Hydrops Fetalis Definition
Hydrops fetalis (also referred to as fetal hydrops or simply hydrops) is a serious complication characterized by severe edema (fluid buildup) in multiple body areas of a fetus or a newborn infant.  In most cases, it is first observed during the second trimester (week 13 to 28) , but can also occur during the first (week 1 to 12) and third trimesters (week 29 to 40). Hydrops is not a condition itself but is triggered by various other factors during pregnancy, which lead to serious developmental problems and even death.
What Causes Hydrops Fetalis
Hydrops occurs when excessive amounts of fluid flows out of the bloodstream and accumulates in various tissues . The principal responsible factors can be classified into:
Immune hydrops develops due to Rh incompatibilities between the mother and baby. If an Rh negative woman has a baby who is Rh positive, the immune system of the mother considers the Rh positive RBCs (red blood cells) of the baby as foreign bodies. So, the antibodies of the mother start attacking the baby’s RBCs, breaking them down and destroying them, which results in anemia. The fetus’s under-developed organs cannot compensate for the lost blood cells. This gradually leads to heart failure, causing fluid buildup in the organs and tissues of the baby .
Factors other than an abnormal immune system response in the mother that can lead to the problem are collectively referred to as the non-immune causes. . However, researchers have not yet found all the non-immune causes likely to cause hydrops fetalis. Risk factors likely to hamper the fetus’s ability of managing fluid properly include:
- Cardiovascular abnormalities: Those involving structural problems of the heart, blood vessel (vascular) abnormalities and heart rate irregularities (arrhythmias) (around 40% of cases)
- Blood (hematologic) complications: Impaired RBC production, fetal hemorrhage and genetic hemolytic disorders (around 10%-27% of cases) 
- Congenital infections: Like herpes, syphilis, parvovirus and cytomegalovirus (around 8% of cases)
- Genetic syndromes: Like Turner syndrome, Down’s syndrome (trisomy 21) and trisomies 10,13,15,18  (around 10% of cases)
- Inherited disorders: Like -thalassemia  and various metabolic disorders
- Tumors and abnormal masses: Like diaphragmatic hernia, sacrococcygeal teratomas, cystic hygroma, cystic adenomatoid malformation and polycystic kidneys (around 10% of cases)
Idiopathic congenital conditions like chylothorax and cardiomyopathy may also trigger the problem.
What are the Symptoms of Hydrops Fetalis?
- Extremely high amniotic fluid levels (polyhydramnios)
- Enlarged heart, liver or spleen in the fetus 
- Thickened placenta 
- Abnormal fluid accumulation in the fetus’s abdomen
- Pale skin coloring (pallor) 
- Liver and spleen enlargement
- Severe swelling or edema in different parts, especially the abdomen
- Difficulty breathing
- Neonatal jaundice
- Neonatal anemia
- Heart failure 
Hydrops Fetalis Prevention
Immune fetal hydrops has become quite rare with the advancement of modern medical science. The Rh compatibility and fetal hemolytic disease responsible for the complication can be prevented if the mother takes a certain medicine called RhoGAM  during pregnancy and post delivery, thus eliminating the chances of hydrops in the baby. However, there is often no way of preventing the nonimmune and idiopathic forms.
How is Hydrops Fetalis Diagnosed?
The doctor studies the medical history of the mother while also performing a thorough physical examination  to detect any signs fetal edema.
- Prenatal ultrasound for evaluating the fetal blood flow and the functioning of various internal organs, for detecting excessive amniotic fluid levels as well as to identify any sign of irregular fluid accumulation
- Fetal blood sampling (e.g. hemoglobin chain analysis) for fetal serum albumin levels and thalassemia 
- Amniocentesis for detecting certain abnormalities like genetic disorders and infectious conditions
- Maternal blood test for differentiating between immune and non-immune hydrops by detecting antibodies associated with incompatibilities between the maternal and fetal blood groups 
Hydrops Fetalis Differential Diagnosis 
|Hepatitis b||Hepatocellular carcinoma||Oliguria|
|Congestive heart failure||Hypoplastic left heart syndrome||Pleural effusion|
|Hypospadias||Gaucher disease||Osteogenesis imperfecta|
|Intussusception||Omphalocele||Polycystic kidney disease|
|Hypercalcemia||Syphilis||Junctional ectopic tachycardia|
|Toxoplasmosis||Thalassemia||Wolff-Parkinson-White syndrome (supraventricular tachycardia)|
|Systemic lupus erythematosus||Noonan syndrome||Gastroschisis|
|Omphalocele||Patent ductus arteriosus||Rhabdomyosarcoma|
|Myelodysplasia||Mucopolysaccharidosis types IV, VI and VII||Neonatal resuscitation|
|Neonatal sepsis||Constrictive pericarditis||Posterior urethral valves|
|Viral myocarditis||Smith-Lemli-Opitz syndrome||Williams’s syndrome|
|Ventricular tachycardia||Ventricular septal defect||Herpes simplex virus infection|
|Hepatoblastoma||Interrupted aortic arch||Hypoprothrombinemia|
|Pyruvate kinase deficiency||Klippel-Trenaunay-Weber syndrome||Hypoxic-ischemic encephalopathy|
|Sinus node dysfunction||Ureteropelvic junction obstruction||Pulmonary hypoplasia and sequestration|
Hydrops Fetalis Management and Treatment Options
The treatment depends on a number of factors including the mother’s medical history, gestational age, severity of the disorder and the baby’s tolerance for specific therapies, medications and procedures .
Treatment during Pregnancy
- Intrauterine fetal blood transfusion (the baby is given blood while in the uterus)
- Maternal anti-arrhythmic medications (such as digoxin) to deal with fetal arrhythmia
- In-utero surgeries such as surgical resection (removal of some damaged gland or organ) and fetal thoracocentesis or paracentesis 
- Early delivery of the baby using medications to induce labor
- Early c-section delivery in case of rapid aggravation of the fetus’s condition 
Treatment after Birth
- Direct intravascular transfusion of packed RBC (compatible with the baby’s blood type) along with an exchange transfusion for eliminating the substances attacking the RBC in the baby’s body
- Removal of the excess fluid from around the baby’s abdomen and lungs using a needle 
- Medicines for controlling heart failure and helping the kidneys to remove the extra fluid
- Application of a breathing machine or supplemental oxygen to help the newborn breathe properly 
Hydrops Fetalis Complications
- Mirror syndrome  (mother suffering from the same symptoms as the fetus) with the symptoms of edema, proteinuria and hypertension. There are generally no long term effects on the mother, but the above symptoms may remain for some time after delivery.
- Brain damage (kernicterus) 
- Hearing loss due to fluid buildup around eardrums
Hydrops Fetalis Prognosis
The outcome usually varies depending on the severity of the problem and its underlying causes. Mild cases often resolve on their own, especially those where the etiology involves conditions like twin-to-twin transfusion syndrome and cardiac arrhythmias . The recurrence risk of nonimmune hydrops depends on the underlying triggering factors .
The overall survival rate ranges between 84% and 90%. A successful intrauterine treatment helps to better the outcome, increasing the life expectancy of the affected newborn. However, the survival rate drops to about 39% when the intrauterine treatment fails to reverse the hydrops. The neurodevelopment is normal in around 90% of the survivors.
Hydrops Fetalis Incidence
The nonimmune form of the complication occurs in about 1 in every 1,000 births .
Hydrops Fetalis ICD-9 and ICD-10 Codes
The ICD-9 codes used for this pregnancy complication are P56, P83.2 .
The ICD-10 codes for hydrops are 773.3, 778.0 .[ref]
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Volume1/760-779/764-779/773/ 773.3.htm [/ref]