The effect pregnancy has on your sense of taste is well known (pickles and ice cream, anyone?), but the effect it can have on your sense of smell is less commonly discussed—and just as real. I learned the hard way about those changes to the olfactory system during pregnancy. As a beauty editor, I own an expansive fragrance wardrobe, and every single scent made me sick during my first trimester. Even my favorite fragrance, Matiere Premiere’s Vanilla Powder, made my stomach turn. I knew pregnancy, with all of its hormonal fluctuations, would bring an onslaught of uncomfortable symptoms, but I didn’t expect any of them to totally rewire my nose.

Turns out, I wasn’t alone in this experience. Anate Brauer, MD, a board-certified reproductive endocrinologist, says the change in how I perceived smells during this time is in line with what other patients experience. Being pregnant isn’t the only time this shift can happen, either; any subtle hormonal fluctuations you experience—across your menstrual cycle, during perimenopause, and while using hormonal contraception—can influence how you perceive scent.

Ahead, experts break down how different hormonal shifts and phases in a woman’s life can impact the sense of smell.

Pregnancy

Brought on by hormonal shifts in pregnancy, changes in how you perceive smell “commonly happen in the first trimester,” says Dr. Brauer, adding that patients typically complain about a heightened sense of smell. There’s an evolutionary explanation, she explains: “When you’re pregnant, your body goes on high alert to protect you and your baby.” For some, that means nausea triggered by everyday smells; for others, this biological reaction means that long-standing fragrance preferences shift overnight.

There’s also an endocrinological explanation in that the biggest hormonal surge during pregnancy happens during these early weeks. Human chorionic gonadotropin (hCG)—the main pregnancy hormone responsible for fetal development—peaks at about 8 to 11 weeks of gestation. This major hormone shift can shock multiple systems in your body, including the olfactory system. But hCG isn’t the only hormone responsible, estrogen and progesterone also come into play.

Estrogen

The endocrine system is more intertwined with your sense of smell than most people realize, and estrogen is the primary hormone to blame if yours shifts significantly, says Dr. Brauer. Estrogen, which is vital to regulating the female reproductive system, fluctuates during pregnancy, puberty, throughout the menstrual cycle, and menopause. It’s the hormone responsible for the development of breasts during puberty, uterine-lining growth, and the formation of fallopian tubes. “There are estrogen receptors throughout the entire central nervous system,” Dr. Bauer points out, and they immediately pick up when your hormones are spiking.

To explain how estrogen impacts smell, Dr. Brauer zooms in closer: The olfactory pathway—from the lining of the inside of your nose to the brain’s scent-processing centers—is dotted with these receptors. When estrogen levels spike, smells can register as more intense. Sometimes that intensity reads as pleasurable, like during ovulation (we’ll get into that shortly); other times, though, it can be overwhelming, which is how I felt when I was rummaging through my fragrance collection, desperate to find anything that wouldn’t make me want to hurl.

Human chorionic gonadotropin (hCG)
For pregnant people, another hormone enters the mix: The aforementioned human chorionic gonadotropin, or hCG, is the hormone that indicates you’re pregnant when you take an at-home test. Produced by the placenta, hCG supports fetal development by signaling the body to maintain the pregnancy and suppress hormones that cause menstruation. It also helps with immune tolerance, ensuring that the mother’s body does not reject the embryo.

“There are receptors for hCG in your central nervous system, too, which can increase the sensation of nausea,” says Dr. Brauer. Nausea itself can heighten aversion, turning once-loved sensory notes into instant triggers. I felt so seen when she told me this; even the mildest eau de toilettes in my fragrance wardrobe had made me feel ill.