Hepatitis E causes large-scale epidemics in endemic areas. The disease, during epidemics, has increased incidence and severity in pregnant women. Sporadic acute viral hepatitis (AVH) is common in endemic areas. The relationship of sporadic AVH and pregnancy has not been well studied. Over a 3-year period we prospectively studied 76 pregnant women and 337 non-pregnant women of childbearing age with sporadic acute viral hepatitis for aetiology, clinical course and outcome of disease. The aetiology in sporadic AVH was hepatitis A virus (HAV) in six (1.5%), hepatitis B virus (HBV) in 62 (15%), hepatitis C virus (HCV) in seven (1.7%), hepatitis D virus (HDV) co-infection in six (1.5%), hepatitis E virus (HEV) in 205 (49.6%), and hepatitis non-A-to-E (HNAE) in 127 (30.7%). Sixty-five (85.5%) pregnant women and 140 (41.5%) nonpregnant women had hepatitis E. The proportion of pregnant women was 31.7% in HEV group and 5.3% in non-HEV group [P < 0.001; OR=8.3 (95%C1 4.2-16.3)]. The prevalence of HEV in pregnant women in first trimester (76.9%), second trimester (88.9%), third trimester (83.8%) and puerperium (100%) did not differ significantly (P=0.09). Forty-seven (61.8%) of the 76 pregnant women developed fulminant hepatic failure (FHF), 69.2% in HEV group and 10% in non-HEV group (P < 0.001). Thirty-four (10.1%) nonpregnant women developed fulminant hepatic failure, 10% in HEV group and 9.7% in non-HEV group (P=0.86). FHF had occurred in four (40%) of 10 patients with HE in first trimester as against 41 (74.5%) of 55 patients in second trimester and beyond (P=0.015). Amongst the major complications of fulminant hepatic failure, cerebral oedema (53.2%) and disseminated intravascular coagulation (21.3%) occurred more often in pregnant women than in nonpregnant women (29.4% and 2.8%; P=0.03 and 0.016, respectively) while infections occurred more often in nonpregnant women (36.1%) than in pregnant women (10.6%; P=0.003). Fifty (61.7%) patients with FHF died [25 (53.2%) pregnant women and 25 (69.5%) nonpregnant women (P=0.06)]. Cerebral oedema and HEV aetiology were independent variables of survival in patients with FHF. Patients with cerebral oedema had worse prognosis and patients with HEV aetiology had best chances of survival. Hence HEV was the most common cause of sporadic AVH in this endemic area. High proportion of pregnant women and increased severity of disease in pregnancy were limited to patients with hepatitis E. Sporadic AVH caused by agents other than HEV did not show any special predilection to or increased severity in pregnancy. FHF in pregnant women caused by HEV was an explosive disease with short pre- encephalopathy period, rapid development of cerebral oedema and high occurrence of disseminated intravascular coagulation and may represent a severe manifestation of a Schwartzmann-like phenomenon.