OBJECTIVES: This study aimed to evaluate a fixed-duration algorithm for gestational age (GA) estimation according to pregnancy outcomes and to describe the GA distribution of pregnancy-related codes in Korea. METHODS: We included 351,055 pregnancy episodes (2019–2022) from linked data between the National Health Insurance Service and the Korea Immunization Registry Information System (KIRIS). GA from claims data was estimated by subtracting fixed durations from the delivery date (algorithm-based GA), and GA derived from KIRIS was defined as the gold standard. Accuracy was evaluated as the proportion of episodes in which the difference between the estimated GA and the reference standard fell within ±2 weeks. We described the distributions of the GA at which each prenatal test, pregnancy complication, and diagnostic code was recorded. RESULTS: Algorithm-based GA estimation showed high accuracy for live births (92.2% within ±2 weeks) but markedly lower accuracy for non-live birth outcomes, including stillbirth (3.3%), termination (7.2%), spontaneous abortion (45.2%), and ectopic pregnancy (20.0%). In additional analyses aimed at identifying potential indicators for improving GA estimation, most events occurred within clinically expected timeframes, although some individual codes exhibited poor temporal alignment. CONCLUSIONS Algorithm-based GA estimation using claims data performed well for live births but demonstrated limited accuracy for non-live birth outcomes. Incorporating information from prenatal tests and pregnancy complications may enhance GA estimation.

Oral corticosteroids (OCS) are frequently used during pregnancy, but patterns of their usage and indications are understudied. We described OCS utilization among pregnant women in South Korea using the Health Insurance Review and Assessment database, 2010–2021. Among 4,574,294 pregnancies, 6.2% (n = 283,001) were exposed to OCS, with the annual prevalence increasing from 4.98% in 2010 to 6.65% in 2021. Methylprednisolone and prednisolone accounted for 90% of OCS use during pregnancy, and the median duration of prescriptions was four days. Respiratory and skin diseases were the most common indications, and prescriptions for pregnancy-associated conditions increased notably after 2017, coinciding with insurance coverage for infertility treatments. OCS prescriptions declined during the first trimester and increased near delivery, suggesting discontinuation upon pregnancy recognition. Our findings highlight the common and increasing use of OCS during pregnancy, mainly for acute conditions, underscoring the need for further research on their safety in pregnant populations.

Oral corticosteroids (OCS) are frequently used during pregnancy, but patterns of their usage and indications are understudied. We described OCS utilization among pregnant women in South Korea using the Health Insurance Review and Assessment database, 2010–2021. Among 4,574,294 pregnancies, 6.2% (n = 283,001) were exposed to OCS, with the annual prevalence increasing from 4.98% in 2010 to 6.65% in 2021. Methylprednisolone and prednisolone accounted for 90% of OCS use during pregnancy, and the median duration of prescriptions was four days. Respiratory and skin diseases were the most common indications, and prescriptions for pregnancy-associated conditions increased notably after 2017, coinciding with insurance coverage for infertility treatments. OCS prescriptions declined during the first trimester and increased near delivery, suggesting discontinuation upon pregnancy recognition. Our findings highlight the common and increasing use of OCS during pregnancy, mainly for acute conditions, underscoring the need for further research on their safety in pregnant populations.

Oral corticosteroids (OCS) are frequently used during pregnancy, but patterns of their usage and indications are understudied. We described OCS utilization among pregnant women in South Korea using the Health Insurance Review and Assessment database, 2010–2021. Among 4,574,294 pregnancies, 6.2% (n = 283,001) were exposed to OCS, with the annual prevalence increasing from 4.98% in 2010 to 6.65% in 2021. Methylprednisolone and prednisolone accounted for 90% of OCS use during pregnancy, and the median duration of prescriptions was four days. Respiratory and skin diseases were the most common indications, and prescriptions for pregnancy-associated conditions increased notably after 2017, coinciding with insurance coverage for infertility treatments. OCS prescriptions declined during the first trimester and increased near delivery, suggesting discontinuation upon pregnancy recognition. Our findings highlight the common and increasing use of OCS during pregnancy, mainly for acute conditions, underscoring the need for further research on their safety in pregnant populations.

Oral corticosteroids (OCS) are frequently used during pregnancy, but patterns of their usage and indications are understudied. We described OCS utilization among pregnant women in South Korea using the Health Insurance Review and Assessment database, 2010–2021. Among 4,574,294 pregnancies, 6.2% (n = 283,001) were exposed to OCS, with the annual prevalence increasing from 4.98% in 2010 to 6.65% in 2021. Methylprednisolone and prednisolone accounted for 90% of OCS use during pregnancy, and the median duration of prescriptions was four days. Respiratory and skin diseases were the most common indications, and prescriptions for pregnancy-associated conditions increased notably after 2017, coinciding with insurance coverage for infertility treatments. OCS prescriptions declined during the first trimester and increased near delivery, suggesting discontinuation upon pregnancy recognition. Our findings highlight the common and increasing use of OCS during pregnancy, mainly for acute conditions, underscoring the need for further research on their safety in pregnant populations.