When is a fetal screen required for an Rh negative woman (gestational age)?  Our procedure used to say that a fetal screen was not required prior to 16 weeks, but that has slowly crept up to 28 weeks.  From what I can find, a fetus's blood volume will be >30 mL sometime around 20-22 weeks gestation.  Does it matter if the pregnancy is continuing or ending (birth or abortion)?  Do you just keep it simple and do fetal screens on all RhIG evaluations regardless of gestational age?  Thanks!

We have always done screening from the booking date (usually around 14 weeks of gestation).

I am absolutely aghast that you would not screen before 28 weeks of gestation.

The problem is that there may be a very low level of allo-anti-D already in the pregnant woman's blood caused by a previous D Positive pregnancy (or, God forbid, a D Positive transfusion), but, as Prof. Patrick Mollison and his workers showed, a minimal volume of D Positive red cells will cause a secondary immune response.  This secondary response can produce a high level of allo-anti-D quite quickly, and, as a result, by 28 weeks of gestation, the haemolytic disease of the foetus (as opposed to the newborn) can be quite profound, and in rare cases it is too late to salvage the foetus (horrible term, but it is the term often used these days).

The date was JUST changed from 22 to 28 weeks and I don't think that we have missed anyone.  I am reverting it to 22 weeks until we can look into this more.  I'm curious- what is a booking date?  I'm guessing that's a British term that I'm not familiar with?

Also, to clarify, we give 1 dose of RhIG.  We are just not doing the fetal screen to see if additional doses are necessary.

2 hours ago, CMCDCHI said:

The date was JUST changed from 22 to 28 weeks and I don't think that we have missed anyone.  I am reverting it to 22 weeks until we can look into this more.  I'm curious- what is a booking date?  I'm guessing that's a British term that I'm not familiar with?

What worries me is the word you missed from your first sentence, which is the word "yet".

The booking date is the first time the pregnant lady attends the antenatal clinic (could be a British term LOL)!

Edited April 29, 20169 yr by Malcolm Needs

2 hours ago, CMCDCHI said:

Also, to clarify, we give 1 dose of RhIG.  We are just not doing the fetal screen to see if additional doses are necessary.

It is not the need for anti-D immunoglobulin prophylaxis about which I was talking.  I was talking about a missed allo-anti-D as a result of a secondary immunisation, which could cause an awful lot of harm.  By 28 weeks of gestation, it could be too late.  It may not result in an IUD, but it could still result in a baby with deafness, blindness, etc, etc.

2 minutes ago, Malcolm Needs said:

It is not the need for anti-D immunoglobulin prophylaxis about which I was talking.  I was talking about a missed allo-anti-D as a result of a secondary immunisation, which could cause an awful lot of harm.  By 28 weeks of gestation, it could be too late.  It may not result in an IUD, but it could still result in a baby with deafness, blindness, etc, etc.

We are doing antibody screens on early prenatals.  My question was only in relation to fetal-maternal bleed screens (rosette test).  If we have an RhIG evaluation ordered and the mom is D negative and does not have immune anti-D, we will give RhIG.  If the baby is less than a certain gestational age, we will just give 1 RhIG without checking for any additional bleeding.  Over a certain age, we will do a rosette test and follow up with a Kleihaur-Betke if needed.  My question is what that age should be.  

I'm not sure I understand the question...

In order to perform a fetal screen (rosette test), you must know the infant's Rh type as it is not valid on a weak D infant.  This is rarely known in an early loss.  For a loss/bleeding up to 20 weeks gestation, we do an antibody screen to make certain that the mother is not previously sensitized to D, and give one full dose.  After 20 weeks, we would perform a Kleihauer-Betke for a loss/bleed if the infant's type is unknown to determine if > one vial is needed.

 

CarrieM- you did answer the question I was asking- it sounds like 20 weeks is your "cut off."  Thanks.

11 minutes ago, CMCDCHI said:

We are doing antibody screens on early prenatals.  My question was only in relation to fetal-maternal bleed screens (rosette test).  If we have an RhIG evaluation ordered and the mom is D negative and does not have immune anti-D, we will give RhIG.  If the baby is less than a certain gestational age, we will just give 1 RhIG without checking for any additional bleeding.  Over a certain age, we will do a rosette test and follow up with a Kleihaur-Betke if needed.  My question is what that age should be.  

I'm sorry CMCDCHI, I have got completely the wrong end of the stick.

There is a saying along the lines of the USA and the UK being huge friends, divided only by a common language, and I think that is what has happened here.  I thought that you were talking about screening for anti-D in the maternal plasma, and I now appreciate that you were talking about something else completely.

Now I know about what you are asking, the answer is that, in the UK, the screen is performed at 20 weeks of gestation and beyond.  Before that, we just give a minimum standard dose of 250 IU (although a higher dose would not hurt), without performing an estimation of the FMH.

My profuse apologies for the misunderstanding on my part.

OK, good But... just to clarify...we would never perform the rosette test without an infant Rh on record.

We perform a Kleihauer and, at 20 weeks of gestation, we presume the foetus is D Positive, just to be on the safe side.

I should've just called it the rosette test from the beginning!  Thanks for your help.

7 minutes ago, CMCDCHI said:

I should've just called it the rosette test from the beginning!  Thanks for your help.

No, it is not down to you to change - it is for me to realise that not everyone speaks or writes "English English"!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Is your facility able to get you a specimen from the fetus on early losses?  We have a tough time even getting a cord on a late term loss!

We perform fetal screens (rosette test) following obstetrical events on Rh negative women at 16 weeks or greater.  In the past, the literature has discussed 20 weeks as the " magical number," so, to error on the side of caution, we perform at 16 weeks.  The Kliehauer Betke is used for a variety of reasons, but if the clinician wants to give RhIg following an event that may cause a bleed - amnio, car accident, miss abort, etc... That is our number. Under 16 weeks we just supply the product after confirmation of Rh neg blood type of the mother.

I'm wondering if you use a different kit than us (Immucor FMH RapidScreen)?  Our package insert states that it can only be performed after delivery of all products of conception (so not after an obstetrical event mid pregnancy) and only on a known D negative mother and recently delivered known D positive child (but not a weak D infant).  In the event of an event <20 weeks, we give one vial.  If >20 weeks w/ unknown infant type (so most amnios), we have to do Kliehauer to quantitate a potential bleed.  We routinely have student interns and our mantra w/ them is "if you don't have a baby, you can't do the rosette test".  If there is another kit option that permits it, I'd love to hear about it!

We will perform a rosette test if the pregnancy has reached 12 weeks but not routinely.  If we have request from the E.D. for RhIg due to a threatened abortion or trauma we would perform the test.  We do not use it for routine antenatal RhIg requests.  Usually we have an antibody screen early in the pregnancy and another performed with the antenatal RhIg request.

Liz & David~

Will the fetal screen kit you use detect the cells of a weak D+ fetus?  Ours (Immucor FMH RapidScreen) doesn't, so we can't do it until after delivery & Rh is known (or we would risk a potential sensitization on the off chance the fetus was weak D+ and a large bleed was missed).  If your kits do detect them, I'd love to hear about it so we could reduce the K-B we perform.  Thanks!

Well- sounds like I have TWO issues to address.  The age that we perform the rosette test AND that we are not using the rosette test correctly.  We currently perform the test on infants/fetus of unknown type.  I don't think the core lab is going to be happy to hear that they may be doing more KBs!

34 minutes ago, CMCDCHI said:

 I don't think the core lab is going to be happy to hear that they may be doing more KBs!

For what it's worth...we really don't do that many.  We are a large hospital (450+beds) w/ trauma center, and we average maybe 1 per week.  We don't even have our 3rd shifters maintain competency. Most of the miscarriages are early enough that they don't need quantitated so we just give one vial.  We just get the occasional amniocentesis or late loss on an Rh negative mom & trauma/fell down and bumped belly to perform the K-B's.  It is on our fetal demise & pregnant trauma order set, but it's just not that common.  Take care

We have always performed Fetal Screen (rosette test) on our 28 week-Antepartum Rhogam patients as well as ER patients that have a trauma or vaginal bleed that are >12 weeks.  It sounds to me like we have been doing this all wrong for years, correct?

20 hours ago, ebjjwilson said:

It sounds to me like we have been doing this all wrong for years, correct?

Unless your kit specifies it can be performed with an unknown fetal Rh type....  Ours  (Immucor FMH RapidScreen) states that it can only be performed after delivery of all products of conception (so not after an obstetrical event mid pregnancy) and only on a known D negative mother and recently delivered known D positive child (but not a weak D infant). 

The following are our criteria for performing a KBT:

Order a KBT on an Rh-negative obstetrical patient for any of the following:

• post-delivery Fetal Screen test is positive,

• trauma during pregnancy (ordered by the physician),

• mother had a vaginal bleed, fetal death, terminated pregnancy, amniocentesis or CVS at > 20 weeks gestation,

• mother had a version procedure, and/or

• neonate is Rh-negative with a positive or invalid Weak D test, or Rh cannot be determined.

At less than 20 weeks we issue one dose of RhIg without further testing, other than the type and screen.

 

CarrieM has nicely summarized the use of the Immucor FMH RapidScreen if that is the kit you are using.

 

Additionally at delivery, we use an on-line calculator recommended by the AABB to determine the amount of RhIg to be given based on the mothers height/weight:

W:\AB\Bloodbank2\CAP AABB RhIG calculation\RHIGCALe.zip\

Edited May 12, 20169 yr by Rapundaa
forgot to add TS to <20 wk category.

We just had a mom with an incompetent cervix who had been bleeding for several days (4 days that we know of) deliver a stillborn at 22 weeks gestation.  Our second shift tech performed a KB and the result was 0.9% with recommendation of 3 vials RhIg.  I wasn't here to look at the slides but a second tech verified with the performing tech.  We didn't get any cord blood so don't know the fetus' Rh status, but from what I'm reading, that seems an unlikely percentage for 22 weeks.  We did give the poor lady all three vials, but it seems like a lot.