Antibiotics usually don't have an effect on sperm, I've never read or heard that it does. As mentioned above, alot of antibiotics are safe to take during pregnancy.If you are still worried, talk to your OB/Gyn about it.
If you post the name of the antibiotic, I can look it up in my Drug Handbook and tell you for sure. I don't know of any antibiotics that excrete through semen, though. Also, most antibiotics are safe even if YOU were to take them so it is unlikely to hurt your baby.
You can take anti biotics while pregnant