These are photos from a 35 year old woman who has had four vaginal births (the last child was born 11 years ago). The couple is trying to conceive a fifth child, so they took the photos because it helps them to determine when she is ovulating.
You can see that her os (opening to the cervix) is a slit shape, which is how the muscle resumes after having dilated during her vaginal births. Also, the diameter of her cervix is larger than of a woman’s who has never given birth.
Her average cycle is 30 to 31 days with a 14 day luteal phase. In this cycle, she ovulated on day 17. Below are a few photos of her cervix; the day number is below each photo.
One day before ovulation
Notice os is open and cervical fluid looks gelatinous/fertile
Two days post-ovulation
Seven days post-ovulation