Time to Pregnancy: Methodological Insights and New Results

Zsuzsanna Makay, Hungarian Demographic Research Institute
Laura Szabó , Hungarian Demographic Research Institute

Postponement of childbirth is one of the main characteristics of the demographic changes that took place in the last decades in developed countries. An important consequence of delayed childbearing is the increase of subfertility and infertility in both women and men. According to previous studies, the probability of conceiving decreases with age, and so does the probability of live birth. Several studies have shown that, as a consequence, female fertility has a “best-before date” of 35 years, while men’s is probably around 40 years. However, the results are not unanimous. Some studies don’t show any effect of age on the probability of conception, while others point to important differences in the results according to the definition of the sample. The aim of our study is to clarify the importance of sample definition showing that in a sample of pregnant women, who are asked about time to conception, results depend mainly on the time scale used in the definition of time to pregnancy (TTP) because of an important bias in the population. Our results show that, in contrast to previous ones which showed a cut-off age of 35, women aged 25 and over already had a longer time to pregnancy than women under this age. The effect of lifestyle factors such as smoking and body mass index, is confirmed as is the fact that having already had a child makes the arrival of a new pregnancy less problematic.

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 Presented in Session 115. Novel Applications of Traditional Tools in Fertility Studies