Most women are familiar with the ups and downs of their menstrual cycle: they get their period and feel fatigued; post-period, their energy rises; mid-cycle, they’re at their most fertile and feel sexy; and then their body prepares to repeat the cycle. Each month, women experience bloating, appetite changes, muscle pain, and/or mood swings, and even voice changes. A recent study published in PLOS One found whether a woman is on the pill or not can influence her voice tone, and potentially how attractive she is perceived by men.

Women who were not using hormonal contraceptives showed some changes in their voice across their menstrual cycle than their counterparts. Specifically, they had a lower minimum pitch in the late follicular phase, near ovulation, when fertility is the highest, compared to the menstrual phase. During the luteal phase, after ovulation and before a woman’s period starts, these women had a lower voice intensity. Meanwhile, women using monophasic hormonal contraceptives — pills that deliver the same amount of estrogen and progestin every day — did not experience any significant vocal changes throughout their menstrual cycle.

Irena Pavela Banai, study author, believes there’s a discrepancy between women on a natural cycle and those on birth control due to their sex hormones. Previous research has found during the ovulatory phase (highest level of estrogen) women had the “best voice”; in the premenstrual phase (least amount of estrogen, increased amount of progesterone) women had the “worst” voice, also referred to as “premenstrual voice syndrome.” Birth control could interfere with these hormone fluctuations.