Congenital malformations, abnormal glucose tolerance, and estriol excretion in pregnancy.

Study of 10,454 consecutive newborn infants showed that 4.1% had a major malformation and 6.5% had a minor malformation. The incidence of major fetal malformations was increased in stillborn infants (14.1%), neonatal deaths (36.7%), and dysmature infants (8.6%), and when there was maternal hypoglycemia (5.8%, hyperglycemia (5.8%), or subnormal urinary estriol excretion (9.8%). Minor malformations were associated with fetal dysmaturity (9.7%) and subnormal estriol excretion (8.8%). Abnormalities of maternal glucose tolerance and urinary estriol excretion were associated with specific types of major malformations. These data showed that hypoglycemia was as important as hyperglycemia in the etiology of fetal malformations.