Decrease in Middle Ear Resonance Frequency During Pregnancy.

Many physiological changes occur during pregnancy. The aim of the study was to reveal whether there is a change in middle ear resonance frequency during pregnancy. A prospective case-control study was designed at a tertiary referral center. The study included 46 pregnant women at the third trimester (27-40 weeks) and 43 nonpregnant voluntary women. All the study subjects underwent pure-tone audiometry and multifrequency tympanometry. Pure-tone hearing levels at frequencies of 250 to 8000 Hz and resonance frequency values were compared between pregnant and nonpregnant women. Impact of age, side of the tested ear, and weight gained in pregnancy on resonance frequency were evaluated. Air conduction threshold values at frequencies of 250 Hz and 500 Hz were significantly higher in pregnant women than in the control group (P<0.001). Middle ear resonance frequency values of both ears in pregnant women were found to be significantly lower than those in control group (P<0.001). There was no statistically significant relation of middle ear resonance frequency values to age or side of the tested ear in both groups (P>0.05). A negative correlation between weight gained in pregnancy and middle ear resonance frequency values was determined for the left ear (correlation coefficient for left ears: -0.348, P=0.018). The results of this study suggest that resonance frequency may be decreased during the pregnancy. More comprehensive studies in which many pregnant women followed regularly before and after pregnancy are needed to have more certain links.