What is polyhydramnios?

Polyhydramnios is an excess accumulation of amniotic fluid — the protective liquid that surrounds the unborn baby in the uterus during pregnancy. The condition occurs in 1 percent to 2 percent of all pregnancies.

Polyhydramnios can be an isolated condition (which means no other birth defect or condition occurs with it), but it is also more common when the unborn baby has certain congenital anomalies (such as duodenal atresia) or a medical condition involving the heart or lungs (such as hydrops fetalis). Polyhydramnios is also associated with various genetic disorders, including Down syndrome (Trisomy 21) and Edward’s syndrome (Trisomy 18), but only when the baby also has a duodenal atresia or other blockage in the gastrointestinal tract.

Severe polyhydramnios may cause a pregnant woman to experience shortness of breath or other discomfort due to the abdomen becoming overly distended. In addition, the condition raises the risk of problems during pregnancy and childbirth, including preterm labor, premature rupture of the amniotic sac (also known as “water breaking”) and placental abruption (the peeling away of the placenta from the inner wall of the uterus). Polyhydramnios is also sometimes associated with a condition known as intrauterine growth restriction (IUGR), which occurs when the unborn baby’s weight is significantly smaller than expected for its gestational age.

Who will be on my care team?

At Midwest Fetal Care Center, a collaboration between Children’s Minnesota and Allina Health, we specialize in individual attention that starts with you having your own personal care coordinator to help you navigate your baby’s treatment process. We use a comprehensive team approach to polyhydramnios and any associated anomalies. That way, you are assured of getting the best possible information by some of the most experienced physicians in the country. For polyhydramnios, your care team will start with a maternal-fetal specialist, and also may potentially include a pediatric surgeon, a neonatologist, a geneticist, a nurse specialist care coordinator, a perinatal social worker and several other technical specialists. This entire team will follow you and your baby closely through the evaluation process, and will be responsible for designing and carrying out your complete care plan.

Meet the team

What causes polyhydramnios?

Identifying the cause of polyhydramnios can be difficult, and in about 40 percent of cases, no clear explanation is found. Several possible causes are known, however. Some involve the baby. Some involve the mother. And others involve the placenta.

Among the baby-related causes are birth defects. These include anomalies that block the baby’s gastrointestinal tract, such as duodenal atresia. Such blockages make it difficult for the unborn baby to swallow the amniotic fluid and excrete it in urine — a process necessary for the regulation of fluid volume within the uterus. Birth defects that affect the baby’s central nervous system can also lead to polyhydramnios. The high levels of fluid may also be related to the baby having fetal anemia or a heart or kidney problem.

Maternal diabetes is a major risk factor for polyhydramnios. When a pregnant woman’s blood sugar levels are not well controlled, the baby’s urine output increases, leading, potentially, to excessive amounts of amniotic fluid.

In some cases involving twins, polyhydramnios is caused by twin-to-twin transfusion (TTT) syndrome, a serious placenta-related condition that results in one twin surrounded by too little amniotic fluid and the other surrounded by too much.

How is polyhydramnios diagnosed?

Polyhydramnios is diagnosed by ultrasound, but not usually at the routine 20-week screening ultrasound. That’s because signs and symptoms of the condition tend not to develop until later in the pregnancy.

Several pathways — all of which result in multiple ultrasounds being taken throughout pregnancy — may eventually lead to a diagnosis of polyhydramnios:

  • If a birth defect or a chromosomal abnormality known to raise the risk of polyhydramnios has been identified through earlier screening
  • If the mother has a history of diabetes or develops gestational diabetes during her pregnancy
  • If the mother is carrying twins
  • If the uterus is larger than normal (as observed by a doctor during a routine prenatal visit) or if the mother reports having difficulty breathing (which can be a symptom of increased amniotic fluid)

In all these cases, the diagnosis of polyhydramnios is confirmed by using the ultrasound image to visually measure a pocket of amniotic fluid in each of the four quadrants of the uterus and then adding up these measurements.

How is polyhydramnios managed before birth?

The prenatal management of babies with polyhydramnios starts with acquiring as much information about the condition as early as possible. To gather that information, we may recommend one or more prenatal screening techniques, including high-resolution fetal ultrasonography, fetal echocardiography and amniocentesis. In cases where there’s a concern that the mother has diabetes, testing for that disease may also be recommended, if it hasn’t been done already.

What is high-resolution fetal ultrasonography?

High-resolution fetal ultrasonography is a non-invasive test performed by one of our ultrasound specialists. The test uses reflected sound waves to create images of the baby within the womb. We will use ultrasonography to follow the development of your baby’s internal organs and the volume of amniotic fluid that surrounds your baby throughout the pregnancy.

What is fetal echocardiogram?

Fetal echocardiography (“echo” for short) is performed at our center by a pediatric cardiologist (a physician who specializes in fetal heart abnormalities).  This non- invasive, high-resolution ultrasound procedure looks specifically at how the baby’s heart is structured and functioning while in the womb. This test is important because babies with any birth defect or genetic problem are at increased risk of heart abnormalities.

What is amniocentesis?

Amniocentesis is a test done during pregnancy to check if your baby has a genetic or chromosomal condition, such as Down syndrome. A small sample of fluid will be removed from the amniotic sac surrounding your baby. The amniotic fluid will contain cells from your baby, and in those cells will be your baby’s chromosomes for us to analyze. The procedure is straightforward and can be done in our clinic. It requires placing a small needle through the abdomen and into the amniotic sac to obtain the fluid sample. Test results will take several days for our laboratory to process. The information obtained from this test will be very important for creating your care plan and for helping the neonatologist care for your infant after birth.

How will my care be managed once my evaluation is completed?

After we have gathered all the anatomic and diagnostic information from the tests, our team will meet with you to discuss the results. Because polyhydramnios is associated with an increased risk of complications during pregnancy and birth, we will recommend that your pregnancy be followed closely, including with extra ultrasound screenings.

Polyhdyramnios related to birth defects is not usually treated before the baby is born. We will, however, take an active, two-fold approach to managing the condition during your pregnancy.

First, we will monitor both mother and baby very carefully, looking for any potential complications that might lead to premature delivery. We will perform regular ultrasounds throughout pregnancy to monitor the growth of the baby, the volume of the amniotic fluid and the baby’s well being. If signs or symptoms of preterm labor or premature rupture of the amniotic sac develop, we may recommend treatment to try to prolong the pregnancy, including an amnioreduction procedure. The mother may need to be hospitalized to manage any pregnancy complications.

Second, we will try to identify any complicating factors — such as birth defects or genetic abnormalities — that might require additional therapies or consultations. That way we can be prepared during and after delivery to optimally care for your infant.

If the polyhydramnios is due to maternal diabetes, we will help you manage your diabetes to control the amount of amniotic fluid in your uterus and the growth of your unborn baby. We may refer you to a diabetic specialist, if you don’t already have one.

What is amnioreduction?

Amnioreduction is a procedure that is used to remove excess fluid that accumulates in the amniotic sac during severe cases of polyhydramnios. Its purpose is twofold: to relieve any fluid-related discomfort or other symptoms in the mother and to reduce the risk of premature birth. The procedure is similar to that of amniocentesis, with the doctor using “real-time” ultrasound images to guide a long, very fine needle into the uterus to withdraw the fluid.

How is polyhdyramnios treated during birth?

Our goal will be to have your baby’s birth occur as near to your due date as possible. Babies with polyhydramnios can be delivered vaginally. There is an increased risk, however, of the baby being in an abnormal position (not “presenting” head first) during delivery, a situation that may require a cesarean section. During labor, your doctor will be prepared for all complications or outcomes.

If there are any concerns of associated birth defects, your baby may be born at The Mother Baby Center at Abbott Northwestern and Children’s Minnesota in Minneapolis or at The Mother Baby Center at United and Children’s Minnesota in St. Paul. Children’s Minnesota is one of only a few centers nationwide with a birth center located within the hospital complex. This means that your baby will be born just a few feet down the hall from our newborn intensive care unit (NICU). Also, many of the physicians you have already met will be present during or immediately after your baby’s birth to help care for your baby right away.

What is my baby’s prognosis?

The prognosis for babies with isolated polyhydramnios is excellent when the condition is diagnosed and treated promptly. In cases where the baby has associated anomalies or conditions related to premature birth, the prognosis is also good, although these babies will require more advanced, long-term medical care.