Acute Fatty Liver of Pregnancy: The Rare Third-Trimester Emergency Every Pregnant Person Should Know
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026
Acute fatty liver of pregnancy (AFLP) is a rare but serious condition — affecting about 1 in 10,000 to 20,000 pregnancies per year — in which too much fat builds up in the liver during the late third trimester (week 36 is the average gestational age at diagnosis). It is a medical emergency that requires immediate delivery of the baby; the liver typically heals itself afterward, with liver function usually returning to normal within 10 days. AFLP is unpredictable and unpreventable, but early recognition of symptoms — nausea, vomiting, upper-right abdominal pain, jaundice, extreme tiredness — and prompt blood testing can be life-saving for both mother and baby.
Quick Answer
What it is: Acute fatty liver of pregnancy (AFLP) is a rare, serious condition in which too much fat builds up in the liver during pregnancy, potentially causing liver failure and other life-threatening complications. It affects about 1 in 10,000 to 20,000 pregnancies each year.
When it happens: AFLP typically starts late in the third trimester — 36 weeks is the average length of the pregnancy at diagnosis — though it can occur up until delivery or sooner.
How it is treated: AFLP is a medical emergency and the treatment is immediate delivery of the baby; once the fetus and placenta are removed, the liver can begin healing itself.
The outlook: With prompt delivery, liver function typically returns to normal within 10 days, but untreated AFLP can be deadly for both mother and baby — which is why any persistent third-trimester symptoms should be reported to a pregnancy care provider right away.
What Is Acute Fatty Liver of Pregnancy?
Acute fatty liver of pregnancy (AFLP) is a rare but serious condition that can cause liver failure, as well as other life-threatening complications. It happens when too much fat builds up in the liver during pregnancy.
AFLP is a medical emergency. Treatment involves delivering the fetus as soon as possible to protect both the mother and the baby.
How Common Is Acute Fatty Liver of Pregnancy?
AFLP is rare. It affects about 1 in 10,000 to 20,000 pregnancies each year.
Key Fact | Detail |
Frequency | About 1 in 10,000 to 20,000 pregnancies each year |
Timing | Usually late in the third trimester |
Average gestational age at diagnosis | 36 weeks |
Predictable? | No — unpredictable and unpreventable |
Treatment | Immediate delivery of the baby |
What Are the Symptoms of Acute Fatty Liver of Pregnancy?
AFLP typically starts late in the third trimester of pregnancy — 36 weeks is the average length of the pregnancy at diagnosis. However, it can occur up until delivery or sooner.
The most common symptoms of AFLP include:
Symptom | Description |
Nausea and vomiting | Persistent digestive distress |
Abdominal pain | Mainly on the upper right side, where the liver sits |
Tiredness | Extreme fatigue beyond normal pregnancy exhaustion |
General unwell feeling | An overall sense of illness |
Loss of appetite | Reduced desire to eat |
Excessive thirst | Unusual, persistent thirst |
Jaundice | Yellowing of the skin and the whites of the eyes |
Confusion | Or being unable to concentrate |
The symptoms of AFLP resemble symptoms of other conditions. Discuss any symptoms you are having during pregnancy with your pregnancy care provider. AFLP is a medical emergency and requires prompt treatment.
What Causes Acute Fatty Liver of Pregnancy?
Researchers are not sure what causes acute fatty liver of pregnancy. The liver is responsible for breaking down fatty acids. With AFLP, there is too much fat in the liver due to a problem with how the liver breaks down fat. The fat clogs up the liver and interferes with how it functions. This can be deadly if left untreated.
Studies show AFLP may be genetic. An enzyme deficiency called long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) may cause AFLP.
LCHAD deficiency is a rare autosomal recessive disorder — this means both biological parents must carry the gene to pass it to the fetus. With LCHAD, the fetus cannot metabolize fatty acids. The fatty acids pass through the placenta into the mother's bloodstream, which in turn can cause fat to build up in the mother's liver.
What Are the Risk Factors for Acute Fatty Liver of Pregnancy?
AFLP may be genetic — inherited from biological parents. Other risk factors include:
Risk Factor | Note |
First pregnancy | Most commonly occurs in first-time pregnancies |
Twins or more | Multiple pregnancies raise the risk |
Expecting a male fetus | Boys appear to carry higher risk |
Diabetes | Pre-existing diabetes is a known factor |
Intrahepatic cholestasis of pregnancy | A separate liver-related pregnancy condition |
Preeclampsia | A blood-pressure pregnancy disorder |
Obesity | Elevated body weight increases risk |
A critical point for expecting parents: your pregnancy care provider cannot predict whether you will get AFLP — even if you have all of the risk factors. Along with being unpredictable, it is also unpreventable.
What Are the Complications of Acute Fatty Liver of Pregnancy?
Acute fatty liver of pregnancy can be deadly. Both the mother and the fetus are at risk of serious complications, including:
Potential Complication | Organ System |
Liver failure | Liver |
Kidney failure | Kidneys |
Lung failure | Lungs |
Infection | Immune system |
Hemorrhage | Blood loss |
How Is Acute Fatty Liver of Pregnancy Diagnosed?
Early diagnosis and quick treatment are essential, because AFLP can lead to organ failure.
The most accurate diagnostic tool is a liver biopsy — the provider examines liver tissue under a microscope. However, a biopsy is not always safe during pregnancy. Often, the provider can diagnose AFLP based on symptoms and health history.
The provider will order blood tests to look for AFLP. Liver function blood test results may raise a red flag and lead the provider to suspect AFLP. These tests often show signs of:
Test Finding | What It Signals |
Higher levels of liver enzymes | Elevated liver enzymes indicating liver stress |
Blood clotting problems | Impaired coagulation |
Increased ammonia, uric acid, and protein | Buildup of waste products in the blood |
Low blood sugar | Hypoglycemia |
Evidence of kidney damage | Early renal impairment |
To make a diagnosis, the provider may also order an ultrasound or computed tomography (CT scan) to get a detailed view of the liver.
How Is Acute Fatty Liver of Pregnancy Treated?
The pregnancy care provider will recommend delivery as soon as possible to avoid life-threatening complications. The liver can begin healing itself once the provider removes the fetus and the placenta.
What Is the Outlook After Acute Fatty Liver of Pregnancy?
AFLP requires immediate delivery. Your liver function typically returns to normal within 10 days of delivery. You may need to remain in the hospital under your provider's care until your liver test values are in a typical range.
Your risk of getting AFLP again is unknown. Your provider may recommend genetic testing to see whether any fatty acid abnormalities contributed to developing AFLP. They may also recommend a maternal-fetal medicine specialist monitor any future pregnancies.
What Happens to the Baby?
In general, the more severe the disease is, the more effects it has on the fetus. Some children are at risk of developing nonketotic hypoglycemia — a condition that prevents them from processing amino acids. Others may develop dilated cardiomyopathy or neuropathy. Notably, the risk to the fetus is usually less than the risk to the mother.
Outcome Aspect | What to Expect |
Mother's liver recovery | Function typically normal within 10 days of delivery |
Hospital stay | Until liver test values return to typical range |
Risk of AFLP recurring | Unknown — genetic testing may help explain the cause |
Baby's liver risk | Nonketotic hypoglycemia (impaired amino acid processing) |
Baby's other risks | Dilated cardiomyopathy, neuropathy |
Relative risk | Risk to the fetus is usually less than the risk to the mother |
Can Acute Fatty Liver of Pregnancy Be Prevented?
AFLP is rare, and there is not anything you can do to prevent it or predict it. The best protection is awareness and communication: share your complete medical history with your pregnancy care provider and report any symptoms you have during pregnancy. Being transparent and honest with your provider is the best way to get the care you need.
When Should a Pregnant Person Contact a Provider?
Contact your healthcare provider if you feel any of the following symptoms during pregnancy:
Warning Symptom | Why It Matters |
Abdominal pain or pelvic pain that doesn't go away | May signal liver or other organ stress |
Extreme tiredness or feeling unwell | Beyond typical pregnancy fatigue |
Nausea and vomiting | Persistent digestive distress |
Headaches that don't go away | A possible sign of pregnancy complications |
How Is AFLP Different From HELLP Syndrome?
HELLP syndrome — Hemolysis, Elevated Liver enzymes, and Low Platelet count syndrome — is a pregnancy condition with similarities to AFLP. The main difference between the two conditions appears in how blood work results change over time. AFLP typically causes clotting issues as well as changes in platelet levels, while HELLP syndrome typically causes a more progressive decline in platelet count.
Additionally, people with AFLP are more likely to have:
Finding More Common in AFLP | Detail |
Severe abnormalities in liver function tests | Marked liver enzyme disruption |
Abnormal blood glucose | Evidence of hypoglycemia |
Signs of abnormal kidney function | Early renal impairment |
High bilirubin | Elevated levels of the waste product |
Acidosis | A buildup of acid in the blood |
Proteinuria | Protein in the urine |
Changes to brain function | Inability to think clearly or confusion |
Is Fatty Liver Normal in Pregnancy?
Fatty liver disease is a common, treatable condition in people who are not pregnant, and most people have some fat in their liver. Fatty liver can, however, progress to liver failure.
During pregnancy, fatty liver is especially dangerous because your liver removes toxins from your body. If your liver — or the fetus's liver — is not functioning properly, harmful substances can clog your bloodstream.
Conclusion
Acute fatty liver of pregnancy is one of the rarest yet most consequential emergencies of the third trimester. Striking in roughly 1 in 10,000 to 20,000 pregnancies, it announces itself in late pregnancy — on average at 36 weeks — with symptoms that masquerade as ordinary late-pregnancy complaints: nausea, vomiting, fatigue, and upper-right abdominal pain. It cannot be predicted and it cannot be prevented. What can be controlled is the response: recognizing the warning signs, calling your pregnancy care provider promptly, and delivering the baby quickly. When that happens, the prognosis improves dramatically — the liver typically heals itself within 10 days of delivery, and the risk to the baby is usually less than the risk to the mother.
If you are in your third trimester and experiencing persistent nausea and vomiting, upper-right abdominal pain, extreme tiredness, or yellowing of the skin or eyes, contact your pregnancy care provider today — do not wait for your next appointment. Ask whether blood tests are needed, ask about AFLP explicitly if liver enzymes come back abnormal, and share your complete medical history, including any diabetes, preeclampsia, or cholestasis, so your care team can act at the first warning sign.
Questions to Ask Your Provider
Do I need to deliver right now?
Is my life at risk? Is my baby's life at risk?
Will AFLP go away?
What treatments do I need?
Will this happen if I get pregnant again?
Do you know why this happened?
Frequently Asked Questions
What is acute fatty liver of pregnancy?
Acute fatty liver of pregnancy (AFLP) is a rare but serious condition that can cause liver failure and other life-threatening complications. It happens when too much fat builds up in the liver during pregnancy. It is a medical emergency that involves delivering the fetus as soon as possible. It affects about 1 in 10,000 to 20,000 pregnancies each year.
When does acute fatty liver of pregnancy usually develop?
AFLP typically starts late in the third trimester of pregnancy — 36 weeks is the average length of the pregnancy at diagnosis. However, it can occur up until delivery or sooner.
What are the first symptoms of acute fatty liver of pregnancy?
The most common symptoms include nausea and vomiting, abdominal pain (mainly on the upper right side), tiredness, a general unwell feeling, loss of appetite, excessive thirst, jaundice (yellowing of the skin and whites of the eyes), and confusion or being unable to concentrate. Because these symptoms resemble other conditions, any persistent symptom during pregnancy should be discussed with a pregnancy care provider.
What causes acute fatty liver of pregnancy?
Researchers are not sure of the exact cause. With AFLP, a problem with how the liver breaks down fat allows too much fat to accumulate, clogging the liver and interfering with its function. Studies suggest AFLP may be genetic: an enzyme deficiency called long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD) may cause it. LCHAD is a rare autosomal recessive disorder — both biological parents must carry the gene. With LCHAD, the fetus cannot metabolize fatty acids, which pass through the placenta into the mother's bloodstream and cause fat buildup in her liver.
What are the risk factors for acute fatty liver of pregnancy?
Risk factors include it being a first pregnancy, carrying twins or more, expecting a male fetus, having diabetes, having intrahepatic cholestasis of pregnancy, having preeclampsia, and having obesity. However, a pregnancy care provider cannot predict who will develop AFLP even if all risk factors are present — the condition is unpredictable and unpreventable.
How is acute fatty liver of pregnancy diagnosed?
The most accurate diagnostic tool is a liver biopsy, though it is not always safe during pregnancy; diagnosis is often made from symptoms and health history. Blood tests looking for AFLP typically show higher liver enzymes, blood clotting problems, increased ammonia, uric acid, and protein in the blood, low blood sugar, and evidence of kidney damage. An ultrasound or CT scan may also be ordered for a detailed view of the liver.
How is acute fatty liver of pregnancy treated?
The pregnancy care provider will recommend delivery as soon as possible to avoid life-threatening complications. Once the fetus and placenta are removed, the liver can begin healing itself. There is no other treatment that reverses AFLP — delivery is the definitive intervention.
How long does recovery from acute fatty liver of pregnancy take?
Liver function typically returns to normal within 10 days of delivery. The mother may need to remain in the hospital until liver test values are in a typical range. The risk of getting AFLP again is unknown; providers may recommend genetic testing and, for future pregnancies, monitoring by a maternal-fetal medicine specialist.
References
Medical Disclaimer: This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Acute fatty liver of pregnancy is a rare but life-threatening medical emergency affecting approximately 1 in 10,000 to 20,000 pregnancies, and it can lead to liver, kidney, and lung failure as well as hemorrhage. Anyone who is pregnant and experiences persistent symptoms such as upper-right abdominal pain, nausea and vomiting, extreme tiredness, jaundice, or confusion should contact a pregnancy care provider or seek emergency care immediately — never wait for a scheduled appointment. Only a licensed healthcare provider can diagnose AFLP and determine the appropriate treatment plan, which may include immediate delivery.
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