The Blonskys are cagey about the appropriate speed at which a foetus would be "dislodged" (their word). At one point they mention around 8gs, then conclude that would probably be a bit much and suggest starting at around 2gs and going up from there.
In a supine position, a human would black out with in a few minutes at 2gs, and quicker at a faster speed.
The Blonskys are well aware of this, and that the birth will have to be achieved by centrifuging alone.
Now, they're probably cagey about the appropriate speed at which to spin a baby out straight out of a uterus because this science has never been tested. In fact, it's hard to find any data as to whether g-forces even *can* make anything shoot out of the pelvis.
To prove or refute the concept of the birth centrifuge, can any astronauts, pilots or others who have had high-g training tell us if they let out a bit of wee or poo when you were in the centrifuge?