HFA was administered by nose-only inhalation to groups of female rats on Days 7-16 of gestation (the day copulation was confirmed was designated Day 1 of gestation), 6 hours/day, at exposure concentrations of 9, 0.11, 1.0, or 6.9 ppm. All females survived to the scheduled sacrifice on Day 22 of gestation. There were no significant differences in the mean maternal weight change of any group during HFA exposure. However, after exposure (days 17-22G) significantly less weight gain occurred in the 7 ppm dams than in controls. This is attributed to embryolethality and an adverse effect on fetal weight in this group rather than maternal toxicity. Feed consumption was never significantly different from controls in any of the HFA-treated groups. Clinical signs observed during exposure in all groups were related to restraint and were not attributed to HFA administration. On postmortem examination, absolute and relative liver weights of dams in the 1 and 7 ppm groups were significantly greater than controls.