What Pregnancy Hormones Really Do (And How To Deal)

Hormones can help us get pregnant and stay pregnant, but what’s really going on in there?

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Exhaustion. Tender breasts. Morning sickness. They’re all signs of pregnancy. But almost as important: They’re all signs that pregnancy hormones have kicked into high gear and they’re doing exactly what they need to do to keep you and your baby healthy. Okay, okay. When you’re running to the bathroom for the third time in an hour, it may not feel like such a great thing. And the ebbs and flows of pregnancy hormones can have you tearing your hair out one minute and then marveling at how thick and lush it is the next. But hormones play a crucial role in helping the body get pregnant, stay pregnant, and prepare for the arrival of a baby. Unlike your skin, hair, and belly, however, hormonal changes occur without us ever seeing them, making for one of the great mysteries of pregnancy. What’s really going on at the hormonal level? When can you expect your pregnancy hormones to spike, and how do they change throughout the course of the nine months (give or take) of making a baby? Let’s dive in!

What’s a hormone anyway?

We might not spend much time thinking about them, but hormones rule our lives. Produced by a number of glands throughout the body—from the pituitary to the thyroid—hormones are essentially chemicals that travel throughout the body, coordinating the functions of our organs and tissues. “Hormones are for essential for life,” says nurse practitioner and certified nurse midwife Patricia A. Evans of MemorialCare Medical Group in Fountain Valley, California. “[They] contribute [to] and influence immune system functionality and can even affect behavior.” Hormones also play a major role in puberty, dictating body changes and—in cisgender females—spurring the beginning of the body’s menstrual cycle. Not having a period? Having periods that are too long or too frequent? All those issues come down to hormones, says Sherry Ross, MD, OB-GYN and women’s health expert at Providence Saint John’s Health Center in Santa Monica, California. And because fertility is directly tied to the body’s menstrual cycles, doctors will typically test a woman for a hormonal imbalance if she walks in the office citing infertility concerns. Correcting that imbalance can be the key to helping solve infertility woes. On the other hand, when all of the hormones are right in line, it’s these chemicals floating around the body, keeping everything in check, that help make conception happen. Not making the connection? That’s okay; you’re not the only one who hasn’t been back to science class in a while. Diana Bitner, MD, an OB-GYN at Spectrum Health in Grand Rapids, Michigan, broke it down for us. “A correct hormone balance is crucial to getting pregnant, and hormones are in good balance when the ovary is functioning well and the brain and the ovary are communicating well,” she explains. “If the ovary is able to make a good quality egg, then the hormones are right.” So how does it work? When a woman is healthy and in the reproductive phase of her life, she’s typically ovulating every 28 to 30 days (depending on a woman’s “normal” cycle). When her period is starting, a new follicle in the ovary is being stimulated by a follicle-stimulating hormone (FSH). “The cells around the immature egg make estrogen in the first half of the cycle,” Bitner explains. Ovulation, which typically occurs smack dab in the middle of your menstrual cycle, is triggered by yet another hormone: luteinizing hormone (LH for short). When the follicle stimulated by FSH syncs up with the LH-stimulated ovulation, the follicle releases an egg, Bitner says, and the body’s cells make yet another hormone called progesterone. “The lining of the uterus is analogous to the ‘lawn,’ and [the hormone] estrogen acts as fertilizer and the progesterone as almost weed-killer to keep it from growing out of control,” Bitner says. Together the hormones help the lining of the uterus mature and get ready for a fertilized egg to plant. If that happens, the fertilized egg will then have a home on the “lawn” to develop into a fetus, the way a seed develops into a flower in your yard.

Pregnancy Hormones: The Big 3

So hormones help you turn all that bedroom fun into an actual pregnancy. Then what? More hormones get in on the action. After an egg is fertilized by the sperm, it heads to the uterus to implant, and hormones kick in to help the body sustain a pregnancy and help the embryo grow into a fetus. The three main pregnancy hormones are human chorionic gonadotropin (hCG), progesterone, and estrogen.

Human Chorionic Gonadotropin (hCG)

A popular fad diet featuring human chorionic gonadotropin (hCG) has gotten the stink-eye from the U.S. Food and Drug Administration (FDA), making the term sound a little scary for a pregnant woman. Fortunately, the hCG produced by the body during pregnancy isn’t just healthy…it’s absolutely vital. While all three major pregnancy hormones will increase in the weeks after conception, hCG is the first, Evans says, and it’s responsible for keeping the other two at appropriate levels while the placenta grows. Once the placenta is developed enough to sustain the growing embryo—at around 10 to 12 weeks, basically the tail end of the first trimester—hCG production slows down as the placenta steps up to the plate.


Initially produced by the ovaries, progesterone kicks in early in the pregnancy, and you’ll start seeing physical changes because of it. A rise in progesterone levels will increase a pregnant woman’s heart rate—and her appetite. It can also lead to some of the more uncomfortable side effects of pregnancy, such as fatigue.   Because progesterone has an impact on the smooth muscles of the body, it affects the lower esophageal sphincter, Evans says, which can cause heartburn and acid reflux, mostly later in pregnancy. Progesterone also softens the cartilage, which contributes to pelvic pain. On the other hand, it’s that softening that helps the hips to expand during childbirth! Low progesterone levels can lead to miscarriage, warns Anita Somani, MD, an OB-GYN with OhioHealth in Columbus, Ohio, so your OB-GYN or midwife may be doing blood tests to keep track of your progesterone levels, especially if you’ve had issues in the past. If you’re looking at the blood tests for answers, here’s a basic guideline. Progesterone levels can range from 9 to 47 ng/mL in the first trimester, with an average of 12 to 20 ng/mL in the first 5 to 6 weeks of pregnancy. But Evans is quick to say that these numbers are not to be taken alone, as each woman’s body is different. “It is not the single value that can predict a healthy pregnancy outcome,” she warns. When in doubt, ask your doctor or midwife. Some OB-GYNs do suggest women who have had a previous miscarriage or have experienced a pre-term delivery take progesterone during their pregnancy in addition to the amount the body produces. Studies on the efficacy of added progesterone are mixed. One 2015 study published in the New England Journal of Medicine concluded that progesterone therapy in the first trimester of pregnancy “did not result in a significantly higher rate of live births among women with a history of unexplained recurrent miscarriages.” Because of studies like these, it’s not recommended that women take progesterone on their own without a doctor signing off. The body’s progesterone production will slow down in the end of the first trimester as the placenta takes center stage.


Along with progesterone, estrogen is produced in the ovaries, and it helps sustain the lining of the uterus in the first trimester, supporting the developing embryo. It’s also one of the two hormones (again, along with progesterone) most responsible for the physical changes we have come to associate with pregnancy. The most pronounced? Those achy, throbbing breasts can be blamed on increased estrogen production in your body. If you’ve got a stuffy nose, you can blame that on estrogen too. The hormone helps increase blood flow through the body. This is good news for your growing fetus, which will depend on that increased blood, but it can result in swelling in your nostrils. (Then again, it’s all that extra blood flow that contributes to a pregnant woman’s “glow.”) The ovaries’ estrogen production will begin to wane near the end of the first trimester.

What about the baby?

While the big three hormones begin to taper off by the time you hit your second trimester, that doesn’t mean hormones aren’t still working on your body. As the embryo grows, so does the placenta. By about week nine of your pregnancy, the placenta takes over pumping out estrogen and progesterone and adds yet another pregnancy hormone, human placental lactogen (hPL), to the mix. One of hPL’s main jobs is to inhibit insulin, preventing glucose from absorbing into a mother’s cells. In turn, that makes your bloodstream glucose levels increase, providing more sugar to the baby so he or she can grow. Overall, hormones produced in the placenta will work together to promote fetal growth while also helping a mother’s body become an even better place for a baby to develop. That means some will spike, decrease, then spike again, and you’re just along for the ride.

Up and Down and Back Again

All that ebbing and flowing of hormone levels may be natural, but let’s face it, it’s not easy having your hormones fluctuate. From exhaustion to wild emotions, hormones can make you feel like you’re on a roller coaster. “Mood swings, fatigue, nausea and vomiting, breast tenderness, sensitivity to smells and odors can be overwhelming at times,” Evans admits. “The good news is that these are temporary and most decrease with time.” In truth, there’s nothing you can do about hormone fluctuations. They’re part of pregnancy. But they also don’t have to plague you the whole nine months. “Change is normal and moods can be affected,” Bitner explains. “The best is self-care and awareness. If a women has underlying mood issues, such as anxiety or depression, the worries of pregnancy, body changes, and relationship changes can add stress and expose coping difficulties. “The best way to cope is to have good self-care in place with a healthy diet, adequate sleep, a support network of family and friends, and (if necessary) counseling to deal with more difficult situations,” she adds. “Women who cope are able to ask for help when needed, believe they deserve to be happy and do well, and keep a network in place. Some women do need medication for mood during pregnancy and there are safe options.” Evans recommends her patients break down the nine months into chunks to get through. “I like to describe the first 20 weeks of pregnancy as [wedding] planning,” she says. “[You’re] busy with anticipation, worries, excitement for the future, and ups and downs of event planning. When the wedding day arrives at around 20 weeks, you find you have more energy and sense of euphoria as the honeymoon begins and you start buying baby clothes and life is grand as the hormones settle in and calm down.” By the last month, however, the honeymoon is over and you’re facing yet another hormone change. “As your body prepares to give up this growing life inside, you can’t breathe, sleep, eat, find clothes that fit and your feet have outgrown every pair of shoes in your closet, and all you want is to meet your new baby, and for the pregnancy to be done so you have more energy and a sense of euphoria never before experienced—the birth of your baby,” Evans says.

After Baby Comes

Once the baby arrives, your hormones will change once again. The placenta leaving the body means it’s no longer producing hormones, and estrogen and progesterone levels fall to low levels rapidly after birth. If you decide to breastfeed, estrogen and progesterone will help support milk production and suppress ovulation (which is why many breastfeeding moms don’t get a period for months or even years after giving birth). These hormonal changes can be dicey for moms who are risk of anxiety or depression, Bitner warns, as the loss of estrogen is associated with less serotonin activity. “Serotonin is the brain chemical which impacts many women in how they cope and how they feel,” she explains. “Lower effective serotonin levels can lead to marked depression and/or anxiety, especially if other risk factors exist, such as sleep deprivation and life stressors.” Depression treatment can start during pregnancy, or you may need to be watched for postpartum depression symptoms. So if you’re worried about the way hormonal fluctuations can affect your mood during and after pregnancy, it’s important to talk to your healthcare provider. There is help available.

What Pregnancy Hormones Really Do (And How To Deal)

Jeanne Sager
Jeanne Sager is a writer and photographer from upstate New York. She has strung words together for The New York Times, The Washington Post, The Atlantic, and more.

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