ABSTRACT
Withthedevelopmentofsophisticatedultrasoundequipmentandtheavailabilityofperinatologistsskilledinitsuse,percutaneousfetalumbilicalbloodsamplingbecamefeasiblein themid1980s(60)(Fig.11).Thisprocedureallowsmeasurementsofallbloodparametersthat canbemeasuredafterbirth(hemoglobin,hematocrit,bloodgroups,DAT,serumbilirubin levels,plateletandleukocytecounts,serumproteinlevels,erythropoietinlevels,andfetalblood gases).Fetalbloodsamplingisthemostaccuratemeansofdeterminingthedegreeofseverity offetalhemolyticdiseaseintheabsenceofhydrops.Theprocedureisrelativelybenign,carrying withitatraumaticfetalmortalityrateofafractionof1%(60).Sinceitdoescarrywithita greatlikelihoodoffetomaternalhemorrhage,itshouldonlybeundertakenwhenserialamniotic fluidJ10D450readingsriseintotheupper65-75%ofmodifiedzone2orwhenananterior placentacannotbeavoidedatamniocentesisandmaternalpregnancyhistoryand/ormaternal
Figure10Sonogramoffetuswithhydropsfetalis .Placentaisenormouslythickenedandedematous (whitearrow).Thefetalabdomen,whichisgrosslydistendedwithasciticfluid,islateraltothearrow. (FromRef.44.)
antibodytitersplacethefetusatrisk.Fetalbloodsamplingmaybepossibleasearlyas18 weeks'gestation;itusuallyisfeasibleby20-21weeks'gestation.Thepreferredsamplingsite isfromtheumbilicalvessel(preferablythevein)atitsinsertionintotheplacenta.Forthis reason,theprocedureistechnicallyeasieriftheplacentaisimplantedontheanterioruterine wall.
