Definition: The baby grows inside the womb in a fluid-filled sac which is called the amniotic sac while the fluid is called amniotic fluid. Normally, amniotic fluid increases gradually to a volume of 1 liter by 36 weeks of pregnancy and decreases thereafter. Excessive amniotic fluid more than 2 liters is called hydramnios.
Incidence is 1 % of all pregnancies Antenatally, amniotic fluid is measured by ultrasonography as amniotic fluid index (AFI, normal 8 – 24 cm) and hydramnios is defined when AFI is > 24 cm
Causes could be many e.g. maternal diabetes, Blood Rh factor incompatibility between mother and fetus, congenital structural abnormalities in fetus like duodenal atresia and anencephaly. In almost half the cases it is unexplained.
Complications during pregnancy can occur. Common are discomfort due to overdistended abdomen and premature labour. Abnormal uterine contractions during labour, premature separation of placenta before or during labour and postpartum hemorrhage can occur immediately after labor. Mild to moderate degrees of hydramnios rarely require treatment. Severe hydramnios may require drainage of amniotic fluid from uterus called amniocentesis. A drug indomethacin can be given in severe hydramnios. However, it is better avoided because of side effects on fetus.