NIHF can happen for different reasons. In most cases, something is affecting the fetus’s ability to balance fluid properly. Some common causes include: 

• Genetic disorders that affect how the body develops and controls fluid.  

• Heart problems that can make it harder for the heart to pump blood normally. Growths or masses that block the flow of fluid through the fetus’s body 

• Liver problems that lower protein levels in the blood, causing fluid to leak out of blood vessels.   

• Infections during pregnancy, such as Parvovirus, that can cause fetal anemia, heart problems, or damage to blood vessels or organs. 

• Severe fetal anemia, which causes stress to the fetal heart over time and leads to fluid buildup.  

• Problems with the placenta, umbilical cord, or amniotic fluid that disrupt fluid balance. Sometimes NIHF has more than one cause. For example, a heart problem may be related to a genetic condition or an infection. 

NIHF is most often found during an ultrasound exam when extra fluid is seen in two or more areas of the fetus’s body.  

Doctors may order more tests to look for the potential cause and guide pregnancy care. These tests may include:  

• Blood tests for the parents to check blood type, blood count, and infections that could affect the fetus 

• A detailed ultrasound to check for problems in the fetal heart, placenta, and umbilical cord or other structures  

• A Doppler ultrasound to check for fetal anemia 

• A fetal echocardiogram to check for heart problems  

• Genetic testing, usually by amniocentesis, to look for genetic conditions 

Finding the cause of NIHF helps guide care during and after birth. It may also help doctors understand the risk in future pregnancies. Sometimes, even with testing, the exact cause is not found. 

The chance of NIHF happening again in a future pregnancy depends on its cause. Some causes have little or no increased risk of recurrence, while certain genetic conditions may have a higher chance of occurring again. Genetic counseling may help families understand their individual risk. 

Yes, in some pregnancies with NIHF, the pregnant person can develop mirror syndrome, a condition in which the pregnant person develops swelling that “mirrors” the swelling in the fetus.  It can happen in up to 1 in 3 pregnancies with NIHF.  

Symptoms for the pregnant person may include:  

• Swelling 

• High blood pressure  

• Protein in the urine  

• Headaches  

• Fluid in the lungs 

• Symptoms similar to preeclampsia 

Mirror syndrome can cause serious complications for the pregnant person. In some cases, treating the cause of hydrops may improve both the hydrops and the pregnant person’s symptoms. In other cases, delivery may be recommended.

NIHF also increases the risk of polyhydramnios (too much amniotic fluid around the fetus) and preterm birth. NIHF often leads to early delivery. Labor may either start early on its own, or early delivery may be needed because it is safer for the pregnant person or fetus. 

How NIHF is managed depends on:  

• The cause of NIHF 

• How far along the pregnancy is  

• The health of the pregnant patient and the fetus 

Care is often managed by a team of specialists, including maternal-fetal medicine subspecialists, neonatologists, and genetic counselors.  

There is no single treatment approach that works for every pregnancy. Options may include:  

Close monitoring 

Some pregnancies may be managed with regular ultrasound exams, blood pressure checks, and lab tests.  Monitoring is tailored to each pregnancy. In some cases, NIHF may remain stable or improve before birth without treatment. 

Fetal treatment 

Depending on the cause of NIHF, options may include:  

•  Medication to treat heart problems in the fetus,  

• Fetal blood transfusion for anemia 

• Medications for the pregnant patient 

• Procedures to drain excess fluid from the fetus  

These treatments are not right for every pregnancy and may involve risks. When successful, treatment before birth can improve the chances of fetal survival.  

Palliative care or abortion  

When NIHF is severe or is caused by a condition that cannot be treated, families may choose palliative care (comfort care) for their newborn after delivery. Abortion may be another option in some areas.   

These decisions are very personal. The health care team will help families weigh their options and make the decision that is right for them.

Vaginal birth may be possible in some pregnancies affected by NIHF. However, cesarean delivery is common in pregnancies complicated by NIHF. The safest way to deliver depends on the health of the pregnant person and fetus, the cause and severity of the hydrops, and whether the baby will need urgent treatment after birth. 

A cesarean delivery may be advised if:  

• The fetus or pregnant person is not doing well during labor  

• The baby will need urgent treatment right after birth  

• There are other medical concerns 

Delivery should take place at a hospital with a higher-level neonatal intensive care unit (NICU) and a team able to care for the newborn. If a family has chosen palliative or comfort care, delivery can take place wherever those services are available.  

The outlook for NIHF varies widely. It depends on the cause, how early it is found, whether it can be treated, and how the fetus responds to treatment.  

• About 1 in 5 pregnancies affected by NIHF end in miscarriage or stillbirth. The risk is higher when NIHF is found earlier in pregnancy.  

• Among babies born alive, about one-half (50%) to two-thirds (66%) survive.  Some babies who survive may have long-term health challenges, while others do well.    

Outcomes may be better when the cause of NIHF is treatable. These include parvovirus and some abnormal fetal heart rhythms and anomalies. This is especially true when treatment is given before birth and hydrops resolves during pregnancy.  

Outcomes may be worse when NIHF is linked to genetic disorders or other causes that cannot be treated during pregnancy.