Najaf Zare - Department of Biostatistics,Infertility Research Center,Shiraz University of MedicalSciences, Shiraz, Iran
Bijan Nouri - Social Determinants of HealthResearch Center, KurdistanUniversity of Medical Sciences,Sanandaj, Iran
Fariba Moradi - Family Health Unit, the Office ofVice Chancellor for HealthAffairs, Shiraz University of Medical Science, Shiraz, Iran
Maryam Parvareh - Social Determinants of HealthResearch Center, KurdistanUniversity of Medical Sciences,Sanandaj, Iran

Background: Time to first pregnancy (TTFP) has never been studied in an Iraniansetting. Lifestyle, occupational and environmental factors have been suggested toaffect the female reproduction.Objective: This study was conducted to measure TTFP in the south of Iran andsurvey the effects of several similar factors on TTFP by frailty models.Materials and Methods: The data on TTFP were available for 882 women whowere randomly selected from the rural population (the south of Iran). Only the firstand the planned pregnancies of every woman were included. The data were collectedretrospectively by using self-administered questionnaires. Frailty and shared frailtymodels were used to determine which factors had the highest impact on TTFP.Results: The median TTFP was 6.4 months and several factors were surveyed.However, only the age of marriage, height, maternal education and regularity ofmenstruation prior to conception were selected in the multivariable models.Conclusion: Among the several factors which were included in the study, the resultof frailty model showed that the height, age of marriage and regular menstruationseemed more notable predictors of TTFP.

Survival models, Frailty models, Fertility, Time to pregnancy