Oligohydramnios is a condition in which a pregnant mother has less amniotic fluid than normal. Amniotic fluid is important for the growth of the fetus in the womb as it helps protect the fetus from trauma. Oligohydramnios can occur at any stage of pregnancy. However, if a pregnant mother has too little amniotic fluid close to delivery due to incomplete placental function, it may affect the fetus. The fetus may receive insufficient nutrients and oxygen, resulting in slow fetal growth (Fetal Growth Restriction – FGR) and increased risk of umbilical cord compression during uterine contractions, reducing blood and oxygen supply to the fetus, possibly causing fetal distress and abnormal heartbeats, which can be life-threatening and may require emergency delivery.
If oligohydramnios occurs during early pregnancy, it may lead to compression, resulting in fetal deformities such as facial deformities, bent limbs, or clubfoot, and underdeveloped lungs (Pulmonary Hypoplasia). Regular prenatal visits with an obstetrician are important, as they help in timely and proper handling of the situation.
What is Amniotic Fluid?
Amniotic fluid (Amniotic Fluid) is a fluid inside the amniotic sac that surrounds and protects the fetus, playing a crucial role in its growth and development.
Components of Amniotic Fluid
- Approximately 98% water
- Nutrients such as proteins, carbohydrates, fats
- Fetal skin cells
- Fetal urine
- Secretions from fetal lungs
What are the important functions of Amniotic Fluid?
- Supports growth Amniotic fluid allows the fetus to move freely, promoting the development of muscles and bones.
- Protects from trauma Amniotic fluid cushions against external shocks, reducing the risk of fetal injury.
- Regulates temperature Amniotic fluid maintains stable temperature, providing an ideal environment for the fetus.
- Supports lung development The fetus practices breathing by inhaling and exhaling amniotic fluid, which helps develop strong lungs.
- Supports digestive system development The fetus swallows amniotic fluid, stimulating the digestive system’s function.
- Prevents infection Amniotic fluid contains substances that inhibit bacterial growth.
- Helps dilate the cervix during labor Pressure from amniotic fluid helps dilate the cervix when the mother is close to delivery.
What is the volume of amniotic fluid in pregnant mothers?
- The volume of amniotic fluid increases continuously with pregnancy age.
- The maximum volume of amniotic fluid is about 800 – 1,000 milliliters in the third trimester. Oligohydramnios is defined as having less than 500 milliliters.
What causes oligohydramnios?
- Premature rupture of membranes
- Fetal abnormalities such as kidney malformations
- Placental insufficiency, leading to reduced blood flow and nutrients to the fetus
- Maternal chronic conditions such as diabetes or high blood pressure, preeclampsia
- Taking certain medications, such as some non-steroidal anti-inflammatory drugs (NSAIDs)
What are the symptoms of oligohydramnios?
Pregnant mothers can observe oligohydramnios from abnormal symptoms as follows:
- Fluid leakage from the vagina
- Significantly decreased fetal movements
- Reduced uterine size
- Weight loss
How dangerous is oligohydramnios to the fetus?
Oligohydramnios can harm the fetus, such as:
- Preterm birth Oligohydramnios increases the risk of preterm birth.
- Fetal lung underdevelopment Causes the baby to have difficulty breathing after birth.
- Umbilical cord compression With low amniotic fluid, the uterus may compress the umbilical cord, causing the fetus to lack oxygen.
- Intrauterine fetal death Especially in early pregnancy from water breaking, causing bands to compress fetal limbs.
- Fetal deformities Due to oligohydramnios from water breaking or threatened abortion in the first trimester, causing Amniotic Band Syndrome (ABS), potentially compressing fetal limbs and causing deformities such as facial, arm, leg, hand, and foot abnormalities.
How to care for a pregnant mother with oligohydramnios?
If a pregnant mother has oligohydramnios, the obstetrician will consider treatment based on the cause, gestational age, and fetal health. The treatment guidelines include:
- Close monitoring If oligohydramnios is mild and the fetus is healthy, the doctor may closely monitor with periodic ultrasounds to track amniotic fluid volume and fetal growth, including prenatal health assessments (e.g. NST, BPP).
- Amnioinfusion In certain cases, particularly at gestational ages 24 – 34 weeks, the obstetrician may consider injecting saline into the uterus through the abdomen to increase amniotic fluid volume, reducing umbilical cord compression and providing more room for fetal movement.
- Treating maternal health conditions If oligohydramnios is caused by maternal chronic conditions such as high blood pressure or diabetes, controlling and treating these conditions may improve the situation.
- Termination of pregnancy If oligohydramnios is severe, the fetus is unwell, or the gestational age is full term, the doctor may consider inducing labor or performing a cesarean section.
How can pregnant mothers prevent oligohydramnios?
- Regular prenatal care and doctor visits as scheduled
- Monitor for abnormal symptoms such as water breaking or decreased fetal movements
- If abnormalities occur, immediately see an obstetrician
Pregnant mothers should not overlook oligohydramnios as it can affect fetal growth. Regular self-observation and scheduled visits to the obstetrician are recommended. If abnormalities occur, promptly inform the obstetrician to ensure the little one is born healthy and strong.
Maternal and Fetal Medicine Specialist
Dr. Teera Wacharaprechanont, Obstetrician, Maternal and Fetal Medicine, Women’s Health Center, Bangkok Hospital
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