I interview applicants. If I interviewed a woman who appeared pregnant, I would not think anything of it and I would not bring it up in the interview to avoid any question of discrimination on that basis. I would not mention it in my write up of the interview unless the applicant asked me to tell the adcom what her plans were with regard to the baby. I think that it is only fair that a woman who is pregnant be judged on the same basis as every other applicant, "why medicine" and evidence in the interview of maturity,integrity, empathy, interests outside of academics, respect for others, and responsibililty.
Presumably, someone who is interviewing for a place in next year's class intends to attend classes. Someone who plans to be a stay-at-home mom in the coming academic year should not be interviewing.
From the perspective of an interviewer, it is my opinion that it doesn't matter if an applicant is married, engaged, pregnant, or whatever.... the question I need to answer is "is our school a good fit for this applicant and if so, how can we persuade this applicant to matriculate here?" Whether the applicant will be a parent at the time of matriculation is not a relevant question.
(We certainly don't ask these questions of women who don't look pregnant but who would be more likely to deliver closer to the start of the school year. And we don't ask questions about parenthood when we interview male applicants. So why should women with "bellies" be any different.)