Occasionally, a pregnancy can produce either too little or too much amniotic fluid, which is the fluid that surrounds the baby. What results is a set of possible risks or complications known as oligohydramnios (OH-lee-go-hy-DRAM-nee-os) and polyhydramnios (pol-ee-hy-DRAM-nee-os).
Amniotic fluid cushions the baby from outside stress and gives the baby enough room to move and grow inside the womb. It also keeps some space between the baby, the umbilical cord, and the uterine wall, so that the cord doesn’t become compressed.
Because the amniotic fluid typically reflects the amount of fetus urine production, it’s used as a measure of the baby’s health and development. Amniotic fluid volume cushions the fetus from physical trauma permits fetal lung growth and provides a barrier against infection. Normal amniotic fluid volume varies. If the amount of fluid is low, it may be an indication that:
- Your water is breaking
- The baby has intrauterine growth restriction (IUGR) Placental insufficiency and fetal growth restriction
- The baby is having kidney or urinary tract problems
- The baby has a rare genetic disorder
- The placenta is separating from the uterine wall prematurely (placental abruption)
- The mother has chronic high blood pressure or is using certain medications, such as ACE inhibitors
An inadequate volume of amniotic fluid, oligohydramnios, results in poor development of the lung tissue and can lead to fetal death. In the latter two-thirds of pregnancy, any condition that interferes with fetal urine production can lead to oligohydramnios. Renal agenesis, cystic kidneys, and bladder outlet obstructions are common.
Too little fluid for long periods may cause abnormal or incomplete development of the lungs called pulmonary hypoplasia.
Causes of Oligohydramnios
Rupture of the membranes is the most common cause of oligohydramnios. However, because the amniotic fluid is primarily fetal urine in the latter half of the pregnancy, the absence of fetal urine production or a blockage in the fetus’s urinary tract can also result in oligohydramnios. Fetal swallowing, which occurs physiologically, reduces the amount of fluid, and an absence of swallowing or a blockage of the fetus’s gastrointestinal tract can lead to polyhydramnios.
Treatment for Oligohydramnios
To increase the amount of amniotic fluid, an amnioinfusion could be performed. This procedure involves filling the amniotic sac with saline using a needle inserted through the mother’s abdominal wall.
The extra fluid may help relieve some problems, such as lifting pressure off a kinked umbilical cord, or it may enhance an ultrasound image so that the doctor can diagnose the underlying problem. Unfortunately, the procedure hasn’t been shown to be effective in the long-term.
Amniotic fluid is a product of placental blood flow and fetal circulation, so it is NOT advised to drink large amounts of water in an attempt to increase amniotic fluid.
Polyhydramnios occurs when there is an excessive accumulation of amniotic fluid. Too much amniotic fluid can cause the mother’s uterus to become overdistended and may lead to preterm labor or premature rupture of membranes. Polyhydramnios has many different causes, and the recommended treatments can vary.
Most cases of polyhydramnios are mild. Amniotic fluid volume increase during pregnancy, the actual volume that constitutes polyhydramnios is dependent on the gestational age of the fetus. Amniotic fluid may have gradually built up during the later stages of pregnancy. Normally, this won’t cause any problems and will go away on its own.
However, severe polyhydramnios may cause outward symptoms, such as shortness of breath, swelling in the feet, ankles, and vulva, and decreased urine production.
Fetuses with polyhydramnios are at risk for a number of other problems including cord prolapse, placental abruption, premature birth, and perinatal death.
Causes of Polyhydramnios
In some cases, polyhydramnios is a symptom of another condition or underlying health issue.
- Rh incompatibility (mother and baby’s blood types are incompatible)
- Fetal anemia (low red blood cell count in the fetus)
- Maternal diabetes
- Genetic conditions
- Complications due to multiple gestation
If left untreated, severe polyhydramnios may increase the chances of complications, such as macrosomia, preterm labor and birth, and placental abruption. Whatever the problem, the earlier it starts, the more time it has to build up excessive fluid, increasing the chances of complication.
Fortunately, your OB-GYN should be able to catch polyhydramnios with a routine ultrasound. If we suspect polyhydramnios, we may need to perform further tests to diagnose the precise cause of the condition.
Treatments for Polyhydramnios
Usually, treating polyhydramnios is as simple as treating the underlying problem causing it. For example, if we determine that the excess fluid is caused by maternal diabetes, then successfully treating the mother’s diabetes should resolve the polyhydramnios.
Doctors can measure the amount of fluid through a few different methods, most commonly through amniotic fluid index (AFI) evaluation or deep pocket measurements.
However, your doctor may recommend treatment that directly targets the build-up of fluid.
Draining the surplus amniotic fluid
An amniocentesis can relieve the uterus of excess fluid. Sometimes more than one amniocentesis is required; this process is called amnioreduction.
The oral medication Indocin can cut down on the baby’s urine production, which will decrease the amount of amniotic fluid. However, this drug is not recommended for use after 31 weeks of pregnancy and carries some risk for fetal heart problems. The baby’s heart will need to be carefully monitored with a Doppler ultrasound or an echocardiogram.
Your doctor will continue to measure your amniotic fluid every 1-3 weeks. Usually, pregnancies with mild and moderate polyhydramnios will be able to be carried to full term. However, in serious cases of polyhydramnios, labor may be induced early to avoid complications.