Factors Associated With Pregnancy and Childbirth Among Married Couples: A Longitudinal Analysis Using the 2012-2018 Korean Health Panel.

Introduction: South Korea is experiencing a demographic paradox of the lowest birth rate worldwide with the longest life expectancy. Many studies on pregnancy and childbirth primarily focused on women's factors, often overlooking the contribution of both spouses. However, men also play a vital role in creating an environment for bearing and raising children. In addition, pregnancy and childbirth are considered part of family formation, based on decisions made by the couple. Therefore, this study aimed to assess factors influencing pregnancy and childbirth in married women of childbearing age and their spouses using seven years of representative survey data from South Korea.

Methods: A total of 2,579 married women aged 20-49 years and their spouses were identified in the 2012-2018 Korean Health Panel (KHP). The outcome variables were pregnancy and childbirth. The generalized estimating equation model was adopted using covariates of women's and men's characteristics, comprising age, education, economic activity, smoking, drinking, physical activity, and body mass index (BMI), alongside having a family with children and income level as couple's characteristics.

Results: In 2012-2017, the annual cases of pregnancies and childbirth were 1.43% and 1.02% in women aged ≥35 years vs. 17.76% and 10.81% in women aged <35 years, among married women identified in the KHP. Maternal and paternal age was the prominent factor: the adjusted odds ratio (aOR) of giving childbirth was 0.23 (95% confidence interval (CI): 0.15-0.29) for women aged ≥35 years and 0.39 (95% CI: 0.27-0.54) for men compared to those aged <35 years. Childbirth was more likely to occur in women with higher education and childless families. In the sub-analysis, women's factors (e.g., alcohol consumption and infertility-related disease) and household income were more significant for women <35 years, but men's factors (e.g., BMI and physical activity) were more significant for women aged ≥35 years.

Conclusions: Our findings presented only partial and heterogeneous relations regarding pregnancy and childbirth, unlike many biomedical and clinical studies emphasizing age, BMI, or health behaviors as fertility indicators. Fertility might be influenced not only by biological factors but also by socioeconomic stability and both women's and men's factors, requiring caution in policy intervention.