EMQ: Transfusion (Obstetric)

Each of the following pregnant women have recently undergone red cell grouping and allo-antibody screening as part of their ante-natal workup. For each result, select the SINGLE most appropriate NEXT course of action with respect to blood tests, paternal sampling and antenatal anti-D prophylaxis (RAADP) from the list above (a-p). Each answer may be used once, more than once or not at all.

Question 1

Seen at 20 weeks of second pregnancy and found to have anti-E at a titre of 1:32. Blood group B RhD positive

Question 2

Seen at 19 weeks of second pregnancy and found to have anti-Jka at a titre of 1:32. Blood group AB RhD negative

Question 3

Seen at 18 weeks of third pregnancy and found to have anti-P1 at a titre of 1:32. Blood group A RhD negative

Question 4

Seen at 15 weeks of first pregnancy and found to have no allo-antibodies. Blood group O Rh D negative

Question 5

Seen at 15 weeks of third pregnancy and found to have anti-D at a titre of 15iU/mL. Blood group A RhD negative

Options:

A. Immediate referral to fetal medicine unit; Obtain paternal sample for grouping. Prophylactic anti-D should not be given

B. Monitor levels antibody levels monthly to 28 weeks then fortnightly to term. Antenatal unit referral as necessary based on these results. Paternal sampling not necessary. Prophylactic anti-D should not be given

C. Monitor levels antibody levels monthly to 28 weeks then fortnightly to term and offer prophylactic anti-D. Antenatal unit referral as necessary based on these results. Paternal sampling not necessary.

D. Monitor levels antibody levels monthly to 28 weeks then fortnightly to term. Antenatal unit referral as necessary based on these results. Obtain paternal sample for grouping. Prophylactic anti-D should not be given.

E. Monitor levels antibody levels monthly to 28 weeks then fortnightly to term and offer prophylactic anti-D. Antenatal unit referral as necessary based on these results. Obtain paternal sample for grouping

F. No additional testing required. Prophylactic anti-D should not be given. Paternal sampling not necessary

G. No additional maternal testing required. Obtain paternal sample for grouping. Prophylactic anti-D should not be given.

H. No additional testing required. Offer antenatal prophylactic anti-D. Paternal sampling not necessary

I. No additional testing required. Offer antenatal prophylactic anti-D. Obtain paternal sample for grouping

J. Repeat testing at 28 weeks and offer antenatal prophylactic anti-D based on results. Paternal sampling not necessary

Answers:

Question 1

D. Monitor levels antibody levels monthly to 28 weeks then fortnightly to term. Antenatal unit referral as necessary based on these results. Obtain paternal sample for grouping. Prophylactic anti-D should not be given.

Question 2

E. Monitor levels antibody levels monthly to 28 weeks then fortnightly to term and offer prophylactic anti-D. Antenatal unit referral as necessary based on these results. Obtain paternal sample for grouping

Question 3

J. Repeat testing at 28 weeks and offer antenatal prophylactic anti-D based on results. Paternal sampling not necessary.

Question 4

J. Repeat testing at 28 weeks and offer antenatal prophylactic anti-D based on results. Paternal sampling not necessary.

Question 5

A. Immediate referral to fetal medicine unit; Obtain paternal sample for grouping. Prophylactic anti-D should not be given

Explanation:

Routine antenatal care in the UK requires antibody screening and blood grouping at booking (12-16 weeks) and at 28 weeks. Detection of alloantibodies at booking requires emergency referral to a fetal medicine unit if they are of clinically significance and of a titre sufficient to risk causing haemolytic disease of the fetus and newborn (HDN).

The clinically significant antibodies are anti-c at levels >7.5iU/ml, D at levels >4iU/ml and K at any titre. Any other significant antibodies such as anti-E, Fy and Jk should be assessed monthly until 28 weeks and fortnightly thereafter and referral made at a threshold level of 1:32, or sooner if there is any history of HDN.

Paternal blood grouping is useful to infer fetal group in some cases and should be attempted in all of these cases. No further additional testing is required for anti-Le or P group antibodies which have never shown an association with HDN.

Routine antenatal anti-D prophylaxis should be offered to all women who are RhD negative, with additional anti-D for sensitising events except in women who have a demonstrated immune anti-D. Weak anti-D reactivity may result from a recent anti-D treatment but rarely exceeds 1iU/mL and is transient.

Panreactive auto-antibodies will not endanger the fetus except in rendering allo-antibody determination more challenging to laboratory staff!

Reference:

British Committee for Standards in Haematology Blood Transfusion Task Force, Gooch, A., Parker, J., Wray, J. and Qureshi, H. (2007), Guideline for blood grouping and antibody testing in pregnancy. Transfusion Medicine, 17: 252–262