Not trying to be preachy or anything here, but your wife shouldn't be shooting when she is pregnant. The report of the gun can damage your baby's hearing inutero.
The actual answer is unknown. Medical opinions and advice vary.
There are no definitive studies on this topic. In studies that have been conducted of pregnant women, high level steady state noise has had observable effects on fetus
behavior. However, the effect on hearing is not measurable. Most studies of hearing effects on the fetus hearing structures are based on non-human studies, and their reliabilty as to humans is unknown and/or questionable.
OSHA [u[guidelines[/u] for pregnant women are 80dB steady state sound level, and 120 dB impulse level. While the steady state guidance has some basis in studies of fetus behavior, the impulse level is based on conjecture.
While CF pistol gunfire at the muzzle usually exceeds 120 dB, that is not the definitive answer. The distance of the fetus from the point of discharge, and the direction of the sound downrange, significantly affect the actual dB level sustained at the point of measurement. In addition, the sound insulation provided by the amniotic fluid is a factor in reducing the dB level inside the womb. Finally, the effect of sound on the actual hearing structures of the developing fetus are unknown.
Exposure to lead and other noxious chemicals is a far more researched and known effect, and should be eliminated while pregnant.
My wife's doctor advised that a occasional qualification on the pistol range was not harmful, provided 1) no other firing was taking place, 2) lead free ammunition was used, 3) she did not clean the pistol afterwards, and 4) normal range hygiene protocols were followed (no eating or drinking, thorough washing afterwards, changing of shoes and clothes before entering the home).
I would not criticize a woman for refraining from shooting while pregnant, nor would I condemn her for electing to shoot under controlled circumstances. As a LE rangemaster for the past 25 years, any pregnant officer who produced a doctor's advice to refrain from shooting, was excused from qualification. After her pregnancy ended, she would be make up any lost qualifications.