Oligohydramnios (Low Amniotic Fluid)

Oligohydramnios occurs when the volume of fluid in the amniotic sac is lower than average, usually because the placenta is not functioning properly. When the placenta isn’t functioning normally, the baby receives fewer nutrients and possibly less oxygen. The baby’s organ systems redirect limited resources to the brain and heart and away from the kidneys, which produce urine. Because the amniotic fluid is mostly made of the baby’s urine, this can result in oligohydramnios, which is a serious health risk. Oligohydramnios can be diagnosed with early screening (via ultrasound and amniotic fluid index measurements) and managed with hospital bed rest, fetal monitoring, hydration, and delivery at the first signs of fetal distress.

Oligohydramnios is associated with:

Oligohydramnios - Low Amniotic Fluid Levels

What Is Amniotic Fluid?

Amniotic fluid is the liquid that surrounds the fetus during pregnancy. Located in the amniotic sac, amniotic fluid provides nutrients to the developing fetus that help it mature, grow, and maintain a consistent body temperature. At the earliest stage of development, amniotic fluid consists mainly of water. At approximately 20 weeks, the baby’s urine becomes the primary substance. The baby “breathes” and swallows amniotic fluid; this fluid aids in nutrition, growth, lung maturation, and temperature maintenance. The volume of amniotic fluid increases as the pregnancy progresses and reaches its peak at about 34 weeks.

Amniotic fluid also provides a cushion around the baby and umbilical cord to prevent cord compression and oxygen deprivation in the baby. A decrease in the levels of amniotic fluid is a serious health risk to the baby.

What Is Oligohydramnios? 

Oligohydramnios is a pregnancy complication characterized by diminished amniotic fluid levels. Oligohydramnios is typically a sign that the placenta is not functioning properly. A mother with low amniotic fluid levels might be required to deliver a premature baby, or she may be induced to deliver before placental dysfunction or umbilical cord compression can harm the infant during labor at term.

Oligohydramnios affects 4 – 8% of pregnancies and must to be diagnosed and managed early to prevent the possibility of future injury, brain damage, or disability in the baby.

Oligohydramnios can cause the following injuries and complications:

If oligohydramnios is diagnosed early, it can typically be managed or treated with hospital bed rest, fetal monitoring, oral or intravenous hydration, and in certain cases, early delivery.

Causes of Oligohydramnios


Placental complications can cause oligohydramnios

The most common cause of oligohydramnios is rupture of the amniotic sac since membrane rupture causes amniotic fluid leakage. Because amniotic fluid is primarily fetal urine in the latter half of pregnancy, the absence or decrease of urine production can also cause oligohydramnios. This can occur if the placenta is not supplying adequate perfusion and nourishment to the baby; this is also known as placental insufficiency.

Oligohydramnios can be chronic and occur over a period of time, or it can be acute and happen very quickly. Both forms of the condition can occur in the presence of fetal hypoxia. Below, we’ll discuss the common causes of oligohydramnios; we’ve broken causes down into (a) maternal causes, (b) placental causes, and (c) fetal causes.

A. Maternal causes of oligohydramnios (associated with uteroplacental insufficiency):

  • Diabetes/nephropathy (damage or disease of the kidneys)
  • Preeclampsia
  • Dehydration
  • Use of certain high blood pressure and heart medications, such as ACE inhibitors
  • Chronic hypertension (high blood pressure)
  • Collagen vascular disease
  • Maternal obesity

B. Placental causes of oligohydramnios:

  • Placental insufficiency or dysfunction
  • Placental abruption
  • Placental thrombosis or infarction (clots or obstructed blood flow in the placenta)
  • Uteroplacental insufficiency (placenta not functioning adequately)
  • Twin-to-twin transfusion (twin polyhydramnnios – oligohydramnios sequence)

C. Fetal causes of oligohydramnios:

  • Growth restriction: A growth restricted fetus may redistribute blood flow away from the kidneys, which decreases fetal urine production and causes lowered amniotic fluid levels.
  • Gastrointestinal abnormalities that block the passage of fluid
  • Fetal demise
  • Postterm pregnancy: Numerous complications can occur when a baby is postterm, such as placental insufficiency or a macrosomic (large) baby.
  • Ruptured fetal membranes (PROM and PPROM)
  • Hydrocephalus
  • Congenital abnormalities, especially those associated with impaired urine production.  This occurs when there are problems with the development or function of one or both of the baby’s kidneys.
  • Chromosomal abnormalities, such as Down’s syndrome, that cause problems with swallowing.

Risk Factors for Oligohydramnios

In some cases, women who develop oligohydramnios have no identifiable risk factors. Because of this, it is crucial for physicians to monitor amniotic fluid levels throughout pregnancy. However, many pregnant women do have risk factors for oligohydramnios.

Risk factors for oligohydramnios include:

Signs and Symptoms of Oligohydramnios

The signs and symptoms of oligohydramnios vary from person to person. Some of the most common signs and symptoms of a lowered amniotic fluid volume are:

  • Rapid growth of the uterus
  • Measurements of size smaller than dates
  • Abdominal discomfort
  • Leaking of the amniotic fluid
  • Little to no or decreasing fetal movement
  • Uterine contractions
  • Abnormal findings on a fetal monitor including fetal distress
Diagnosing Oligohydramnios

Abnormal findings on a fetal monitor (such as fetal distress) can indicate oligohydramnios

Oligohydramnios Diagnosis

Oligohydramnios typically is diagnosed through a combination of:

  • Physical examination
  • Assessment of personal history
  • Ultrasound

Monitoring Oligohydramnios During Pregnancy: Measuring Amniotic Fluid Index

Ultrasonic diagnosis of oligohydramnios is performed by obtaining a measurement called the amniotic fluid index, or the AFI. AFI is calculated by measuring the depth of the amniotic fluid in four sections of the uterus and adding them together. The assessment of amniotic fluid is used in conjunction with the biophysical profile (BPP) and non-stress test (tests that evaluate the baby’s heart rate, breathing, movements and muscle tone) as part of an assessment of fetal well being.

Near-term, an AFI between 10 and 18 centimeters is considered normal, with a mean of 14 centimeters. An AFI less than 10 centimeters is considered abnormal. An AFI less than 5 centimeters indicates oligohydramnios.

High-risk pregnancies, or women with risk factors for oligohydramnios, should have an AFI assessment once a week. Twice-weekly AFI assessments are justified if measurements are between 5 and 9 centimeters at a gestational age of fewer than 41 weeks.

All women at 41 weeks of gestation or higher should have twice-weekly AFI assessments with a modified BPP.  However, the frequency of testing should be based on the clinical circumstances of each woman; the more unstable the maternal or fetal condition, the more frequent the testing.

Research indicates that all pregnant women diagnosed with oligohydramnios should undergo a nonstress test (NST) and AFI or BPP once or twice weekly until delivery (especially in cases in which the cause of the condition is unknown), depending on the maternal and fetal condition.

Managing Oligohydramnios Throughout Pregnancy

Can You Increase Amniotic Fluid Levels?

There is no long-term treatment for oligohydramnios. However, a few things can temporarily increase amniotic fluid levels: 

  • Oral intake of fluids: Some medical professionals may advise women to stay hydrated if they have oligohydramnios. Hydration can increase amniotic fluid levels in the short term. Oral hydration is simplest, but in some cases, intravenous hydration (through an IV) may be needed.
  • Installation of a saline solution into the amniotic sac (amnioinfusion) during labor. During amnioinfusion, doctors use an intra-amniotic catheter to add more liquid to the amniotic fluid. This may help ‘pad’ the umbilical cord, reducing the risks of umbilical cord compression, which could cut off oxygen flow to the baby.
  • Other intravenous fluid delivery methods

It is important to note, however, that the above techniques, if successful, are temporary. They do not treat the underlying cause of the oligohydramnios. In many cases, the condition can indicate issues with the uteroplacental circulation. Depending on the circumstances, in situations where the baby’s circulation may be compromised, the baby may need to be delivered to provide them with medical treatment. Mothers with low amniotic fluid should be monitored very closely with serial ultrasounds to check on the health of their baby. Low amniotic fluid increases the risk of umbilical cord compression and hypoxic-ischemic encephalopathy (HIE). Delivery is typically performed when fluid is low depending on gestational age.

Managing Oligohydramnios During the First Trimester

Reduced amniotic fluid during the first trimester is a rare finding, and information regarding the causes of this diagnosis are equally as rare. Serial ultrasounds are helpful for following the natural history of the pregnancy, and they help to generate a plan for the care of the condition following the diagnosis.

Managing Oligohydramnios During the Second Trimester

Management and prognosis of oligohydramnios during the second trimester depend on the cause and severity of lowered amniotic fluid volume. In amniotic fluid levels that border on normal, the prognosis is typically positive. Medical professionals typically recommend serial ultrasounds to determine if the condition is stable, resolved, or has progressed into more severe oligohydramnios or fetal growth restriction. More severe oligohydramnios in the second trimester may cause fetal complications or pregnancy loss.

Managing Oligohydramnios During the Third Trimester

Cases of oligohydramnios during the third trimester can result in serious injury to the baby. Due to this risk, pregnant women with oligohydramnios should undergo assessment of acute and long-term fetal conditions at each prenatal visit. The frequency of the testing is dependent on the amniotic fluid volume and the trend of decreasing fluid levels. Refer to the “Monitoring Oligohydramnios During Pregnancy” section for more information. 

The longer the duration of oligohydramnios, the higher the risk of death and injury to the infant. Physicians typically expect favorable outcomes when they know what is causing lowered amniotic fluid levels, and when the baby is being carefully monitored. Whether the cause of oligohydramnios is known or unknown, fetal testing and monitoring may lead to a recommendation for delivery, which can include a recommendation for Cesarean delivery. Care standards require physicians to discuss the risks and benefits of various management plans with their patients.

Managing Oligohydramnios in Post-Term Pregnancies

Oligohydramnios in post-term pregnancies is associated with higher incidence of meconium-stained fluid and an increased need for C-section delivery. Medical personnel must utilize continuous fetal heart rate monitoring during labor. If the fetal heart rate becomes abnormal, delivery should occur right away to prevent birth injuries and hypoxic-ischemic encephalopathy (HIE). Afterward, appropriate surveillance of a post-term baby is crucial.

Oligohydramnios and Medical Malpractice

Improperly managed oligohydramnios can have devastating health consequences for the baby. Therefore, it is essential that physicians follow standards of care and carefully monitor the mother and baby during pregnancy, particularly when risk factors for oligohydramnios are present.

Some areas that may constitute medical negligence in the management or treatment of oligohydramnios include:

  • Failure to obtain a thorough history of the mother, thereby missing risk factors for lowered amniotic fluid levels
  • Failure to properly monitor the mother and baby during pregnancy and recognize low amniotic fluid, decreasing amniotic fluid, placental insufficiency, fetal distress, or risk factors for the condition
  • Failure to prevent conditions that can cause decreased amniotic fluid volume, such as gestational diabetes, dehydration, chronically high blood pressure, and use of ACE inhibitors
  • Failure to follow standards of care regarding timely delivery of the baby, including failure to order and/or perform a timely delivery
  • Failure to obtain adequate informed consent from the mother regarding the risks, benefits, and alternatives of various methods of treatment pertaining to amniotic fluid deficiency and associated delivery

Babies with injuries resulting from oligohydramnios often go on to live with permanent disabilities, specialized lifestyle needs, and complex health problems. If a medical professional fails to properly handle decreased amniotic fluid levels and the result is injury, it is considered medical negligence. These victims may be entitled to compensation from a successful medical malpractice lawsuit.

Trusted Legal Help for Oligohydramnios and Birth Injury Cases

Michigan Birth Trauma Attorneys with a National Presence

Improperly handled oligohydramnios can cause permanent disability. Children with birth injuries often go on to require expensive, specialized health and lifestyle supports. If you feel your pregnancy was managed improperly and this caused your baby to sustain an injury, please contact the birth injury attorneys at Reiter & Walsh ABC Law Centers. Our attorneys focus solely on birth injury cases, and we have handled cases involving oligohydramnios, intrauterine growth restriction (IUGR), cerebral palsy, hypoxic-ischemic encephalopathy (HIE), and intellectual and developmental disabilities (I/DD).

If you’d like to speak to us regarding your case, please know that your information will always be 100% confidential. We have a no-fee guarantee – you will never pay out of pocket, and we only get paid if we make a recovery for you.

The Reiter & Walsh, P.C. birth trauma attorneys handle cases all over the United States, in places including Michigan, Pennsylvania, Wisconsin, Tennessee, Mississippi, Texas, Ohio, Washington D.C., Arkansas, and more. Additionally, our team handles cases involving military hospitals and federally funded clinics. To begin your free case review, please contact Reiter & Walsh ABC Law Centers in any of the following ways:

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Video: Emergency C-Sections

As we discussed on this page, oligohydramnios may prompt the need for Cesarean delivery. Learn more about C-sections in this video:


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