Introduction

The pathophysiology of immune and nonimmune fetal hydrops is multifactorial and complex. Fetal hydrops is a sign, not a diagnosis, and should prompt the question “What is the cause?”

The fetal component signs of hydrops, usually identified by ultrasound imaging, are:

In addition to the fetal morbidity and mortality associated with fetal hydrops, a secondary maternal “mirror syndrome” can occur, with findings of:

Fetal hydrops is conventionally divided into two etiologic groups:

IFH now accounts for only 10–15% of all cases of fetal hydrops. The incidence has decreased significantly since the introduction of preventative antenatal prophylaxis programs directed against rhesus D (RhD) red cell antigen isomimmunization. This commonly involves administration of anti-D immunoglobulin at 28 weeks for all RhD-negative pregnant women, and postpartum administration of anti-D for RhD-negative women with an RhD-positive newborn. The other RBC surface antigens that cause IFH do not have a directed immunoglobulin prophylaxis treatment available. Thus, they now comprise a greater proportion of IFH cases. The red cell antigens that are particularly common in this respect are antigens E, c, and Kell. Antigens FYa (Duffy) and JKa (Kidd) present much less commonly.

NIFH comprises 85–90% of total fetal hydrops cases. The causes include genetic (recessive or dominant inheritance, or chromosomal abnormalities), structural malformations, infection, metabolic causes, and monochorionic twin placental vascular anomalies.

Perinatal mortality and morbidity for fetal hydrops is high irrespective of the cause. Prenatal fetal therapy for IFH using intrauterine transfusion has been very successful in reducing the incidence of perinatal mortality when initiated early in the pathophysiological process. The management options for IFH are discussed in Chapter 12.