Is a pregnancy relevant during a custody case?

I have noticed within the past couple of months my son's mother has gotten a very large bump in her midsection and looks very much pregnant-- I'm talking 5 months along or so. Under normal circumstances I wouldn't care to know, because it is really none of my business. However, I feel that if she is pregnant then my son's behavior is inevitably going to continue to worsen (he's in kindergarten and has had 23 in-school suspensions for his behavior). If she can't get our son under control now, I can only imagine how much worse things will get if she has to divert so much of her attention to a new baby. We have a guardian ad litem and she is recommending that I get custody which greatly increases my chance of getting the judge to agree to a custody change. However, I feel a pregnancy is something relevant to my child in this case. Would it be relevant in court? Would I just have my attorney request a response from her and her attorney?