My partner has low sperm count; can he still have a baby without special treatments?

Possibly: Many men with 'low' numbers can produce pregancnies ata normal rate, and many will eventually be succesful even if it takes longer. It depends on how low overall, and which parameters, are low. It may also depend on 'why' he's low, but this often isn't important. If you have numbers to share, i can try being more specific.

How Low: As a general rule, you can always get pregnant spontaneously. The question is what is the chance for that to happen: high, low or minimal? The answer depends on how low the sperm count is, what are the other sperm parameters and what are the other fertility factors e.G the fallopian tube, age and ovarian reserve. These need to be evaluated.