Morbidity and Mortality of Very-Low-Birthweight Twin Infants according to Their Sex and the Sex of the Co-Twin: A Retrospective Cohort Study

Fermin García-Muñoz Rodrigo; Lourdes Urquía Martí; Carlos Zozaya Nieto; Gloria Galán Henríquez; Desiderio Reyes Suárez; Alejandro Avila-Alvarez; Josep Figueras Aloy; Maximo Vento

doi:10.1159/000531106

Morbidity and Mortality of Very-Low-Birthweight Twin Infants according to Their Sex and the Sex of the Co-Twin: A Retrospective Cohort Study

Neonatology. 2023;120(6):718-726. doi: 10.1159/000531106. Epub 2023 Aug 24.

Authors

Fermin García-Muñoz Rodrigo¹, Lourdes Urquía Martí¹, Carlos Zozaya Nieto², Gloria Galán Henríquez¹, Desiderio Reyes Suárez¹, Alejandro Avila-Alvarez³, Josep Figueras Aloy⁴, Maximo Vento⁵

Affiliations

¹ Department of Neonatology, Hospital Universitario Materno-Infantil, Las Palmas de Gran Canaria, Spain.
² Department of Neonatology, La Paz University Hospital, Madrid, Spain.
³ Division of Neonatology, Complexo Hospitalario Universitario de A Coruña (CHUAC), SERGAS, A Coruña, Spain.
⁴ Department of Neonatology, Hospital Clinic, Barcelona, Spain.
⁵ Division of Neonatology, University and Polytechnic Hospital La Fe, Valencia, Spain.

PMID: 37619541
DOI: 10.1159/000531106

Abstract

Introduction: The concept of male disadvantage regarding the prognosis of premature newborns was introduced more than half a century ago, and it has been corroborated over time. However, the influence of the sex of one twin on the outcomes of the other has yielded contradictory results.

Objective: The aim of the study was to determine if, in twin pregnancies of VLBW infants, the outcomes of one twin are modified by the sex of the co-twin.

Methods: A multicentre retrospective study of a cohort of infants admitted to the collaborating units of the Spanish SEN1500 neonatal network was conducted. Liveborn VLBW twin infants, from 23+0 to 31+6 weeks of gestational age (GA), admitted from 2011 to 2020 were included. Outborn patients, infants with major congenital anomalies, and cases with only one twin admitted were excluded. The main outcomes were survival until first hospital discharge, survival without moderate or severe bronchopulmonary dysplasia (BPD), survival without major brain damage (MBD), and survival without major morbidity. Incidence rate ratios (IRR) and 95% confidence intervals (CI) were calculated.

Results: 2,111 twin pairs were included. Male infants exhibited worse outcomes than females (IRR; 95% CI) regarding survival (0.96; 0.94, 0.98), survival without moderate or severe BPD (0.89; 0.86, 0.93), survival without MBD (0.94; 0.91, 0.97), and survival without major morbidity (0.87; 0.81, 0.93). Differences disappeared when the co-twin was a female infant: survival (1.00; 0.97, 1.03), survival without moderate or severe BPD (0.96; 0.91, 1.01), survival without MBD (0.99; 0.95, 1.04), and survival without major morbidity (0.94; 0.85, 1.03). Results for female infants did not change significantly with co-twin sex.

Conclusions: Among VLBW twins from 23+0 to 31+6 weeks of GA, male infants have higher risk of morbidity and mortality overall. In cases of pregnancies with different-sex foetuses, males seem to improve their results, while these do not change for females. The underlying mechanism of this influence deserves further investigation.

Keywords: Effect of co-twin sex; Morbidity; Survival; Very-low-birthweight twin infants.

MeSH terms

Bronchopulmonary Dysplasia* / epidemiology
Female
Gestational Age
Humans
Infant
Infant Mortality*
Infant, Newborn
Infant, Very Low Birth Weight
Male
Morbidity
Pregnancy
Retrospective Studies
Twins