Oligohydramnios

Oligohydramnios – Low Amniotic Fluid Levels in Pregnancy

Amniotic fluid is an integral part of your baby’s development in the womb. It acts as a shock absorber, preventing and protecting your developing baby from outside shocks. It is what makes fetal movements possible in the womb and plays an important role in regulating the womb temperature and guarding it against pathogens. 

During pregnancy, your doctor will regularly monitor the level of amniotic fluid through ultrasounds to make sure the right amount of it is maintained. If the level is higher than the normal expected range, it is referred to as polyhydramnios while a low level of amniotic fluid is called oligohydramnios. 

How is the amniotic fluid level in the womb maintained?

In about two weeks after conception, amniotic fluid begins to fill up the amniotic sac from the mother’s blood circulation. In the second trimester, the baby learns to swallow amniotic fluid. Baby’s developing kidneys start functioning and release it into the surrounding fluid in the form of urine, which is swallowed again along with the amniotic fluid.

Thus, in a normal pregnancy, the volume of amniotic fluid keeps building up until around 35 weeks after which it starts to decrease. However, in oligohydramnios condition, the level of amniotic fluid falls below 5 cm mostly during the third trimester. 

What are the symptoms of low amniotic fluid level?

Most often, there are no symptoms of oligohydramnios. Some women may find leakage of the fluid through the vagina or constant wet panty liners. Also, the size of the belly might be smaller and weight gain could be lower for the gestational age. 

What are the causes of low amniotic fluid?

• Abnormalities in the development of fetal kidneys: Fetal urine production is critical in maintaining the level of amniotic fluid. If there is a congenital or developmental defect in the formation or functioning of the fetal kidneys, it may affect the normal urine output. 
• Placental complications: Any risks that can hinder the supply of oxygen and nutrients to the fetus through the placenta may cause a low level of amniotic fluid. Partial placental abruption is one such condition in which the placenta gets partially stripped off from the uterine wall. 
• Rupture of amniotic membrane: Even a small rupture in the amniotic membrane is going to leak its fluid content. Until it’s healed and sealed back to the place, which usually happens naturally, there is going to decrease in the level of amniotic fluid. 
• Maternal health: The health of the pregnant mother can sometimes cause oligohydramnios. Gestational diabetes, preeclampsia, high blood pressure, and chronic dehydration are a few maternal indicators to the low level of amniotic fluid. 
• Pregnancy beyond full-term:  Women who continue carrying the baby over and beyond 40 weeks or full-term have known to have reduced amniotic fluid levels. 

How does a low amniotic fluid level affect the baby? 

How oligohydramnios can affect the growing baby depends on where in pregnancy the mother is. The complications of low amniotic fluid during the first and second trimesters are more serious than if it occurs in late pregnancy, like congenital abnormalities or stillbirth. 

Low amniotic fluid in the third trimester may pose the following problems:

• Premature delivery
• Compression of umbilical cord
• A release of baby’s first poo (meconium) inside the womb, which can lead to choking and fetal death
• Growth restrictions of the fetus
• Cesarean delivery 

How is low amniotic fluid level treated? 

• If there are signs of fetal distress or no fetal movements, the possibility of taking the baby out will be discussed. When the pregnancy is close to full term, it is relatively less complicated as either labor can be induced or a cesarean delivery can be performed. 
• Injecting fluid through amniocentesis may be considered just before delivery.
• Rehydration of the mother’s blood circulation with an intravenous supplement or oral rehydration may, in some cases, bring back the amniotic fluid level to normal. 
• During labor, a catheter may be inserted through the vagina to add fluid to the womb in order to prevent any risk to the umbilical cord. 

APA. Low amniotic fluid (oligohydramnios). American Pregnancy Association. http://americanpregnancy.org/pregnancy-complications/oligohydramnios/

Panda, S., Jayalakshmi, M., Shashi Kumari, G., Mahalakshmi, G., Srujan, Y., & Anusha, V. (2016). Oligoamnios and Perinatal Outcome. Journal of obstetrics and gynaecology of India, 67(2), 104-108 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5371525/

Peipert JF and Donnenfeld AE. (1991). Oligohydramnios: a review. Obstet Gynecol Surv. 46(6):325-39 - https://www.ncbi.nlm.nih.gov/pubmed/2067755