Smaller twins are not at risk of neonatal morbidity compared to their larger co-twins

Objective The purpose of this study was to evaluate whether smaller twins have an increased risk of neonatal morbidity compared to their co-twins.

Study design We reviewed medical records of a total of 478 twin pairs (gestational age at 24 weeks or more). Pregnancies complicated by in-utero fetal death or structural anomalies were excluded. There were 90 pairs of MCDA twin and 388 pairs of DCDA twin, and each group was subdivided into concordance group and discordance group. Discordance was defined as 25% or more of weight difference at birth. Neonatal morbidity was defined as one or more complications including respiratory distress syndrome, bronchopulmonary dysplasia, neonatal necrotizing enterocolitis and brain lesions such as periventricular leukomalacia, intraventricular hemorrhage and hypoxic-ischemic encephalopathy.

Results 1) In MCDA twins; Mean gestational age at birth was 35.9±3.0 weeks. Mean birth weights of each group were 2091±591 gram and 2435±592 gram respectively (p <.01). However, neonatal morbidity was not significantly different between smaller twins and their co-twins (5.6% (5/90) vs. 10.0% (9/90), NS). Even among 12 discordant twin pairs, there was no significant difference between smaller newborns and their co-twins (16.7% (2/12) vs. 25.0% (3/12), NS). 2) In DCDA twin; Mean gestational age at birth was 36.2±3.0 weeks and mean birth weights of each group were 2236±550 gram and 2543±577 gram (p<0.01). However, neonatal morbidity was not significantly different between the smaller twins and their co-twins (24/388 (6.2%) vs. 32/388 (8.3%), NS). Even among 38 discordant twin pairs, there was no significant difference between smaller twins and their co-twins (10.5% (4/38) vs. 15.8% (6/38), NS).

Conclusion This study suggests that neonatal morbidity is comparable between smaller twins and their co-twins irrespective of chorionicity.

Smaller twin - discordance - neonatal morbidity