Bijun Shi,1– 4 Xiaohua Tan,1 Qian Chen,1 Danfang Lu,5,* Shuhua Ren,6,* Kang Huang,7,* Wei Shen,8,* Zhifeng Chen,9,* Jin Liu,10,* Chuming You,11,* Guifang Li,12,* Hong Jiang,13,* Hongping Rao,14,* Jianwu Qiu,15,* Xian Wei,16,* Yayu Zhang,17,* Xiaobo Lin,18,* Haiyan Jiang,19,* Shasha Han,20,* Fan Wang,21,* Xiufang Yang,22,* Yitong Wang,23,* Niyang Lin,24,* Lizi Lin,25 Xinzhu Lin,8 Qiliang Cui1 

1Department of Neonatology, Guangdong-Hong Kong-Macao Greater Bay Area Higher Education Joint Laboratory of Maternal-Fetal Medicine, The Third Affiliated Hospital, Guangzhou Medical University, Guangzhou, 510150, People’s Republic of China; 2Department of Neonatology, Guangdong Provincial Key Laboratory of Major Obstetric Diseases, Guangzhou, 510150, People’s Republic of China; 3Department of Neonatology, Guangdong Provincial Clinical Research Center for Obstetrics and Gynecology, Guangzhou, 510150, People’s Republic of China; 4Department of Neonatology, Guangzhou Key Laboratory of Neonatal Intestinal Diseases, Guangzhou, 510150, People’s Republic of China; 5Department of Pediatrics, Peking University Third Hospital, Beijing, 100000, People’s Republic of China; 6Department of Neonatology, Sichuan Jinxin Xinan Women & Children’s Hospital, Chengdu, 610001, People’s Republic of China; 7Department of Neonatology, Affiliated Hospital of Guizhou Medical University, Guiyang, 550000, People’s Republic of China; 8Department of Neonatology, Women and Children’s Hospital, School of Medicine, Xiamen University, Xiamen, 361000, People’s Republic of China; 9Department of Neonatology, The Tenth Affiliated Hospital of Southern Medical University, Dongguan, 523000, People’s Republic of China; 10Department of Neonatology, The First Affiliated Hospital of Shaoyang University, Shaoyang, 422000, People’s Republic of China; 11Department of Neonatology, The Affiliated Guangdong Second Provincial General Hospital of Jinan University, Guangzhou, 510000, People’s Republic of China; 12Department of Neonatology, Cangzhou People’s Hospital, Cangzhou, 061000, People’s Republic of China; 13Department of Neonatology, Yanan University Affiliated Hospital, Yan’an, 716000, People’s Republic of China; 14Department of Neonatology, Huizhou Central People’s Hospital, Huizhou, 516000, People’s Republic of China; 15Department of Neonatology, Affiliated Yuebei People’s Hospital of Shantou University Medical College, Shaoguan, 512026, People’s Republic of China; 16Department of Neonatology, Xiaogan Hospital Affiliated to Wuhan University of Science and Technology, Xiaogan, 432000, People’s Republic of China; 17Department of Neonatology, The Affiliated Hospital of Inner Mongolia Medical University, Hohhot, 010000, People’s Republic of China; 18Department of Neonatology, The Second Affiliated Hospital of Shantou University Medical College, Shantou, 515000, People’s Republic of China; 19Department of Neonatology, The Third Staff Hospital of Baogang Group, Baotou, 014000, People’s Republic of China; 20Department of Neonatology and Pediatrics, The First Affiliated Hospital of Jinan University, Jinan University, Guangzhou, 510000, People’s Republic of China; 21Department of Neonatology, Lanzhou University Second Hospital, Lanzhou, 730000, People’s Republic of China; 22Department of Neonatology, Zhongshan City People’s Hospital, Zhongshan, 528400, People’s Republic of China; 23Department of Neonatology, The Binhaiwan Central Hospital of Dongguan, Dongguan, 523000, People’s Republic of China; 24Department of Neonatology, The First Affiliated Hospital of Shantou University Medical College, Shantou, 515000, People’s Republic of China; 25Department of Occupational and Environmental Health, School of Public Health, Sun Yat-sen University, Guangzhou, 510000, People’s Republic of China

*These authors contributed equally to this work

Correspondence: Xinzhu Lin, Email xinzhufj@163.com Qiliang Cui, Email cuiql_gysy@163.com

Background: Twin pregnancies, accounting for a rising proportion of births globally, present significant public health challenges in China. Birthweight discordance (BWD), a critical complication, remains understudied in its epidemiological context, particularly regarding its population-level associations with adverse neonatal outcomes.
Methods: This multi-center, retrospective cohort study leveraged data from 21 hospitals across 18 Chinese cities (2018– 2020) to assess BWD and its epidemiological implications. Ordinal logistic regression with random effects was used to explore their association. BWD was defined as: [(larger birthweight − smaller birthweight) / larger birthweight] × 100% and categorized into four grades: I (≤ 15%), II (> 15% to 20%), III (> 20% to 25%), and IV (> 25%).
Results: Among 6437 twin pairs, 73.6% were classified as Grade I (no BWD), while 10.7%, 7.1%, and 8.6% constituted Grades II, III, and IV discordance, respectively. Dose-response relationships emerged: each incremental BWD elevated risks of small vulnerable newborns (aOR = 1.83, 95% CI 1.76– 1.90), small for gestational age (aOR = 1.23, 95% CI 1.18– 1.29), low birthweight (LBW, aOR = 1.16, 95% CI 1.13– 1.20), very LBW (aOR = 1.63, 95% CI 1.53– 1.73) and extreme LBW (aOR = 1.82, 95% CI 1.61– 2.05). Smaller twins exhibited disproportionately higher adverse outcome rates than larger twins. Sensitivity analyses confirmed robustness across specific subgroups.
Conclusion: BWD exceeding 20% affects 15.7% of live-born twins in China, mirroring rates in high-income settings. BWD demonstrates strong dose-response relationships with adverse outcomes, validating its utility for twin health stratification. These findings call for integrating BWD assessment into prenatal surveillance and risk-adapted care to reduce neonatal morbidity/mortality, urging clinicians and policymakers to prioritize perinatal outcome equity.

Keywords: twins, birthweight discordance, perinatal epidemiology, adverse birth outcomes, public health, multi-center study