As a wife of a commercial pilot I asked his opinion on this matter. He says
that it is not so much the concern about being "trapped" with an imminent
delivery, although this is rather daunting, but they have to consider the
possibility of a rapid " de-compression" if the pressurisation system or
aircraft structure should fail. This would cause a rapid ( virtually
immediate) fall in cabin  pressure and terrible consequences to all on
board, most of all a pregnant  woman. Everyone would suffer ruptured
eardrums and epistaxis, for example.They would need to use supplemental O2
and if the pregnant mother was slow to use it what consequences would this
have on her unborn child?? Statistically it has been proven that passengers
go into " shock" at the sight of O2 masks and require prompting to don them.
Also the pressure at cruising altitude (typically 35,000-40,000 feet) would
be equivalent to 6,000 feet above sea level in a pressurised airplane. This
is a quite a big difference to the pressure on the ground and would increase
the risk of rupturing membranes.

Just an opinion from someone on the control-end of a plane.

Janelle Gridley
[log in to unmask]