How many women are affected by morning sickness during pregnancy??

I had it with 2 o my 3 pregnancies. With my boy I had it for 26 weeks, it was a pain in the . With my second (ended in M/C) I didn't have it and in the 3rd (ended in M/C at 9 weeks) I was in the hospital for 5 days due to my excessive vomiting. For me it happens around 5 weeks and last a long time. I don't think is hereditary. Some women don't have morning sickness, some have it in the 1st trimester and some have it for 9 months. So everybody is different. Hope this helps!