Should spontaneous or timed intercourse guide couples trying to conceive?

H.K.A. Snick

Department of Obstetrics and Gynaecology, Ziekenhuis Walcheren, Vlissingen, The Netherlands

Present address: 78, boulevard Tixador, 66140 Canet en Roussillon, France. E-mail: herman.snick{at}freesbee.fr

Sir,

Natural family planning (NFP) methods to conceive, based on timed intercourse in the fertile window, are promoted as reducing the time to pregnancy and improving the chances of conception.

This view is promoted in the lay press and in a multitude of websites and was recently put forward in this Journal (Brosens et al., 2004Go; Gnoth et al., 2003Go, 2005Go). The view is based on observational studies without a comparison group (Hilgers et al., 1992Go; Gnoth et al., 2003Go).

Observational studies without a comparison group do not allow assessment of associations (Grimes and Schulz, 2002Go). Nevertheless, the authors claimed that the higher cumulative probability of conception, compared with previously published studies, accounts for the effects of information on the fertile period and of repeated timed intercourse. The question arises if these observations are sufficient evidence to replace spontaneous coital habits among couples who want children.

In 1994 we investigated in Walcheren, The Netherlands, the time to pregnancy in the general population.

Walcheren GPs and independent midwives, the main care-givers of obstetrics in The Netherlands, and all four gynaecologists working in Walcheren, asked successive consulting pregnant women how much time had passed between the cessation of contraceptive activities and the onset of their pregnancy. Of the 729 registered pregnancies, nearly half of the annual number in Walcheren, 10 occurred during oral contraception and were excluded. The cumulative conception rate after 1, 3, 6 and 12 months was 40, 75, 89 and 97% respectively in the 719 included couples.

Our results are nearly identical to those described by Gnoth et al. in couples using the NFP method of fertility oriented intercourse (Figure 1).



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Figure 1. Cumulative pregnancy rate without natural family planning (NFP) (Walcheren; n = 719) and with NFP (Gnoth et al.; n = 304). Data from text in Gnoth et al. (2003)

 
.

In the NFP population study, only cycles with the intention to become pregnant and with at least one episode of unprotected intercourse in the fertile window were taken into account. Couples with ovulatory problems were excluded, as were couples with previous fertility problems. The women in the German NFP population were trained and instructed by experienced NFP teachers and the higher social class levels were over-represented in the sample. These inclusion criteria tend toward higher fertility.

In contrast, the Walcheren study included consecutively pregnant women from the entire general population, whether or not they ovulated regularly, had regular coital activities or intended to become pregnant. Couples currently under subfertility investigation were not included.

The age of the women was comparable in both populations, as was the definition of pregnancy and the degree of subfertility. Gnoth et al. reported the time to pregnancy in cycles, the Walcheren study did it in months; they registered the time to pregnancy prospectively, whereas the Walcheren study was retrospective. Unintended pregnancies are not included in prospective studies. Juul et al., (1999)Go Found that 42.5% of pregnancies in West Germany were unplanned.

We realize that the differences between the samples preclude definite conclusions. Nevertheless, we believe that the results presented suggest strongly that the effectiveness of the NFP methods in enhancing the chance to conceive is not proven.

The NFP concept seems attractive, but there is a need for better evidence of benefit. Meanwhile, the National Institute for Clinical Excellence (NICE) Guidelines (2004)Go conclude: ‘Timing intercourse to coincide with ovulation causes stress and is not recommended.’

Given the enormous impact of NFP methods, with ~4x106 hits in the Google search engine, the promoters of NFP methods for use among fertile couples have a duty to demonstrate the efficacy of their method in well-designed clinical trials. While waiting for those trial results, use of these methods is not justifiable.

References

Brosens I, Gordts S, Valkenburg M, Puttemans P, Campo R and Gordts S (2004) Investigation of the infertile couple: when is the appropriate time to explore female infertility? Hum Reprod 19,1689–1692.[Abstract/Free Full Text]

Gnoth C, Godehardt D, Godehardt E, Frank-Herrmann P and Freundl G (2003) Time to pregnancy: results of the German prospective study and impact on the management of infertility. Hum Reprod 18,1959–1966.[Abstract/Free Full Text]

Gnoth C, Godehardt E, Frank-Herrmann P, Friol K, Tigges J and Freundl G (2005) Definition and prevalence of subfertility and infertility. Hum Reprod 20,1144–1147.[Abstract/Free Full Text]

Grimes DA and Schulz KF (2002) An overview of Clinical research: the lay of the land. Lancet 359,57–61.

Hilgers TW, Daly KD, Prebil AM and Hilgers SK (1992) Cumulative pregnancy rates in patients with apparently normal fertility and fertility-focused intercourse. J Reprod Med 37,864–866.[ISI][Medline]

Juul S, Karmaus W, Olsen J and The European Infertility and Subfecundity Study Group (1999) Regional differences in waiting time to pregnancy: pregnancy-based Survey from Denmark, France, Germany, Italy and Sweden. Hum Reprod 14,1250–1254.[Abstract/Free Full Text]

NICE Guidelines (2004) Clinical Guideline 11. Fertility: assessment and treatment for people with fertility problems. February 2004. (http://www.nice.org.uk/pdf/CG011niceguideline.pdf)





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