Pregnancy Hormones: The Roles They Play and Symptoms They Cause

I’ve been pregnant three times, which means I’ve experienced more than my fair share of pregnancy symptoms. And when I asked about them at my prenatal appointments, the answer was always: “It’s your hormones.” From nosebleeds to bizarre dreams to lightning crotch, pregnancy hormones were always the culprit.

The explanation makes sense: The minute you get pregnant, several different hormones start rising, helping turn your body into a welcome home for baby. These pregnancy hormones continue to fluctuate in preparation for birth. Some of them drop down postpartum, while others stay elevated for a while.

Basically, being pregnant is like riding a hormone roller coaster. Here’s what to know about how and why pregnancy hormones change, plus what you can expect when you’re along for the ride.

Key Takeaways

• The most important pregnancy hormones are: human chorionic gonadotropin (hCG), progesterone, estrogen, oxytocin, prolactin, relaxin and human placental lactogen (hPL).
• When do pregnancy hormones arrive? Some pregnancy hormones rise as soon as you get pregnant and stay elevated until you give birth, while others increase later in pregnancy and stay high for weeks or months postpartum.
• While they play an important role in maintaining a healthy pregnancy, pregnancy hormones are also the driver behind most pregnancy symptoms—and some can even trigger postpartum depression when they drop after birth.

What Are the Main Pregnancy Hormones?

The main pregnancy hormones are:

• Human chorionic gonadotropin (hCG)
• Progesterone
• Estrogen
• Oxytocin
• Prolactin
• Relaxin
• Human placental lactogen (hPL)

These hormones are behind nearly everything that happens during the trying-to-conceive (TTC) period, pregnancy and postpartum starting with ovulation and implantation and ending with labor and breastfeeding. Below, what you should know about each of these key pregnancy hormones.

hCG

In short, hCG announces that you’re expecting in the first place; it’s the hormone that triggers that all-important second line on a home pregnancy test. It’s also often responsible for early-pregnancy morning sickness.

• When do levels of this hormone rise? Your body starts producing hCG about eight days after you conceive, says Dr. Alexander M. Kotlyar, MD, an ob-gyn and reproductive endocrinologist at Genesis Fertility in New York. Levels multiply quickly, doubling every few days for the first 10 weeks of pregnancy, according to Cleveland Clinic.

• What’s the hormone’s purpose in pregnancy? Made by the placenta, hCG helps you develop a stable environment for baby during their earliest stages of growth by supporting the development of the corpus luteum. This is a temporary organ that forms in the ovary after ovulation and triggers the production of progesterone, which is important for the health of your uterus during pregnancy.

• What symptoms does this pregnancy hormone cause? Rising hCG levels cause many women to have classic early pregnancy symptoms like nausea, fatigue, tender breasts and food cravings.

• When do levels of this hormone fall? Again, it shoots up rapidly in the first trimester, peaking around week 10 of pregnancy. Then it slowly starts to decline and eventually goes back to normal after birth.

Progesterone

Progesterone is critical during pregnancy because it thickens your uterine lining—which supports baby’s growth.

• When do levels of this hormone rise? Progesterone first rises after ovulation, then drops back down a bit—but if you become pregnant, it starts ramping up again, starting at around week 9 of pregnancy. It typically peaks around 32 weeks of pregnancy.

• What’s the hormone’s purpose in pregnancy? One of the most important things progesterone does during pregnancy is thicken your uterine lining, according to Cleveland Clinic. This supports baby’s growth throughout most of pregnancy.

Progesterone also prevents contractions that could cause preterm labor and gets your breasts ready for producing milk.

• What symptoms does this pregnancy hormone cause? High levels of progesterone are a common cause of pregnancy fatigue and mood swings, notes Johns Hopkins Medicine.

• When do levels of this hormone fall? Progesterone levels stay high throughout the rest of pregnancy, but quickly drop after birth. This rapid decline is one cause of the “baby blues” and likely also plays a role in postpartum depression (PPD).

Estrogen

Estrogen is one of the busiest pregnancy hormones, promoting healthy blood flow and helping make breastfeeding possible. (Of course, it’s also responsible for a few unpleasant symptoms.)

• When do levels of this hormone rise? Estrogen first rises before ovulation, increasing your chances for conception. If you become pregnant, your estrogen levels will steadily increase throughout pregnancy, finally peaking in the third trimester.

• What’s the hormone’s purpose in pregnancy? Estrogen promotes healthy blood flow and creates breast tissue for future breastfeeding, according to research. It also supports fetal growth—particularly for baby girls (it helps their reproductive organs form).

• What symptoms does this pregnancy hormone cause? Because estrogen is part of the initial trifecta of early hormones (estrogen, progesterone and hCG), it’s responsible for causing all kinds of unpleasant first-trimester symptoms, like morning sickness, nasal congestion, breast tenderness and sensitivity to smells.

Some of these symptoms are related to the extra blood flow estrogen creates. “My biggest early symptom was getting really hot,” says Toni T., a mom of one in California. “The increased blood flow and hormones just made me [prone to] overheating.”

• When do levels of this hormone fall? Like progesterone, estrogen also begins falling quickly within just a few hours of giving birth.

Relaxin

Relaxin literally relaxes many of your body’s tissues. While it plays a key role in helping the placenta grow, it can also cause unpleasant digestive symptoms and weaken your pelvic floor.

• When do levels of this hormone rise? Relaxin starts increasing as soon as you get pregnant, and peaks sometime between 12 and 16 weeks of pregnancy, according to Cleveland Clinic. There’s also a second surge that happens right before you give birth.

• What’s the hormone’s purpose in pregnancy? The initial surge of relaxin serves a few purposes: It promotes placental growth, prevents premature contractions and dilates blood vessels so more blood can flow to the placenta. Then, the increase in relaxin at the end of pregnancy prepares your body for delivery, helping to loosen ligaments and soften the cervix.

• What symptoms does this pregnancy hormone cause? Relaxin can slow down gut motility and cause symptoms like constipation, gas and bloating.

It can also weaken your pelvic floor and leave you more prone to injury by making it harder for your joints and ligaments to support your changing body. Unsurprisingly, relaxin is responsible for round ligament pain.

Relaxin is also a common cause of pregnancy-related carpal tunnel syndrome, as Hayley S., a mom of two and podcast host in California, found out: “With my first, I had really painful wrist joints in the last few months—a lot of numbness, and it was extremely uncomfortable.”

• When do levels of this hormone fall? After birth, your relaxin levels quickly drop—in fact, relaxin levels are basically undetectable in blood samples of postpartum women just a few days after delivery.

hPL

Research suggests that HPL can support breastfeeding and help make sure baby’s getting enough nutrients during pregnancy.

• When do levels of this hormone rise? HPL is a placental hormone that starts rising during the first trimester and steadily increases throughout the rest of pregnancy. It peaks around 34 weeks of pregnancy.

• What’s the hormone’s purpose in pregnancy? Experts don’t know exactly what hPL does, but studies show it ensures baby gets enough nutrition throughout pregnancy and supports breastfeeding.

• What symptoms does this pregnancy hormone cause? Usually, changing hPL levels don’t cause hugely noticeable symptoms. But because of its role in lactation, hPL can cause breast changes like tenderness, hyperpigmentation and swelling.

Research shows that expectant moms with higher hPL levels are at higher risk for gestational diabetes, which can cause symptoms like frequent urination, extreme fatigue and blurry vision.

• When do levels of this hormone fall? Your hPL levels go back to normal once you’re no longer pregnant.

Oxytocin

Often called the “love hormone,” oxytocin helps you produce breast milk and bond with baby.

• When do levels of this hormone rise? Unlike other pregnancy hormones, oxytocin doesn’t significantly increase until the third trimester. Once you go into labor, oxytocin starts skyrocketing and eventually peaks as baby’s being born.

• What’s the hormone’s purpose in pregnancy? Oxytocin stimulates contractions when it’s time for labor, and helps you produce breast milk.

• What symptoms does this pregnancy hormone cause? Because oxytocin ramps up just before and during labor, the main symptom it causes is uterine contractions. It also plays an important role in breastfeeding, not only helping you produce milk but triggering the let-down reflex.

• When do levels of this hormone fall? Oxytocin tends to stay high during the postpartum period to help you breastfeed and bond with baby. Studies suggest oxytocin slowly decreases in the first month or two after delivery.

Prolactin

Prolactin is known as the breastfeeding hormone: Unlike some of the others, it can stay high for a few months after birth (if you’re nursing or pumping).

• When do levels of this hormone rise? Prolactin levels begin rising after conception and continue on a steady increase throughout pregnancy, climbing by as much as 10 to 20 times the normal amount.

• What’s the hormone’s purpose in pregnancy? Prolactin’s main job during pregnancy is to form mammary glands in breast tissue. This allows your breasts to produce milk.

• What symptoms does this pregnancy hormone cause? As prolactin gets to work on priming your breasts for nursing, it can cause many different breast changes throughout pregnancy, including swelling, tenderness, nipple sensitivity, darkening areolas and even some discharge or leakage.

• When do levels of this hormone fall? If you decide to breastfeed, postpartum prolactin levels will stay high for several months, then gradually trend down and drop completely after weaning, explains Dr. Roy Handelsman, MD, an ob-gyn and reproductive endocrinology and infertility specialist at HRC Fertility Encino in California.

Elevated prolactin can often delay the return of your period, but not always: “Unlike most women, I started my period within three months of giving birth even though I was breastfeeding,” says Linda C., a mom of two in New Jersey. “I breastfed both [of my] babies for over a year.”

If you choose not to breastfeed, prolactin levels will go back down to normal within a few weeks after delivery.

Pregnancy Hormones Chart

As you can see, your body is busy making hormones during pregnancy—and there’s always a hormone hard at work to help support you and baby. Basically, your riding the waves, physically and emotionally, so give yourself grace as you face the many symptoms they cause. As you can see in the pregnancy hormones chart below, there’s a lot happening simultaneously!

To Sum It Up

Pregnancy and the postpartum period are full of hormonal fluctuations from the moment you conceive all the way until you give birth or stop breastfeeding baby. That translates to many months of changing levels of estrogen, progesterone, prolactin, oxytocin and more, each one operating on their own timeline, serving their own unique purpose—and causing their own weird set of symptoms.

As annoying and confusing as they can be, pregnancy hormones make pregnancy happen: They prepare your body for baby, help baby grow and develop in the womb and—eventually—tell your body when it’s time for baby to make their grand entrance.

That said, these dramatic shifts can also contribute to physical and mental health symptoms, so if you’re experiencing anything concerning, including depression or anxiety during pregnancy or the postpartum period, reach out to a healthcare provider for help.

How We Developed This Article

To put it lightly: Your hormones are all over the place during pregnancy, and it can cause a lot of symptoms and concerns. To help you understand exactly what’s happening inside your body, we spoke with two ob-gyns who are also fellowship-trained reproductive endocrinologists, and consulted a variety of medical studies and institutions, including Cleveland Clinic and Johns Hopkins Medicine. We also chatted with five real moms to learn about their experiences with changing pregnancy hormones and the havoc they wreaked. Finally, this article was fact-checked and medically reviewed through our thorough editorial and medical review process.

About the author: Sarah Bradley knows what it’s like to deal with fluctuating pregnancy hormones, having experienced the physical and mental highs and lows of pregnancy three times. As a freelance writer, she combines her love of writing with her parenting experience, writing personal essays, product reviews and reported features for a number of online parenting and health publications. Because she homeschools her three boys, works part-time from home and helps her husband run a small side gig, her life is never, ever boring.

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.