Ultrasound monitoring is necessary during IVF stimulation to determine if the ovary's response to IVF meds is adequate.
When the response to the hormones administered is too low, the woman may be qualified as a poor responder, or ovulation may occur too early. Being a poor responder means that, out of all the ovarian follicles available in the woman's egg supply, just 2 or 3 are able to become antral follicles.
If the reason is early ovulation, it means that the medications used to stop the function of the pituitary gland didn't work. As a result, the LH surge causes the ovary to release the eggs, which makes it impossible for the specialist to collect them through ovum pick-up.
Depending on each case and the cause of poor response, the most effective action to take would be to cancel the cycle or use alternative methods in order not to cancel it.