I recognize that, but otoh, having been on the bad end of it, I'm less sympathetic. I was pregnant with my first when the managers (a husband/wife couple) resigned to move to another state. They recommended me to replace them. Instead, the owner hired his buddy, a recently divorced history teacher with no experience whatsoever in restaurants of any sort. I ended up doing my job (day shift supervisor) AND training him to do his job (which basically entailed ME doing it because he wasn't interested, and didn't understand it, and just wanted to get into the pants of the coeds working for us). I stuck it out for a year. About 5 months after son was born I'd had enough. Found a job on campus (ex was still in grad school) and never looked back.
Yes, you can get burned hiring a pregnant woman. You can also get burned hiring a closet alcoholic, a hypochondriac, an addict, etc. Of the four, I'd take the pregnant woman...especially if she NEEDS the job.
That sounds to me more like someone wanting an excuse to hire his buddy than someone actually hesitant about the potential ramifications of hiring/promoting a pregnant woman.