A 21-year-old pregnant female of known rheumatic heart disease presented to us for evaluation of central cyanosis during her late pregnancy. Though she was investigated for any associated congenital heart disease or pulmonary arteriovenous fistula, but incidentally she was diagnosed of having acquired methemoglobinemia. Her serum methemoglobin level was 33% which was far above the normal range. Ultimately, she was managed conservatively and delivered through elective caesarean section. Though the delivered baby was lethargic after birth, but later he was improved and discharged. This was the first case reported so far that a pregnant patient of rheumatic heart disease developed cyanosis due to methemoglobinemia.
Key words: Methemoglobinemia. Pregnancy, Rheumatic heart disease.