Relationship of mode of conception and sex concordance with mortality/morbidity in preterm twins.

OBJECTIVE

To assess the association of mode of conception and sex concordance with neonatal outcomes in very preterm twins.

STUDY

DESIGN

Twin pairs born at gestational age ≤ 32 weeks and admitted to a Level 3 neonatal intensive care unit (NICU) in 2010-2011 were retrospectively identified from the Canadian Neonatal Network™ database. A composite outcome representing neonatal mortality or any severe morbidity (intraventricular hemorrhage grades ≥ 3 or periventricular leukomalacia, retinopathy of prematurity stages ≥ 3, bronchopulmonary dysplasia, or necrotizing enterocolitis stages ≥ 2) was compared between twins conceived using assisted reproduction technologies (ARTs) or spontaneously (SP), and tested for association with sex concordance in individual-level and pair-wise multivariable logistic regression analyses.

RESULTS

Study subjects included 1,508 twins from 216 ART (53 [25%] male-male, 104 [48%] male-female, and 59 [27%] female-female) and 538 SP (192 [36%] male-male, 123 [23%] male-female, and 223 [41%] female-female) pairs. No statistically significant association was detected between mode of conception and the composite outcome of mortality/morbidities. The composite outcome was significantly higher in same-sex than in opposite-sex twins (OR = 1.68; 95% CI = [1.09, 2.59]). This relationship was most pronounced in ART pairs (OR = 2.25; 95% CI = [1.02, 4.98]), with increased rates in one or both twins from male-male versus opposite-sex ART pairs (OR = 3.0; 95% CI = [1.07, 8.36]).

CONCLUSION

Same-sex pairing was associated with higher mortality/morbidities in very preterm twins admitted to the NICU, and can be used in clinical practice to identify twins at higher risk of adverse neonatal outcomes.