10,000 IU/day is very safe during pregnancy. Doctors in the know about the benefits of vitamin D3 during pregnancy suggest 20,000 IU/day to 30,000 IU/day vitamin D3 during late stages of pregnancies. It can work relatively fast in controlling/preventing CH.
The way I see it, vitamin D3 is the best gift you can give your Tummy Thumper. It builds a strong immune system.