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. 1972 Dec;6(3):271-9.
doi: 10.1002/tera.1420060304.

Independent effects of maternal age and birth order on the incidence of selected congenital malformations

S Hay, H Barbano

Independent effects of maternal age and birth order on the incidence of selected congenital malformations

S Hay et al. Teratology. 1972 Dec.

Abstract

PIP: Incidence rates, specific for maternal age and birth order, were calculated for 16 categories of congenital malformations reported on birth certificates from a population of more than 8 million registered, white, single livebirths. With maternal age held constant, none of the malformations showed increasing incidence as birth order increased. Hypospadias, esophageal defects, omphalocele, and Down syndrome showed evidence of decreasing incidence as birth order increased. Some of the other malformation categories showed an excess of 1st births in most age groups, while no relation to birth order was observed in the incidence of other malformations. By contrast, most of the malformations analyzed exhibited increasing incidence as maternal age increased. Especially high rates of several malformations were observed among 1st births to women over age 40.

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