Human Reproduction, Vol. 18, No. 9, 1959-1966,
September 2003
© 2003 European Society of Human Reproduction and Embryology
Time to pregnancy: results of the German prospective study and impact on the management of infertility
1 Department of Reproductive Medicine and Gynaecological Endocrinology, Staedtische Kliniken Duesseldorf gGmbH, Frauenklinik Benrath and Institute of Natural Family Planning, Heinrich-Heine University of Duesseldorf, 2 Biometric Research Group, Clinic for Thoracic and Cardiovascular Surgery, Heinrich-Heine University of Duesseldorf and 3 Department of Gynaecological Endocrinology, University of Heidelberg, Germany
4 To whom correspondence should be addressed at: Staedtische Kliniken Duesseldorf gGmbH, Frauenklinik Benrath, Urdenbacher Allee 83, 40593 Duesseldorf, Germany. e-mail: gnoth{at}uni-duesseldorf.de
BACKGROUND: The likelihood of spontaneous conception in subsequent cycles is important for a balanced management of infertility. Previous studies on time to pregnancy are mostly retrospective and biased because of exclusion of truly infertile couples. The study aim was to present a non-parametric estimation of cumulative probabilities of conception (CPC) in natural family planning (NFP) users illustrating an ideal of human fertility potential. METHODS: A total of 346 women was observed who used NFP methods to conceive from their first cycle onwards. The couples practising NFP make optimal use of their fertility potential by timed intercourse. The CPC were estimated for the total group and for couples who finally conceived by calculating Kaplan-Meier survival rates. RESULTS: A total of 310 pregnancies occurred among the 346 women; the remaining 36 women (10.4%) did not conceive. Estimated CPC for the total group (n = 340 women) at one, three, six and 12 cycle(s) were 38, 68, 81 and 92% respectively. For those who finally conceived (truly fertile couples, n = 304 women), the respective pregnancy rates were 42, 75, 88 and 98% respectively. Although the numbers of couples in both groups were similar, the impact of age on time to conception, as judged by the Wilcoxon test, was less in the truly fertile than in the total group. CONCLUSIONS: Most couples conceive within six cycles with timed intercourse. Thereafter, every second couple is probably either subfertile or infertile. CPC decline with age because heterogeneity in fecundity increases. In the subgroup of truly fertile couples, an age-dependent decline in CPC is statistically less obvious because of high homogeneity, even with advancing age.
Keywords: cumulative probability of conception/management of infertility/natural family planning/survival rates/time to pregnancy
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