What are the chances of getting pregnant after 'no sperm seen' on post-vasectomy sperm test? dr said husband is considered sterile after 1 test but i am having cramps 1 week before period and am worried.

Pregnancy test: Conception occurs within day or so of the sex. It takes about 3 weeks for the embryo to make enough HCG for a positive pregnancy test. Blood test may be done a day after a missed period. Home pregnancy tests should be done 4-5 days after the missed period. If the result is negative repeat the test in 4-5 days. Use first morning urine and follow instructions for the test carefully.