Natural family planning indicators of ovulation.

Indirect evidence of the occurrence of ovulation, which is generally accepted, is an increase in plasma or serum progesterone. Pelvic ultrasonography can estimate the probable time of ovulation within 12 h. There is a close association between the rise in progesterone, luteinizing hormone (LH) and oestrogen peaks and ovulation. A WHO study reported that ovulation occurred at a median time of 8 h after the rise in plasma progesterone, 15 h after the LH peak and 24 h after the oestrogen peak. The basal body temperature (BBT) method is the most effective in determining the premenstrual infertile period, but it is unreliable for an accurate determination of ovulation and the postmenstrual infertile period. Nor is BBT an effective method of predicting ovulation during postpartum lactational amenorrhoea. Therefore, BBT is usually used as a secondary indicator of ovulation and is combined with more reliable indicators. Observed changes in cervical mucus patterns can be used to define the probable fertile period, although this method produces a wide range of days. The peak mucus symptom is closely correlated with ovulation. Mucus symptoms can be used as a guide for the timing of blood or urine samples for estimation of LH, oestrogen and progesterone or their metabolites. Symptothermal methods incorporate other symptoms such as cervical changes, intermenstrual pain, breast tenderness and backaches, but these are secondary signs of ovulation and are recommended to be used in conjunction with mucus and BBT.