Hormonal indices of ovulation and the fertile period.

Abstract

Pregnancy rarely occurs in women under the age of 14 years or over the age of 50, and for the majority the most fertile time of life lies between the ages of 20 and 35 years [1]. During this period the ovaries are fully functional, and alternately undergo a series of cyclical changes that culminate in the release of an oocyte into one of the oviducts every 25-33 days [2]. The average healthy woman will have approximately 400 menstrual cycles and ovulation may occur at any time between days 12-25, but most frequently around day 16 [3]. Accordingly, the time when coitus may lead to pregnancy is a periodic phenomenon and can be described only in statistical terms due to uncertainty about the occurrence and exact time of ovulation, the variable lifespans of the gametes and their ability to meet in the female reproductive tract. Nevertheless, a variety of methods have been developed to identify the outer limits of the fertile period during each menstrual cycle, and a couple may use this information to help avoid or achieve a pregnancy by having sexual intercourse at the appropriate times [4]. More recently, tests have been devised which signal the time of maximum conception probability to aid the management of subfertile patients who wish to conceive [5,6].