Antibody screening in pregnancy

Antibody screening in pregnancy


1% of pregnant women have clinically significant antibodies


12 weeks (10-16)

§        ABO & D type and antibody screening (by IAT – enzyme technique not necessary)

§        C, c, D, E, e, K, k, Fya, Fyb, Jka, Jkb, S, s, M, N, Lea

§        D positive and screen negative

§        Retest at 28 week

§        Still negative

§        No further action

§        D negative and antibody screen negative

§        Sensitising events

§        Prophylactic anti-D

§        Retest at 28 weeks

§        Still negative

§        Routine prophylactic anti-D at 28 weeks

§        Routine prophylactic anti-D at 34 weeks

§        Birth, test fetal sample

§        Baby D-positive

¨        Anti-D

¨        Quantify FMH

§        D negative and screen positive

§        Anti-D as above

§        Past history of IUT, severe HDN, refer to FMU before 20 weeks

§        Identify antibody

§        Anti-D or anti-c

¨        Quantify

¨        Test partner

¨        Test at 4 weekly intervals until 28 weeks

¨        28 weeks – repeat antibody screen

Ø        test at 2 weekly intervals

Ø        Prophylactic anti-D now and at 34 weeks if no immune anti-D

¨        Birth

Ø        Cord sampling for DAT and D type

§        Anti-K

¨        Quantify

¨        Test partner

Ø        Partner K negative

Ø        Retest at 28 weeks and follow normal pathway

Ø        Partner K positive

§        Test at 4 weekly intervals until 28 weeks

Ø        28 weeks – repeat antibody screen

§        Test at 2 weekly intervals

§        Prophylactic anti-D now and at 34 weeks if no immune anti-D

Ø        Birth

§        Cord sampling for DAT and D typing

§        Other clinincally significant antibodies

¨        Repeat screen at 28weeks

¨        If increasing or >32

Ø        Refer FMU, Doppler, repeat at 34 weeks, consider early delivery

¨        Birth

Ø        DAT and D-typing

§        D positive and screen positive

§        As above but without anti-D prophylaxis



§        For maternal/ foetal samples use reagents which do not detect Dvariant

§        All pregnant women found to be D negative should be issued with blood group cards


Antibody screening

§        Testing for levels of anti-A and anti-B not recommended as their presence doesn’t predict ABO HDN

§        Test everyone at 28 and 34 weeks

§        No evidence that antibodies detected only in 3rd trimester cause HDN


Antibodies and HDN

§        Anti-D

§        Determine whether immune or prophylactic (likely to be <1)

§        Anti D prophylaxis should be continued until confirmation that immune

§        <4iu/mL – HDN unlikely

§        4-15iu/mL – moderate risk

§        >15iu/mL – high risk of hydrops

§        >4, increasing or history of HDN, refer to FMU

§        If father herterozygous can D type the baby from a maternal blood sample >16 weeks

§        Apparent anti-C and anti-D, may actually be anti-G and therefore will need routine anti-D prophylaxis

§        Assess fetal anaemia with MCA doppler – increased flow = low Hb

§        Anti-c

§        <7.5iu/mL – continue to monitor

§        7.5-20iu/mL – moderate risk, refer FMU

§        >20iu/mL  severe risk, refer to FMU

§        Anti-K

§        Low HB

§        Inhibition of early erythroid progenitor cells or promotion of their immune destruction

§        Severity not correlated with titre

§        Incidence can be reduced by selecting K negative units for females of child bearing potential (<60years)

§        K type the father

§        Others associated with HDN

§        Anti-C

§        Anti-E

§        Anti-Fya

§        Anti-Jka

§        Consider early delivery


DAT at birth

§        Only indicated if mum had red cell antibodies

§        May be false positive from prophylactic anti-D and Wharton’s jelly

§        Can be positive by IAT for 8 weeks or more following anti-D

§        If positive - Check Hb and bilirubin



§        500iu IM = treats 4ml FMH (ie. 125iu/ ml IM 100iu/ml IV)

§        Large or multiple doses needed, consider limiting batch exposure

§        Informed consent

§        Deltoid muscle (Gluteal but absorption will be delayed if only reaches subcut tissue)

§        Audit trail to allow traceability

§        Informed consent


Sensitising events (Rh D neg) (PETITE APH)

§        Pre-eclampsia

§        Ectopic pregnancy

§        Termination /  Miscarriage / Intrauterine death

§        Interventions

§        Amniocentesis / Cordocentesis

§        Chorionic villous sampling

§        In-utero therapeutic interventions

§        Trauma / fall

§        External cephalic version

§        APH







Test and treatment


< 12 weeks

No action for uncomplicated miscarriage or painless vaginal bleeding

Everything else (eg intervention / termination), check ABO and D type

Confirm D negative and absence of immune anti-D

250iu anti-D IM

12-20 weeks

ABO and D type as above

250iu anti-D IM

Recurrent PV bleeding – 250iu should be given at a minimum of 6 weekly intervals

20-28 weeks

ABO and D-type as above

Assess FMH (every 2 weeks if recurrent PV bleeding)

If Kleihauer suggests >2ml - flow

At least 500iu anti-D IM and repeat Kleihauer at 72 hours

If recurrent, 500iu at least 6 weekly with Kleihauer 2 weekly – if positive additional 500iu, more if >2mls with repeat Kleiuhaer at 72 hours

28-34 weeks

28 weeks  = 1st routine dose of 500iu

Group and antibody screen must be taken prior to this injection

34 weeks

34 weeks = 2nd routine dose of 500iu


BABY – ABO and D-type

DAT not routinely indicated as may be positive because of antenatal prophylaxis

MATERNAL – ABO and D-type

Assess FMH if baby D-positive

At least 500iu if baby D-positive

More may be required depending on FMH

If very large (>80 mls) consider IV anti-D (100iu for 1 ml bleed) and check babys Hb

Repeat kleihauer at 48h (IV) or 72h (IM)  and give further doses of anti-D if +ve

If negative – check anti-D – if absent give further dose anti-D


§        If pregnancy non-viable and no sample can be obtained from baby, prophylactic anti-D should be administered if mum is D negative

§        Following sensitising events, anti-D should be administered ASAP and within 72 hours

§        May be some protection up to 10 days

§        Passive anti-D is usually <1iu/ml


Assessment of FMH

§        Sensitising event after 20 weeks

§        After delivery of a D-positive baby

§        Kleihauer

§        Flow using original sample if > 2mls

§        Number of fetal rbcs/ number of maternal rbcs x 2400 = mls of bleed

§        Maternal blood volume = 1800mL x 1.22 (fetal cells larger)/0.92 (only 92% stain darkly) = 2400

§        500iu is adequate for up to 4 mls, then calculate on 125iu/ 1ml IM or 100iu/ ml IV

§        Follow-up maternal sample at 72 hours (48 hours if given iv) after anti-D administration for an FMH of >4mls

§        More anti-D may be necessary if fetal red cells not cleared. If fetal cells cleared, test maternal serum for presence of anti-D, if no free anti-D, administer further routine dose.


Routine Prophylaxis

§        D-negative non-sensitised women

§        DVI – may develop anti D and should be considered D negative as compared to weak D which is considered D positive

§        28 and 34 weeks

§        500iu


§        Single dose of 1500iu IM at 28 weeks may be adequate


§        Routine doses should not be affected by previous doses for a sensitising event


Trasnfusion testing

§        Antibody screens may detect circulating passive anti-D

§        May need to use a panel of D-negative cells to look for other antibodies


§        Anti-D may be passive or immune

§        If there is doubt, send sample for anti-D quantitation

§        Passive anti-D rarely exceeds 1iu/mL


§        If anti-D administered within 8 weeks and level <1, test further sample at 28 weeks and continue prophylaxis

§        If no record of anti-D administration, test at 4 weekly intervals until 28 weeks and then every 2 weeks

§        If rising it is probably immune

§        Continue prophylaxis unless immune nature is confirmed


Transfusion of D positive platelets

§        D negative platelets should be transfused to D-negative women of child bearing potential

§        If D-pos have to be given, 250iu anti-D will cover up to 5 adult doses


Transfusion of D-positive blood

§        <15mls transfused – appropriate dose of anti-D

§        >15mls

§        Consider using the 2500iu IM injection

§        If > 2 units

§        Consider red cell exchange

§        Single volume – 65-70% reduction

§        Double volume – 85-90% reduction

§        Assess residual volume of D-pos cells and calculate anti-D dose (iv)

§        Follow-up flow every 48 hours until no detectable D-pos cells

§        Passive anti-D may be detectable for up to 6 months, and tests for immune anti-D may not be positive for several months



§        Exceedingly rare in caucasians, higher in Asians, blacks

§        Stronger expression of A,B antigens

§        O mum and Aor B baby

§        DAT may be negative because of low antigen expression on fetal red cell