בשל "הגנת זכויות יוצרים" מובא להלן קישור לתקציר המאמר. לקריאתו בטקסט מלא, אנא פנה/י לספרייה הרפואית הזמינה לך. 

 Infant boys have worse outcomes than girls. In twins, the ‘male disadvantage’ has been reported to extend to female co-twins via a ‘masculinising’ effect.

We studied the association between sex pairing and neonatal outcomes in extremely preterm twins.

Setting Eleven countries participating in the International Network for Evaluating Outcomes of Neonates.

Patients Liveborn twins admitted at 23–29 weeks’ gestation in 2007–2015.

Main outcome measures We examined in-hospital mortality, grades 3/4 intraventricular haemorrhage or cystic periventricular leukomalacia (IVH/PVL), bronchopulmonary dysplasia (BPD), retinopathy of prematurity requiring treatment and a composite outcome (mortality or any of the outcomes above).