Danielle Bean has an interesting discussion about family size at her website.
My husband says he wants one more and then he's done. Hmm. He keeps reminding me of the number I quoted before we were married as though it were part of the contract.
Father Hilliar: Michelle, do you promise to love, honor and cherish Bill all the days of your life?
Me: I do.
FH: Do you promise to be open to life, to having children and raising them in the faith of the Catholic Church?
Bill: Oh, Father, remember we've specified that number?
FH: Oh. Right. Michelle, do you promise to have between four and six children, raise them Catholic and all that?
Uh, no. Perhaps at the time I would have, but since that wasn't an option, and it wasn't vowed before God and man, I won't be held to it. I don't think a prior verbal agreement is legally valid over a latter verbal agreement made before witnesses.
That said, I plan to take things one pregnancy at a time. No sense in wasting energy on what could be a moot point. I know two women who each lost her uterus, one after her fifth child and one after her second. They didn't choose instantaneous infertility. I know another couple who unhappily discovered they were having their fifth. Now, they both eagerly await the arrival of their seventh.
Another woman I know, while pregnant with her sixth, said that her husband often worries about having so many children. "I just get into bed naked. It's not my fault if he finds me irresistable."
Circumstances and people change. At least Bill and I agree that permanent, self-inflicted infertility (vasectomy or tubal ligation) is not a good solution for what may be a temporary desire to limit family size.
Right now, neighbors and friends who see the typical 2 year space between my children are already starting to ask me if I'm pregnant yet. The Army Ten Miler is in early October. I've paid the entry fee, I know I can do it having done 8 miles a few weeks ago, and I don't want nausea or sciatica to keep me from that goal.
My answer: ask me in November.