If someone were faking a pregnancy and went to the hospital when they had their period as if it miscarriage would doctors know that never pregnant?

If a person went to the hospital claiming to have a miscarriage while actually menstruating, doctors would likely be able to tell that they were never pregnant. Menstrual blood and pregnancy-related bleeding can appear similar, but there are differences. Pregnancy-related bleeding tends to be lighter and shorter than menstrual bleeding; cramping tends to be milder: pregnancy tests would come back negative; vaginal ultrasound results will demonstrate the absence of a fetus, gestational sac, placenta, and signs of an early miscarriage: pelvic or transvaginal exam may also indicate that the uterus is relatively small for the stated gestational age and the cervix will demonstrate changes associated a true miscarriage:

In cases where there is uncertainty, doctors may order additional tests like hormone level checks or imaging