What are the chances of pregnancy 4 weeks after a vasectomy?

The chances of pregnancy occurring four weeks after a vasectomy are low but not zero. It typically takes about 8 to 12 weeks and several semen analyses to confirm that the sperm count has reached zero. During this initial period, residual sperm may still be present in the vas deferens, which can result in potential pregnancy if unprotected intercourse occurs. Couples are generally advised to use alternative contraception until a doctor verifies the absence of sperm.