Objectives. To examine the effect of in vitro fertilization (IVF) treatment on acoustic properties of women's voice. Study Design. Prospective case series. Methods. Ten women undergoing IVF treatment participated in the study. All participants were recorded repeatedly in three successive sessions, before and during treatment, in addition to collecting hormonal assays, endometrial thickness measurements, and follicular growth data. Recordings were performed while sustaining an isolated vowel repeatedly and during a reading task. Acoustic analyses included a limited set of fundamental frequency (F-0) measures, as well as frequency-and amplitude perturbation measures. Repeated-measure analyses of variance were performed to test for the treatment effect, and the correlations between the acoustic measures and the hormonal as well as endometrial thickness data were examined. Results. A significant reduction in the two F-0 measures and in the amplitude perturbation measure was found throughout the treatment (P < 0.05). Before treatment, a negative correlation was found between F-0 and estrogen levels. After treatment, however, a negative correlation was found between F-0 and endometrial thickness. Conclusion. An association was found between IVF treatment and specific voice properties. In addition, the possibility of a ceiling effect for the influence of estrogens on female vocal folds was introduced.