Is cardiac disease the most common cause of fetal hydrops regardless of gestational age?

Is Cardiac Disease the Most Common Cause of Fetal Hydrops?

Yes, cardiovascular abnormalities are the most common single cause of non-immune hydrops fetalis (NIHF) overall, accounting for 17-35% of cases across all gestational ages. 1

Cardiovascular Causes Predominate Across Gestational Ages

• Cardiac etiologies represent the leading identifiable cause of NIHF in most large series, regardless of when hydrops is diagnosed. 1

• The cardiovascular category encompasses structural cardiac defects (particularly right heart lesions), arrhythmias (supraventricular tachycardia, atrial flutter, congenital heart block), cardiomyopathy, cardiac tumors, and vascular abnormalities. 1

• These cardiac causes lead to hydrops through increased central venous pressure from structural malformations or inadequate diastolic ventricular filling. 1

Important Gestational Age Nuance

• Before 24 weeks gestation, chromosomal abnormalities (particularly Turner syndrome and trisomy 21) become the predominant cause, accounting for 45% of early-onset cases. 2, 3

• After 24 weeks, cardiac causes—especially fetal tachyarrhythmias and structural defects—reassert dominance as the most common etiology. 3

• In prenatal series focusing on early gestation, aneuploidy may be reported as the most common cause, but this reflects the timing of diagnosis rather than overall prevalence. 1

Other Major Etiologies

• Chromosomal abnormalities account for 7-16% of all NIHF cases across gestation. 1

• Hematologic disorders (including alpha thalassemia, which causes 28-55% of cases in Southeast Asian populations but only ~10% elsewhere) represent 4-12% overall. 1

• Infectious causes contribute 5-7%, thoracic abnormalities 6%, and twin-twin transfusion syndrome 3-10%. 1

• Idiopathic cases still comprise 15-25% despite thorough evaluation. 1

Clinical Implications

• The poor prognosis of cardiac structural abnormalities is critical—combined fetal and infant mortality reaches 92%, primarily due to the severity of defects causing in utero congestive heart failure. 1

• Fetal tachyarrhythmias, while cardiac in origin, are among the most treatable causes and should be managed with transplacental antiarrhythmic medications. 1

• Comprehensive fetal echocardiography is mandatory in every hydrops workup to identify these cardiac causes, as they are both the most common etiology and carry critical prognostic implications. 4

Common Pitfall

• Do not assume chromosomal abnormalities are the most common cause overall—while they predominate in early gestation (<24 weeks), cardiovascular causes are the leading single etiology when all gestational ages are considered together. 1, 3