by caryn » Fri Apr 20, 2012 09:44 am
Oddly, this is *exactly* what the theory says you should be seeing. Let me back up a bit and explain...
They think PE is a genetic conflict between mother and father over how big the baby can grow, since the dad wants a big kid with good survival odds after delivery, and we want it both to live after delivery *and* to fit out. So we "modulate" the depth of the implantation of the paternal cells that develop the placenta, so that the placenta cannot draw down quite so many maternal resources, so that we can restrict the rate of growth of the fetus. And probably we only do this if our genes detect the presence of paternal genes that will result in a big baby.
So first pregnancy - shallow implantation - compromised blood flow and small baby.
In the second and later pregnancies, the uterine spiral arteries have persistent remodeling from the first placenta which the second placenta can use. So it can dig in more deeply, even if we argue with it. Second/third pregnancy - implantation is still shallow but is better - blood flow is still compromised but better - bigger baby, 'cause it has the genes for it.
Does that make sense?
Oddly, this is *exactly* what the theory says you should be seeing. Let me back up a bit and explain...
They think PE is a genetic conflict between mother and father over how big the baby can grow, since the dad wants a big kid with good survival odds after delivery, and we want it both to live after delivery *and* to fit out. So we "modulate" the depth of the implantation of the paternal cells that develop the placenta, so that the placenta cannot draw down quite so many maternal resources, so that we can restrict the rate of growth of the fetus. And probably we only do this if our genes detect the presence of paternal genes that will result in a big baby.
So first pregnancy - shallow implantation - compromised blood flow and small baby.
In the second and later pregnancies, the uterine spiral arteries have persistent remodeling from the first placenta which the second placenta can use. So it can dig in more deeply, even if we argue with it. Second/third pregnancy - implantation is still shallow but is better - blood flow is still compromised but better - bigger baby, 'cause it has the genes for it.
Does that make sense?