Late period after vasectomy

Patient: My periods late but my husband had vasectomy 4 months ago and we used pull out method since.

Doctor: It is told that the residual seminal reserve after vasectomy is exhausted after about 15 ejaculations. Some may take mor e time to reach that. A pregnancy test needs to be done in this case. Please consult your doctor if you test positive, or are not able to get your periods one week past your dates.