When the ovaries are not ovulating, there is a chance of getting pregnant when you have sex without using contraception. The size of this chance is mainly related to the size of the follicle.
If the ovaries are not ovulating at the time of the ultrasound and the follicles are small, for example, less than 12 millimeters, the chances of getting pregnant without using contraception are small. This is because the follicle has not yet matured and will not ovulate in a short period of time.
If the follicle is already large on ultrasound, such as 18 millimeters or more, the chances of getting pregnant without contraception are relatively high. This is because sperm can survive in the woman’s body for about 72 hours after sex. After the follicle grows to 18 millimeters, it may ovulate at any time, as long as it ovulates within these 72 hours, the chances of pregnancy are relatively high.