Organ asymmetries as correlates of other anomalies.

Fetuses with deviations in the normal left versus right weight relationships of the paired viscera were examined for correlation with particular malformations, syndromes, or other common factors. Alterations of the normal pattern were observed among cases with cytogenetic anomalies, diaphragmatic hernia, renal duplication, dyshydramnios, and single umbilical artery. A reversal of the left versus right weight pattern was found in the adrenals of cases with hepatic situs inversus but not in those with heterotaxic cardiac lesions. Recipient twins in the twin-twin transfusion syndrome had reduced left lung weights, presumably because of inhibition of lung growth by the enlarged heart. The side of umbilical artery absence did not predict either the nature or complexity of associated malformations. However, it is suggestive that there is discordance between the side of the missing artery and unilateral renal abnormality and that there is preferential absence of the right or left artery, depending on the karyotype.