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Original Articles
Evaluation of gestational age by pregnancy outcomes and distribution of pregnancy-related codes in Korean claims data
Woo-Jung Kim, Yunha Noh, Yongtai Cho, Eun-Young Choi, HyunJoo Lim, Hyesung Lee, Ju-Young Shin
Epidemiol Health. 2026;48:e2026007.   Published online February 4, 2026
DOI: https://doi.org/10.4178/epih.e2026007
  • 3,216 View
  • 101 Download
AbstractAbstract AbstractSummary PDFSupplementary Material
Abstract
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.
Summary
Korean summary
본 연구는 국내 전국민 단위 청구자료와 예방접종 등록자료를 연계하여 고정 임신기간 기반 알고리즘의 재태연령 추정 정확도를 임신 결과별로 체계적으로 검증하였다. 출생아에서는 ±2주 기준 92.2%의 높은 정확도를 보였으나, 사산·인공임신중절·자연유산·자궁외임신 등 비출생 결과에서는 현저히 낮은 정확도를 보여 결과 유형에 따른 성능 이질성이 확인되었다. 산전검사 및 임신 합병증과 같은 시간 민감적 임상지표를 통합한 계층적 접근이 청구자료 기반 재태연령 추정의 타당도 향상에 기여할 수 있다.
Key Message
Using nationwide linked claims and immunization registry data in Korea, this study systematically validated the performance of a fixed-duration algorithm for gestational age estimation across pregnancy outcomes. While high accuracy was observed for live births (92.2% within ±2 weeks), substantially poorer performance was identified for non–live-birth outcomes, indicating marked outcome-specific heterogeneity. Integration of time-sensitive clinical indicators, including prenatal tests and pregnancy complications, may enhance the validity of gestational age estimation in administrative data research.
Impaired pulmonary function mediates the impact of preterm birth on later-life stroke: a 2-step, multivariable Mendelian randomization study
Xingzhi Guo, Peng Tang, Chen Hou, Yue Liu, Rui Li
Epidemiol Health. 2023;45:e2023031.   Published online March 3, 2023
DOI: https://doi.org/10.4178/epih.e2023031
  • 18,842 View
  • 204 Download
  • 7 Web of Science
  • 6 Crossref
AbstractAbstract AbstractSummary PDFSupplementary Material
Abstract
OBJECTIVES
Observational studies have suggested an association between preterm birth and stroke in late adulthood, but it remains unclear whether the association is causal. The purpose of this study was to evaluate the causal effects of gestational age on stroke and to determine the pathophysiological mechanisms underlying the causal associations.
METHODS
Two-sample Mendelian randomization (MR) was performed to assess the causal effects of fetal gestational duration, early preterm birth (EPB), preterm birth, or postterm birth on stroke and its subtypes. Two-step Mendelian randomization (TSMR) and multivariable Mendelian randomization (MVMR) were additionally used to determine the role of common stroke risk factors, including cardiovascular diseases, hypertension, pulmonary impairment, inflammation, and metabolic diseases, in mediating the causal associations between gestational age and stroke and its subtypes.
RESULTS
Genetically predicted EPB increased the risk of cardioembolic stroke (CES; odds ratio [OR], 1.115; 95% confidence interval [CI], 1.036 to 1.200; p=0.004) and large artery stroke (LAS; OR, 1.131; 95% CI, 1.031 to 1.241; p=0.009). The TSMR results showed that EPB was associated with a lower forced expiratory volume in the first second and forced vital capacity ratio (FEV1/FVC) (β=-0.020; 95% CI, -0.035 to -0.005; p=0.009), which increased the risk of CES and LAS. Further MVMR analysis showed that the associations between EPB and stroke disappeared after adjustment for FEV1/FVC.
CONCLUSIONS
Our data demonstrate that EPB is causally associated with an elevated risk of CES and LAS, and that pulmonary dysfunction mediates the causal impact of EPB on CES and LAS.
Summary
Key Message
Genetically predicted early preterm birth (EPB) is significantly associated with an increased risk of cardioembolic stroke (CES) and large artery stroke (LAS). Further multivariable Mendelian randomization analysis demonstrates that pulmonary impairment mediates the causal impact of EPB on CES and LAS in adulthood.

Citations

Citations to this article as recorded by  
  • Association between triglyceride glucose-waist-adjusted waist index and incident stroke in Chinese adults: a prospective cohort study
    Yaqin Ye, Zhenyi He, Jingguo Wu, Junlin Wu, Yanbing Liang
    Frontiers in Nutrition.2025;[Epub]     CrossRef
  • Causal associations of mood swings with preterm birth: a Mendelian randomization analysis
    Yuting Xia, Jianan Zhang, Yun Shang
    The Journal of Maternal-Fetal & Neonatal Medicine.2025;[Epub]     CrossRef
  • Methodological approaches, challenges, and opportunities in the application of Mendelian randomisation to lifecourse epidemiology: A systematic literature review
    Grace M. Power, Eleanor Sanderson, Panagiota Pagoni, Abigail Fraser, Tim Morris, Claire Prince, Timothy M. Frayling, Jon Heron, Tom G. Richardson, Rebecca Richmond, Jessica Tyrrell, Nicole Warrington, George Davey Smith, Laura D. Howe, Kate M. Tilling
    European Journal of Epidemiology.2024; 39(5): 501.     CrossRef
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    Mingzheng Li, Peng Shi, Huajie Yang, Suyuan Tong, Nianfeng Qiu, Fan Yao, Yuan Du, Shuhua Xi, Fei Wang
    Ecotoxicology and Environmental Safety.2024; 270: 115896.     CrossRef
  • Causal associations of circulating Helicobacter pylori antibodies with stroke and the mediating role of inflammation
    Xingzhi Guo, Peng Tang, Xin Zhang, Rui Li
    Inflammation Research.2023; 72(6): 1193.     CrossRef
  • Causal relationship between Helicobacter pylori antibodies and gastroesophageal reflux disease (GERD): A mendelian study
    Jiaqin Chen, Junning Zhang, Xiaolu Ma, Yuehan Ren, Yi Tang, Zhongmian Zhang, Wangyu Ye, Xiyan Zhang, Zili Lin, Lan Wang, Zhihong Li, Yasin Sahin
    PLOS ONE.2023; 18(12): e0294771.     CrossRef
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