Dark brown amniotic fluid-identification of contributing pigments.

A total of 208 second trimester amniotic fluid samples were examined visually and spectrophotometrically for pigmentation. Of these, 15 samples had dark brown colouration. Fourteen of the 15 samples had chemically detectable haemoglobin derived pigments and one had meconium only. All 15 of the pigmented amniotic fluid samples had haemoglobin A and eight also had haemoglobin F. None of the remaining 193 amniotic fluid samples contained abnormal pigmentation. Four of the pregnancies from which the dark brown amniotic fluid was obtained failed to continue to term; in three of these myoglobin was detected.