SMFM Clinical Guideline: Nonimmune Hydrops Fetalis

By the Society for Maternal-Fetal Medicine with the assistance of Mary Norton, MD; Suneet P. Chauhan, MD; and Jodi Dashe, MD

This is a summary of the evidence-based SMFM guidelines for the evaluation and management of nonimmune hydrops fetalis (NIHF). The guidelines review the epidemiology, risk factors, work-up, prognosis, and treatment of pregnancies complicated by NIHF.

Q: What is the definition and frequency of hydrops fetalis?

A: Hydrops fetalis is a Greek term that describes pathological accumulation of fluid (‘ὕδωρ’ meaning water) in fetal soft tissues and serous cavities. The features are detected by ultrasound, and are defined as the presence of 2 or more abnormal fluid collections in the fetus. These include ascites, pleural effusions, pericardial effusion, and generalized skin edema (defined as skin thickness >5 mm). Other frequent sonographic findings include placental thickening (typically defined as a placental thickness >4 cm in the second trimester or >6 cm in the third trimester) and polyhydramnios (Figure 1). NIHF refers specifically to cases not caused by red cell alloimmunization.

With the development and widespread use of Rh (D) immune globulin, the prevalence of Rh (D) alloimmunization and associated hydrops has dramatically decreased. As a result, NIHF now accounts for almost 90% of cases of hydrops, with the prevalence in published series reported as 1 in 1700–3000 pregnancies.

Q: What are the risks factors for and causes of NIHF?

A: NIHF can result from a large number of underlying conditions (Table 1). The differential diagnosis is extensive, and success in identifying a cause partially depends on the thoroughness of efforts to establish a diagnosis. In 85% of cases of NIHF overall, a cause is identified; in 60% of cases, the determination is made prenatally.

Q: What is the work-up for NIHF?

A: Figure 2 describes one proposed algorithm for the work-up and evaluation of NIHF.

Q: What are the risks and frequency of complications of NIHF?

A: Polyhydramnios and preterm birth occur frequently with NIHF, with reported incidences as high as 29% and 66%, respectively. Women with NIHF may develop mirror syndrome, an uncommon complication in which the mother develops edema that “mirrors” that of her hydropic fetus. Mirror syndrome may represent a form of preeclampsia, and is characterized by edema in approximately 90%, hypertension in 60%, and proteinuria in 40% of cases. Because it is uncommon and likely underdiagnosed, the incidence is unclear. Resolution occurs with either treatment of the hydrops or delivery.

Q: What is the antenatal and delivery management for NIHF?

A: Management is guided by the presence or absence of additional anomalies. Sonographic evaluation should include a detailed survey for anomalies of the fetus, umbilical cord, and placenta, and estimation of amniotic fluid volume. A fetal echocardiogram should be performed, because fetal cardiac anomalies are among the most common causes of NIHF.

Recommended treatment depends on the underlying etiology and gestational age; preterm delivery is recommended only for obstetric indications, including development of mirror syndrome. Corticosteroids and antepartum surveillance may be an option for NIHF with an idiopathic etiology, an etiology amenable to prenatal or postnatal treatment, and when intervention is planned. should fetal deterioration occur. Antepartum surveillance is generally used in the setting of maternal or pregnancy complications associated with an increased risk of fetal demise, and when findings from surveillance will assist with delivery decisions.

In the absence of clinical deterioration or other indication for earlier intervention, delivery by 37 to 38 weeks should be considered. We recommend delivery in most cases if mirror syndrome develops.

If the parents and their physician have decided not to intervene for fetal indications (ie, to provide only comfort care upon delivery) vaginal delivery is preferred unless otherwise contraindicated. In general, fetuses with NIHF should be delivered at a facility equipped to stabilize and treat critically ill newborns.

Q: What is the prognosis of NIHF?

A: The prognosis depends on etiology, response to therapy if treatable, and the gestational age at detection and delivery. Aneuploidy confers a poor prognosis, and even in the absence of aneuploidy, neonatal survival is often less than 50%. In one recent prenatal series, survival was approximately 50%, and survival without major morbidities was only 25%. Hydrops that develops from treatable causes, such as fetal arrhythmia or infection with parvovirus B19, has a better prognosis. 

Reference

Norton ME, Chauhan SP, Dashe JS. Society for Maternal-Fetal Medicine (SMFM) Clinical Guideline #7: nonimmune hydrops fetalis. Am J Obstet Gynecol. Dec. 2014 [Epub ahead of print].