Rh Factor....

[deleted74029]

I know if a woman is Rh- has an Rh+ baby she would produce antibodies to protect herself, and this could lead to the destruction of fetal RBCs in the next baby she has if it is also RH+. My question is: Why isn't the first baby affected when the woman produces the anti-Rh antibodies.

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[DrYoda]

I think it has to do with during birth if there is a breach in the blood barrier then the anti-bodies are made after the fact, but still ready for the next baby. That's how my kaplan instructor explained it anyway.

 

[FutureInternist]

Just like any other immune response the first time mom gets exposed to fetal RBCs she starts making Abs (which takes 5-7 days). Since this exposure usually happens during birth, the first baby is long gone by the time the mom's IgG kicks in. In this way the 1st baby is able to avoid any harm, leaving behind an armada of armed & ready Igs for it's wanna-be sibling

For the MCATs, it is sufficient to know that the 2nd pregnancy is at risk, however it is not that simple. Other times that the mom can get exposed to fetal RBCs are
a) trauma (car accidents etc),
b) diagnostic procedures (amniocentesis).
This makes giving a Rhogam shot mandatory whenever an Rh(-) mom has these episodes (& the baby's Rh status is unknown)
Rhogam is Anti-Rh Ab which binds to any fetal RBCs. This "masks" the Rh(+) RBCs from mom's immune system so mom never makes her own Abs

Another point is that while this may be the woman's first KNOWN pregnancy she may have had a spontaneous abortion of a Rh(+) fetus (& the only indication may be a heavier than normal period), in which case the FIRST (known) pregnancy is also at risk since the abortion --> mixing of fetal RBCs into mom's circulation and subsequent Ab production.

 

[silverlion]

Since this exposure usually happens during birth, the first baby is long gone by the time the mom's IgG kicks in.

Long story short!!

 

[FutureInternist]

Long story short!!

Well, immunology is my favourite subject & I wanted to give as complete a picture as I could so if others had Rh Qs they might be answered as well.
See your point though.

 

[silverlion]

Lol....Yeah...Youre the med student...so who am I kidding!

I like immunology a lot too...Was one of my favorite subjects when i was majoring in Biochem....

 

[engineeredout]

Just like any other immune response the first time mom gets exposed to fetal RBCs she starts making Abs (which takes 5-7 days). Since this exposure usually happens during birth, the first baby is long gone by the time the mom's IgG kicks in. In this way the 1st baby is able to avoid any harm, leaving behind an armada of armed & ready Igs for it's wanna-be sibling

For the MCATs, it is sufficient to know that the 2nd pregnancy is at risk, however it is not that simple. Other times that the mom can get exposed to fetal RBCs are
a) trauma (car accidents etc),
b) diagnostic procedures (amniocentesis).
This makes giving a Rhogam shot mandatory whenever an Rh(-) mom has these episodes (& the baby's Rh status is unknown)
Rhogam is Anti-Rh Ab which binds to any fetal RBCs. This "masks" the Rh(+) RBCs from mom's immune system so mom never makes her own Abs

Another point is that while this may be the woman's first KNOWN pregnancy she may have had a spontaneous abortion of a Rh(+) fetus (& the only indication may be a heavier than normal period), in which case the FIRST (known) pregnancy is also at risk since the abortion --> mixing of fetal RBCs into mom's circulation and subsequent Ab production.

Thats cool. I wanna be a med student

And I'm glad I was born first.

 

[FutureInternist]

Thats cool. I wanna be a med student

You might regret those words when you are elbow deep in cadaver fat .
Good luck, though.