Hey, I'm 5 ft 8 in tall. Other than coach class seat in airlines (which were designed by sadists who always fly first class -- all airline executives should be required, by law, to fly long distances in the narrowest seats with the least pitch of any aircraft operated by their airline), I'm usually not cramped (except when there are 400 pounders in the adjacent seat on Metro North. Or people who don't stand close enough to the soap when they bathe. Frequently, these are the same people).

In any case, I've never run across a parent who had a full term baby who fit the '0-3 month size', including my sister, whose kids tended to bounce along at the bottom of the growth charts.