Inclusion and exclusion criteria for malformations in newborn infants exposed to potential teratogens

The surveillance of newborn infants exposed to potential teratogens often relies on the findings in routine physicians' examinations to identify malformations. Exposed newborn infants can have a wide variety of physical features, including malformations, birth marks, positional deformities, and minor anomalies. The routine physician's findings are not standardized. Some physicians record a wide variety of physical features and others do not. The purpose of this study was to develop criteria and definitions for identifying malformations and for identifying the more common and less severe physical features that would be excluded as not being malformations.

The physical features recorded by the examining pediatricians were obtained from a review of the medical records of a consecutive sample of 1000 liveborn and stillborn infants and elective terminations for fetal anomalies.

A malformation, defined as a structural abnormality with surgical, medical or cosmetic importance, was present in 18 (2.8%) of the infants; 222 other recorded features were identified and excluded: malformations attributed to dominant or recessive genes (4) or chromosome abnormalities (6), minor anomalies and normal variations (65), birth marks (110), positional deformities (6), prematurity-related features (5), physiologic findings (4) and findings identified by prenatal ultrasound (but not by the examining pediatrician) (20), functional abnormalities (1) and findings in newborn screening (1).

Investigators should establish, in advance, the exclusion criteria to be used in programs, such as malformation surveillance programs or pregnancy registries, whose findings are based on a review of the routine examinations in medical records. It is essential that the same criteria be used in evaluating the drug-exposed and the unexposed comparison group.