Friday, April 27, 2012

Rhesus incompartibility

Every woman @ first prenatal visit, do Rh screen and Rh Ab titre.

In Rh negative woman, consider as sensitized if Ab titre is >1:4

If Ab titre> 1:16, do amniocentesis @ 16-20 wks gestation, check fetal cells for rhesus factor
If not sensitized or <1:16, repeat Ab titre @28 wks

If fetal cells r rhesus positive and mother's Ab titre >1:16 then fetus is at risk of Erythroblastosis
If fetal cells r rhesus negative, then there's no risk for the fetus even though mother is sensitized, continue usual prenatal care.

If fetus is rh + and at risk, check if fetus is already hemolysing : serial amniocetensis for amiotic fluid bilirubin
if mild, repeat in 2-3wks, if moderate, repeat in 1-2 wks, if severe consider intervention:
       Is fetus anemic?
       How low is Hct?
       umbilical cord blood hematocrit <25% ----intrauterine transfusion or deliver if >34 wks G.A

Give anti D immunoglobulin to all Rh negative pregnant women who remain unsensitized at 28 wks. Repeat after delivery if baby is rh positive.
If already sensitized, Rhogam is of no value, focus on fetal monitoring and intervene as appropriate.

After an abruptio or other events with suspected fetomaternal haemorrhage,
Do a rosette test (qualitative) to confirm fetomaternal haemorrhage.
If positive, do a kleihauer - Betke test to quantify the haemorrhage.
For every 15mls of fetal blood in maternal circulation, give 300microgram of Rhogam up to a maximum of 1500microgam.

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