OBJECTIVES: Limited evidence is available regarding the impact of paternal occupation and its combined effect with maternal occupation on preterm birth. Therefore, we assessed the association of maternal and paternal occupations with preterm birth. METHODS: We used the national birth data of Korea between 2010 and 2020. Parental occupations were divided into 5 categories: (1) managers; (2) professionals, technicians, and related workers; (3) clerks and support workers; (4) service and sales workers; and (5) manual workers. A multinomial logistic regression model was used to calculate the adjusted odds ratios (aORs) of extremely, very, and moderate-to-late preterm births per occupational category considering individual risk factors. RESULTS: For the 4,004,976 singleton births, 40.2% of mothers and 95.5% of fathers were employed. Compared to non-employment, employment was associated with a lower risk of preterm birth. Among employed mothers, service and sales occupations were associated with a higher risk of preterm birth than managerial occupations (aOR, 1.06; 95% confidence interval [CI], 1.01 to 1.10 for moderate-to-late preterm births). The father’s manual occupation was associated with a higher risk of preterm birth (aOR, 1.09; 95% CI, 1.05 to 1.13 for moderate-to-late preterm) than managerial occupations. When both parents had high-risk occupations, the risk of preterm birth was higher than in cases where only the mother or neither of the parents had a high-risk occupation. CONCLUSIONS Paternal occupation was associated with preterm birth regardless of maternal employment and occupation and modified the effect of maternal occupation. Detailed occupational environment data are needed to identify the paternal exposures that increase the risk.

We explored the annual risks of mild and severe preeclampsia (PE) among nulliparous women. Using the National Health Information Database of South Korea, 1,317,944 nulliparous women who gave live births were identified. Mild PE increased from 0.9% in 2010 to 1.4% in 2019 (P for trend=0.006), while severe PE decreased from 0.4% in 2010 to 0.3% in 2019 (P=0.049). The incidence of all types of PE (mild and severe) showed no linear change (P=0.514). Adjusted odds ratio (OR) of severe PE decreased in 2013 (0.68; 95% confidence interval [CI]: 0.60, 0.77) and beyond compared to that in 2010, while the OR of mild PE increased in 2017 (1.14; 95% CI: 1.06, 1.22) and beyond. Mild PE was found to be less likely to progress to the severe form since 2010; however, the overall risk of PE among women did not change.

Background: We aimed to assess the risk of maternal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and early abortive outcomes after the association between coronavirus disease 2019 (COVID-19) vaccination during the preconceptional period and preclinical pregnancy, which are likely to be inadvertent vaccination. Methods: We used data from the Korea Disease Control and Prevention Agency-COVID19-National Health Insurance Service cohort from December 2020 to December 2021. The vaccinated pregnant women were matched to unvaccinated pregnant controls at a 1:4 ratio.The risks of SARS-CoV-2 infection and intensive care unit (ICU) admission within 14 days of infection were analyzed to assess its effectiveness. For safety measures, the adjusted relative risks (aRRs) of early abortive outcomes for the first COVID-19 vaccination during the preconceptional and preclinical periods were calculated considering covariates. We compared the risk of early abortion between mRNA and viral vector vaccines. Results: The overall COVID-19 vaccination rates during the preconceptional period and preclinical pregnancy were 3.1% (6,662/215,211) and 2.6% (5,702/215,211), respectively.The cumulative incidence of ICU admission within 14 days of SARS-CoV-2 infection was 6/100,000 in the unvaccinated group, whereas there were no ICU admissions in the vaccinated groups. The risks of early abortive outcomes were not significantly different between the preconceptional vaccination group and the unvaccinated group (aRR, 1.04; 95% confidence interval [CI],0.99–1.10) or between preclinical pregnancy vaccination and their matched controls (1.02; 95% CI, 0.96–1.08). mRNA and viral vector vaccines have shown similar risks for early abortive outcomes and miscarriages. Conclusion Our findings have provided compelling evidence regarding the effectiveness and safety of COVID-19 vaccination prior to and during early pregnancy. Further research is required to extend the safety and efficacy profiles of COVID-19 vaccines to pregnant women and their babies.