The association between female fetal sex and hyperemesis gravidarum is well established in European and North American populations. The association between female fetuses and severity of hyperemesis remains uncertain. A retrospective study based on case notes review of 166 Asian women hospitalised for hyperemesis was performed. Female fetuses were significantly associated with hyperemesis in our population (P= 0.004, OR 1.6, 95% CI 1.2-2.2) as well as associated with severe ketonuria and high urea. When both severe ketonuria and high urea were present at initial hospital admission for hyperemesis, 83% (95% CI 66-93) of the fetuses were female.