Cumulative pregnancy rates in patients with apparently normal fertility and fertility-focused intercourse

J Reprod Med. 1992 Oct;37(10):864-6.


Fifty consecutive clients achieved pregnancy using a standardization modification of the Billings ovulation method (the Creighton Model Natural Family Planning System). Of 50 clients followed, 38 (76%) achieved pregnancy in the first cycle of fertility-focused intercourse, 45 of 50 (90%) achieved pregnancy by the third cycle and 49 of 50 achieved pregnancy by the sixth cycle (98%).

PIP: The effectiveness of the standardized modification of the Billings ovulation method of natural family planning in fertility focused intercourse was evaluated in a study over 12 months of 50 clients aged 22-38 years. 27 had prior pregnancy/s. All clients had normal fertility. The results indicated a higher probability of conception when the couple was aware of their peak fertile time than previously expected. No clients became pregnant when intercourse was confined to the infertile period. Within 1 cycle, 76.0% became pregnant. By the 3rd cycle, 90.0% became pregnant. By the 6th cycle, 98% (49 out of 50) achieved pregnancy. 71.4% of those with a prior pregnancy conceived after the 1st cycle. 80.9% of nulligravida women achieved pregnancy after 1 cycle, 89.3% of multiparous women became pregnant after the 4th cycle, and 100% of the nulligravida women became pregnant after the 4th cycle. The method entailed learning about the presence or absence of cervical mucus discharge around the time of ovulation. The beginning of the mucus cycle began with a sticky (a quarter of an inch), cloudy or tacky discharge until the last day when the mucus became clear and stretchy or lubricative. The last mucus was considered the peak day. Clients recorded all acts of intercourse and were assessed at follow-up visits every 2 weeks in the 1st 2 months, and then at 3, 6, 9, and 12 months. The fertile period was defined as the 1st day of mucus discharge through 3 full days past the peak day. Ovulation is considered possible +or- 2 days of the peak day for 95.4% of cycles. Studies of random acts of intercourse show less efficient conception rates. A study by Barrett and Marshall found, by using the Vollman basal body temperature method, that daily intercourse around the period of alleged fertility increased the possibility of conception from 24% to 31% for every 3-4 days to 68% for daily. The WHO fertility figure for the ovulation method in a multicentered trial is 66.7%.

MeSH terms

  • Adult
  • Cervix Mucus
  • Female
  • Follow-Up Studies
  • Humans
  • Natural Family Planning Methods*
  • Pregnancy*
  • Prospective Studies