Late period besides being pregnant, what could be another reason a girl could be late for her period after having sexual intercourse?

As : As doctors, anytime a fertile, sexually active woman has an abnormally light or missed period, the first thing we do is rule out pregnancy. You can either take a home pregnancy test as long as it has been 6 weeks since your last normal period, or you can go see your doctor and they can test you. A blood test can tell if you are pregnant as soon as 7 days after conception and a doctor's urine pregnancy test can tell if you are pregnant around when you next period should come. Other reasons for a missed period are: stress, poor diet, excessive exercise, and hormone imbalance such as with polycystic ovarian syndrome (pcos) or thyroid disorder. It is always better to be safe than sorry and to know sooner rather than later so you may want to call your doctor is you continue to miss periods. Good luck!

Late period: Reasons for missed /late periods: low body weight, obesity, marked weight gain or loss, over-exercise such as in endurance athletes, breast-feeding, stress, illness, eating disorders (bulimia or anorexia), travel, hormone irregularities, drug use, medications (i.e., birth control) or med problem (polycystic ovary syndrome or Asherman’s syndrome. #1 reason is pregnancy.