Kippley, J. F. (1996). Scientific bases for NFP beyond question. CCL family foundations, 22(5), 1-3.
Kippley JF. Scientific bases for NFP beyond question. CCL Family Found. 1996;22(5):1-3.
Kippley, J. F. "Scientific bases for NFP beyond question." CCL family foundations, vol. 22, no. 5, 1996, pp. 1-3.
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Abstract
The Couple to Couple League (CCL) is pleased that an article and an editorial in the December 1995 issue of the well-respected New England Journal of Medicine confirm that natural family planning (NFP) has value and is scientifically based, a fact the CCL has known for many years. The research covered in the article entitled Timing of Sexual Intercourse in Relation to Ovulation found that the only fertile days were the five days before ovulation and the day of ovulation itself. Most conceptions (76.4%) occurred during the day of and the first and second days before ovulation. CCL's slide showing the extent of the fertile time reflects the data of the report, but also includes the possibility of a second ovulation occurring within 24 hours of the first ovulation. The study found that women conceived in only 37% of cycles in which intercourse took place during the six-day fertile period. This rate is not much different than that claimed by a NFP physician many years ago (about 30%). The study showed the highest conception probability to be when the couple had sexual intercourse every day during the fertile period (37% vs. 33% for every other day). CCL advises couples to abstain until the fertile period then follow one coital frequency period during one cycle (e.g., every day) and the other pattern the next cycle (e.g., every other day). The study refuted claims that the timing of coitus relative to ovulation was not associated to the sex of the baby and that aging sperm do not reduce the viability of the fetus and/or cause birth defects. In fact, aging sperm rarely fertilize the ovum. The only way to positively detect ovulation is seeing the ovum burst out of the ovary. Hormone analyses of blood or urine and observations of cervical mucus and basal body temperature allow an estimate of the day of ovulation. NFP is not based on detecting ovulation but on identifying the limits of the fertile period.
This multicenter study has produced a database of 7017 menstrual cycles contributed by 881 women. It provides improved knowledge on length and location of the "fertile window" (identified as of up to 12 days duration) and the patterns and level of daily conception probability. The day of ovulation was identified in each cycle from records of basal body temperature and mucus symptoms. By referencing days of intercourse to the surrogate ovulation markers, estimates of daily fecundability were computed either directly or by the Scwartz model, both for single and multiple acts of intercourse in the fertile window. The relationship between coital pattern and fecundability has been explored. Univariate analysis underlines the significant link with fecundability only of the woman's reproductive history.
Past practices of Natural Family Planning (NFP) have included such techniques as: 1) calendar rhythm in which a constant mathematical relationship was calculated between the day of ovulation and the beginning of the succeeding menstrual period, 2) temperature rhythm in which sexual intercourse is permitted by observing that the basal body temperature rises at the time of ovulation, 3) a combination of calendar and temperature rhythm methods, 4) paper test strips which measure glucose and electrolytes in vaginal secretions, 5) electronic devices of various sorts which record changes in the potentials of the pelvic organs at the time of ovulation, and 6) recent developments in computer technology which measure a number of variables. All of these techniques depend upon the identification of the fertile and infertile periods of the menstrual cycle. More recent studies by the World Health Organization have analyzed the teaching phase of NFP and the effectiveness phase of NFP using the detection of ovulation by following changes in the quality of cervical mucus. These studies tested 869 women with varied backgrounds in 5 countries. The data support the fact that many motivated women can detect ovulation reasonably accurately by following changes in their cervical mucus (the Billings method), although teaching time and motivation are considerable. Long-term and detailed data are necessary to determine the value of these methods. The advantage of NFP is the avoidance of drugs and devices. Disadvantages are that demands are placed on the sex life of couples, and there are associations between failures and increased rates of congenital abnormalities.
A significant number of women worldwide use periodic abstinence as their method of family planning. Many of them use some type of calendar-based approach to determine when they should abstain from unprotected intercourse to avoid pregnancy; yet they often lack correct knowledge of when during their menstrual cycle they are most likely to become pregnant. A simple method of natural family planning (NFP) based on a fixed formula to define the fertile window could be useful to these women. This article reports the results of an analysis of the application of a fixed formula to define the fertile window. A large existing data set from a World Health Organization study of the Ovulation Method was used to estimate the theoretical probability of pregnancy using this formula. Information about the variable probability of pregnancy on different cycle days relative to ovulation also was considered in the analysis. Results suggest that a fixed formula in which days 8-19 of the menstrual cycle are considered to be the fertile window would provide the appropriate basis of a simple, effective, family planning method.
Physicians who counsel women for preconception concerns are in an excellent position to give advice to couples regarding the optimal timing of intercourse to achieve pregnancy. The currently available evidence suggests that methods that prospectively identify the window of fertility are likely to be more effective for optimally timing intercourse than calendar calculations or basal body temperature. There are several promising methods with good scientific bases to identify the fertile window prospectively. These include fertility charting of vaginal discharge and a commercially available fertility monitor. These methods identify the occurrence of ovulation clinically and also identify a longer window of fertility than urinary luteinizing hormone kits. Prospectively identifying the full window of fertility may lead to higher rates of conception. Proper information given early in the course of trying to achieve pregnancy is likely to reduce time to conception for many couples, and also to reduce unnecessary intervention and cost.