Screen for fetalmaternal hemmorhage

[David Saikin]

I have always thought that in cases of abortion or fetal demise that a rosette test was not warranted until after 16 weeks of gestation. I cannot find any documentation for this in any of my texts . . . they all say that post-partum there should be an evaluation for FMH of greater than 30mL of whole blood. Have I been laboring under a delusion?

[Deny Morlino]

Part of our protocol for RhIg workup is a division by gestational age of the testing we perform. Less than 13 weeks, we perform an ABO, Rh, and IAT. From 13 to 28 weeks we also perform the fetal bleed screen. After 28 weeks we would not perform the IAT. The logic that accompanies these cutoffs follows that at less than 13 weeks the fetal blood volume is small enough that even with a total bleed of the fetus, the volume would be less than 30ml so a single dose of RhIg will cover any bleed up to that point. During the 13 to 28 week period the fetal blood volume is such that a test for quantitation of fetal-maternal bleed is necesssary. After week 28 the antibody screen will be positive for any Rh negative mother due to the administration of RhIg. The important part is quantitating the bleed to determine if any additional RhIg is necessary.

Looking in the AABB Practical Guide to Transfusion Medicine under the discussion of Rh Immune Globulin a reference is made to the fact that:

"If spontaneous or induced abortion or termination of an ectopic pregnancy occurs before the 12th week of gestation, then a mini-dose of Rh Immune Globulin (BayRho-D Mini-Dose; MICRhoGAM) may be administered instead of a full dose. ... The 12th week of gestation is the cutoff for the use of a mini-dose, because the volume of RBCs in a 12-week-old fetus does not exceed 2.5ml."

This is what our pathologist based the cutoffs for our testing on I believe. I will see if any other additional references are at hand.

[Mary**]

I think we used to use 20 weeks as the cut off.

[bduff]

We also use 20 weeks for the cut off.

[Brenda K Hutson]

I have a comment about a different aspect of your posting based on the scenario you gave. When the Rh type of the baby is unknown, we go straight to a KB; not a Rosette Test. Without knowing the Rh Type, if the Rosette Test is positive, that may be helpful information (though you would then proceed to KB anyway to quantitate). If the Rosette is Negative, you would then not know if it was because the fetus was Rh Negative, or because there was not a large bleed.

Brenda Hutson

[David Saikin]

Very good point . . . thanks

I have a comment about a different aspect of your posting based on the scenario you gave. When the Rh type of the baby is unknown, we go straight to a KB; not a Rosette Test. Without knowing the Rh Type, if the Rosette Test is positive, that may be helpful information (though you would then proceed to KB anyway to quantitate). If the Rosette is Negative, you would then not know if it was because the fetus was Rh Negative, or because there was not a large bleed.

Brenda Hutson

[jnadeau]

I have always thought that in cases of abortion or fetal demise that a rosette test was not warranted until after 16 weeks of gestation. I cannot find any documentation for this in any of my texts . . . they all say that post-partum there should be an evaluation for FMH of greater than 30mL of whole blood. Have I been laboring under a delusion?

There was a paragraph in the AABB Technical Manual- 15th edition saying "At <20 weeks, the fetal blood volume is rarely more than 30 ml, small enough that a single dose of 300 ug Rh immune globulin will be sufficient for prophylaxis for any FMH. Therefore, it is not necessary to quantitate fetal red cells in the maternal circulation before 20 weeks of gestation." This section was removed from later editions!? Don't know why.

We perform a fetal screen at 20 weeks or greater - the mother will receive one RhIg regardless if the baby is Rh pos or neg. If the fetal screen is positive we follow up with the KB.

[John C. Staley]

We considered 20 weeks the cut off for years and then one day the corporate transfusion service medical director had a little chat with a neonatologist and suddenly the cut off became 13 weeks.

[mjshepherd]

AABB has the cut off as 20 weeks.

[David Saikin]

Where did you find that documentation? Thanks in advance

AABB has the cut off as 20 weeks.

[mjshepherd]

The 15th edition of the AABB Technical Manual (page 549) "at < 20 weeks, the fetal blood volume is rarely more than 30 mL, small enough that a single dose of 300 ug RHIG will be sufficient for prophylaxis for any feto-maternal hemorrhage. Therefore it is not necessary to quantitate fetal red cells in the maternal circulation before 20 weeks of gestation."

Also, "When the gestation age is less than <20 weeks one 300 microgram dose of Rh Immune Globulin should be sufficient to cover a fetal-maternal bleed since the expected fetal blood volume is not likely to exceed that which is covered by the standard dose." Trauma During Pregnancy, by Haywood Brown, MD and Thomas Luley, DO

[LaraT23]

We use the KB stain route when the RH of the baby cannot be determined. It is a protocol in our Women's services area that all abdominal trauma get the KB stain. As far as miscarriages, one vial of RH immune globulin is give is the mom is 20 weeks or less, anymore than that and we give the vial and do the KB stain just to make sure we don't need more. As far as the rosette, we only do that one if the RH of mom and baby are known.