The 6 Pregnancy Hormones: How They Affect Your Body & Support Baby

As chemical messengers, hormones help manage your body’s functions, from blood pressure to appetite to hair growth. And once you get pregnant, your pregnancy hormones prepare your body to have a baby—and they come with some fun (or not so fun) side effects too.

You might experience things like morning sickness or heartburn, which can both be caused by pregnancy hormones, or you might feel nothing at all. “Hormone changes are often noticeable and can cause physical and emotional symptoms,” says Dr. Dallas Reed, ob-gyn, medical geneticist and principal medical advisor for SneakPeek fetal DNA testing. “Some women report intuitively ‘feeling’ when hormones are shifting, especially with mood or energy changes, but these perceptions vary widely.” 

So what all is there to expect from these hormone changes during pregnancy? Here’s what’s going on in your body over the next nine-ish months.

Human Chorionic Gonadotropin (hCG)

HCG is the hormone that tells the rest of your body that you’re pregnant. It’s what pregnancy tests detect to give you that positive (or negative) symbol, and because of this, it’s the most well-known of all the pregnancy-related hormones, Dr. Reed says. In fact, it only shows up in the body because of pregnancy—your body only starts producing hCG after a fertilized egg attaches to your uterine lining.

What symptoms does hCG cause?

HCG is the most likely pregnancy hormone behind morning sickness, since higher levels are correlated with more intense vomiting and nausea. It’s one of the first symptoms that you might notice, says Dr. Melanie Lagomichos, board-certified ob-gyn and medical director at Pediatrix Medical Group, and one of the main reasons for those initial suspicions that you’re pregnant. “The good news is that the nausea that follows is a sign of a healthy pregnancy. But in the moment, I think any pregnant woman dealing with nausea and vomiting will tell you that they’d happily skip these symptoms.”

You might notice the effects of hCG fairly early on—as soon as two to three weeks after conception, Dr. Lagomichos says. After that, hCG levels continue to rise very quickly, peaking at about week 10 of pregnancy, Dr. Reed says. Once things level out around that time, those early pregnancy symptoms should start to subside.

Progesterone

This hormone, released by the ovaries first and then later by the placenta, plays a key role in supporting your pregnancy throughout each trimester. And it’s also the hormone that’s responsible for the most changes during pregnancy, Dr. Reed says. “‘Progesterone’ roughly translates to ‘a hormone that promotes gestation or pregnancy.’ This reflects progesterone's primary role in preparing and maintaining the uterus for pregnancy. It is responsible for many of the body changes, and its influence on mood, digestion and energy levels makes it a key player in the pregnancy journey.”

Changes in progesterone levels can cause a lot of different (often irritating) symptoms, but it also serves a few really important purposes: maintaining a healthy uterus and thick uterine lining, preventing your body from rejecting the fetus and preventing premature contractions.

What symptoms does progesterone cause?

Progesterone, being the workhorse that it is, can cause a pretty wide variety of both physical and emotional symptoms, from headaches and bloating to food cravings and those infamous pregnancy mood swings. Its levels skyrocket in the first trimester and only continue to rise right up until your baby is born—at which point your progesterone levels will plummet, and you’re likely to feel a dramatic withdrawal (more on that in a bit). 

Estrogen

While progesterone is working on maintaining the uterus, estrogen is doing the same for the placenta. It’s also ensuring your baby gets the right support by increasing blood flow, and it helps develop your milk ducts as your body prepares for breastfeeding. 

What symptoms does estrogen cause?

Much like with progesterone, changes in estrogen levels can affect both your body and your emotions, with the most well-known symptoms being mood swings and nausea. “Studies have shown that a higher level of estrogen makes nausea more common,” Dr. Lagomichos says. It’s also why some studies have suggested that you might experience worse morning sickness if your baby is a girl, she says.

And that increased blood flow mentioned above? That’s where your heightened sense of smell and pregnancy “glow” come from, as well as spider veins and increased appetite.

Relaxin

Relaxin doesn’t get the same amount of attention compared to the other pregnancy hormones, Dr. Reed says, but the name says it all. Relaxin makes your ligaments relax, helping your body adjust to the physical changes it’ll experience as your baby grows. When the time comes to give birth, relaxin allows your pelvis to open so your baby can be born. 

It’s also responsible for softening your cervix so that it can widen enough for your baby to pass through—remember, your cervix has to go from completely closed to 10 centimeters wide, and it wouldn’t be able to do that without relaxin.

The increased flexibility is certainly advantageous, but relaxin has its downsides too.

What symptoms does relaxin cause?

“The unfortunate downside of this flexibility may be pelvic and lower back pain, symphysis pubis dysfunction (pain in your pelvic girdle) and foot pain during pregnancy,” Dr. Reed says.

That’s right: foot pain. It makes sense that relaxin would cause some discomfort in your pelvis and lower back, since those areas are so greatly affected by your growing baby (and your growing belly) and by preparing for birth. But relaxin doesn’t target specific ligaments—all of your ligaments are affected, including the ones in your feet. In fact, many women experience permanent changes to the shape of their feet after pregnancy, including lost arch height and increased shoe size. 

Oxytocin

There’s a decent chance that oxytocin might be everyone’s favorite hormone. It exists outside of pregnancy too, and it’s what floods your brain during sex, exercise, listening to good music and being near a loved one, giving you an overall feeling of love and well-being.

During pregnancy, your oxytocin levels begin slowly creeping up from the very beginning, but skyrocket once it’s time for labor. Oxytocin is what stimulates your contractions during labor, but the vast majority of its work (and symptoms) comes after you give birth, like preparing your body for breastfeeding, kickstarting letdown and shrinking your uterus back to pre-pregnancy size.

What symptoms does oxytocin cause?

Unlike the other pregnancy hormones, you won’t feel any effects of oxytocin while you’re still pregnant. But once your baby is born, you might notice a sort of “high” any time you hold your baby—that’s because oxytocin’s key symptom is a feeling of bonding. It’s what gives you the urge to touch your baby even when you’re not holding them, or to look at all the photos you’ve taken of them while they’re asleep in their bassinet.

Prolactin

As its name suggests, prolactin helps your body produce milk. When you’re pregnant, prolactin levels go up an average of five to ten times their normal amount in order to prep your mammary glands for milk production. But much like with oxytocin, prolactin’s real work begins during the postpartum period.

What symptoms does prolactin cause?

Even while you’re still pregnant, before your breast milk has come in, you might feel some symptoms of increased prolactin levels. According to the Cleveland Clinic, prolactin can cause a decreased sex drive and vaginal dryness leading to discomfort during sex.

Hormones in the Fourth Trimester

If you thought the past nine months of pregnancy were a wild time for your hormones, they’ll continue to change dramatically from the moment you give birth. While hCG, progesterone, estrogen and relaxin decrease, oxytocin and prolactin continue to increase. 

Let’s start with what’s still high: “Oxytocin surges continue with breastfeeding, strengthening bonding and relaxation,” Dr. Reed says. “These shifts are usually quite noticeable as the body recalibrates, especially in the first six weeks postpartum.” You’ll notice it as your uterus shrinks back down (which usually takes about six weeks), and you’ll also notice it every time you nurse, cuddle, kiss and smell your baby as it brings you that sense of maternal comfort and love for your baby.

The increased prolactin has a similar timeline with similar effects. Unless you’re breastfeeding consistently, those levels will decrease after the first six weeks postpartum. But besides the production of breast milk, “[prolactin also] aids maternal bonding and has calming effects, making it a vital hormone in the postpartum period,” just like oxytocin, Dr. Reed says. It’s not all sunshine and rainbows and baby snuggles, though—maintaining high levels of prolactin can also mean symptoms like vaginal dryness and dry skin, Dr. Lagomichos says.

And when it comes to the hormones that decrease, you’ll feel those effects too. “This is when you feel the intense fatigue, irritability, mood changes, hair loss and skin dryness,” Dr. Lagomichos says. “Both estrogen and progesterone play a pivotal role in your mental health, which is why it is so important to follow up closely with your ob-gyn during this time to make sure your symptoms aren’t progressing from the ‘[baby] blues’ to full-blown postpartum depression.”

If you feel sad or down for longer than two weeks, you’ll want to contact your doctor for some support. While there isn’t a definitive link between hormone level changes in the fourth trimester and perinatal mood and anxiety disorders, it’s a good idea to have support in place before you give birth—whether that looks like lining up a therapist, asking friends and family to drop off home cooked meals or setting boundaries around visitors in the first weeks after baby arrives. 

Most importantly, keep in mind that the entire process of growing, delivering and nurturing a baby comes with a lot of physical and emotional changes, so be gentle with yourself.