Hydrops fetalis is a condition characterized by abnormal fluid accumulation in fetal compartments. It can be immune or non-immune in origin. Immune hydrops is caused by maternal antibodies crossing the placenta, while non-immune hydrops has other underlying causes like genetic disorders, infections, tumors, or cardiovascular/lymphatic issues. Evaluation involves ultrasound to detect fluid accumulation and testing mothers for conditions like TORCH infections. Management may include in-utero procedures to drain fluid or treat the underlying cause if possible. Prognosis is generally poor especially if structural abnormalities or genetic disorders are present, though early detection and treatment can sometimes improve outcomes.

1. Hydrops fetalis
DR. ABDIRIZAKI

2. Introduction
Hydrops fetalis is a condition in the fetus characterized by the abnormal interstitial fluid
collection in two or more compartments of the fetal body (peritoneal cavity, pleura, and
pericardium).
An alternative definition discusses liquid accumulation in two fetal anatomical areas or effusion
in one site and anasarca.
Traditionally, the diagnosis was made after the delivery of a massively edematous neonate that
was often stillborn. With sonography, hydrops fetalis has become a prenatal diagnosis.
With condition progression, edema is invariably a component, often accompanied by
placentomegaly and hydramnios

3. Hydrops fetalis may result from a wide range of conditions with varying pathophysiologies, each
with the potential to severely affect the fetus.
It is divided into two categories, namely immune and non-immune.
If found in association with red cell alloimmunization, it is termed immune hydrops fetalis.
Otherwise, it is called non-immune hydrops fetalis.
Immune hydrops or erythroblastosis fetalis results from antibodies in the maternal circulation
that pass through the placenta and react with the fetal antigens, resulting in fetal hemolysis.
Non-immune hydrops result from causes other than antigen-antibody reactions.

5. Etiology
Hydrops fetalis is not a consequence of heart failure but rather hypervolemia and the high
vascular permeability of fetuses. In contrast, heart failure is a very late consequence of a long-
standing overworked heart.
Immune hydrops fetalis: Isoimmunization such as Rh isoimmunization and ABO incompatibility,
anti-c, C, e, E, Duffy antibodies, and Kell alloimmunization are the causes of immune hydrops
fetalis. A detailed discussion of the immune hydrops is beyond the scope of this activity.
Non-immune hydrops (NIHF): This type of hydrops fetalis accounts for approximately 80 to 90
percent of all cases of the condition. It occurs when an underlying disease, genetic disorder, or
birth defect interferes with the fetal body's ability to manage fluid. NIHF can result from many
various underlying conditions, such as:

6. Cardiac causes: Paroxysmal supraventricular tachycardia, hypoplastic left heart, endocardial cushion
defects, and congenital pulmonary airway malformation
Chromosomal anomalies: Turner syndrome, Down syndrome, and Edward syndrome
Lymphatic causes: Congenital lymphatic dysplasia
Infections: Parvovirus B19 (fifth disease), cytomegalovirus, and syphilis infections in pregnant women
Metabolic diseases: Niemann-Pick disease type-C (NPC), Gaucher disease type 2, and beta-
glucuronidase enzyme deficiency
Tumors: Teratoma (sacrococcygeal teratoma), hepatic tumors, and neuroblastoma
Maternal diseases: Diabetes mellitus and hyperthyroidism
Urinary causes: Congenital nephrosis and prune belly syndrome
Digestive causes: Volvulus and meconium peritonitis

7. Hematologic causes: Alpha-thalassemia, twin-to-twin transfusion syndrome (TTTS) in
monochorionic twin pregnancies, and leukemias
Disorders of red blood cell (RBC) metabolism: Glucose phosphate isomerase deficiency,
pyruvate kinase deficiency, and glucose-6-phosphate dehydrogenase (G6PD) deficiency
Disorders of RBC production: Congenital dyserythropoietic anemia, Diamond-Blackfan
syndrome, and Fanconi anemia
Disorders of RBC membrane: Hereditary spherocytosis, hereditary elliptocytosis, hereditary
pyropoikilocytosis, and hereditary stomatocytosis syndromes

8. Hydrops fetalis and erythroblastosis
fetalis

9. Pathophysiology
Hydrops fetalis is mainly found in any condition that increases the rate of fluid transudation from
the vascular compartment or delay in lymphatic return to the circulation.
This is mainly due to the developmental defects in the microcirculation and lymphatic system.
Hypoxia is another consequence of both immune and non-immune hydrops fetalis. Hypoxia
results in an increase in catecholamines, a decrease in hepatic and renal blood flow because of
the redistribution of blood to the brain, heart, adrenals, and ductus venosus.

10. This causes the renin-angiotensin system's activation, an increase in the anti-diuretic hormone,
and a decrease in albumin.
These mechanisms elevate central venous pressure and lead to a decreased return of lymphatic
flow into the systemic circulation and further complicate the loss of intravascular volume,
resulting in severe and progressive edema in the fetuses.
Although the pathophysiology of non-immune hydrops fetalis is not completely understood, it
often results from various mechanisms depending on the underlying cause. Decreased
ventricular filling during diastole is the most common mechanism of NIHF in tachyarrhythmias.

11. In contrast, increased central venous pressure resulting from increased right heart pressure is
mainly seen in cardiac tumors and subendocardial fibroelastosis.
Obstructed lymphatic drainage in thoracic and abdominal cavities results from masses like cystic
hygroma, increased capillary permeability, and decreased osmotic pressure in congenital
infections and nephrosis.
Hence, the management should mainly focus on reversing the underlying diseases

12. History and Physical
Hydrops fetalis presents with an abnormal fluid collection in two or more cavities or
compartments, mainly pleural effusion, ascites, pericardial effusion, and skin edema.
The number of fluid collection sites is directly correlated to the neonatal prognosis.
The diagnosis is mainly based on prenatal ultrasound or the postnatal evaluation of the fetus.
Other features include anemia, placentomegaly, polyhydramnios, and hepatosplenomegaly.
Pleural effusion can be unilateral or bilateral.

13. Ascites can be an early manifestation of hydrops fetalis and is seen as early as 20 weeks of
gestation. As isolated fetal ascites is seen in many other systemic diseases, it is essential to
differentiate hydrops fetalis from other causes.
Skin edema is defined as the subcutaneous tissue thickness on the scalp greater than 5mm.
Anemia in hydrops fetalis is caused mainly by red cell alloimmunization and parvovirus-B19
infection. Other causes include alpha thalassemia, Bart hemoglobin, and a mutation in the
alpha-globin chain.

14. Polyhydramnios is the vertically measured amniotic fluid volume in the single deepest pocket of
more than 8 centimeters or amniotic fluid index of more than 24 centimeters.
Placentomegaly is an abnormally enlarged placenta which occurs due to disruption in the
oncotic gradient. It is mainly seen in high cardiac output diseases like anemia and sacrococcygeal
teratoma.
Hepatosplenomegaly is diagnosed in the second and third trimester of pregnancy. It is usually
associated with myeloproliferative disease in trisomy 21

15. Dermatitis, along with or without hepatosplenomegaly, suggests the presence of TORCH
(toxoplasmosis, other infections such as rubella, cytomegalovirus, and herpes simplex)
infections.
Neonates with cyanosis and no response to oxygen supplement should raise the suspicion of the
presence of underlying cardiac diseases.

16. Evaluation
Hydrops fetalis is mostly an incidental finding on routine prenatal workup.
The underlying cause has a direct influence on the development of symptoms and its prognosis.
Hydrops due to chromosomal abnormalities is usually detected during early pregnancy, whereas
cardiac causes are detected in the second or third trimester.
Hence, a detailed prenatal workup should be done in suspected cases. The following are the
various diagnostic modalities for the evaluation of hydrops fetalis.

17. The first detailed ultrasound is done between 18 to 22 weeks of gestation. The most common
findings detected during early pregnancy are ascites and skin edema (>5 mm thickness) in the
fetal head, back of the neck, thorax, and abdomen.
The cause of generalized skin edema is most probably due to aneuploidy or associated
anatomical defects.
Polyhydramnios and placental edema are most commonly seen before 20 weeks, whereas
pleural effusion and pericardial effusion in the fetus is rarely seen before 15 weeks of gestation.

18. It is mandatory to look for the possibility of maternal toxoplasma, rubella, cytomegalovirus,
herpes (TORCH), and parvovirus B19.
Parvovirus B19 infection is most commonly associated with fetal anemia and ascites; however,
cytomegalovirus and toxoplasmosis present with congenital malformations like
ventriculomegaly, microcephaly, and hyperechogenic bowel.
Hence, the antibody screen for TORCH infections should always be considered

19. Elevated alpha-fetoprotein (AFP) during pregnancy indicates the feto-maternal hemorrhage,
which causes fetal anemia and nonimmune hydrops. Hence, AFP levels are monitored closely.
Direct and indirect Coomb test is used for detecting immune hydrops fetalis, but they do not
correlate the disease severity.
Echocardiogram, thyroid hormone levels, complete blood count, and metabolic panel also
detect other causes of NIHF after birth.

20. Treatment / Management
Careful evaluation and monitoring and effective resuscitation techniques are essential in
improving the survival rate in affected neonates. Structural heart abnormalities and
chromosomal disorders cannot be intervened with, and hence the prognosis is very poor
Intrauterine interventions like thoracocentesis and peritoneal-amniotic shunt can be performed
if the ultrasound detects mediastinal shift, polyhydramnios, fetal edema, or rapid accumulation
of fluid, to confirm alveolar development and also helps in releasing the excessive amniotic fluid.

21. In severe anemia and arrhythmias, intrauterine transfusion and antiarrhythmic drugs can be
utilized, respectively. Intrauterine transfusions in patients with parvovirus-B19 infections can
reverse hydrops, which may sometimes result in healthy live births. A few teratomas can be
resected surgically in utero.
Postnatal management includes initial resuscitation, identification, and treatment of the
underlying cause. Most of the infants with hydrops fetalis will require endotracheal intubation
because of respiratory depression.
Thoracentesis, paracentesis, and sometimes cardiocentesis are performed if the neonate
presents with pleural effusion, ascites, and pericardial effusion.

22. Despite aggressive treatment, the survival rate is as low as 10 percent with neurodevelopmental
and cognitive defects in surviving infants.
The recurrence rate is highest in mothers whose infants have chromosomal abnormalities or Rh
incompatibility.
Hence, autopsies, including histopathologic evaluation, placental examination, molecular and
genetic studies, are performed to determine the cause of hydrops

23. End
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