Hydrops fetalis means the abnormal collection of fluid in fetal soft tissues and serous cavities. Nonimmune hydrops fetalis (NIHF) includes cases not affected by red cell alloimmunization. The incidence of NIHF is 1:1500 to 1:4000. At the moment, NIHF includes about 90% of hydrops fetalis cases (1-2).
The prenatal diagnosis of hydrops fetalis is based on ultrasound examination findings, including two or more of the following: ascites, pleural effusion, pericardial effusion, Skin edema (>5 mm). The etiology is determined in 60% to 85% of cases, prenatally or postnatally (3). The etiology of hydrops cases is related to the gestational age of presentation. NIHF before 24 weeks of gestation is usually related to an aneuploidy, whereas cardiac and pulmonary anomalies, and infectious disease cause most cases after 24 weeks of gestation (4). Cardiovascular abnormalities are reported in 40% of cases of NIHF (5). Aneuploidy is responsible for seven to 16% of NIHF cases. The most common aneuploidy associated with NIHF is monosomy X (5). Severe fetal anemia due to high output cardiac failure (6) accounts for 10% to 27% of cases (5). Infections are responsible for five to 10% percent of NIHF cases (7). Parvovirus B19 is the most common infection in hydropic fetuses. Thoracic anomalies account for 10% of the cases. Primary congenital pulmonary lymphangiectasis results from thoracic duct obstruction, while secondary congenital pulmonary lymphangiectasis results from thoracic masses or congenital heart disease (8-9). Fetal/placental vascular tumors due to arteriovenous shunting and high cardiac output failure can lead to hydrops. Metabolic disorders include a group of autosomal recessive diseases present in the fetal period as NIHF (7). Skeletal dysplasias may be the cause of nonimmune hydrops fetalis (7).
NIHF is associated with a perinatal mortality rate of 50% to 98% (10-12). Prognosis depends on the etiology, the gestational age at the onset of hydrops, the gestational age at delivery, and the presence of pleural effusions. Generally, the early hydrops is associated with poorer outcome. Pleural effusions and polyhydramnios before 20 weeks of gestation due to increased risks of pulmonary hypoplasia and preterm delivery are poor prognostic factors. The absence of aneuploidy and major structural anomalies have a better outcome (13).
The present report explains a case of hydrops fetalis with unknown etiology and complete resolution after birth.

 

Case Presentation

A 31 years old gravid2 woman with a previous cesarean delivery was referred to Yas hospital at 30 weeks of gestation. The chief complaint was labor pain, and the patient had an ultrasound report of polyhydramnios (AF=38) that had been performed about two weeks ago. Our center's ultrasonographic examination showed severe hydrops fetalis with generalized edema, bilateral hydrothorax and collapsed lungs, and pericardial effusion (see Figures 1-7). The amniotic fluid index was 45cm; neither anemia nor fetal anomaly was detected. Biometric parameters were appropriate for the gestational week. A detailed ultrasound examination for anomalies of the fetus, placenta, and the umbilical cord was done before delivery by a maternal-fetal specialist, and no abnormal finding was found. An overview of maternal docu-ments and the first and second-trimester aneuploidy screening was indicative of low risk. Nucal thickness in the first trimester was in the normal range; detailed ultrasound examination for anomaly scanning at 20 weeks of gestation was normal. Due to the rapid progression of labor to the active phase, the cesarean section was done in the presence of a neonatologist, and a female infant weighing 1800 g, with Apgar 3 and normal ABG, was delivered. Intubation was done, and the newborn was admitted to neonatal intensive care unit (NICU). Further evaluation to detect the cause of hydrops fetalis was done after delivery.
After birth, in neonatal evaluation, a detailed examination of the newborn was done by a neonatologist, and there was no abnormal finding. Polymerase chain reaction (PCR) test for toxoplasma, rubella, parvovirus B19 of blood specimens, and PCR test for cytomegalovirus (CMV) on urine specimen were negative. As congenital cardiac diseases are one of the most well-known causes of NIHF, we performed neonatal echocardiography after birth, and it was normal (we did not have enough time to do it before delivery). Fetal heart rate (FHR) pattern before birth was regular. The middle cerebral artery Doppler studies to assess fetal anemia and newborn hemoglobin were in the normal range (14.9); therefore, anemia was not considered.
The umbilical cord and placenta appeared normal and histopathologic examination by a pathologist showed no abnormality.
In maternal evaluation, complete blood cell count and indices were normal. The maternal blood group was A+, the antibody screen was negative, serologic test for syphilis, and antibodies for toxoplasma, CMV, rubella, and parvovirus B19 were negative.
Genetic abnormalities as a cause of NIHF must be excluded. Familial history to rule out an inherited disorder in the family is essential. In our case, family history was negative, and karyotype evaluation after birth showed a normal female chromosomal complement, and no further evaluation was done. The analysis of thoracentesis fluid was normal with negative culture. In the end, we did not find any abnormal findings.

 
Figure 1. Bilateral pleural effusion in Transverse view of the fetal thorax
 
 
Figure 2. Coronal view of the face with normal lip and mouth
 

Figure 3. Maximal vertical pocket
 
 
Figure 4. Transverse view of the fetal abdomen without ascites
 
 
Figure 5. Sagittal view of the fetus with severe pleural effusion
 
 
Figure 6. Fetal skull with skin edema
 

Figure 7. The middle cerebral artery Doppler

The newborn was admitted to NICU and thoracentesis was done (20 cc). Ventilatory support and surfactant replacement were carried out to treat respiratory distress syndrome (RDS), similar to other premature infants. The infant was discharged after 48 days in good condition. The child was entirely healthy, physical and neurodevelopmental status was normal till 6 months after delivery.