What is the relationship between menstruation and pregnancy

Patient's question:

Married
Detailed medical condition and consultation purpose: I had my period on November 27th, and it has been over 50 days since then. When I was at the hospital at 47, I had an ultrasound, and I have also tested my urine multiple times, finding no signs of pregnancy. Currently, I am taking Huangtai Tonghe and Nvjin capsules. I want to know what could be the reason for this and whether it is possible to be pregnant?

Doctor's answer:

As a result of long-term use of birth control pills, endocrine disorders can also cause delayed menstruation. According to the feedback from patients, doctors have also found that a new generation of gastric motility drugs, metoclopramide (also known as domperidone), may also cause this. Since metoclopramide does not easily cross the blood-brain barrier, it is believed to have no inhibitory effect on central dopamine receptors. When central dopamine receptors are inhibited, the amount of releasing factors from the hypothalamus entering the anterior lobe of the pituitary gland decreases, leading to a reduction in the secretion of gonadotropins and corticotropin from the anterior lobe of the pituitary gland, which in turn causes menstrual cessation and delayed ovulation.