One of the findings that causes the most anxiety during a pregnancy scan is when the doctor mentions that the amniotic fluid around the baby is low. For many mothers, this is the first time they have heard the word oligohydramnios, and the combination of an unfamiliar medical term and an unexpected finding during what they thought would be a routine scan can be deeply unsettling. At Jhansi Diagnostics & Fetal Medicine Centre, Dr Furquan Ahmad, MBBS MD, regularly assesses amniotic fluid levels as part of every pregnancy scan and takes time to explain exactly what any finding means and what needs to happen next. Understanding oligohydramnios before you find yourself facing it in a scan room is far better than trying to process the information in the moment.
Here is everything you need to know about amniotic fluid, why it matters, and what oligohydramnios means for your pregnancy.
What Is Amniotic Fluid?
Amniotic fluid is the clear liquid that surrounds the baby inside the amniotic sac throughout pregnancy. In the early weeks of pregnancy, amniotic fluid is produced primarily by the mother’s body. From around 16 weeks onwards, the baby begins to contribute significantly to amniotic fluid volume by swallowing fluid and excreting urine. By the second and third trimesters, fetal urine is the primary source of amniotic fluid.
This fluid serves several critical functions. It cushions the baby against physical pressure and impact from outside the womb. It maintains a stable temperature around the baby. It allows the baby to move freely, which is essential for normal musculoskeletal development. It provides fluid for the baby to breathe and swallow, which is necessary for the normal development of the lungs and digestive system. And it acts as a barrier against infection from the external environment.
The volume of amniotic fluid changes throughout pregnancy, increasing steadily through the second trimester and reaching a peak around 34 to 36 weeks before gradually decreasing towards the end of pregnancy. Dr Furquan Ahmad measures amniotic fluid volume at Jhansi Diagnostics & Fetal Medicine Centre using two standard methods: the amniotic fluid index, which measures the deepest pocket of fluid in each of four quadrants of the uterus and adds them together, and the single deepest pocket measurement, which identifies the largest vertical pool of fluid visible on ultrasound. You can read more about the pregnancy scanning services available at the centre on the ultrasound page.
What Is Oligohydramnios?
Oligohydramnios is the medical term for abnormally low amniotic fluid volume. It is diagnosed on ultrasound when the amniotic fluid index falls below 5 centimetres or when the single deepest pocket of fluid measures less than 2 centimetres. Borderline oligohydramnios refers to fluid levels that are low but not yet critically reduced, and these cases require close monitoring to ensure they do not deteriorate further.
Oligohydramnios can occur at any stage of pregnancy, though it is most significant and most carefully monitored in the second and third trimesters when adequate fluid is essential for fetal lung and musculoskeletal development. The consequences of severely reduced amniotic fluid depend significantly on the gestational age at which it occurs and the underlying cause.
What Causes Oligohydramnios?
Understanding why the amniotic fluid is low is as important as knowing that it is low. The cause shapes the management plan and determines how urgently intervention is needed.
The most common cause in the third trimester is uteroplacental insufficiency, where the placenta is not functioning adequately and the baby is receiving reduced blood flow. When blood flow to the kidneys is reduced, the baby produces less urine, and since fetal urine is the primary source of amniotic fluid in the third trimester, fluid levels fall. This is closely linked to intrauterine growth restriction and is one of the reasons Dr Furquan Ahmad always assesses amniotic fluid alongside fetal biometry and Doppler studies in growth monitoring scans.
Premature rupture of membranes, where the amniotic sac develops a tear or break before labour begins, causes amniotic fluid to leak out and is another common cause of oligohydramnios. Mothers who notice fluid leaking from the vagina during pregnancy should seek medical attention the same day rather than waiting for a scheduled scan.
Fetal kidney abnormalities are an important cause of oligohydramnios, particularly when it is detected in the second trimester. If the baby’s kidneys are not developing normally or are absent, the baby cannot produce adequate urine and fluid levels fall. This is one of the reasons kidney assessment is a standard part of the anomaly scan at 18 to 20 weeks at Jhansi Diagnostics & Fetal Medicine Centre.
Post-term pregnancy, where the pregnancy continues significantly beyond 40 weeks, is associated with a natural reduction in amniotic fluid as the placenta ages. Certain medications, particularly non-steroidal anti-inflammatory drugs and some antihypertensive medications taken during pregnancy, can also reduce fetal urine output and lower amniotic fluid levels. Dehydration in the mother can contribute to reduced fluid levels and in mild cases may be addressed simply by increasing fluid intake. The fetal medicine page at the centre has more information on how these conditions are assessed and managed.
Why Does Amniotic Fluid Level Matter So Much?
The importance of amniotic fluid to fetal development cannot be overstated. In the second trimester, adequate fluid is essential for fetal lung development. The baby needs to breathe amniotic fluid in and out to stimulate lung growth. When fluid is severely reduced during this period, the lungs may not develop normally, a condition called pulmonary hypoplasia, which can be life-threatening after birth. This is why severe oligohydramnios detected in the mid-trimester is one of the most serious findings a pregnancy scan can reveal.
In the third trimester, reduced amniotic fluid is associated with cord compression. The umbilical cord, which is normally cushioned by fluid, can become compressed between the baby and the uterine wall when fluid is low. Cord compression reduces blood flow to the baby and can cause fetal distress, particularly during labour when the cord is under additional pressure with each contraction. This is one of the reasons oligohydramnios in late pregnancy often influences the timing and mode of delivery.
Fetal movement is also affected by low fluid. A baby with significantly reduced amniotic fluid has less space to move and may show reduced fetal movements as a result. Reduced fetal movements in any pregnancy should always be reported and assessed promptly, and in the context of known oligohydramnios, they warrant immediate evaluation.
How Is Oligohydramnios Monitored and Managed?
The management of oligohydramnios depends entirely on the underlying cause, the gestational age, and the severity of the fluid reduction. Dr Furquan Ahmad tailors the monitoring plan at Jhansi Diagnostics & Fetal Medicine Centre to each patient’s specific situation.
When oligohydramnios is identified, a detailed assessment is performed to look for the underlying cause. This includes a careful examination of the fetal kidneys and bladder, a Doppler assessment of umbilical and fetal blood flow, a biometric assessment to check for growth restriction, and a review of the placenta. If premature rupture of membranes is suspected, this is investigated clinically alongside the ultrasound assessment.
Mild or borderline oligohydramnios may be managed with increased monitoring, typically weekly or fortnightly scans to track fluid levels and fetal wellbeing, alongside advice on maintaining good maternal hydration. More significant oligohydramnios associated with growth restriction and abnormal Doppler findings requires more intensive monitoring and close liaison with the obstetric team regarding delivery timing.
In some cases, particularly where oligohydramnios is caused by uteroplacental insufficiency in a baby that has reached a viable gestational age, the safest management is delivery. The decision about when to deliver balances the risks of continued compromise in the womb against the risks of prematurity outside it. These decisions require specialist fetal medicine input and experienced obstetric management.
For families managing this diagnosis in Jhansi, having access to detailed monitoring scans and expert interpretation locally rather than travelling long distances for every appointment is a significant advantage. You can explore the full range of monitoring services on the our services page at Jhansi Diagnostics & Fetal Medicine Centre.
What Should You Do If Your Scan Shows Low Fluid?
If your scan report mentions low amniotic fluid, borderline fluid, or oligohydramnios, the most important thing is to follow through promptly on whatever monitoring or follow-up Dr Furquan Ahmad recommends. Do not wait and see if it resolves on its own without medical guidance.
Ensure you are well hydrated. While hydration alone does not reverse oligohydramnios caused by placental insufficiency or fetal kidney problems, it can help in cases where mild dehydration is a contributing factor. Monitor your baby’s movements carefully and report any reduction immediately. Avoid non-steroidal anti-inflammatory medications unless specifically advised by your doctor.
Attend every follow-up scan that is scheduled. Amniotic fluid levels can change relatively quickly, and consistent monitoring is the only way to catch any deterioration early enough to act on it safely.
If you have questions after receiving a scan report that mentions amniotic fluid concerns, the team at Jhansi Diagnostics & Fetal Medicine Centre is available through the contact us page. Common questions about pregnancy scans are also addressed on the FAQs page. Appointments can be booked through the booking appointment page.
Amniotic fluid is not a background detail on a pregnancy scan. It is one of the most important indicators of how your baby is doing. When it is low, the right monitoring makes all the difference.
