The Use of Time to Pregnancy for Estimating and Monitoring Human Fecundity From Demographic and Health Surveys.

Background: Available studies on the prevalence of infertility have proved to have certain limitations, with a scarcity of population-based studies and inconsistent reporting from surveys in countries at all income levels. We wanted to test the applicability of the current duration approach to data from the important Demographic and Health Surveys (DHS) program, funded by USAID since its inception in 1985, https://dhsprogram.com/.

Methods: The current duration approach assumes that there is a well-defined time of initiation of attempts to get pregnant and defines the current duration of a still ongoing pregnancy attempt as the time interval from initiation to interview. The DHS interviews do not have an explicit question about initiation. We focused on nullipari and substituted date of "establishment of relationship with current partner" for initiation. Our study used the current duration approach on 15 datasets from DHS during 2002-2016 in eight different countries from sub-Saharan Africa, Asia, and Latin America.

Results: Well-established statistical techniques for current duration data yielded results that for some countries postulated surprisingly long median times to pregnancy and surprisingly high estimates of infertility prevalence. Further study of the data structures revealed serious deviations from expected patterns, in contrast to our earlier experience from surveys in France and the United States where participants were asked explicitly about time of initiation of attempts to become pregnant.

Conclusions: Using cohabitation as a proxy for the initiation of attempts to get pregnant is too crude. Using the current duration approach with DHS data will require more explicit questions during the DHS interviews about initiation of pregnancy attempt.