Nonimmune Hydrops Fetalis
Hydrops fetalis is the presence of excessive fluid in two or more fetal compartments including skin edema, pleural effusion, pericardial effusion, ascites, and polyhydramnios. Fetal hydrops can be immune or nonimmune. Ninety percent are nonimmune (not the result of red cell alloimmunization).
Nonimmune hydrops fetalis (NHF) can present as uterine size greater than dates due to polyhydramnios, decreased fetal movement, fetal compromise on fetal testing, and ultrasound findings. The diagnosis is made when increased amounts of fluid are seen in at least two fetal compartments. Ascites is an early sign and must be differentiated from pseudoascites. Pleural effusions may be unilateral or bilateral. Skin edema is usually a late sign and subcutaneous or scalp edema of greater than 5 mm is pathologic. Polyhydramnios is present in the majority of cases. The placenta may be abnormal in appearance (intervillous edema) and in thickness (thicker in certain infections or thin or compressed with polyhydramnios).
When the results both antenatal and postnatal evaluation are included, etiology of NHF can be determined in 60-85% of cases. Some common etiologies are:
- Aneuploidy has been reported in about 13% of cases. Monosomy X is the most common chromosomal cause. Trisomies 21, 18, 13, other very rare trisomies, and tetraploidy/triploidy are associated with most of the remainder. The prognosis is poor and NHF likely results from fluid accumulation due to cystic hygromas, obstruction or abnormalities in the lymphatic system, or cardiac defects. Certain genetic syndromes may also be associated, including skeletal dysplasias.
- Fetal metabolic storage diseases cause hydrops due to congestion caused by accumulation of metabolites in the liver and other abdominal viscera. Recurrence in subsequent pregnancies may be as high as 25%.
- Cardiovascular anomalies account for 20% of cases. Common intracardiac structural defects include hypoplastic left heart and isolated ventricular and atrial septal defects. Tachy- and bradyarrhythmias may cause high or low output cardiac failure. Vascular abnormalities including chorioangiomas of the placenta, fetal tumors, hemangiomas, umbilical cord aneurysms, and obstruction of the vena cava, portal vein, or femoral vessels can cause high output failure.
- Thoracic abnormalities such as congenital adenomatoid malformations of the lung increase intrathoracic pressure and obstruct venous return to the heart, resulting in peripheral venous congestion. Lymphatic obstruction may cause lymphedema.
- Anemia from hemorrhage, hemolysis, defective red cell production or abnormal hemoglobin production accounts for up to 25%. The pathogenesis involves high output cardiac failure. Hydrops may resolve in some cases when the anemia is corrected.
- Congenital Infections with toxoplasmosis, rubella, cytomegalovirus, and herpes (TORCH) organisms, parvovirus B19, syphilis, varicella, adenovirus, and coxsackie virus cause up to 8% of NHF. The mechanism is not clearly understood with all infections. Parvovirus causes hemolysis, hepatitis, and myocarditis.
- Gastrointestinal tract anomalies such as midgut volvulus result in ascites, edema, and polyhydramnios.
- Twin-to-twin transfusion syndrome in monochoroionic twins may result in NHF.
- Patient history regarding ethnicity, genetic abnormalities, metabolic diseases, and recent exposure to infections
- Ultrasound examination for structural defects
- Doppler assessment for middle cerebral artery peak systolic velocity for detection of anemia
- Laboratory tests include:
- Complete blood count with RBC indices
- Blood type and screen
- Serologic evaluation for infection
- Kleihauer-Betke acid elution
- Fetal karyotype
- Amniotic fluid assessment
- Umbilical blood sampling as indicated
Management depends on the cause. Mortality can be high and is generally higher with earlier gestational age at onset and with etiologies not amenable to intrauterine intervention. Management may include pregnancy termination, therapeutic interventions when appropriate, and supportive care as needed. Antenatal surveillance includes nonstress testing, biophysical profile, and Doppler studies as needed. Delivery should occur at a tertiary center with coordination by subspecialty personnel.
Society for Maternal-Fetal Medicine (SMFM), Norton ME, Chauhan SP, Dashe JS. Society for maternal-fetal medicine (SMFM) clinical guideline #7: nonimmune hydrops fetalis. Am J Obstet Gynecol. 2015 Feb;212(2):127-39. doi: 10.1016/j.ajog.2014.12.018. Epub 2014 Dec 31.
Initial approval January 2009; Revised January 2018. Reaffirmed July 2019
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