Hormonal changes may also play a role in AF volume
regulation. There are not significant numbers of receptors for
estrogen or progesterone in fetal membranes after early pregnancy.
Receptors for decidual prolactin, however, are widely expressed by
both fetal and maternal tissues with increasing numbers as
pregnancy progresses. There is evidence that decidual prolactin has
an effect on amniotic permeability, although this is probably not
the only hormonal or growth factor-related mechanism