Hydramnios (excess amniotic fluid)

During pregnancy, your baby is surrounded by amniotic fluid in the womb. This fluid, which is produced by the placenta and your baby, provides a cushioned environment at the right temperature and allows room for your baby to grow and move. By the 36th week of pregnancy, there's normally about 1 liter of amniotic fluid. An excess of this fluid is called hydramnios or polyhydramnios. This condition occurs in about 1 percent of pregnancies and varies in severity, usually with a mild to moderate excess (2 to 3 liters) of amniotic fluid.


Causes/associated factors
The cause of hydramnios is unknown in up to 70 percent of cases. Moderate to severe cases can be associated with birth defects of the nervous and intestinal systems, such as anencephaly (the absence of part or all of the brain) and esophageal atresia (improper development of the esophagus). Other birth defects associated with hydramnios may include:
respiratory defects, such as cystic adenomatoid malformation of the lung, a condition that can lead to serious respiratory problems
skeletal defects, such as spina bifida, in which part of the spine remains open, leaving the spinal cord exposed and unprotected
chromosomal defects, such as trisomy 18, a serious condition in which multiple abnormalities may be present
Other conditions associated with hydramnios include:

hydrops fetalis, a severe condition in which fluid collects in the baby and results in heart failure and respiratory distress
multiple pregnancy (twins or higher order multiple)
diabetes in the mother (Hydramnios is more likely to develop in the third trimester if you have elevated blood sugar levels. In turn, the baby's elevated blood sugar levels and increased urine production are thought to contribute to hydramnios.)
macrosomia (a larger than normal baby)

Signs/symptoms
Hydramnios may develop rapidly (acute hydramnios) or gradually (chronic hydramnios).
Acute hydramnios usually occurs earlier in pregnancy, as early as 16 weeks in some cases. The uterus may rapidly become very large, resulting in severe symptoms or even premature labor. Symptoms may include:

an enlarged abdomen (more than would be expected for the gestational age)
shortness of breath with any exertion and when lying down
swelling in the legs, feet, abdomen and perineum (the area between the vulva and the anus)
decreased urination due to obstruction of the ureters (the tubes that run from the kidneys to the bladder) by pressure from the enlarged uterus
Chronic hydramnios is characterized by a gradual accumulation of amniotic fluid. Chronic hydramnios may cause few symptoms for the mother.


Diagnosis
Your doctor may suspect hydramnios due to the increased size of the uterus. During a physical exam, he or she may have difficulty feeling the baby and hearing the heartbeat.
To estimate the amount of fluid in the amniotic sac, the doctor may do an ultrasound. If a more accurate measurement is needed, he or she may use the amniotic fluid index (AFI) -- a measurement of the fluid pockets surrounding your baby. How the AFI is measured depends on how long you've been pregnant. If you're less than 20 weeks pregnant, the diameters of the largest fluid pocket on the right side of your uterus and the largest pocket on the left are added together to determine the AFI. If you're more than 20 weeks pregnant, the uterus is divided into four equal parts and the diameters of the largest pocket in each section are added together. Normal AFI varies with gestational age. After 30 weeks, it's usually between 8 and 24 centimeters. Hydramnios is diagnosed when the AFI is 24 to 25 or more.

If you're diagnosed with hydramnios, various tests (including a complete ultrasound exam of the baby) will be done to check for birth defects or other complications.


Treatment
If you have hydramnios, you'll be monitored at least weekly until delivery. The amniotic fluid level will be checked with ultrasounds and other tests. Nonstress tests (which measure the response of your baby's heartbeat to its movements) may be done to evaluate your baby's well-being.
Mild hydramnios usually needs no treatment. Some mild cases may even resolve on their own. Even moderate hydramnios may need no treatment if the discomfort is tolerable and the membranes don't rupture or labor doesn't begin early. In some cases, treating the cause may be all that's needed, such as controlling blood sugar levels if you have diabetes.

If symptoms such as difficulty breathing or walking are severe, hospitalization may be needed. Your doctor may place you on bedrest and suggest steps to prevent constipation and straining (which could provoke premature rupture of the membranes), such as a high-fiber, high-protein diet and possibly a stool softener. You may be given indomethacin, a nonsteroidal anti-inflammatory medication that reduces the amount of amniotic fluid by decreasing your baby's urine production. You may need medication to stop contractions if premature labor begins. In some cases, amniocentesis (withdrawal of amniotic fluid through a needle inserted into your abdomen) may be done. This procedure provides only temporary relief, however, since about a liter of amniotic fluid is replenished within a day after the amniocentesis. The procedure may need to be repeated often, although it increases the risk of premature rupture of the membranes and infection. Finally, labor may be induced if your symptoms are severe.


Complications
Hydramnios can be associated with serious complications for both mother and baby, including:
premature labor and birth due to the overdistended uterus
umbilical cord prolapse when the membranes rupture
fetal malpresentation at birth, such as breech (feet first)
placental abruption (a complication caused by the accumulation of blood between the placenta and the wall of the uterus) occurring after the rupture of the membranes when the uterus rapidly decreases in size
uterine dysfunction, characterized by lack of progress during labor
postpartum hemorrhage
In some cases of severe hydramnios, the baby's survival may be threatened.