I am currently pregnant with my second child. I have an Rh negative blood type, which for most women means they require a shot of RhoGAM or else risk the baby’s life. However, I declined the shot since my husband is also Rh negative, and therefore our children must be Rh negative. I thought the genetics were very straightforward.
However, my dad mentioned that his blood used to be Rh negative and later became Rh positive. I was skeptical and assumed that there was a testing error at some point. But I googled it and discovered that there is a thing called a Du variant that can cause a person’s blood type to change from Rh negative to Rh positive. Or perhaps it’s more accurate to say that it causes an Rh positive person to appear to be Rh negative on tests.
It sounds like the Du variant test is not normally done. Does this mean that I don’t really know for certain that my husband is Rh negative, and it’s possible our child could be Rh positive? I’m afraid this question is beyond my obstetricians’ expertise!
It would be easy enough, and wise, to re-test your husband’s blood type, perhaps with an extended typing.
IANAD, but my understanding is that the risks to a fetus with an Rh- mother are sufficiently grave that RhoGAM is strongly recommended even for a first child. Any prior pregnancy with an Rh+ father can set up the immune reaction - even one aborted or miscarried very early.
Why decline a treatment that can help ensure a healthy baby, based on maybes and unknowns?
Yes, dad can test as Rh negative and have “weak D” - just a small amount of D antigen that does not show on testing usually but enough to still sensitize. Or a variant form of D, “partial D”, which makes a lot but is a variant that can be missed, yet still can sensitize.
More rarely other, not tested for, Rh antigens can cause problems.
And of course from the OB’s POV there is always the chance that the husband is not actually the father, no matter what the Mom says.
Mild side effects are common, and severe side effects are possible. I see no reason to run the risk of side effects of a completely unnecessary treatment. Up until now, I didn’t have any doubts that it was completely unnecessary in my case. I still don’t know if there is any reason to doubt, because I really don’t have the expertise to understand how the Du variant works. My doctor did not challenge my reasons for foregoing the shot.
If my husband is in fact Rh negative, there is no possibility of a problem. My previous child tested as Rh negative, and the child I am carrying is Rh negative as well, assuming my husband is. Even if I somehow had a previous undetected pregnancy and miscarriage from an Rh positive man, it would not affect my Rh negative fetus.
My husband’s blood type was tested about four and a half years ago, so we aren’t relying on memories of an childhood test or anything. I’m sure our insurance isn’t going to pay for extensive testing of his blood type.
Yes, my obstetrician last pregnancy told me that they always recommend the RhoGAM shot. He was a bit evasive about the reasons and didn’t disagree when I suggested it was because women sometimes deny the true identity of the baby’s father. His position makes sense from a public health standpoint, but in my individual case, I know the identity of the baby’s father, so I am comfortable making decisions based on that information. My current obstetrician checked the records and confirmed that my first baby was Rh negative and didn’t challenge my choice. Both doctors seemed to believe that the genetics are straightforward and had other reasons for recommending it.
A part of the problem, which OBs might not have time to present or argue about, is in what I said above: what you think is your first pregnancy might not be. A very early miscarriage, hardly more than a worrisome-late period, can be enough to create the antibodies and cause trouble with a ‘first’ child.
First of all, a miscarriage does not ordinarily lead to maternal exposure to fetal blood. Some kind of trauma has to occur for the fetal blood to get into the mother’s bloodstream. I’m not sure there is even a theoretical possibility of this happening with a very early miscarriage. But regardless, as I pointed out above, it doesn’t matter if I’ve become Rh sensitized if the current baby is Rh negative.
According to the ACOG, which my doctors have frequently cited for the source of their recommendations, “If the mother and father are both Rh negative, the baby also will be Rh negative.” It seems irresponsible of them to state this if it’s not exactly true. Or at least there should be a caveat that ordinary blood testing for Rh factor cannot determine a person’s Rh status with certainty (if I’m understanding correctly).
I do not know precisely for Rh, but in the AB system, it is entirely possible for two type O parents to have a type A child (or conceivably AB, although that would be incredibly rare).
A geneticist I used to know explained it to me. The A antigen is made by a process that involves several steps, each carried out by a specific enzyme. To simplify, imagine it is a two step process catalyzed by E1 and E2. Now imagine that, generally speaking, type O and type B people lack E1 but usually have E2. Now suppose two people marry and one lacks E1 but has E2, so is a normal type O, while the other has E1, but is the rare person who lacks E2. Now they mate and the child, as it happens gets a gene for E2 from the first parent and for E1 from the second. Now the child has the machinery for making the A antigen.
Of course, the real life situation is much more complicated, but that is the idea. I see no reason it couldn’t happen with Rh. But the thing I am suprised by is this. Generally Rh problems arise only in the second pregnancy and only when the first-born was Rh+ while the mother is Rh-. This happened with my DIL and their son is Rh+. They gave her some special treatment at the time in case she became pregnant again (she hasn’t so far and unlikely to now). The treatment was supposed to prevent–or at least minimize–the development of Rh antibodies.
It’s like vaccination. When the first baby is born, the mother’s body “sees” the Rh antigen for the first time and makes antibodies, but by the time they’re up and running, the baby is long gone. However, the mother’s immune system remembers, and when the second baby comes along, her body is primed and ready to attack it.