Understanding Low Amniotic Fluid In Late Pregnancy

My last two doula clients were both induced due to a diagnosis of Oligohydramnios – low amniotic fluid. I have heard many of my students report that they were induced for the same reason, or that it was a very big concern for their care provider. I decided it was time to really understand the ins and outs of this condition.

What is amniotic fluid?
By the 12th day after conception, the amniotic sac will start to form. Within this protective barrier lives the baby, the placenta, the umbilical cord and the baby’s amniotic fluid. The amniotic fluid is a clear, slightly yellowish, odorless substance. At the onset of pregnancy, as the amniotic fluid starts to build in the amniotic sac, it comes from the mother. Over time, the fetus adds to the supply of amniotic fluid through a shedding of skin cells, along with floating stem cells and the baby’s own urine. As the baby breathes in and ingests the fluids, it urinates them out, and this is the basic cycle that continues until the baby is born.

What is the importance of the amniotic fluid?
The amniotic fluid has many roles. For one, it acts as a buffer or cushion should the mother slip or experience jerky, jarring movements. The baby is basically floating around in this big sac of fluid, so should the mother stumble, the baby will not likely feel the impact. This “floating” idea also helps protect the baby from compressing its umbilical cord, which would deprive the baby of oxygen and put the baby in distress. This pool of fluid also gives the baby room to move, which helps the baby build muscle tone and a strong skeleton, protecting it against infection.

Amniotic fluid is also important with regard to the healthy development of the lungs and gastrointestinal system. When there’s little fluid (in the case of a congenital abnormality of the bladder or missing kidneys, for example) the trachea and other respiratory structures don’t mature, indicating that the pressure and nature of the fluid is important in these organs’ growth. Because the lungs are one of the last systems to emerge in fetal development, fluid levels may be a greater concern earlier in pregnancy, especially when there is a premature rupture of the membranes.

What are the concerns with “low fluids”?
Low fluids can be of concern because there will be a higher likelihood of cord compression during labor. As discussed above, the fluid helps keep the baby buoyant.

Low fluids can be an indication of other problems, such as:

*Kidney or urinary tract issues for the baby
*Pre-eclampsia, diabetes, or high blood pressure for the mother
*Partial abruption of the placenta
*PROM – Premature Rupture of the Membranes
*Intrauterine Growth Restriction (IUGR)

How is it measured?
Amniotic fluid is measured with an ultrasound. The technician measures the fluids in 4 quadrants of the uterus and adds the measurements together to see how many centimeters of fluid are in the uterus. The AFI or Amniotic Fluid Index rates the fluids, with 5 cm being too little fluid and 25 cm being too much.

What can be done if this condition is suspected?
In the US, oligohydramnios is a complication in 0.5-5.5% of all pregnancies, and severe oligohydramnios (meaning less then 400 ml of fluids) is a complication in 0.7% of pregnancies. Oligohydramnios is more common in pregnancies beyond term because the AFV (Amniotic Fluid Volume) normally decreases at term. It complicates as many as 12% of pregnancies that last 41 weeks and longer. According to Anne Frye, in Holistic Midwifery “If abnormal quantities of fluid is suspected, assess the situation over the course of several prenatal visits; fetal growth spurts and lags as well as fluid volume are not always consistent from week to week in normal pregnancy” The “wait, see and re-asses” approach may be helpful in determining what kind of reaction is necessary.

Also, since dehydration may be a cause for the low fluid levels, you might ask your care practitioner if you can hydrate and return the next day to be retested.

Another option is an amnio-infusion, which reintroduces fluids into the amniotic sac. During labor, the doctor can pass a catheter through the cervix and add a warm saline solution. This is helpful if the concern is cord compression.

A similar approach can be used if the mother is not already in labor and it is too early to induce her. The doctor can perform an amniocentesis to reintroduce fluid into the amniotic sac. Although oligohydramnios often returns soon after this procedure, it can help your doctor visualize the fetal anatomy and accurately determine fetal development.

The final solution for oligohydramnios is to induce labor.

Final food for thought: a study from The Johns Hopkins Hospital which discusses the outcome of births with suspected low fluids.

Low Levels of Amniotic Fluid No Risk To Normal Birth

Doctors may not have to deliver a baby early if it has low levels of amniotic fluid surrounding it, Johns Hopkins obstetricians report.

In a study to be presented Feb. 7 [2003] at the annual meeting of the Society for Maternal-Fetal Medicine in San Francisco, researchers show that babies born under such conditions fared similarly to those born to women whose wombs held normal amounts of amniotic fluid. No significant differences were found in the babies’ birth weights, levels of acid in the umbilical cord blood, or lengths of stay in the hospital.

Typically, doctors have been concerned about women with low levels of amniotic fluid during the third trimester – a condition called oligohydramnios – because too little fluid can be associated with incomplete development of the lungs, poor fetal growth and complications with delivery. Amniotic fluid is measured by depth in centimeters. Normal amounts range from 5 to 25 centimeters; any amount less than 5 centimeters is considered low.

“These study results are very surprising – they go against the conventional wisdom,” says Ernest M. Graham, M.D., senior author of the study and assistant professor of gynecology and obstetrics. “Amniotic fluid stems from the baby’s urine, and the urine results from good blood flow, so if we see low fluid we assume there probably is not good blood flow and the fetus is compromised. This study shows the fluid test is not as good as we thought, and there is most likely no reason to deliver the baby early if other tests are normal.”

The researchers studied 262 women (131 with oligohydramnios and 131 with normal amounts of amniotic fluid) who gave birth at The Johns Hopkins Hospital between November 1999 and July 2002, comparing the babies’ health at birth. Patients with oligohydramnios were delivered sooner, but were less likely to need Cesarean sections. Babies born to moms with isolated low amniotic fluid were normal size and were at no increased risk of respiratory problems, immature intestines or brain disorders.

Study co-authors were Rita Driggers, Karin Blakemore and Cynthia Holcroft.

Abstract # 318: Driggers, R. et al, “Are Neonatal Outcomes Worse in Deliveries Prompted by Oligohydramnios?”