Definition - What does Oligohydramnios mean?
Oligohydramnios is a condition in which the amniotic fluid surrounding the baby in the uterus decreases to a low level. The fluid in which the baby floats serves as a cushion protecting the baby against any jerks or blows to the mother's uterus. The fluid also helps the baby develop properly, including the development of lungs and keeping the body parts lubricated so they do not fuse. Insufficient amniotic fluid levels have a negative impact on a baby's development.
FertilitySmarts explains Oligohydramnios
What causes Oligohydramnios?
The following conditions can decrease the amount of amniotic fluid:
- Chromosomal abnormalities in the unborn baby (e.g, aneuploidy)
- Any condition that reduces the production of urine such as a malformed kidney, including renal agenesis - a birth defect in which one or both the kidneys in the baby are missing (since a large amount of the late amniotic fluid volume is urine)
- Procedures like chorionic villus sampling
- Premature rupture of membranes: Causes excessive leakage of the fluid
- Infections in the mother that can cross the placenta (such as toxoplasmosis, rubella, chlamydia, and herpes)
- Conditions in the mother associated with abnormalities or insufficiency in the function of the placenta (like preeclampsia and abruptio placentae): They restrict the growth of the baby in the uterus. This causes the blood vessels supplying the kidneys of the fetus to narrow, thereby, decreasing the production of urine
- Overdue pregnancy (one that has extended beyond 42 weeks of pregnancy)
What are the effects of Oligohydramnios on the baby?
Low amniotic fluid levels interfere with the growth of the fetus's body, leading to deformed limbs and face and underdeveloped lungs - a constellation of findings referred to as Potter sequence. Additionally, nodules can develop on the protective placental covering surrounding the fetus - a condition called amnion nodosum.
How is Oligohydramnios diagnosed?
On examination, the size of the uterus is much smaller than the period of menstrual age. Reduced fetal movements are also noticed.
A confirmatory diagnosis of oligohydramnios requires the presence of an amniotic fluid index (AFI) of less than the fifth percentile or less than 5 cm, or the deepest fluid pocket of less than 2 cm as detected by serial ultrasound scans
How is Oligohydramnios treated?
Bed rest and vigorous hydration are the mainstay of treatment to promote the production of amniotic fluid.