Follicular puncture or oocyte retrieval is a mild procedure that involves little risk of complications.
The most severe risks that can occur during or after this procedure are damage to pelvic organs (intestines, bladder...), bleeding, or infections. These complications are very rare, as it is an ultrasound-guided procedure, which means that the gynecologist can monitor the sites being approached.
Other side effects, though less severe, include dizziness and vomiting due to anesthesia, or abdominal pain during the first days after the procedure.