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"Pregnancy brain is real," Savannah Guthrie, expectant mom and Today show co-host, tweeted after she made an on-air goof about the date. And she's right: "Not since puberty have there been so many changes going on in a woman's brain at once," explains Louann Brizendine, M.D., a clinical psychiatrist at the University of California, San Francisco and author of The Female Brain. Throughout pregnancy, a woman's brain is marinated in neurohormones manufactured by the fetus and placenta, Brizendine says. And while not all women will share the exact same pregnancy-related cognitive changes, here's a look at what your pre-mommy brain could look like.

Before You're Even Pregnant

Just a quick whiff of a friend or sibling's baby can cause a chemical shift in your head that may increase your lust for rug rats of your own, Brizendine says. Babies secrete chemicals called pheromones that, when sniffed, can stimulate the release of oxytocin in a woman's noodle, research shows. Also known as the love hormone, oxytocin has been tied to sensations of attachment and familial love.

The First Trimester

Massive hormonal changes start as soon as a fertilized egg implants itself in the wall of your uterus and hooks into your blood supply, which happens sometime within two weeks of conception, Brizendine says. A sudden flood of progesterone in the brain not only increases sleepiness but also stokes hunger and thirst circuits, research shows. At the same time, brain signals related to appetite can become finicky, screwing with your reactions to certain smells or foods. (Pickles may be your new favorite thing, while a sniff of yogurt may make you vomit.) This sudden change happens because your brain is worried about eating something that might harm your fragile fetus during the first few months of pregnancy, Brizendine explains.

Stress chemicals like cortisol also surge in response to the physical changes taking place in your body. But the tranquilizing effect of progesterone, as well as elevated estrogen levels, moderates your brain and body's response to those stress chemicals, keeping you from feeling too frazzled, Brizendine says.

The Second Trimester

Your body is becoming more familiar with the hormonal changes, which means your stomach settles down and you may have the desire to eat everything in sight, Brizendine says. At the same time, your brain recognizes the first fluttery feelings in your abdomen as the baby's movements, which fire up "love circuits" related to attachment, she says. As a result, you're primed to fall in love with your baby. From this point on, every new kick may trigger fantasies: What it will be like to hold, nurse, and care for your child, she adds.

The Third Trimester

The fight-or-flight stress chemical cortisol has continued to rise and is now at levels on par with strenuous exercise. This happens to keep you focused on protecting yourself and the baby, but it can make it difficult to focus on less essential tasks, Brizendine says. There's also a surge of activity in the right half of your brain, which helps manage your emotions, new research from University College London shows. This is especially true when pregnant women look at baby faces, explains Victoria Bourne, Ph.D., who coauthored the U.K. study. Bourne can't explain why this happens, but the change may help prepare a mother to bond with her new child once he or she is born. Thoughts about how you'll handle labor can also elbow out more mundane, day-to-day considerations, Brizendine adds.

After Your Child Is Born

During the first few days following labor, elevated oxytocin levels help imprint your new baby's smells, sounds, and movements on your brain's circuitry, Brizendine says. In fact, studies show new mothers can distinguish their own baby's scent from that of another newborn with 90 percent accuracy. (Wow.) Lingering high levels of stress hormones, as well as several other brain chemicals, may also trigger feelings of post-partum depression, research shows. But, more than anything, the brains of new moms tend to become hyper vigilant about protecting their child, Brizendine says. It's just nature's way of ensuring the survival of your offspring, and the human species, she adds.