Ultrasounds and incompetent cervix

I am a first time mother and all is going well. I am a little stressed as my mother had an incompetent cervix and I don’t know if I do as well. I have had my 8 and 12 week ultrasounds and the doctor said everything looks fine. Do they check the cervix at those ultrasounds? I don’t have another ultrasound until 21 weeks and I’m afraid if I do have a problem it will effect me prior to that (from some experiences I have read). Feeling a little uneasy about it.