Oligohydramnios (Low Amniotic Fluid)
Amniotic fluid is the fluid around the baby that protects them in the womb. It is first made up of water from the mother, but over time becomes made up of fetal urine (1). Oligohydramnios occurs when the volume of fluid in the amniotic sac is too low. Roughly 4% of pregnant women are diagnosed with oligohydramnios.
What is amniotic fluid?
Amniotic fluid is the liquid that surrounds the fetus during pregnancy. Located in the amniotic sac, amniotic fluid protects the growing baby and provides nutrients to the developing fetus that help it mature, grow, and maintain a consistent body temperature (1). 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 causes oligohydramnios?
Oligohydramnios can occur any time during pregnancy, but is most commonly diagnosed in the third trimester. Oligohydramnios is typically caused by the following (1):
- Placental issues: If the placenta isn’t providing enough nutrients for the baby, then the baby may stop recycling fluid, therefore lowering the amniotic fluid.
- Birth defects: Certain birth defects cause problems in the fetal urinary tract and kidneys, leading to insufficient urine production.
- Premature rupture of membranes PROM: When the water breaks before labor begins.
- Leaking of amniotic fluid: A tear in the membrane can cause a gush or a trickle of amniotic fluid to leak.
- Post-date pregnancy: A pregnancy that goes past 42 weeks is at risk of oligohydramnios because the amniotic fluid can decrease by half after this time. Moreover, one study of 3050 uncomplicated pregnancies with singleton fetuses between 40 and 41.6 weeks gestation found that 11% of them presented with oligohydramnios (2).
- Maternal problems: Maternal conditions, such as diabetes, dehydration, hypertension, and preeclampsia have an effect on amniotic fluid levels.
See our section below called “Managing oligohydramnios throughout pregnancy” for more details on the causes of oligohydramnios in each individual trimester.
Oligohydramnios must to be diagnosed and managed early to prevent the possibility of future injury, brain damage, or disability in the baby.
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 (1).
Risk factors for oligohydramnios include:
- Maternal hypertension/preeclampsia
- Maternal diabetes
- Maternal dehydration
- Maternal hypoxia
- Placental issues
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 (2, 3, 4):
- Leaking of the amniotic fluid
- Low amniotic fluid on an ultrasound
- Measurements of size smaller than what is normal for gestational age
- Low maternal weight gain
- Prelabor Rupture of membranes
- Abdominal discomfort
- Sudden drop in fetal heart rate
- Little to no fetal movement, or decreasing fetal movement
- Abnormal findings on a fetal monitor, including fetal distress
Oligohydramnios is typically diagnosed by (2):
- An incidental finding in a routine ultrasound or an ultrasound given for another reason
- An ultrasound given to test amniotic fluid level in someone who is at risk
- An ultrasound given in response to a uterine size that is less than expected for gestational age
- An ultrasound given in response to a patient who presents with premature rupture of membranes (PROM)
Ultrasonic diagnosis of oligohydramnios is performed by obtaining a measurement called the amniotic fluid index, or the AFI (1). 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. AFI is calculated by measuring the depth of the amniotic fluid in four sections of the uterus and adding them together (2). The doctor can take objective measurements using the AFI, and will diagnose oligohydramnios when the amniotic fluid index is less than 5 and the single deepest pocket is less than 2 cm. The doctor can also use a dye-dilution method to quantify the volume of amniotic fluid. The doctor must also look to downward trends in amniotic fluid over time.
An AFI less than 5 centimeters indicates oligohydramnios. A borderline AFI of 5-10 centimeters, however, has been associated with many risks, including (5):
- Fetal heart rate deceleration
- Meconium aspiration
- Low Apgar score
- Low birth weight
- NICU admission
- Non-reactive non-stress tests
- Immediate cesarean delivery
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 10 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.
Complications of oligohydramnios
Oligohydramnios can cause the following injuries and complications:
- Increased chance of miscarriage or stillbirth
- Compression of fetal organs that can lead to birth asphyxia or hypoxic-ischemic encephalopathy (HIE)
- Premature birth
- Intrauterine growth restriction
- Cord compression
- Cerebral palsy
- Preterm birth
- Meconium aspiration
Managing oligohydramnios throughout pregnancy
Can you increase amniotic fluid levels?
There is no long-term treatment for oligohydramnios (2). 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 (2). 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 (2). This may help ‘pad’ the umbilical cord, reducing the risks of umbilical cord compression, which could cut off oxygen flow to the baby.
- Investigational therapies: Certain investigational therapies are used to increase amniotic fluid, including tissue sealants, a combination of hydration and DDAVP (desmopressin), and other 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. In situations where the baby’s circulation may be compromised, the baby may need to be delivered in order to receive medical treatment.
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 rare (2). 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
Second trimester oligohydramnios diagnosis can result from fetal or maternal issues (2). Some fetal disorders may be present, such as intrinsic renal disorders, obstructive lesions in the urinary tract, and other fetal kidney/urinary tract issues. Maternal issues that can cause second trimester oligohydramnios include placental issues, rupture of fetal membranes, and others.
Management and prognosis of oligohydramnios during the second trimester depend on the cause and severity of lowered amniotic fluid volume (2). In amniotic fluid levels that border on normal, the prognosis is typically positive. Medical professionals usually 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 are often caused by maternal conditions, such as preeclampsia or maternal vascular diseases (2). These conditions are often related to preterm premature rupture of membranes or uteroplacental insufficiency.
Third trimester oligohydramnios can result in serious injury to the baby (2). 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.
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
Amniotic fluid normally decreases post-term, so oligohydramnios is common (2). 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 (1). 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 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 children may be entitled to compensation from a successful medical malpractice lawsuit.
Trusted legal help for oligohydramnios and birth injury cases
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 ABC Law Centers. Our attorneys focus solely on birth injury cases, and 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.
If you’d like to speak to us regarding your case, please know that your information will always be 100% confidential. To begin your free case review, please contact 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:
- Low Amniotic Fluid Levels: Oligohydramnios: Causes & Treatment. (2017, May 26). Retrieved February 8, 2019, from http://americanpregnancy.org/pregnancy-complications/oligohydramnios/
- Beloosesky, R., & Ross, M. (n.d.). Retrieved February 9, 2019, from https://www.uptodate.com/contents/oligohydramnios
- Oligohydramnios. (n.d.). Retrieved April 15, 2019, from https://www.marchofdimes.org/complications/oligohydramnios.aspx
- What to Expect, E. (2019, April 01). Low Amniotic Fluid (Oligohydramnios) During Pregnancy. Retrieved April 15, 2019, from https://www.whattoexpect.com/pregnancy/pregnancy-health/complications/oligohydramnios.aspx
- Asgharnia, M., Faraji, R., Salamat, F., Ashrafkhani, B., Dalil Heirati, S. F., & Naimian, S. (2013). Perinatal outcomes of pregnancies with borderline versus normal amniotic fluid index. Iranian journal of reproductive medicine, 11(9), 705-10.