To model the cumulative probability of pregnancy among couples with subfertility without a definitive diagnosis, according to different treatment strategies. A beta distribution of fecundity was fitted that reproduced the cumulative probability of pregnancy in prospective studies of natural fertility, and this distribution was applied to simulated cohorts starting with one million couples each. Probabilities of pregnancy were generated for each cycle of each couple. Simulation study. PATIENT(S): Hypothetic subfertile population. INTERVENTION(S): After 2 or 4 years of attempting pregnancy and diagnostic evaluation to exclude anovulation, tubal obstruction, and severe male factor, simulated treatments were applied to the remaining nonpregnant couples, with treatment effects based on published literature. MAIN OUTCOME MEASURE(S): Simulated cumulative probability of pregnancy. RESULT(S): Initially, the cumulative probability of pregnancy was highest for early treatment with IVF, but over time, conservative treatment or frequent intercourse approached the same cumulative probability. CONCLUSION(S): In couples without clear indications for IVF, the main benefit of early IVF may be to shorten time to pregnancy, a benefit that must be weighed against costs and potential adverse outcomes. Couples should be encouraged to maintain regular intercourse to maximize chances of pregnancy, even after unsuccessful treatment attempts.
Ecochard R et al., 2008·Reprod Biol Endocrinol·
Open Access
To assess the amount of variability in ovarian follicular growth rate and maximum follicular diameter related to different centers, women and cycles of the same women in a multicenter observational study of follicular growth. Secondary analysis of a prospective cohort study from eight centers in Europe. There were 533 ultrasound examinations in 282 cycles of 107 women with normal fertility. A random effects model with center, woman and cycle as hierarchical units of variation was used to analyze mean follicular diameter on days preceding ovulation. Follicular growth did not differ by center. There was homogenous growth across women and cycles, and the maximum follicular diameter before ovulation varied substantially across cycles but not across women. Many (about 40%) women had small maximum follicular diameter on the day before ovulation (<19 mm). Pre-ovulatory cycle length was not related to maximum follicular diameter. In normal fecundity, there is a substantial variation in maximum follicular diameter from cycle to cycle based on variation in the duration of follicular development, but the variation could not be explained by different characteristics of different women. Explanation of variation in follicular growth has to be found on the cycle level.
To model the effectiveness that can be obtained if levonorgestrel-only emergency contraception (EC) acts only through disrupting ovulation, in relation to other effects that may occur before or after fertilization and accounting for delays in administration. We modeled follicular growth as a function of follicular size, using known day-specific probabilities of conception and known disruption of ovulation by levonorgestrel-only EC, to estimate the expected effectiveness of EC. Combined data from multiple clinical studies. PATIENT(S): Simulation models. INTERVENTION(S): Disruption of ovulation. MAIN OUTCOME MEASURE(S): Effectiveness in the form of proportion of pregnancies prevented. RESULT(S): With disruption of ovulation alone, the potential effectiveness of levonorgestrel EC ranged from 49% (no delay) to 8% (72-hour delay). With complete inhibition of fertilization before the day of ovulation, the potential effectiveness of levonorgestrel EC ranged from 90% (no delay) to 16% (72-hour delay). CONCLUSION(S): The gap between effectiveness of levonorgestrel EC estimated from clinical studies and what can be attributed to disruption of ovulation may be explained by overestimation of actual effectiveness and supplementary mechanisms of action, including postfertilization effects. Additional data with follicular ultrasound and precise measures of delay between intercourse and EC administration would yield greater insight into effectiveness and mechanisms of action.
Mikolajczyk RT et al., 2006·Paediatr Perinat Epidemiol·
Approaches to measuring fecundity include the assessment of time to pregnancy and day-specific probabilities of conception (daily fecundities) indexed to a day of ovulation. In this paper, we develop an additional approach of calculating expected pregnancies based on daily fecundities indexed to the last day of the menstrual cycle. Expected pregnancies can thus be calculated while controlling for frequency and timing of coitus. Comparing observed pregnancies with expected pregnancies allows for a standardised comparison of fecundity between studies or groups within studies, and can be used to assess the effects of categorical covariates on the woman or couple level, and also on the cycle level. This can be accomplished in a minimal data set that does not necessarily require hormonal measurement or the explicit identification of ovulation. We demonstrate this approach by examining the effects of age and parity on fecundity in a data set from women monitoring their fertility cycles with the Creighton Model FertilityCare System.
To develop a new method for estimating the effectiveness of emergency contraception (EC) by using information about previous menstrual cycle length, accounting for the variation in the day of ovulation within the menstrual cycle, and comparing the validity of the new and previous methods. METHOD(S): Secondary analysis of a data set with a biological marker of ovulation and its distribution in the cycle. Based on a sample of cycles with known length and a known biological marker of ovulation, we simulated trials of predetermined EC effectiveness and then calculated estimates of EC effectiveness based on old and new methods. RESULT(S): Under some conditions, all methods produced biased estimates of effectiveness with simulated trials, especially when the actual effectiveness was low. The systematic bias was minimized with the new method. The new method was robust with regard to the distribution of the day of intercourse in women presenting for EC. CONCLUSION(S): Future studies of EC effectiveness should consider both the uncertainty in predicting the day of ovulation and previous cycle length. Our estimates of daily fecundity should be replicated with other data sets.
Baerwald et al. (1) proposed a new model for ovarian follicular development in the human menstrual cycle. They showed additional waves of follicular development in the follicular and luteal phase of normal ovulatory cycles. Although no additional ovulation was observed, the authors speculated that the anovulatory follicles from the additional waves of follicular development may be able to ovulate in the presence of an additional LH surge.
A discrepancy exists between the interest in modern methods of natural family planning (NFP) and their actual use in developed countries. To explore reasons for this discrepancy, we analyzed data from a questionnaire administered to postpartum women in Berlin (n = 223) and Cracow (n = 233). Knowledge of NFP, past use of NFP and expected effects of abstinence on the partnership were independently associated with interest in using NFP, but not the choice to do so among those interested. Desire for future pregnancies, importance of religious belief and location in Cracow were independently associated with the choice to use NFP among those interested. Perceived accuracy of observation to identify the fertile time and acceptance of own body were independently associated with both interest in and choice to use NFP. Frequency of intercourse had no effect on interest. These results suggest that increased access and cultural support would likely lead to a higher prevalence of NFP use in developed countries.
There are many potential mechanisms of action for the intrauterine device (IUD), which vary by type of IUD (inert, copper, or hormonal). This paper reviews the evidence for each potential mechanism of action. On the basis of available data for fertilization rates and clinical pregnancy rates, the relative contribution of mechanisms acting before or after fertilization were quantitatively estimated. These estimates indicate that, although prefertilization effects are more prominent for the copper IUD, both prefertilization and postfertilization mechanisms of action contribute significantly to the effectiveness of all types of intrauterine devices.