Amniotic fluid is a clear, slightly yellowish liquid that surrounds the fetus during pregnancy in the amniotic sac. During pregnancy, the baby floats in the amniotic fluid. The amniotic fluid constantly moves (circulates) as the baby swallows and “inhales” the fluid, and then releases it.
The amount of amniotic fluid is greatest at about 34 weeks of pregnancy, when it averages 800 mL. After that , 600 mL of amniotic fluid surrounds the baby at full term (40 weeks gestation).
Why do you need Amniotic fluid?
The amniotic fluid helps:
• The developing baby to move in the womb, which allows for proper bone growth
• The lungs to develop properly
• Keep a constant temperature around the baby, protecting from heat loss
• Protect the baby from outside injury by cushioning sudden blows or movements
What is the source of Amniotic fluid?
In the first trimester of pregnancy the amniotic fluid is mainly made up of fluid supplied by the mother via the placenta.
In the second trimester the baby becomes the main producer of amniotic fluid. The two main sources of fluid are the baby’s urine and fluid excreted from their lungs. The baby also removes amniotic fluid by swallowing it.
As the baby grows in size it produces more amniotic fluid and the amount increases until around 32 weeks. The fluid level then remains constant until the baby is full term (37 to 42 weeks) when the levels start to decline.
How do you measure Amniotic fluid?
An ultrasound scan gives information about the amount of amniotic fluid surrounding a baby. After several measurements are taken the amniotic fluid index (AFI) is calculated.
In general, an AFI of five centimetres to 25 centimetres is normal.
When should you worry about the quantity of Amniotic fluid?
In some pregnancies, the fluid levels goes too little or there is extra production. Both conditions require prompt medical attention as these can place the mother and baby at risk of various complications.
When there is too little amniotic fluid in the womb it is called – Oligohydramnios
When there is extra production of Amniotic fluid, it is called – Polyhydramnios
What you need to know about reduced levels of Amniotic fluid ( Oligohydramnios)
• The Amniotic Fluid Index ( AFI) is less than 5 cms, the absence of a fluid pocket 2-3 cm in depth, or a fluid volume of less than 500mL at 32-36 weeks gestation, Oligohydramnios may be suspected.
• The main causes include ruptured membranes, a problem with baby’s kidney or urinary tract, problem with placental function, post date pregnancy (greater then 42 weeks), maternal complications like hypertension, dehydration, pre-eclampsia etc.
• For many women the cause of the oligohydramnios is often unknown.
• The problems associated with oligohydramnios vary according to the cause and the stage of the pregnancy.
• Generally, the earlier that oligohydramnios occurs the more serious it is.
• Reduced amniotic fluid can pose serious risks to the developing baby including impaired lung development, preterm birth, increased chance of miscarriage, birth defects, breech presentation, Intra-Uterine Growth Restriction ( IUGR), infection if the membranes are ruptured etc.
• There is limited effective treatment for oligohydramnios. To improve ultrasound imaging, temporary replacement of the fluid via a needle (amnioinfusion) may be considered.
• Regular medical care and ultrasound scans will be required to monitor the amniotic fluid levels as the pregnancy progresses.
What you need to know about increased levels of Amniotic fluid ( Polyohydramnios)
• The Amniotic Fluid Index ( AFI) is more than 25 cms, Polyhydramnios may be suspected.
• It is a relatively rare condition that happens in about one percent of pregnancies.
• For many women the cause of the Polyhydramnios is often unknown.
• Moderate to severe Polyhydramnios could be caused due to a congenital birth defect in the baby, Maternal Diabetes, Twin To Twin Transfusion Syndrome ( TTTS) in case of twin pregnancy, mismatched blood types etc.
• Moderate to Severe Polyhydramnios may cause symptoms like difficulty in breathing, swelling of legs, tight belly or feeling of fullness, constipation etc.
• Mild polyhydramnios usually does not cause complications. But in severe cases, there are certain risks, including pre term labour, premature birth, excess fetal growth, postpartum haemorrhage etc.
• Treatment depends on the severity of the condition and what is causing it. Mild cases of polyhydramnios usually do not require any treatment. Regular medical care and ultrasound scans will be required to monitor the amniotic fluid levels as the pregnancy progresses
Amniotic fluid not only serves as a cushion for the growing fetus, but also serves to facilitate the exchange of nutrients, water, and biochemical products between mother and fetus. If you have any issues with the fluid levels, it is very important to follow your doctor’s advice for the best outcome for you and your baby.
This article is only intended for information and educational purposes. It does not intend to replace any medical advice or diagnosis.