345 - Mortality and Morbidity in Extremely Preterm Twins with Birth Weight Discrepancies: A Nationwide Cohort Study from Japan

Publication Number: 345.5750

Chi-Nien Chen, National Taiwan University Hospital Hsinchu Branch, Hsinchu, Hsinchu, Taiwan (Republic of China); Yasuhisa Ikuta, National Center for Child Health and Development, Okura, Setagaya-ku, Tokyo, Japan; Hidehiko Maruyama, National Center for Child Health and Development, Setagaya, Tokyo, Japan; Masayo Kokubo, Nagano Children's Hospital, Azumino, Nagano, Japan; Hidehiko Nakanishi, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan; Shinya Hirano, Osaka Women's and Children's Hospital, Izumi, Osaka, Japan; Po-Nien Tsao, National Taiwan Univsersity Hospital, Taipei, Taipei, Taiwan (Republic of China); Yushi Ito, National Center for Child Health and Development, Tokyo, Tokyo, Japan; Satoshi Kusuda, Neonatal Research Network of Japan, Taito, Tokyo, Japan; Tetsuya Isayama, National Center for Child Health and Development, Setagaya-ku, Tokyo, Japan

Background: Discordant twins may have a higher risk of mortality and morbidity compared to concordant twins. Previous studies have mainly analyzed twins born at later gestational ages, leaving the evidence for extremely preterm births unclear.

Objective: This study aims to assess how birth weight discrepancy affects mortality and morbidity in preterm infants born before 28 weeks of gestation.

Design/Methods: This study utilized data from the Neonatal Research Network Japan with extremely preterm twins born between 2003 and 2022. We compare the mortality rate and risk of other major complications between discordant twins with a birth weight discrepancy (BWD) of over 20% and concordant twins (BWD < 20%). Generalized Linear Mixed Models (GLMM) were used, and comparisons were made among twins with BWD of < 20%, 20-30%, 30-40%, 40-50%, and > 50% to assess the presence of a dose-response relationship. Odds ratios (ORs) with 95% confidence intervals (CI) were estimated, adjusted for potential confounders, and stratified by gestational age, birth year, and chorionicity.

Results: A total of 3,762 twin pairs were analyzed, of which 978 pairs (26%) were discordant twins, the majority of whom were monochorionic (Figure 1) (Table 1). In terms of in-hospital mortality, both the smaller (adjusted Odds Ratios [aORs] 2.29, 95% CI 1.53-3.42) and larger (aORs 1.55, 95% CI 1.06-2.27) discordant twins showed higher mortality risks compared to concordant twins in the adjusted model (Table 2). Further analysis based on BWD range revealed that in smaller discordant twins, the mortality risk increased progressively with greater BWD. In subgroup analysis by chorionicity, monochorionic twins with a larger range of BWD exhibit a significant dose-response effect, particularly in the smaller monochorionic twin. Regarding severe neonatal morbidity outcomes, smaller discordant twins showed significantly increased risks for necrotizing enterocolitis (NEC) or spontaneous intestinal perforation (SIP). Conversely, larger discordant twins exhibited significantly increased risks for bronchopulmonary dysplasia (BPD) and death, periventricular leukomalacia (PVL), and NEC or SIP.

Conclusion(s): In discordant extremely preterm twins, both the larger and smaller cases exhibit increased mortality and associated severe morbidity risks compared to concordant twins. This study confirms that in smaller discordant twins, the risk of mortality shows a dose-response increase with greater weight discrepancy. For clinical follow-up of extremely preterm twins, it is recommended to develop targeted risk monitoring plans when there is a significant weight discrepancy.

Figure 1. Flow chart of study participants


Table 1. Clinical characteristics of study participants
*The statistical analyses were conducted using t-tests for continuous variables and chi-square tests for categorical variables to examine group differences.

Table 2. Association between mortality and different birth weight differences among discordant and concordant twins.
*Adjusted with gestational age, z-score for birth weight, gender, birth year, maternal age at childbearing, maternal hypertensive disorders during pregnancy, antenatal steroid administration, cesarean delivery, and chorionicity. The reference group for the adjusted regression is the concordant twin group.