How to Diagnose Oligohydramnios

Oligohydramnios is a generic term meaning too little amniotic fluid. Amniotic fluid allows the lungs to develop and protects the fetus from infection and physical trauma. Oligohydramnios causes poor development of the lungs or some other congenital defect in 20 percent of cases and can lead to death of the fetus. It occurs in 4 percent of pregnancies and usually requires delivery in a tertiary care setting. Read on to learn more.

Instructions

Difficulty: Challenging

1. Consider less than 300 ml amniotic fluid at term to be oligohydramnios. Amniotic fluid level normally increases throughout pregnancy and peaks in the 800 to 1,000 ml range.
2. Measure the largest vertical pocket of amniotic fluid and the deepest one sonographically. Oligohydramnios is defined as a maximum vertical measurement of less than 7 cm and a maximum depth measurement less than 2 cm.
3. Determine the cause of oligohydramnios. The most common source is a premature rupture of the membranes or chronic leakage of the amniotic fluid.
4. Examine the fetal urinary tract. Amniotic fluid consists primarily of fetal urine during later stages of pregnancy so it could be caused by problems with the fetus such as renal insufficiency, polycystic kidneys or a urinary obstructive lesion. This can cause a deformation of the fetus called Potter syndrome.
5. Check for other causes. Oligohydramnios also can be caused by maternal diabetes, placental insufficiency or an overdue pregnancy. Another possibility is the mother's use of angiotensis-converting enzyme inhibitors or prostaglandin synthase inhibitors.