For most of her reproductive life, a woman will experience fertile ovulatory cycles. However, all women will experience infertile variants of the ovulatory cycle, particularly during breastfeeding, approach of menarche and menopause, periods of stress, andduring and after hormonal contraception. The hormone patterns and therefore the symptoms in these infertile cycles differ from the fertile ovulatory cycle. Recognizing these variants is particularly important for pregnancy achievement.
Ovulation -the release of an ovum by the ovary and therefore the only timeduring the cycle when the ovum is exposed for fertilization–is the central event ofthe fertile ovarian cycle. It determines the time when pregnancy can occur from an actof intercourse which is the period of 3-4 days (rarely 5-6 days depending on thecervical mucus) before ovulation determined by the fertilizing life span of the spermand up to 24 hours after ovulation determined by the fertilizable life span of the ovum.Outside this time period a woman cannot conceive from an act of intercourse nomatter how hard she tries. Even within this time period, pregnancy from an act ofintercourse is not a certainty, the chances vary depending on the couple and the timingof intercourse in relation to ovulation. Maximum fertility is reached during the periodof 24 hours before ovulation and several hours afterwards. If the chances of pregnancy at this time are 70% per cycle, it takes two cycles for 90% of couples havingintercourse on the most fertile day to achieve pregnancy. If the chances at the beginning of the fertile period are 10% per cycle, it takes 24 cycles for 90% of coupleshaving intercourse at this time to achieve pregnancy