You really have two choices: 1) try to interview this year; 2) put it off a year, make your application even better, and apply next year. But really, you only have one choice - plan a gap year and apply in the match the year following.
There may not be a choice at all, depending upon how much maternity leave you are planning. The ABIM requires 36 months of training be completed, and this can be shortened to 35 months if your PD/CCC agrees and is willing. That means that you can take 4 weeks + vacation and still graduate on time -- so basically 6 weeks (because you really don't want to use up all of your vacation doing this). And that assumes that all goes well, you don't need bedrest before you deliver, etc.
Interviewing this year is going to be very difficult, if not impossible. Could you interview while on maternity leave? That's an interesting question. Due to the crazy way that our country/legal system works, maternity leave is usually considered medical leave, and you are paid while on leave (unless you take FMLA time, which is an unpaid personal leave). technically, working while on medical leave is fraud. Whether attending interviews is "working" is unclear. Personally I've never heard of anyone getting into trouble for this, but most new moms really don't want to leave their new baby (and the baby is not coming with you on interviews).
The other option is to put it off for a year. This allows you to take a longer maternity leave (if you want), extend your training by 1-3 months to make up for that leave. Then, you're completely free for interviews in Oct and Nov. You work as a hospitalist and make money to cover expenses, ideally at wherever you are in residency. Or just moonlight shifts. Then you start your fellowship one year later. Note that while on Maternity leave, you have lots of time to work on research projects, because you won't be sleeping at night anyway.
One other piece of advice -- lots of people think that their family will provide child care. But a new baby needs 24/7 attention. You may have family that help out once in awhile, but real support for a new baby will require that someone basically live with you all of the time. Perhaps that's what your family has in mind. But often, parents are the ones that are up all night with their new baby. Be careful not to overestimate how much help you will receive, plus you may come to cherish the time you spend with your newborn and I would be careful outsourcing that to someone else.
So, bottom line:
1. You should review your programs Maternity leave policy, determine how much time you can take before needing to extend training.
2. If you discover that you can have a baby, a 4-6 week leave, and still finish on time, then you could consider trying to participate in the fellowship match this summer. But doing so will be very difficult unless you only apply to a few, local programs.
3. Honestly, the best plan is to delay the fellowship match by a year, take whatever maternity leave you want, extend training as needed, work the gap as moonlighting / hospitalist, and use the extension of time to further improve your application.
