Low amniotic fluid is called oligohydramnios meaning the fluid cushioning your baby in the womb is lower than expected for your stage of pregnancy. In other words, there is not as much fluid protecting your baby as there should be at your stage of pregnancy. It is detected through an ultrasound scan and not through any signs that you may notice yourself.
Amniotic fluid is a clear, slightly yellow-coloured liquid that develops around the fetus during pregnancy. It is a protective liquid that forms inside the amniotic sac nearly after 12 days of conception. The function of amniotic fluid is to protect the unborn baby from infections, umbilical cord compressions, injury and temperature changes in the body. It also allows the safe movement of the fetus in the womb. Additionally, amniotic fluid supports the development of your baby’s digestive and respiratory systems.
According to the Amniotic Fluid Index measurement, the amount of amniotic fluid is 800 mL (greatest at 34 weeks of gestation). By full-term pregnancy, that is, by 40 weeks of gestation, the amniotic fluid is about 600 mL.
Low amniotic fluid is a condition in which the amniotic fluid is at lower levels than expected as per your baby’s gestational age. This condition is medically known as oligohydramnios.
Low amniotic fluid can cause various health problems in your fetus affecting your baby’s development. This condition can also increase your chances of pregnancy and birthing complications. Low amniotic fluid can also be an indicator of an underlying condition.
The amniotic fluid is measured using the Amniotic Fluid Index (AFI), reported in centimetres on an ultrasound. AFI rises through the second trimester, peaks around 32–34 weeks, and then gradually declines towards term. It is completely normal and not itself a cause for concern.
The table below shows typical AFI values for the last few weeks of pregnancy, based on an Indian reference study of low-risk pregnancies.
| Week of pregnancy | Average AFI | Typical range |
|---|---|---|
| 34 weeks | ≈14.6 cm | ≈11–18 cm |
| 35 weeks | ≈14.3 cm | ≈11–17 cm |
| 36 weeks | ≈13.2 cm | ≈10–16 cm |
| 37 weeks | ≈12.5 cm | ≈9–15 cm |
| 38 weeks | ≈12.2 cm | ≈9–15 cm |
| 39 weeks | ≈11.4 cm | ≈8–14 cm |
| 40 weeks | ≈12 cm | ≈9–16 cm (5th percentile ≈8.7 cm) |
An AFI below 5 cm, or a single deepest fluid pocket below 2 cm, is used to diagnose oligohydramnios at any gestational age. These are population averages, not a diagnosis — your own doctor will always interpret your specific scan against your pregnancy history.
Low amniotic fluid symptoms are more prevalent during the last trimester of pregnancy. It is not always possible to identify when you may have low amniotic fluid. Your Low Amniotic Fluid Doctor may suspect that you may have this condition based on the following low amniotic fluid symptoms include:
Based on these symptoms, your healthcare provider may order an ultrasound scan to measure your amniotic fluid index (AFI).
After about the second trimester, a considerable portion of the amniotic fluid is made up of urine from your baby. In this case, therefore, the volume of fluid is also an indication of the functionality of the baby’s kidneys and that of the placenta in delivering the necessary nutrients. It is for this reason that the doctor attaches great importance to a low volume of fluid, even when you are perfectly healthy, because it may be an indicator of your baby’s wellbeing.
There are no exact and identifiable low amniotic causes that we know of. Several factors contribute to low amniotic fluid causes:
The small size of the baby
A baby who is considerably smaller in size will produce less amount of amniotic fluid leading to oligohydramnios.
Maternal health issues
Underlying health concerns in the mother before or during pregnancy can also lead to low amniotic fluid. Common conditions contributing to this illness are diabetes, hypertension, preeclampsia and lupus.
Placenta problems
Several problems with the placenta including a partial abruption (peeling away of placenta from the inner wall of the uterus) can cause low amniotic fluid.
Premature rupture of membranes
It is common to experience leaking of fluid due to ruptured membranes. This condition can happen at any point in your pregnancy. However, it is one of the less common amniotic fluid causes.
Carrying multiples
Your risk of low amniotic fluid increases when you are expecting twins or triplets. It is more common in the case of twin-to-twin transfusion syndrome (a condition in which one twin has more amniotic fluid than the other).
Increased gestational age
You are about two weeks past your due date, you can expect low amniotic fluid.
Dehydration
Low amniotic fluid can also develop due to lesser consumption of fluids resulting in dehydration.
Congenital anomalies
Birth defects are a common cause of oligohydramnios. Fetal abnormalities, especially those affecting the baby’s kidneys or urinary tract can lead to this condition.
It is common to experience a gradual dip in amniotic fluid towards the end of pregnancy till it averages about 600 mL. However, low amniotic fluid during the first and second trimesters can have potential complications for the baby.
Common low amniotic fluid complications include:
Low amniotic fluid complications during the third trimester include:
An ultrasound scan helps in the diagnosis of low amniotic fluid. Your doctor will examine the level of amniotic fluid and measure it based on the gestational age of your baby.
The low amniotic fluid treatment is dependent on the stage of your pregnancy, the health of the fetus and whether you have any associated complications. You will be monitored closely to devise the treatment protocols.
If you are close to 36-37 weeks pregnant, the safest option for the low amniotic fluid treatment is delivery. If the gestational age is less than 37 weeks, your doctor will ensure that your baby continues to grow normally.
You may receive care in the form of labour induction or cesarean delivery. Babies delivered as a result of preventing low amniotic fluid complications may also be treated at the neonatal intensive care unit (NICU).
You cannot prevent oligohydramnios but there are some short-term steps you can take to manage low amniotic fluid symptoms.
Yes, your baby is most likely to be healthy. However, he/she may require additional care.
If you have low amniotic fluid at 30 weeks gestation, you will receive additional monitoring, prenatal testing and biophysical profile to ensure that your baby is healthy.
Yes, there can be a significant increase in stress hormones in the amniotic fluid.
Yes, normal delivery is possible with oligohydramnios.
Around 36 weeks, a typical AFI averages roughly 13 cm, with most healthy pregnancies falling somewhere between about 10 and 16 cm. Your doctor will compare your specific reading against your overall pregnancy picture rather than this number alone.
Sometimes, particularly if dehydration or a treatable cause is behind it, drinking more fluids and treating the underlying issue can help fluid levels recover somewhat. The levels caused by placental or fetal factors are less likely to improve, which is why ongoing monitoring matters more than a single reading.
This depends on your gestational age and the suspected cause, but many women are monitored weekly or twice-weekly with ultrasound and fetal heart rate tracing (a biophysical profile) once low fluid is confirmed, especially in the third trimester.
Not always. If you are close to 36–37 weeks, early delivery is often the safest option. Earlier in pregnancy, your doctor will usually monitor you and your baby closely rather than delivering immediately, unless there are signs your baby is in distress.
It can help in some cases, particularly when dehydration is a contributing factor, and it is a simple, low-risk step most doctors recommend. It is not a guaranteed fix if the underlying cause is related to the placenta or the baby, so it is used alongside monitoring rather than instead of it.
Low amniotic fluid (oligohydramnios) means levels are below the expected range but some fluid is still present. “No amniotic fluid”, or anhydramnios, means essentially no fluid pocket can be measured on ultrasound at all. Anhydramnios is less common, more serious, and is managed with closer monitoring and, often, earlier delivery.
