O-198 Fecundity – a marker of health and survival?
Authors: Lindahl-Jacobsen R , Tavlo Petersson M , Runge Kjøbeløv Bjerregaard M , Saabye Simonsen C , Juel Ahrenfeldt L , Kold Jensen T 
Published: June 2022

Abstract

Study question
Fecundity (the ability to conceive) may be declining in many high income countries. Does long time to pregnancy reflect a worse of health condition and survival potential in couples?

Summary answer
We find that time to pregnancy as a marker of fecundity to be a strong maker of both health and survival in couples.

What is known already
Women have postponed their childbearing with an increased risk of infertility with age and many young men have a low semen quality. The effect of reduced fecundity on the societal level is obvious; a contribution to the reduced fertility in the Western world. The health consequences for the individuals suffering from reduced fecundity themselves have been studied to a less extend and mostly for males. Most of the research done within the research area have been based on produced offspring. One intrinsic and less explored question is how the ability to conceive influence health and survival in the affected couples.

Study design, size, duration
We performed a registry-based cohort study on 18,359 mothers and fathers with information on time to pregnancy. The mothers in the study population were first time mothers who attended prophylactic antenatal care between 1977 and 1987 at the department of Gynecology and Obstetrics at Odense University Hospital, Denmark. The study participants were followed up for survival and hospitalizations until 2018.

Participants/materials, setting, methods
Information on reproduction (including TTP), medical, occupational, and lifestyle histories was collected as a part of the first routine antenatal examination. Nationwide registries were used for gathering more information: Biological fathers were identified in the Danish Medical Birth Registry, total and causes of death was retrieved from the Danish Causes of Death Registry, information on dates of migrations from the Danish Population Registry, and hospitalizations from the Danish Hospital Discharge Registry.

Main results and the role of chance
We find a strong association between time to pregnancy and survival. Mothers with more than 12 months waiting time to pregnancy had an adjusted higher instant risk of dying compared to mothers with less than 12 months of waiting time to pregnancy (HR: 1.3, 95%CI: 1.1-1.5). Similar results were found for fathers (HR:1.2, 95%CI: 1.1-1.3). A clear dose-response association between time to pregnancy and survival in mothers and fathers was found. E.g. more than 60 months of waiting-time to pregnancy resulted in HR: 2.0, 95%CI 1.6-2.6 (mothers) and HR: 2.4, 95%CI:2.0-2.8 (fathers). No specific causes of death explained the overall increased mortality as increased risks was observed for nearly all causes. Time to first hospitalization was shorter for both fathers and mothers with long time to pregnancy (e.g HR: 1.32 , 95% CI: 1.16-1.51 for mothers with more than 60 months of waiting time to pregnancy) and a clear dose-respond effect was observed (p-trend&lt;0.001). No specific disease groups explained the overall higher hospitalization risk for persons with long waiting time to pregnancy as increased risks was observed for nearly all disease groups.

Limitations, reasons for caution
The study is comprised of couples conceiving a child and thus leave out those who fails. Thus, the found association between time to pregnancy and health and survival can only be inferred for mothers and fathers. We adjust for social-conditions, lifestyle and demographics but there may still be unknown confounders.

Wider implications of the findings
Our results suggest fecundity measured as time to pregnancy as an important marker of health and survival and may be a signal of increased environmental influence om reproductive and individual health.

Trial registration number
not applicable