Why You Might Have a Heightened Sense of Smell During Pregnancy

For many people, pregnancy feels surreal: Your body is producing a living being from scratch, leading to uncomfortable and even weird symptoms. During my first pregnancy, I craved artichokes. (Lucky for me, I guess—there are worse things?) More disturbingly, simply looking at the color gray—pillows, T-shirts, my gray couch—aggravated my 24/7 nausea. Not so convenient for my everyday life. While I haven’t yet met anyone else with a color aversion, some of my friends did struggle with a heightened sense of smell during pregnancy, resulting in unusual aversions to common odors, like fried chicken or cologne.

“I could smell food cooking in the apartment a few doors down from us in my first pregnancy,” says Lauren Barth, associate content director of The Bump and mom of three. “Unfortunately, my neighbor wasn’t baking chocolate-chip cookies in there. She was rendering chicken fat or boiling tofu or burning broccoli. No one else seemed bothered, but I was constantly affronted with these less-than-pleasant odors.”

Although there isn’t good scientific evidence that our sense of smell actually changes in pregnancy, doctors say that, anecdotally, hyperosmia is a symptom shared by many of their pregnant patients. So why do you have this super-sensitive sense of smell during pregnancy? Read on to learn the potential causes, plus what you can do about it.

What Is Hyperosmia in Pregnancy?

Hyperosmia is a heightened sense of smell; this often is reported among expecting moms. While it’s a common complaint, there isn’t a lot of solid scientific evidence to prove this phenomenon is real. Alessandra Hirsch, MD, an ob-gyn at NewYork-Presbyterian/Columbia University Irving Medical Center in New York City, points to a 2022 meta-analysis, which reviewed 234 studies on pregnant women and assessed 13 for their findings on change of smell during pregnancy. The researchers couldn’t find a reliable link between pregnancy and sensitivity to—or even ability to distinguish between—odors.

When Does a Heightened Sense of Smell in Pregnancy Start?

Most women seem to notice a heightened sense of smell during the first trimester, around the six-week mark. “In my experience, it goes hand-in-hand with nausea and vomiting of pregnancy," says Hirsch. “Some women experience this before they take a pregnancy test, and it can even alert them to the fact that they’re pregnant.”

What Causes a Heightened Sense of Smell in Pregnancy?

As with all symptoms in pregnancy, hormonal changes may play a role in this heightened sense of smell. It’s “likely a response to rising progesterone and hCG (human chorionic gonadotropin) levels,” explains Mahino Talib, MD, an ob-gyn and clinical assistant professor at the Department of Obstetrics and Gynecology at NYU Grossman School of Medicine. “The acuity and number of receptors on the olfactory nerve increases.”

Because taste and smell are linked, people with worse nausea and vomiting in pregnancy and/or food aversions tend to be more sensitive to smells. “If you are already more likely to throw up, it’s certainly more likely that smells that are significantly stronger can trigger this response!” says Talib.

Although doctors believe there’s distortion of odor perception in pregnancy, “we still don’t quite know why or how,” says Hirsch. “There’s probably an evolutionary reason for it.” The most common theory: smell and food aversions could help pregnant women avoid harmful substances, such as rotten food. An extra-sensitive sniffer might also help moms better recognize their babies after birth. One study in mice found that pregnancy activates dormant stem cells, leading to creation of neurons linked to smell.

On the other hand, there’s also some evidence that pregnant people are less sensitive to odors, possibly due to changes in the brain in areas related to smell perception, like the amygdala. “It’s possible that, as the brain changes to accommodate motherhood, some of the olfactory pathways get suppressed along the way,” says Hirsch, though these changes don’t last after delivery. She adds that most studies assess people’s ability to identify sweet or nice-smelling odors, so it’s possible that pregnant people are better at identifying unappealing—and potentially harmful—odors.

What Can You Do About Your Heightened Sense of Smell in Pregnancy?

There’s not anything you can do to prevent a heightened sense of smell during pregnancy: Unfortunately, you’ll have to learn to live with it. So if something smells bad, avoid it. If noxious smells are unavoidable, you may find that a whiff of citrus, mint, or ginger helps.

When Will Your Heightened Sense of Smell in Pregnancy Taper Down?

Many people notice a peak in heightened smell between weeks 7 and 9 of pregnancy, says Talib. This will gradually decline when nausea and vomiting subsides, often after the first trimester. That said, your sense of smell may remain amplified throughout pregnancy; some people reporting sensitivity intensified during the third trimester, says Hirsch. Fortunately, based on brain changes during pregnancy and after, your sense of smell should return to normal after delivery, she adds. Talib estimates your smell will be normal within two to six weeks after birth.

A heightened sense of smell can be an unpleasant side-effect of pregnancy, especially if you can no longer eat your favorite foods (or find yourself on a crowded subway on a hot summer day). Fortunately, as with other pregnancy symptoms, it should pass soon after you deliver.

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Please note: The Bump and the materials and information it contains are not intended to, and do not constitute, medical or other health advice or diagnosis and should not be used as such. You should always consult with a qualified physician or health professional about your specific circumstances.