian)(tian)(tian)(tian)左(zuo)右。為(wei)(wei)了(le)保險(xian)(xian)起見，我(wo)們將(jiang)排(pai)(pai)卵日的(de)前(qian)5天(tian)(tian)(tian)(tian)(tian)和后(hou)4天(tian)(tian)(tian)(tian)(tian)連同排(pai)(pai)卵日在(zai)內共10天(tian)(tian)(tian)(tian)(tian)稱為(wei)(wei)排(pai)(pai)卵期(qi)。一(yi)般來說，正常生育年齡的(de)女性(xing)卵巢每月只排(pai)(pai)出一(yi)個卵子(zi)(zi)。卵子(zi)(zi)排(pai)(pai)出后(hou)可存(cun)活(huo)1-2天(tian)(tian)(tian)(tian)(tian)，精子(zi)(zi)在(zai)女性(xing)生殖道里可存(cun)活(huo)2-3天(tian)(tian)(tian)(tian)(tian)，受精能(neng)力多在(zai)排(pai)(pai)卵后(hou)的(de)24小時(shi)(shi)之內，超過2-3天(tian)(tian)(tian)(tian)(tian)精子(zi)(zi)即失去與卵子(zi)(zi)結合(he)的(de)能(neng)力。因此，在(zai)排(pai)(pai)卵前(qian)2-3天(tian)(tian)(tian)(tian)(tian)和排(pai)(pai)卵后(hou)1-2天(tian)(tian)(tian)(tian)(tian)性(xing)交，就有可能(neng)受孕，這個時(shi)(shi)期(qi)叫易孕期(qi)或危險(xian)(xian)期(qi)。