Do understand there's only so far programs can go with this...
Programs with only a small number of residents will feel the hurt even
more when someone is out on maternity leave, so a bigger program might
be better in that way. That all said, you have family leave rights
under FMLA, but there is a limit to how many weeks of time you can
take off in derm residency set by the board (14 weeks total for 3
years I think).
Residency can be a convenient time to have a baby because everyone
else "has" to cover for you which is not the case in private practice,
but it can be tough on your colleagues with call, consults, clinic
loads, etc. I've heard of women timing it really well to have one
baby first year and another in the third year, which is probably a bit
much. My philosophy is that your colleagues will usually be willing
and able to help, but will start to resent things when there is a hint
of abuse.