This is just an observation, ie: what I've seen in clinical area, with no
research back up.  Fertility after pregnancy seems higher than if parents
try to space babies using some sort of birth control.  In other words if
you had trouble becoming pg in first place and want more children, don't do
anything to prevent, take what comes, even if interval between babies is
less than optimum.  I think I've read that secondary infertility is more
common than primary infertility. (that is -  having trouble getting pg
again after a having no trouble the first time).  Which is all interesting
in view of the fact that we know lactation suppresses fertility.  Go
figure.  Sincerely, Pat in SNJ