Low amniotic fluid levels:
Oligohydramnios
Amniotic fluid is
part of the child's survival system. It protects your baby and helps in the
development of muscles, limbs, lungs and digestive system. Amniotic fluid is
produced shortly after the formation of the amniotic sac, about 12 days after
conception. At first it consists of water that the mother gives, then from
about 20 weeks the fetal urine becomes the main substance.
As the baby grows, it
moves and enters the uterus with the help of amniotic fluid. In the second
trimester, the baby will begin to breathe and swallow amniotic fluid. In some
cases, the amniotic fluid may be too low or too high. If the amniotic fluid
measurement is too low, it is called oligohydramnios. If the amniotic fluid
measurement is too high, it is called polyhydramnios.
What is oligohydramnios?
Oligohydramnios is a
condition in which there is little amniotic fluid. Doctors can measure the
amount of fluid in a variety of ways, most commonly by assessing the amniotic
fluid index or by measuring in deep pockets. If the fluid index shows a fluid
level of less than 5 centimeters (or less than the 5th percentile), no fluid
pocket 2–3 cm deep, or a fluid volume of less than 500 ml at 32–36 weeks of
gestation, the diagnosis of oligohydramnios may be suspected.
About 8% of pregnant
women may have low amniotic fluid levels, and about 4% are diagnosed with
oligohydramnios. It can happen at any stage of pregnancy, but is more common in
the last trimester. If a woman's due date is two weeks or more, she may be at
risk of low amniotic fluid levels, as the amount of fluid may drop by half when
she reaches the 42nd week of pregnancy. Oligohydramnios can lead to
complications in about 12% of pregnancies beyond 41 weeks.
What causes low amniotic fluid levels?
- Birth defects. Problems with the development of the kidneys or urinary
tract, which can cause low urine output, resulting in low levels of amniotic
fluid.
- Placental problems. If the placenta does not supply the baby with enough
blood and nutrients, the baby may stop recirculating fluids.
- Leaking or rupture of membranes. This may be a splash of liquid or a slow
steady trickle of liquid. This is due to rupture of the membrane. Premature
rupture of the membranes can also lead to low amniotic fluid levels.
- Post date pregnancy. Post-date pregnancy (lasting more than 42 weeks) may
have low amniotic fluid levels, which may be the result of reduced placental
function.
- Maternal complications. Factors such as maternal dehydration, hypertension,
preeclampsia, diabetes, and chronic hypoxia can affect amniotic fluid levels.
Why is low amniotic fluid dangerous?
The risks associated
with oligohydramnios often depend on how far along the pregnancy is. Amniotic
fluid is essential for the development of muscles, limbs, lungs, and the
digestive system. In the second trimester, the baby begins to breathe and
swallow fluids, which helps his lungs develop and mature. Amniotic fluid also
helps babies develop muscles and limbs by giving them enough room to move
around.
If oligohydramnios is
detected in the first half of pregnancy, complications can be more serious and
include:
- Compression of fetal organs resulting in birth defects
- Increased chance of miscarriage or stillbirth
If oligohydramnios is detected in the second half of
pregnancy, complications can include:
- Intrauterine growth restriction
- Preterm birth
- Labor complications such as cord compression, meconium-stained fluid, and cesarean delivery
What treatments are available?
Treatment for low amniotic fluid depends on gestational age. If you are not full term yet, your doctor will monitor you and your levels very closely. Tests such as non-stress tests and contraction tests may be done to monitor your child's activity. If you're close to your due date, delivery is usually recommended by most doctors if your amniotic fluid is low.