Determining zinc coproporphyrin in maternal plasma--a new method for diagnosing amniotic fluid embolism.

We measured the concentration of zinc coproporphyrin I (ZnCP-I), a characteristic component of meconium, in maternal plasma by fluorometry after HPLC. We obtained plasma samples from 89 women: 35 at weeks 10-40 of normal pregnancy, 41 shortly after normal delivery, 4 from patients with amniotic fluid embolism (AFE), and 9 from non-AFE patients with intra- or postpartum shock caused by genital bleeding. The plasma ZnCP-I concentration was 97 (SD 83, range 38-240) nmol/L in the AFE patients, 11 (SD 9.2) nmol/L in the non-AFE patients, 12 (SD 7.9) nmol/L during normal pregnancy, and 26 (SD 10) nmol/L shortly after normal delivery. We suggest that measuring ZnCP-I in maternal plasma by fluorometry on HPLC is a rapid, noninvasive, and sensitive method for diagnosing AFE and propose 35 nmol/L as the cutoff value for the ZnCP-I concentration in maternal plasma for the diagnosis of AFE.