What is Low Amniotic Fluid?
The medical term for a condition when there isn't sufficient amniotic fluid is oligohydramnios.
The levels of amniotic fluid naturally fluctuate throughout pregnancy, reaching their peaks at 32 to 34 weeks of gestations and decreasing from then onwards. However, sometimes its levels decline drastically, especially in overdue pregnancies, putting the baby at risk of serious complications.
Causes of Low Amniotic Fluid
Although the reasons for low amniotic fluid are not always clear, the most common causes include the following:
Birth defects can lower the baby's urine output, especially when concerning kidneys, since urine is the main component of the amniotic fluid.
Placental problems might prevent the baby from getting sufficient blood and nutrients, which can reduce urine production, thus causing low amniotic fluid.
Raptured amniotic membranes might cause leakage of the fluid and decrease its total volume.
Post-date pregnancy can result in a natural decline in amniotic fluid up to 50% of its volume.
Maternal health, like having hypertension, preeclampsia, diabetes, or lupus, can increase the risk of oligohydramnios.
Medications, like those for hypertension or congestive heart disease, can often cause a decrease of amniotic fluid.
Signs and Symptoms of Low Amniotic Fluid
Oligohydramnios produces very easily recognizable signs and symptoms that are crucial for its prompt diagnosis. They include:
Symptoms of Oligohydramnios
Fluid leaking from vagina
Poor growth of your uterus
Slow baby movements
Signs of Oligohydramnios
Amniotic fluid index: less than 5 cm
Amniotic fluid volume: less than 500 mL
Maximum vertical pocket: less than 2 cm
Low Amniotic Fluid Tests
Various tests can be used to diagnose and monitor the levels of decreased amniotic fluid:
The most common tools used to diagnose oligohydramnios include:
Ultrasound is used to measure several pockets of amniotic fluid in the uterus to determine its total level, a method called a “Single Deepest Pocket.”
Amniotic Fluid Index (AFI) is a scale used to estimate amniotic fluid volume. An AFI score below 5 cm and 500 mL are considered low, in comparison to a normal range in the third trimester, which is 5-25 cm and 800-1000 mL.
Other tests that can assess your baby's well-being include:
Non-stress test is used to evaluate the heartbeat.
Biophysical profile test is used to evaluate if the baby is getting enough oxygen.
Contraction stress test measures the baby's heart rate during uterine contractions.
Counting kicks can help women monitor their baby's activity throughout the day.
Effects of Low Amniotic Fluid on Pregnancy
Oligohydramnios does not always cause serious complications nor does it endanger the life of the mother.
When it is diagnosed in early pregnancy, it tends to be more severe and almost always ends in a miscarriage. When detected later on in pregnancy, it can have the following effects on the baby:
Poor fetal growth, or Intrauterine growth restriction (IUGR)
Malformations due to the compression of baby's organs
Labor complications, especially with the umbilical cord
Treatment and Management of Low Amniotic Fluid
The treatment of oligohydramnios depends on how far along you are in your pregnancy, the severity of your symptoms, and whether your baby is developing properly.
First and second trimester
Management usually involves close monitoring and drinking plenty of fluids to increase amniotic fluid levels naturally, but it might require the following procedures to increase the fluid around the baby:
Amnio-infusion: an injection of saline into the womb through a woman's vagina or abdomen.
Maternal re-hydration with oral fluids or IV fluids can increase amniotic fluid.
At 37 or 38 weeks of gestation delivering the baby is the safest treatment for low amniotic fluid. During delivery, a flexible catheter providing saline solution might be inserted into the cervix to prevent unforeseen complications.
As with most pregnancy complications, low amniotic fluid comes unexpectedly and causes a lot of disturbance. Luckily, it tends to affect women towards the end of their pregnancies when the baby is developed enough to be safely delivered to avoid further problems. Women with other pregnancy complications, such as preeclampsia, might require more a specialized care and treatment plan to suit their medical needs.
- American Pregnancy. (2017). Low Amniotic Fluid Levels: Oligohydramnios. Retrieved January 18, 2018 from http://americanpregnancy.org/pregnancy-complications/oligohydramnios/
- Journal of Obstetrics and Gynecology of India. (2014). Low Amniotic Fluid Index at Term as a Predictor of Adverse Perinatal Outcome. Retrieved January 18, 2018 from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3984654/
- Journal of Pregnancy. (2015). Reference Ranges of Amniotic Fluid Index in Late Third Trimester of Pregnancy: What Should the Optimal Interval between Two Ultrasound Examinations Be? Retrieved January 18, 2018 from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4312643/
- March of Dimes. (2013). Oligohydramnios. Retrieved January 18, 2018 from https://www.marchofdimes.org/complications/oligohydramnios.aspx
- Platt. E. et all. (2008). 100 Questions and Answers about your Hisk-Risk Pregnancy. Sudbury, Massachussets: Jones and Bartlett Publishers.
- Australian Journal of Ultrasound in Meidicine. (2013). Amniotic fluid as a vital sign for fetal wellbeing. Retrieved January 18, 2018 from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5029989/