Correct Answer: C. Third trimester
Acute fatty liver of pregnancy (AFLP) is a rare but life-threatening condition that manifests almost exclusively in the third trimester, typically after 30 weeks of gestation, with peak incidence between 35–36 weeks. The pathophysiology involves impaired mitochondrial β-oxidation of fatty acids, often triggered by placental insufficiency and metabolic stress in late pregnancy. The condition presents with prodromal symptoms (nausea, vomiting, malaise, abdominal pain) progressing to jaundice, coagulopathy, encephalopathy, and acute liver failure. The strong temporal association with the third trimester is explained by the exponential increase in fetal metabolic demands and placental dysfunction as pregnancy advances. Indian obstetric practice (per FOGSI guidelines and DC Dutta's Obstetrics) recognizes AFLP as a medical emergency requiring immediate delivery as the definitive treatment. The incidence is approximately 1 in 7,000–15,000 pregnancies in India, with maternal mortality ranging 5–18% if untreated. Early recognition and prompt termination of pregnancy are critical for maternal and fetal survival.
Why the other options are wrong
A. First trimester — AFLP does not occur in the first trimester because placental insufficiency and the metabolic stress that triggers mitochondrial dysfunction have not yet developed. First-trimester liver dysfunction is typically from other causes (viral hepatitis, drug-induced, autoimmune). This is a temporal trap—students may confuse AFLP with hyperemesis gravidarum, which peaks in the first trimester but does not cause acute hepatic failure. B. Second trimester — While liver disease can occur in the second trimester (e.g., intrahepatic cholestasis of pregnancy, HELLP syndrome), AFLP is distinctly a third-trimester phenomenon. The second trimester lacks the severe placental dysfunction and fetal metabolic burden required to trigger the mitochondrial β-oxidation defect. Confusing AFLP with other pregnancy-related liver diseases is a common NBE trap. D. Both a and b — This option incorrectly suggests AFLP can present in both first and second trimesters, which contradicts the well-established third-trimester predominance. The inclusion of this distractor tests whether students understand the specific temporal pattern of AFLP versus other pregnancy-related conditions. AFLP is virtually never seen before 30 weeks.
High-Yield Facts
- AFLP peak incidence: 35–36 weeks gestation; virtually never before 30 weeks (third trimester only).
- Pathophysiology: Impaired mitochondrial β-oxidation of fatty acids due to placental insufficiency and fetal metabolic stress.
- Definitive treatment: Immediate delivery (vaginal or cesarean) is the only curative intervention; supportive care alone is insufficient.
- Maternal mortality: 5–18% if untreated; reduced to <5% with early recognition and prompt delivery in Indian tertiary centers.
- Classic presentation: Prodrome (nausea, vomiting, abdominal pain) → jaundice → coagulopathy → encephalopathy → acute liver failure.
- Associated risk factors: Primigravida, male fetus, multiple pregnancy, obesity, preeclampsia/HELLP overlap.
Mnemonics
AFLP Timing = LATE Pregnancy Late (third trimester, >30 weeks) | Acute (rapid onset) | Termination (delivery is cure) | Emergency (life-threatening). Use this to anchor the third-trimester timing and the urgency of management. Third Trimester Liver Diseases: HELLP-AFLP-ICP** HELLP (hemolysis, elevated LFTs, low platelets) | AFLP (acute fatty liver) | I**CP (intrahepatic cholestasis). All three are third-trimester phenomena, but AFLP is the most fulminant and requires immediate delivery.
NBE Trap
NBE pairs AFLP with "pregnancy-related liver disease" to lure students into selecting second trimester (intrahepatic cholestasis) or first trimester (hyperemesis). The key discriminator is the third-trimester-specific temporal pattern and the fulminant presentation with coagulopathy and encephalopathy, not just cholestasis or transaminitis.
Clinical Pearl
In Indian tertiary obstetric units, a primigravida presenting with jaundice + vomiting + abdominal pain after 34 weeks should trigger immediate AFLP workup (PT/INR, fibrinogen, liver enzymes, blood glucose, ammonia) and obstetric consultation for delivery planning. Delay in recognition is the leading cause of maternal death in AFLP cases in India.
_Reference: DC Dutta's Obstetrics, 8th ed., Ch. 21 (Medical Disorders in Pregnancy); FOGSI Guidelines on Obstetric Emergencies; Harrison's Principles of Internal Medicine, Ch. 297 (Liver Disease in Pregnancy)_