Shooting While Pregnant: Dangerous or Not?
By Elizabeth Kennedy and Fabrice Czarnecki, M.D.
Noise, especially very loud noise and chronic exposure to loud noise, is usually considered as detrimental during the pregnancy. In most European countries, health regulations forbid pregnant women to work in surroundings with a level over 80 dB continuous noise and rapid impulse noise changes of 40 dB, which is much less than the noise of a firearm. In the United States, the Department of Labor limits for impulse (not continuous) noise is 140 dB (Dept. of Labor Bulletin #334, 1971) with additional regulations for ongoing noise. The sound levels of firearms are about 125-140 dB for rimfire rifles, 140-150dB for rimfire pistols, and 150-160 dB for centerfire rifles, pistols, and shotguns.
...Numerous studies demonstrate that exposure to noise during pregnancy, has been linked to such disorders as miscarriage, intrauterine growth retardation, premature delivery (less than 37 weeks), decreased birth weight, hearing loss in babies and children, altered immune response in the fetus and hypertension during pregnancy (a potentially severe disorder). Interestingly, one study showed that a combined exposure to noise and lead seemed to have an increased toxicity, causing heart lesions, which was not observed for either of those agents in isolation. The question again, is "how relevant are the studies to our very specific question?" The answer again, is "we just don't know." Is it something we want to chance?
One thing we do know is that fetal response to sounds begins at about 16 weeks, and the ear is structurally complete by 24 weeks. (At 25 weeks, a baby will move in rhythm to an orchestra drum!) According to The American Academy of Pediatrics, "the hearing threshold (the intensity at which one perceives sound) is approximately 40 dB at 27-29 weeks, and decreases to a nearly adult level of 13.5 dB by 42 weeks of gestation." It would appear that even though the structures are all in place, the sense is not full developed until birth. We also don't know at what point the fetus is most susceptible to noise damage of the ear, whether it's during the first trimester, second or third.
Interestingly, "the vestibular system, [the part of the ear] designed to register head and body motion, as well as the pull of gravity, begins developing at eight weeks." It is believed that "receptive hearing begins with the skin and skeletal framework, [and] is then amplified with vestibular and cochlear information as it becomes available. Hearing is clearly a major information channel operating 24 weeks before birth."
Source - Shooting while pregnant