Acute Fatty Liver of Pregnancy: Symptoms

Acute fatty liver of pregnancy symptoms can be easy to miss in the early stages, yet prompt recognition is essential to protect both mother and baby. This rare but serious obstetric emergency typically develops in the third trimester, causing rapid liver dysfunction that can escalate to life-threatening failure if not identified and treated quickly. Early features such as nausea, vomiting, and upper abdominal discomfort are often mistaken for normal pregnancy complaints, making awareness of the full symptom picture critical. This article explains what to look for, how diagnosis is made on the NHS, and what the risks are if the condition is left untreated.

What is acute fatty liver of pregnancy and how common is it in the UK?

AFLP is a rare but life-threatening obstetric emergency in which fat accumulates in liver cells during the third trimester, affecting approximately 1 in 7,000 to 1 in 20,000 pregnancies in the UK.

Acute fatty liver of pregnancy (AFLP) is a rare but serious obstetric emergency in which fat accumulates abnormally within liver cells during the third trimester, causing rapid and potentially life-threatening liver failure. It is distinct from other liver conditions of pregnancy, such as intrahepatic cholestasis or HELLP syndrome, although these can sometimes overlap in presentation and distinguishing between them can be clinically challenging. The condition typically arises after 28 weeks of gestation, most often in the late third trimester, though earlier cases and cases presenting in the early postpartum period have been reported.^[9][12]

UK incidence estimates vary across published studies; figures in the range of approximately 1 in 7,000 to 1 in 20,000 pregnancies have been cited in the literature, though the precise rate depends on the population studied and the diagnostic criteria applied.^[1] Data from UK Obstetric Surveillance System (UKOSS) studies and MBRRACE-UK reports provide the most reliable UK-specific information on incidence and outcomes. Certain factors have been reported to increase the likelihood of developing AFLP, including multiple pregnancies (particularly twins), carrying a male fetus, and a fetal deficiency in long-chain 3-hydroxyacyl-CoA dehydrogenase (LCHAD), an enzyme involved in fatty acid metabolism.^[1][9] When the fetus cannot process long-chain fatty acids normally, these accumulate and are thought to contribute to maternal liver injury, though the strength of evidence for individual risk factors varies.^[6][9]

Because AFLP is uncommon, recognition can be delayed, and early identification is critical: outcomes for both mother and baby depend heavily on how quickly the diagnosis is made and delivery is arranged. UK specialist obstetric and maternal medicine teams, guided by frameworks such as the RCOG Green-top Guideline on Liver Disease in Pregnancy and BSG/BASL guidance on abnormal liver tests in pregnancy, play a central role in managing suspected cases. Any woman presenting with unexplained liver dysfunction in late pregnancy or the early postpartum period should be assessed promptly in a hospital setting.

What are the early warning signs and symptoms to watch for?

Early symptoms include nausea, vomiting, fatigue, and upper abdominal discomfort; jaundice, confusion, dark urine, and hypoglycaemia indicate progression and require urgent hospital assessment.

The early symptoms of acute fatty liver of pregnancy are often non-specific, which is one reason the condition can be difficult to recognise in its initial stages. Nausea, vomiting, and abdominal discomfort, particularly in the upper right quadrant, are among the most commonly reported early features, typically appearing in the days to weeks before the condition becomes severe. Fatigue and a general sense of feeling unwell are also frequently described. Symptoms can occasionally begin in the early postpartum period rather than before delivery.

As AFLP progresses, more distinctive features may emerge. These include:

• Jaundice, which reflects impaired liver function and bilirubin processing

• Polydipsia and polyuria, which have been reported in some cases and are thought to relate to transient diabetes insipidus associated with AFLP, though this is not universal^[2][16]

• Headache and confusion, which may indicate developing encephalopathy

• Oedema and fluid retention, though these are non-specific in pregnancy and also occur in pre-eclampsia and other conditions, so their presence alone should not be attributed to AFLP

• Dark urine and pale stools, which can accompany jaundice and warrant prompt assessment, though they are not specific to AFLP

In more advanced cases, signs of acute liver failure can develop rapidly, including coagulopathy (abnormal clotting), hypoglycaemia, and renal impairment. Ascites (fluid in the abdomen) may also be present.

Any pregnant woman in the third trimester, or in the early postnatal period, who develops persistent nausea and vomiting, jaundice, or unexplained abdominal pain should seek urgent medical assessment. These symptoms should not be attributed to normal pregnancy discomfort without appropriate investigation. Women experiencing these symptoms should contact their midwife or maternity unit promptly, or call NHS 111 for urgent advice if they are unable to reach their care team. If symptoms are severe, such as confusion or collapse, emergency services (999) should be called immediately.

How is acute fatty liver of pregnancy diagnosed on the NHS?

Diagnosis combines clinical assessment, blood tests, and imaging using the Swansea criteria; six or more criteria, including elevated liver enzymes, coagulopathy, and hypoglycaemia, support the diagnosis.

Acute fatty liver of pregnancy is diagnosed through a combination of clinical assessment, blood tests, and imaging, with no single test being definitively diagnostic on its own. When AFLP is suspected, a woman will typically be admitted to hospital for urgent investigation. The Swansea criteria, first described by Ch'ng and colleagues and subsequently validated in UK practice, are widely used to support diagnosis: a woman is considered likely to have AFLP if she meets six or more of the defined criteria in the absence of another explanation. The criteria include vomiting, abdominal pain, polydipsia or polyuria, encephalopathy, elevated bilirubin, elevated uric acid, leucocytosis, hypoglycaemia, elevated transaminases, elevated creatinine, coagulopathy, and microvesicular steatosis on liver biopsy or imaging.

Key blood test findings that support a diagnosis of AFLP include:

• Elevated liver enzymes (alanine aminotransferase and aspartate aminotransferase)

• Raised bilirubin, indicating impaired liver excretion

• Prolonged prothrombin time and low fibrinogen, reflecting coagulopathy

• Hypoglycaemia, which can be profound and requires close monitoring

• Elevated creatinine and urea, suggesting renal involvement

• Raised white cell count and elevated uric acid

• Thrombocytopaenia (low platelet count)

Ultrasound of the liver may show increased echogenicity consistent with fatty infiltration, though imaging findings can be subtle or absent. If cross-sectional imaging is required, MRI is generally preferred in pregnancy given the absence of ionising radiation; CT may occasionally be used but should be justified and should not delay management when clinical suspicion is high.^[9]

Liver biopsy, which would show microvesicular steatosis on histology, is rarely performed during pregnancy due to the associated risks, particularly in the context of coagulopathy.^[12][13] Diagnosis is therefore largely clinical and biochemical. Where possible, maternal stabilisation, including correction of hypoglycaemia and coagulopathy with blood products, should be undertaken alongside diagnostic assessment. Once AFLP is confirmed or strongly suspected, the multidisciplinary team, including obstetricians, maternal medicine specialists, hepatologists, obstetric anaesthetists, intensivists, and neonatologists, will plan urgent delivery, as this is the definitive treatment. Transfer to a tertiary centre with appropriate facilities should be considered where local resources are insufficient.

What are the risks to mother and baby if it is left untreated?

Untreated AFLP can progress to fulminant liver failure, multi-organ failure, and maternal death, while the baby faces risks of fetal distress, preterm birth, and stillbirth.

If acute fatty liver of pregnancy is not recognised and treated promptly, it carries significant risks of serious maternal and fetal harm. For the mother, untreated AFLP can progress rapidly to fulminant liver failure, which may be complicated by severe coagulopathy, gastrointestinal bleeding, acute kidney injury, and hepatic encephalopathy. Sepsis and multi-organ failure are recognised complications in the most severe cases. Historically, maternal mortality from AFLP was very high; UK data from UKOSS and MBRRACE-UK reports indicate that outcomes have improved considerably with better recognition and intensive care, though the condition remains potentially fatal without timely intervention.^[1][9]

For the baby, the risks are also substantial. Fetal distress, preterm birth, and stillbirth are all recognised complications, particularly when diagnosis is delayed. Neonates born to mothers with AFLP should be assessed for LCHAD deficiency, as this inherited metabolic disorder, if present, requires specific dietary management to prevent serious harm to the child.^[6][19] This testing is not part of the routine UK newborn blood spot programme and requires input from paediatric metabolic or clinical genetics services.^[7][8]

Delivery of the baby is the cornerstone of treatment for AFLP, regardless of gestational age, as the liver typically begins to recover once the pregnancy has ended.^[9][10] Supportive care in a high-dependency or intensive care setting is usually required, including correction of hypoglycaemia, management of coagulopathy with blood products, and close monitoring of renal and hepatic function. Laboratory values typically begin to normalise in the days to weeks following delivery, though the trajectory varies between individuals.

Women who have had AFLP should receive postnatal follow-up, including monitoring of liver function tests until they return to normal, to confirm liver recovery and to discuss the implications for future pregnancies. Recurrence in subsequent pregnancies has been reported, and women should be referred for preconception counselling and early monitoring by a maternal medicine team if they are considering a further pregnancy. Referral to clinical genetics or paediatric metabolic services for LCHAD-related counselling and family testing may be appropriate. Any concerns following discharge should be raised with a GP or the postnatal care team.

Frequently Asked Questions