Edema or water retention due to swelling, is a common problem during the second trimester of pregnancy. It is usually benign and restricted to the ankles and knees. It is due to the pressure on the veins in the legs exerted by the pregnant uterus. Relaxing your muscles, with legs suspended above the abdominal level may help.
Sleeping with a pillow under legs is another option. Doctors recommend lying in the left lateral position to reduce the pressure of uterus on the veins.
In some cases infections, cardiac conditions, tumours, respiratory issues and portal hypertension are few other causes of intractable edema that requires urgent aid. Following up with the doctor in the pre-natal period is strictly recommended.