Zhong-Cheng Luo1, Fengxiu Ouyang2, Jun Zhang2, Mark Klebanoff3. 1. Ministry of Education, Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China; Department of Obstetrics and Gynecology, Sainte-Justine Hospital, University of Montreal, Montreal, QC, Canada. Electronic address: zhongcheng_luo3@163.com. 2. Ministry of Education, Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital, Shanghai Jiao-Tong University School of Medicine, Shanghai, China. 3. Research Institute at Nationwide Children's Hospital and the Departments of Pediatrics and Obstetrics and Gynecology, Ohio State University, Columbus, OH.
Abstract
OBJECTIVE: Second-born twins on average weigh less than first-born twins and have been reported at an elevated risk of perinatal mortality. Whether the risk differences depend on their relative birth size is unknown. The present study aimed to evaluate the association of birth order with perinatal mortality by birth order-specific weight difference in twin pregnancies. STUDY DESIGN: In a retrospective cohort study of 258,800 twin pregnancies without reported congenital anomalies using the US matched multiple birth data 1995-2000 (the available largest multiple birth dataset), conditional logistic regression was applied to estimate the odds ratio (OR) of perinatal death adjusted for fetus-specific characteristics (sex, presentation, and birthweight for gestational age). RESULTS: Comparing second vs first twins, the risks of perinatal death were similar if they had similar birthweights (within 5%) and were increasingly higher if second twins weighed progressively less (adjusted ORs were 1.37, 1.90, and 3.94 if weighed 5.0-14.9%, 15.0-24.9%, and ≥25.0% less, respectively), and progressively lower if they weighed increasingly more (adjusted ORs were 0.67, 0.63, and 0.36 if weighed 5.0-14.9%, 15.0-24.9%, and ≥25.0% more, respectively) (all P < .001). The perinatal mortality rates were not significantly different in cesarean deliveries or preterm (<37 weeks) vaginal deliveries but were significantly higher in second twins in term vaginal deliveries (3.1 vs 1.8 per 1000; adjusted OR, 2.15; P < .001). CONCLUSION: Perinatal mortality risk differences in second vs first twins depend on their relative birth size. Vaginal delivery at term is associated with a substantially greater risk of perinatal mortality in second twins.
OBJECTIVE: Second-born twins on average weigh less than first-born twins and have been reported at an elevated risk of perinatal mortality. Whether the risk differences depend on their relative birth size is unknown. The present study aimed to evaluate the association of birth order with perinatal mortality by birth order-specific weight difference in twin pregnancies. STUDY DESIGN: In a retrospective cohort study of 258,800 twin pregnancies without reported congenital anomalies using the US matched multiple birth data 1995-2000 (the available largest multiple birth dataset), conditional logistic regression was applied to estimate the odds ratio (OR) of perinatal death adjusted for fetus-specific characteristics (sex, presentation, and birthweight for gestational age). RESULTS: Comparing second vs first twins, the risks of perinatal death were similar if they had similar birthweights (within 5%) and were increasingly higher if second twins weighed progressively less (adjusted ORs were 1.37, 1.90, and 3.94 if weighed 5.0-14.9%, 15.0-24.9%, and ≥25.0% less, respectively), and progressively lower if they weighed increasingly more (adjusted ORs were 0.67, 0.63, and 0.36 if weighed 5.0-14.9%, 15.0-24.9%, and ≥25.0% more, respectively) (all P < .001). The perinatal mortality rates were not significantly different in cesarean deliveries or preterm (<37 weeks) vaginal deliveries but were significantly higher in second twins in term vaginal deliveries (3.1 vs 1.8 per 1000; adjusted OR, 2.15; P < .001). CONCLUSION: Perinatal mortality risk differences in second vs first twins depend on their relative birth size. Vaginal delivery at term is associated with a substantially greater risk of perinatal mortality in second twins.
Authors: Yoshie Yokoyama; Aline Jelenkovic; Reijo Sund; Joohon Sung; John L Hopper; Syuichi Ooki; Kauko Heikkilä; Sari Aaltonen; Adam D Tarnoki; David L Tarnoki; Gonneke Willemsen; Meike Bartels; Toos C E M van Beijsterveldt; Kimberly J Saudino; Tessa L Cutler; Tracy L Nelson; Keith E Whitfield; Jane Wardle; Clare H Llewellyn; Abigail Fisher; Mingguang He; Xiaohu Ding; Morten Bjerregaard-Andersen; Henning Beck-Nielsen; Morten Sodemann; Yun-Mi Song; Sarah Yang; Kayoung Lee; Hoe-Uk Jeong; Ariel Knafo-Noam; David Mankuta; Lior Abramson; S Alexandra Burt; Kelly L Klump; Juan R Ordoñana; Juan F Sánchez-Romera; Lucia Colodro-Conde; Jennifer R Harris; Ingunn Brandt; Thomas Sevenius Nilsen; Jeffrey M Craig; Richard Saffery; Fuling Ji; Feng Ning; Zengchang Pang; Lise Dubois; Michel Boivin; Mara Brendgen; Ginette Dionne; Frank Vitaro; Nicholas G Martin; Sarah E Medland; Grant W Montgomery; Patrik K E Magnusson; Nancy L Pedersen; Anna K Dahl Aslan; Per Tynelius; Claire M A Haworth; Robert Plomin; Esther Rebato; Richard J Rose; Jack H Goldberg; Finn Rasmussen; Yoon-Mi Hur; Thorkild I A Sørensen; Dorret I Boomsma; Jaakko Kaprio; Karri Silventoinen Journal: Twin Res Hum Genet Date: 2016-04 Impact factor: 1.587