How often do you get Cervical length measurments?

Amber
My last pregnancy I delivered my daughter at 26 weeks with spontaneous preterm labor. Just curious about how often I should expect to get my cervix measured this time around? At 8 weeks I measured 3.8 and my next measurement isn't scheduled until 14 weeks. I start p17 injections at 16 weeks. Anyone have experience with cervical length measurements? If so how often?