Causes of oligohydramnios in the third trimester

Placental function may be affected by pregnancy-related high blood pressure, restricted fetal growth or some maternal health conditions. Certain medicines can alter fetal kidney blood flow. Occasionally, a low reading has no clear cause, and repeat assessment helps show whether it persists.

Amniotic fluid cushions the fetus and leaves room for movement. Late in pregnancy, a reduced volume may give the umbilical cord less protection during contractions and can accompany placental insufficiency, which is why fetal wellbeing and growth are assessed together with the fluid level.

One measurement does not explain the cause by itself. Clinicians may repeat the scan, check growth and placental blood flow, monitor the fetal heart rate, measure maternal blood pressure and assess whether watery vaginal loss represents ruptured membranes.

Attend the scheduled scans and monitoring even if you feel well. Pay attention to your baby's usual pattern of movement and use the contact instructions supplied by your maternity unit. Continue normal hydration unless your own care team has advised a fluid restriction.

The obstetric plan balances the benefit of remaining pregnant against signs that delivery would be safer. Gestational stage, growth, heart-rate monitoring, placental blood flow, membrane status and any maternal condition all influence that decision. Induction is one possibility, not an automatic result of every low reading.

Call your maternity unit without delay for reduced or changed fetal movement, a gush or persistent trickle of clear fluid, vaginal bleeding, or contractions before the planned time of birth. Staff can tell you where to attend for monitoring.

Severe headache, visual changes, pain beneath the ribs, sudden swelling, fever or feeling acutely unwell also warrant urgent maternity advice. These symptoms matter because they can occur with maternal or pregnancy complications alongside low fluid.

Ask whether the fluid level is stable, whether fetal growth and blood-flow checks are reassuring, and how often monitoring is needed. Discuss what would prompt delivery, which birth options are suitable and exactly whom to contact if movement or fluid loss changes.