Assessment of gestational age in twins.

Pairs of twins born concordant for weight score equally on both neurological and external criteria. The assessed gestational age of discordant twins is significantly different; while scoring equally on neurological criteria, the lighter twin scores less on external criteria. It is suggested that this pattern of underscoring may also be present in growth retarded singletons. If external criteria are used in estimating the gestational age of growth retarded infants, the results should be interpreted with caution.