Gestational Age– and Altitude-Specific Hemoglobin Thresholds and Candidate Windows for Preterm Birth
13 affiliations
- 1Yunnan Provincial Key Laboratory of Public Health and Biosafety & School of Public Health, Kunming Medical University, Kunming, Yunnan, China
- 2School of Nursing, Kunming Medical University, Kunming, Yunnan, China
- 3First Affiliated Hospital of Kunming Medical University, Kunming, Yunnan, China
- 4Lijiang Maternal and Child Health Hospital, Lijiang, Yunnan, China
- 5Qujing Maternal and Child Health Hospital, Qujing, Yunnan, China
- 6Wenshan Zhuang and Miao Autonomous Prefecture People’s Hospital, Wenshan, Yunnan, China
- 7Linxiang District Maternal and Child Health Hospital, Lincang, Yunnan, China
- 8Global Research Center, School of Public Health, Kunming Medical University, Kunming, Yunnan, China
- 9Kunming Maternal and Child Health Hospital, Kunming, Yunnan, China
- 10The Second Affiliated Hospital of Kunming Medical University, Kunming, China
- 11University of Macau, Macau, China
- 12Yunnan University, Kunming, Yunnan, China
- 13School of Public Administration, Hangzhou Normal University, Hangzhou, Zhejiang, China
Abstract
Importance: Maternal hemoglobin is a clinically accessible biomarker of preterm birth (PTB) risk, but abnormal thresholds are inconsistent and do not account for variation by gestational age or altitude.
Objectives: To evaluate the association between maternal hemoglobin concentration and PTB across gestational ages and altitudes, including PTB subtype, and to define gestational age–specific, altitude-adapted hemoglobin thresholds and assessment windows.
Design, Setting, and Participants: This multicenter, retrospective cohort study used a multisource database integrating electronic medical records, preconception examination, and geospatial data from 5 medical centers in Yunnan, China, a region with a marked altitudinal gradient, and consecutively included singleton pregnancies delivered between January 1, 2017, and July 31, 2025.
Exposure: Prepregnancy and prenatal hemoglobin values were assessed. Prenatal measurements were grouped into 2-week intervals (target gestational week ±7 days), with 36 weeks analyzed separately.
Main Outcomes and Measures: Preterm birth was operationally defined as live birth from 28 weeks 0 days through 36 weeks 6 days of gestation.
Results: Of 141 943 singleton live births among women (mean [SD] maternal age, 29.7 [4.6] years), 12 607 (8.88%) were PTBs. Maternal hemoglobin measurement showed a gestational age–dependent U-shaped association with PTB, and thresholds varied across gestation. Compared with the intermediate group, a low hemoglobin concentration measured at 13 weeks (<12.00 g/dL; adjusted odds ratio [AOR], 1.46; 95% CI, 1.17-1.80) was associated with PTB, persisting from 27 weeks onward (<11.00 g/dL; AOR, 1.48; 95% CI, 1.25-1.74). A high hemoglobin concentration from 19 weeks onward was associated with PTB (>13.50 g/dL; AOR, 1.28; 95% CI, 1.04-1.55). At high altitude, thresholds were generally higher, and a low hemoglobin concentration from 21 weeks was persistently associated with PTB. Subtype analyses showed earlier low hemoglobin concentration associations for medically indicated PTB and middle- to late-pregnancy high hemoglobin concentration associations for both subtypes.
Conclusions and Relevance: In this cohort study, hemoglobin thresholds associated with PTB varied across gestation and were generally higher at high altitude; low- and high-hemoglobin assessment windows differed and varied by altitude. These findings may help refine gestational age– and altitude-specific interpretation of routine hemoglobin measurements and PTB risk assessment, pending external validation.
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BibTeX
@article{yan2026gestational,
title = {{Gestational Age– and Altitude-Specific Hemoglobin Thresholds and Candidate Windows for Preterm Birth}},
author = {Guanghong Yan and Xin Ning and Xueying Chen and Li Geng and Ping He and Tingting Xiao and Xiaomei Wang and Xiao Nong and Jiahui Xu and Yang Yang and Yongmei Wu and Ying Zhao and Songyuan Tang and Yuan Huang and Hua Bai and Yizhi Zhang and Zaiqing Qu and Mengqi Tao and Xiaofeng Zhang and Xiaoling Guo and Xinyue Jiang and Siguo Chen and Mengmei Liu and Sifan Duan and Hongtao Lei and Yani Li and Fahui Chen and Wenjing Xia and Lu Lu and Chang Shu and You Ren and Jiezi Yang and Jidong Huang and Jingjing Wang and Hongqing Zhang and Ye Li and Dingyun You},
journal = {JAMA Network Open},
year = {2026},
month = nov,
doi = {10.1001/jamanetworkopen.2026.42037},
url = {https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2856247},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - JOUR
TI - Gestational Age– and Altitude-Specific Hemoglobin Thresholds and Candidate Windows for Preterm Birth
AU - Guanghong Yan
AU - Xin Ning
AU - Xueying Chen
AU - Li Geng
AU - Ping He
AU - Tingting Xiao
AU - Xiaomei Wang
AU - Xiao Nong
AU - Jiahui Xu
AU - Yang Yang
AU - Yongmei Wu
AU - Ying Zhao
AU - Songyuan Tang
AU - Yuan Huang
AU - Hua Bai
AU - Yizhi Zhang
AU - Zaiqing Qu
AU - Mengqi Tao
AU - Xiaofeng Zhang
AU - Xiaoling Guo
AU - Xinyue Jiang
AU - Siguo Chen
AU - Mengmei Liu
AU - Sifan Duan
AU - Hongtao Lei
AU - Yani Li
AU - Fahui Chen
AU - Wenjing Xia
AU - Lu Lu
AU - Chang Shu
AU - You Ren
AU - Jiezi Yang
AU - Jidong Huang
AU - Jingjing Wang
AU - Hongqing Zhang
AU - Ye Li
AU - Dingyun You
PY - 2026
DA - 2026/11/04
JO - JAMA Network Open
DO - 10.1001/jamanetworkopen.2026.42037
UR - https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2856247
AB - Importance: Maternal hemoglobin is a clinically accessible biomarker of preterm birth (PTB) risk, but abnormal thresholds are inconsistent and do not account for variation by gestational age or altitude. Objectives: To evaluate the association between maternal hemoglobin concentration and PTB across gestational ages and altitudes, including PTB subtype, and to define gestational age–specific, altitude-adapted hemoglobin thresholds and assessment windows. Design, Setting, and Participants: This multicenter, retrospective cohort study used a multisource database integrating electronic medical records, preconception examination, and geospatial data from 5 medical centers in Yunnan, China, a region with a marked altitudinal gradient, and consecutively included singleton pregnancies delivered between January 1, 2017, and July 31, 2025. Exposure: Prepregnancy and prenatal hemoglobin values were assessed. Prenatal measurements were grouped into 2-week intervals (target gestational week ±7 days), with 36 weeks analyzed separately. Main Outcomes and Measures: Preterm birth was operationally defined as live birth from 28 weeks 0 days through 36 weeks 6 days of gestation. Results: Of 141 943 singleton live births among women (mean [SD] maternal age, 29.7 [4.6] years), 12 607 (8.88%) were PTBs. Maternal hemoglobin measurement showed a gestational age–dependent U-shaped association with PTB, and thresholds varied across gestation. Compared with the intermediate group, a low hemoglobin concentration measured at 13 weeks (<12.00 g/dL; adjusted odds ratio [AOR], 1.46; 95% CI, 1.17-1.80) was associated with PTB, persisting from 27 weeks onward (<11.00 g/dL; AOR, 1.48; 95% CI, 1.25-1.74). A high hemoglobin concentration from 19 weeks onward was associated with PTB (>13.50 g/dL; AOR, 1.28; 95% CI, 1.04-1.55). At high altitude, thresholds were generally higher, and a low hemoglobin concentration from 21 weeks was persistently associated with PTB. Subtype analyses showed earlier low hemoglobin concentration associations for medically indicated PTB and middle- to late-pregnancy high hemoglobin concentration associations for both subtypes. Conclusions and Relevance: In this cohort study, hemoglobin thresholds associated with PTB varied across gestation and were generally higher at high altitude; low- and high-hemoglobin assessment windows differed and varied by altitude. These findings may help refine gestational age– and altitude-specific interpretation of routine hemoglobin measurements and PTB risk assessment, pending external validation.
SN - 2574-3805
ER -