Time required for conception in 1727 planned pregnancies

Use-effectiveness of oral and intrauterine contraception

Lewitt S et al., 1971 · Fertil Steril

The use-effectiveness of oral contraception and intrauterine contraception was studied in 3 family planning centers in the United States: Grady Memorial Hospital in Atlanta, Georgia; State University of New York, Downstate Medical Center, in Brooklyn; and the Planned Parenthood Center in Buffalo, New York. In each locality 1000 women were selected for the study. 2900 women accepted intrauterine devices (IUDs) or oral contraceptives (OCs) as their first method of contraception. In Brooklyn 3 out of 4 women chose OCs; in Atlanta and Buffalo roughly equal numbers selected each method. The mean age of admission was 25.7 years in Buffalo, 24 years in Brooklyn, and 23.8 years in Atlanta. IUD acceptors were older than those choosing OCs. The difference was greatest in Buffalo (3.3 years) and smallest in Atlanta (.8 years). A special one-page, self-coding questionnaire was designed to collect the information required. In all 3 clinics contraceptive termination rates were markedly lower for the IUDs than for OCs. At 1 year of use for the first method only about one-fourth the women who chose the IUD had discontinued its use. Women on OCs terminated at rates from 10-20% higher. Termination rates for all contraception, both first-method and substitution, were lower than for first-method alone and lower for IUDs than for OCs. The highest continuation rate for all contraception was 92.5% for IUD users in Brooklyn while OC users in Atlanta were at the lowest level at 60.5%. Pregnancy rate studies demonstrated higher failure rates with OCs than with IUDs in all 3 clinics. Statistics by age showed that termination rates for both IUD and OC users declined with age. Women who selected IUDs as their method of contraception were more persistent users of contraception. Even after discontinuing IUD use, they were more likely to adopt another contraceptive method.

The IUD and the pill: extended use-effectiveness

Lewit S et al., 1971 · Fam Plann Perspect

The extended use-effectiveness of IUD and oral pills as measured by 1) their theoretical effectiveness 2) consistency of use and 3) continuation of use in preventing unwanted pregnancies was studied for 2900 women who had chosen either method as their first contraceptive in family planning clinics in Atlanta Georgia and in Brooklyn and Buffalo New York for a 12-18 month period. The greater persistence among IUD users to continue the method or use another method and the less likelihood there was of these women to have an unplanned pregnancy (the difference between IUD users and pill users increasing with months of exposure) suggest the necessity of greater support from the clinics to help women using pills prevent unwanted pregnancies. IUD users were generally older than pill acceptors and among IUD contraceptors the greater tendency to continue using the IUD and contraception may indicate that older women use contraception to terminate rather than to space childbirth.

Statistical evaluation of contraceptive methods: Use-effectiveness and extended use-effectiveness

Lewit S et al., 1968 · Demography

The recent advent of national family planning programs and the expansion of local programs have created an acute need for accurate statistical evaluation of contraceptive methods. Effectiveness in terms of pregnancy rates and continuation or discontinuation of use of the contraceptive method or methods under study have emerged as the major criteria in such evaluations.

The clinical effectiveness of contraceptive methods

Tietze C, 1959 · Am J Obstet Gynecol

Physiologic effectiveness is the measure of protection against unwanted pregnancy afforded by a specific contraceptive method under ideal conditions ie, used consistently and according to instructions-without omissions, or errors of technique. Such ideal conditions are rarely present. Even when they are, it is not practicable to observe and verify them. Physiologic effectiveness, although not accessible to direct measurement, is by definition higher than the observed clinical effectiveness of the same method in the hands of the most …

Time to pregnancy: results of the German prospective study and impact on the management of infertility

Gnoth C et al., 2003 · Hum Reprod

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. 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. 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. 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.

Daily fecundability: first results from a new data base

Colombo B et al., 2002 · Demogr Res · Free to read

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.

Ovulationstermin und Konzeptionsfähigkeit bei der Frau

Ogino K, 1930 · Arch. Gynak.