The neonatal morbidity and mortality rate of 335 twin pairs born during the years
1965-1973 was investigated. 649 twins were born alive. 29 % of the twins were preterm.
31 % of the twins were small for date infants, and 41 % weighed less than 2 500 g.
Mean birth weight was 2 590 g in A twins and 2 560 g in B twins. The neonatal mortality
(0-28 days) was 7.1 %. The most common causes of death were the respiratory distress
syndrome, intracranial haemorrhage and anoxia. Low one minute Apgar scores occurred
more often in B twins than among A twins. Breech delivery gave low one minute Apgar
scores more often than did spontaneous vertex delivery in both twins. Full term twins
and infants weighing more than 2 500 g had fewer low one minute Apgar scores than
the preterm infants and those with low birth weight. Neonatal disorders were equally
common in both twins except the birth asphyxia and/or aspiration syndrome, which were
more frequent in the B twins. The respiratory distress syndrome was diagnosed in 8
% of A twins and 12 % of B twins. Hypoglycaemia was recorded for 8 %, and hyperbilirubinaemia
exceeding 15 mg % for 7 %. Infections occurred in 6 %. Transfusion syndrome was verified
in 7 % and malformations in 6 %. Although mortality in twin pregnancies has declined,
neonatal morbidity is very high. Twin pregnancies thus form a high risk group for
obstetricians and pediatricians.