A friendly memo to tenure-track faculty who don't have as many publications as they think they might need for tenure and are getting stressed out about this:
Don't blame your lack of productivity on the fact that the wife of one of your male graduate students or postdocs had a baby or even on the fact that one of your female graduate students or postdocs had a baby during your probationary years.
There are various reasons why this is not cool, but the main one in my opinion is that many of us (male and female) have advised unproductive graduate students and/or postdocs (male and female) for a stunning array of reasons, most of which have nothing to do with starting a family.
It is indeed difficult for assistant professors who have to deal with unproductive research group members, no matter what the reason, especially if the unproductive ones are supported by a grant involving a finite amount of time and money (as grants tend to be). I definitely feel the pain of anyone who has experienced this. If you are in this situation as a tenure-track faculty member, it is important to communicate with mentors and/or your department chair and try to figure out the best strategy for moving forward with the research despite dysfunctional research group members.
Even so, the birth or adoption of a child is typically an anticipated event, so, assuming that your advisees inform you of the upcoming event, you can try to plan for the disruption of your research program. If possible, avoid organizing your research program so that your entire future depends on your research group members and their significant others remaining childless throughout your probationary period.
Another reason why it's not cool to blame your lack of productivity on the reproductive activities of those in and associated with your research group is that it's hard to avoid appearing to accuse women specifically for causing your problems. Your suspicion that other people's babies are incompatible with your tenure won't make up for a weak tenure file (which might not even be as weak as you think/fear it is).
If you are stressed out and just feel like ranting about research group (re)productivity to a friend while you're at a cafe, in the gym, blogging, or wandering the halls of academe, that's fine. Go for it. If, however, you are considering making your hypothesis part of your tenure dossier, first consider the people who are going to be reading your file: your faculty colleagues, various administrators, promotion & tenure committees, and so on. Some of these people might even be women and men who had (or have) babies themselves, not to mention that most, if not all, have likely had a wide range of advising experiences. Some may sympathize with you, but I'm guessing (perhaps incorrectly) that many will not.
10 years ago