The amount of amniotic fluid in the womb steadily increases up to around 1 quart by week 36 of pregnancy. After this time, the amount of fluid tends to decrease.
In this article, we look at the signs and symptoms of having too much amniotic fluid. We also cover possible causes and potential risks for the woman and baby.
What is polyhydramnios?
The amount of amniotic fluid in the womb should decrease after week 36 of pregnancy.
Polyhydramnios, or hydramnios, refers to an excessive amount of amniotic fluid around the fetus in the uterus.
The fetus’s kidneys produce the amniotic fluid, which flows into the womb via the fetus’s urine.
The fetus then swallows the fluid and reabsorbs it with its breathing motions. This act of swallowing helps balance the amount of amniotic fluid in the womb.
This process maintains a dynamic balance between the production and absorption of amniotic fluid. When a disruption affects the balance, complications can arise for the woman and fetus.
Signs and symptoms
Women with polyhydramnios often have no signs or symptoms. When symptoms do occur, they can include difficulty breathing, premature contractions, or, if polyhydramnios is severe, pain in the abdomen.
When the uterus is larger than expected for the fetus’s age, this could indicate that there is too much amniotic fluid. A woman can usually tell that her belly is growing very quickly.
Causes
Polyhydramnios can develop for several reasons, such as:
- multiple pregnancies, which are those with two or more fetuses in the womb
- maternal diabetes, which doctors also refer to as gestational diabetes
- the fetus having difficulty swallowing the amniotic fluid
- the fetus producing an increased amount of urine
- congenital malformations, such as a blockage of the fetus’s gastrointestinal or urinary tract, or an abnormal development of the brain and spinal cord
- problems affecting the fetus’s genetic makeup, lungs, or nervous system
- an infection in the fetus
- anemia, or a lack of red blood cells, in the fetus
Sometimes, a doctor may find no cause for polyhydramnios. In these cases, they would describe the cause as idiopathic.
Risks and complications
Premature contractions may be a sign of polyhydramnios.
Research has linked polyhydramnios to an increased risk of certain complications for both the woman and baby.
Possible complications for the woman include:
- longer labor
- premature contractions leading to preterm delivery
- premature separation of the placenta from the wall of the womb
- the water breaking too early
- difficulty breathing
- excessive relaxation and lack of tone of the womb after labor
- uncontrolled bleeding after labor
Possible complications for the baby include:
- congenital abnormalities
- abnormal size or positioning, which can lead to difficulties with delivery
- dangerous positioning of the umbilical cord, which can cause the cord to become trapped against the fetus, limiting the oxygen supply
- in the most severe cases, death
Diagnosis
Doctors diagnose polyhydramnios before the baby is born. To make a diagnosis, they will perform an ultrasound examination. Using ultrasound waves, they measure the amount of amniotic fluid in the womb and look for any fetal abnormalities.
Doctors can also test the woman for issues that can cause polyhydramnios. These tests may include:
- blood tests to check for maternal diabetes or infection
- a procedure called amniocentesis, in which a doctor collects a sample of amniotic fluid from the womb and sends it to a laboratory for genetic analysis
Treatment
To treat polyhydramnios, doctors try to reduce the amount of amniotic fluid in the womb. This can prolong the pregnancy and improve the woman’s well-being.
A doctor may use one of the following methods to reduce the volume of fluid:
- Reduction amniocentesis, also called amnioreduction. This is a procedure in which doctors draw fluid from the womb. However, the medical community has not yet reached an agreement about how much fluid to remove or how quickly to withdraw it.
- Medications. These could include prostaglandin synthetase inhibitors or sulindac, which is a nonsteroidal anti-inflammatory drug.
Polyhydramnios can increase the risk of complications, so doctors usually monitor the fetus carefully, beginning at 32 weeks of pregnancy.
Summary
Polyhydramnios is the medical term for having too much amniotic fluid in the womb. It has several possible causes, including maternal diabetes, multiple pregnancies, or abnormalities in the fetus. In some cases, doctors are unable to identify the cause.
Women with polyhydramnios may experience premature contractions, longer labor, difficulties breathing, and other problems during delivery. The condition can also cause complications for the fetus, including anatomical problems, malposition, and, in severe cases, death.
Treatment aims to remove excess amniotic fluid. A doctor may withdraw fluid in a procedure called amnioreduction, or they may recommend medications. In most cases, doctors will carefully monitor the fetus to check for signs of complications.
