Turner syndrome morphology and morphometrics: Cardiac hypoplasia as a cause of midgestation death.

Background: A female fetus with massive truncal-limb hydrops and large, loculated, nuchal hygromas in midgestation is highly likely to have Turner syndrome. This phenotype is recognized to be usually lethal, with only more mildly affected fetuses surviving to term birth.

Methods: The morphology and morphometrics of 117 midgestation fetuses with phenotypic Turner syndrome were analyzed.

Results: More than 90% of fetuses with phenotypic Turner syndrome were found to have heart weights below the 2.5 centile, as well as lung hypoplasia and restricted limb growth for brain weight standards, although brain weight was only mildly reduced for gestational age. In contrast, subnormal heart weight was much less common among fetuses with other etiologies of hydrops, hygromas, or pleural effusions.

Conclusions: We hypothesize that myocardial hypoplasia is a primary defect in Turner syndrome, and it leads to or is a major contributor to the phenotypic features that end in midgestational death.