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What are the post delivery time constraints for a sample to screen for FMH?

We require maternal sample taken at least 45 minutes post delivery, but is there a maximum limit and where are the regulations for this?

I can't see anything in the BSH guidelines (for UK bods)

We had a delivery sample which we had to reject (minimum data set not met), so we issued 500IU anti-D and requested a repeat sample which did not get taken until the day after.

Would foetal cells (with prophylactic anti-D, already sensitising them) be being removed from circulation, would this affect the dosage required or are we only interested in removing what remains?


p.s. my spellchecker wants me to change some spelling. It can go and ........!

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I saw a discussion once that said draw it as soon as you can post delivery (ours is at 1 hour) - but that drawing it is more important than the time of the draw.  I think I remember that they discussed up to one week post delivery (sort of ridiculous to think about).  I have never really seen a maximum time for drawing.  

Make sure your procedures allow for double checking RH neg mom's with Rh pos babies - make sure L&D has some checkpoints and that your techs have some checkpoints to make sure tubes get drawn and tests get done.  Make sure the testing gets done and documented and the RHIG gets given - that is the most important part.

good luck

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Check the product insert for the RgIG that is issued at your facility. Rhophylac and RhoGAM both say to collect the Fetal Bleed Screen/Kleihauer Betke one hour after delivery. You don't want to make your policy too rigid to comply with however, so ours says that we draw specimens as close to 1 hour of delivery as possible. As Carolyn said, the most important thing is to make sure that the specimen gets drawn.

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  • 4 weeks later...
On 3/15/2021 at 6:14 PM, RichU said:

I can't see anything in the BSH guidelines (for UK bods)


5.3 Timing of samples The maternal sample for FMH estimation should be taken when sufficient time has elapsed to allow fetal cells to be distributed within the maternal circulation following delivery, manual removal of placenta or sensitising event. A period of 30-45 minutes is considered adequate (BCSH 2006a).

BCSH FMH Guidelines 2009

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