Pregnancy Hormones: What’s Really Happening and What Actually Helps
Your body becomes a pharmaceutical factory during pregnancy. Here’s what the hormones actually do—and the evidence on managing their effects
From the moment of conception, the pregnant body begins producing hormones at levels you’ve never experienced before. By the end of pregnancy, some hormone levels will be 10 to 100 times higher than normal. These chemicals reshape pregnancy physiology in ways that can feel bewildering.
The good news: science now explains most of what’s happening. The better news: evidence-based strategies exist for managing the symptoms. The reality check: some of the advice women receive is outdated or simply wrong.
Let’s go through what the hormones actually do—and what the research says about dealing with it.
The Cast of Characters
The body produces dozens of hormones during pregnancy, but six do most of the heavy lifting:
Human chorionic gonadotropin (hCG) is what makes your pregnancy test turn positive. The placenta produces it starting about a week after conception. Levels rise rapidly, peaking around weeks 8-10, then dropping and staying lower for the rest of pregnancy. hCG tells your ovaries to keep producing progesterone in early pregnancy until the placenta can take over.
Progesterone starts high and keeps rising throughout pregnancy. By the third trimester, levels are about 10 times higher than peak menstrual cycle levels. Progesterone relaxes smooth muscle everywhere in your body—which is essential for keeping the uterus from contracting, but has side effects in your digestive system, blood vessels, and elsewhere.
Estrogen also rises dramatically, eventually reaching levels about 100 times higher than normal. It promotes tissue growth in both mother and baby, supports the placenta, and prepares the breasts for milk production.
Relaxin peaks at the end of the first trimester, then stays elevated throughout pregnancy. It loosens ligaments and joints to prepare your body for delivery.
Cortisol, the stress hormone, rises to about 2.5 times pre-pregnancy levels. This is necessary for fetal brain development, but contributes to some of the cognitive and mood changes women experience.
And then there’s GDF15—a hormone most people have never heard of, but which recent research has identified as the primary cause of pregnancy nausea and vomiting.
Nausea and Vomiting: We Finally Know the Cause
For decades, the cause of pregnancy nausea was mysterious. Textbooks blamed hCG, estrogen, or progesterone. Some physicians still dismissed severe morning sickness as psychological.
A landmark 2024 study in Nature changed everything. Researchers demonstrated that a hormone called GDF15 (growth differentiation factor 15) is the primary driver of nausea and vomiting in pregnancy—including its most severe form, hyperemesis gravidarum.
Here’s how it works: The fetus and placenta produce large amounts of GDF15 starting in early pregnancy. This hormone acts on receptors in the brainstem that trigger nausea and suppress appetite. GDF15 levels in maternal blood are significantly higher in women who experience vomiting compared to those who don’t.
But here’s the fascinating part: it’s not just about how much GDF15 the baby produces. It’s also about how sensitive the mother is to it.
Women who have chronically low GDF15 levels before pregnancy—whether due to genetics or other factors—are more sensitive to the sudden rise when they become pregnant. Women with chronically high GDF15 (such as those with beta-thalassemia) report almost no nausea during pregnancy. Their bodies are already “desensitized” to the hormone.
This discovery explains why some women are devastated by morning sickness while others sail through. It also points toward future treatments: either blocking GDF15 during pregnancy or “priming” women with GDF15 before conception to reduce sensitivity.
What Actually Helps
Current evidence supports a stepped approach:
For mild nausea: Ginger is effective. A meta-analysis found ginger significantly reduced nausea scores compared to placebo. The American College of Obstetricians and Gynecologists recommends 250 mg four times daily. Vitamin B6 (pyridoxine) also works—and at doses of 35-500 mg, ginger and B6 appear equally effective.
For moderate symptoms: Doxylamine plus vitamin B6 (sold as Diclegis/Bonjesta) is the only FDA-approved treatment for pregnancy nausea. Despite being pulled from the market in the 1980s due to unfounded litigation, subsequent studies involving millions of pregnancies found no increased risk of birth defects. It’s safe.
For persistent symptoms: Antihistamines like dimenhydrinate are effective and safe. Metoclopramide and ondansetron are equally effective for more severe cases. A systematic review found ondansetron has no significant association with birth defects, though some earlier studies raised questions that have largely been put to rest.
What about acupressure and acupuncture? The evidence is mixed but suggests some benefit. A 2024 systematic review found acupuncture was as effective as conventional medication for some outcomes. Acupressure at the P6 (Neiguan) point reduced the need for antiemetic drugs. These are reasonable options for women who want to try non-pharmacological approaches first.
Fatigue and Sleep: Progesterone’s Sedating Effect
First-trimester fatigue is legendary. Many women describe needing to nap in their cars at lunch or falling asleep by 7 PM.
Progesterone is largely responsible. It acts on the same brain receptors (GABA-A receptors) that sedative medications target. Animal studies show progesterone increases slow-wave sleep and reduces wakefulness. In early pregnancy, when progesterone rises most rapidly, the sedating effect is strongest.
Sleep architecture changes throughout pregnancy:
First trimester: Total sleep time actually increases (on average from 7.4 to 8.2 hours), largely through daytime napping
Third trimester: Sleep time decreases (6.6 to 7.8 hours) due to discomfort, frequent urination, and difficulty finding comfortable positions
Sleep disorders increase: By the third trimester, up to 66% of women report significant sleep disturbance
Poor sleep in pregnancy isn’t just uncomfortable—it’s associated with increased risk of depression, longer labor, more cesarean deliveries, and possibly preterm birth.
What Actually Helps
Sleep hygiene matters: Consistent bedtime, cool room temperature, limiting fluids before bed (though staying well-hydrated during the day), and avoiding screens before sleep.
Position: Sleeping on your side, particularly the left side, is recommended in later pregnancy to optimize blood flow to the uterus. Pregnancy pillows can help maintain comfortable positions.
Restless legs syndrome affects up to 15% of pregnant women in the third trimester. Iron and folate deficiency may contribute. A small study found folate supplementation dramatically reduced restless legs (9% vs 80% in the control group), though this finding needs replication.
Medications: Most sleep medications lack safety data in pregnancy. Doxylamine (which is also used for nausea) has sedating effects and is considered safe. Sedating tricyclic antidepressants like amitriptyline may be considered for severe insomnia and haven’t been associated with increased birth defect risk. Benzodiazepines and newer sleep medications like zolpidem should generally be avoided due to limited safety data.
Heartburn and Constipation: Smooth Muscle Rebellion
Progesterone relaxes smooth muscle throughout your body. This is essential in the uterus—preventing premature contractions. But smooth muscle lines your entire digestive tract, and when it relaxes, digestion slows dramatically.
Heartburn affects 30-80% of pregnancies, depending on the population studied. About 25% of pregnant women experience it daily. Progesterone relaxes the lower esophageal sphincter—the muscular valve between your esophagus and stomach—allowing acid to flow upward. Add the mechanical pressure of a growing uterus pushing on the stomach, and reflux is nearly inevitable by the third trimester.
Constipation results from the same mechanism. Slowed intestinal motility means food moves through more slowly, and more water is absorbed, leading to harder stools. This is compounded by iron supplementation (which most pregnant women take) and reduced physical activity.
What Actually Helps
For heartburn:
Lifestyle changes first: Eating smaller, more frequent meals; avoiding eating within 2-3 hours of bedtime; elevating the head of the bed; and avoiding trigger foods (spicy, acidic, or fatty foods) all help.
Antacids are effective for mild symptoms. Calcium-containing antacids (like Tums) are preferred—they’re safe and provide extra calcium. About 30-50% of women manage their heartburn with antacids alone.
H2 blockers (famotidine, ranitidine) are safe in pregnancy and more effective for moderate symptoms.
Proton pump inhibitors (omeprazole, lansoprazole) are safe despite older FDA category C labeling. Large studies involving tens of thousands of pregnancies have found no increased risk of birth defects. They’re appropriate for severe symptoms that don’t respond to other treatments.
For constipation:
Fiber and fluids first. Increasing fiber intake (fruits, vegetables, whole grains, or fiber supplements like psyllium) and drinking plenty of water is the first step.
Stool softeners (docusate) are safe and can be used regularly.
Osmotic laxatives (polyethylene glycol/Miralax) are safe for short-term use.
Stimulant laxatives (senna, bisacodyl) should be used sparingly but are not contraindicated when other approaches fail.
Skin Changes: The Melanin Surge
Up to 90% of pregnant women experience some form of hyperpigmentation. The hormonal cocktail of estrogen, progesterone, and placental hormones increases melanin production, darkening areas that already have more pigment.
Linea nigra—the dark vertical line running from the pubic bone to the belly button (and sometimes higher)—appears in about 80% of pregnancies, typically becoming visible around 20 weeks. It’s caused by increased melanin deposition along the linea alba, an existing connective tissue line.
Melasma (the “mask of pregnancy”) affects 45-75% of pregnant women, causing irregular brown patches on the face, particularly on the cheeks, forehead, and upper lip. Women with darker skin types are more commonly affected.
Darkening of areolas, nipples, and genitalia is nearly universal.
These changes begin in the first trimester and may intensify throughout pregnancy. The linea nigra and areola darkening often don’t fully return to their original color after pregnancy. Melasma may persist for years in some women, though it often fades.
What Actually Helps
Sun protection is essential. UV exposure intensifies hyperpigmentation. Broad-spectrum sunscreen with SPF 30 or higher, wide-brimmed hats, and avoiding peak sun hours all help minimize darkening. Mineral sunscreens (zinc oxide, titanium dioxide) are preferred during pregnancy as they sit on the skin rather than being absorbed.
Avoid bleaching agents during pregnancy. Hydroquinone and retinoids should not be used while pregnant. Topical vitamin C, kojic acid, and azelaic acid are considered safer options for managing melasma, though expectations should be modest.
Folic acid may help. There’s some suggestion that adequate folate reduces the intensity of linea nigra, possibly by influencing melanin metabolism.
Time is your friend. Most pregnancy-related hyperpigmentation fades significantly in the months after delivery as hormone levels normalize. Melasma can be treated more aggressively postpartum if it persists.
Joint Pain and Instability: The Relaxin Question
Many pregnant women experience pelvic pain, back pain, and a feeling of joint looseness. Relaxin—a hormone that loosens ligaments to prepare the pelvis for delivery—has long been blamed.
But the evidence is surprisingly weak.
A systematic review examining six studies found low-quality evidence for the association between relaxin levels and pelvic girdle pain. High-quality studies consistently found no correlation between relaxin levels and pain. Two studies found an association, but both were rated as low quality.
More recent research suggests pelvic and low back pain in pregnancy is multifactorial—involving mechanical factors (shifting center of gravity, increased load on the pelvis), muscle changes, and possibly progesterone’s effects on tissues. Relaxin may contribute to joint laxity, but laxity doesn’t necessarily cause pain.
About 50% of pregnant women experience lumbopelvic pain at some point, and 25% still have pain a year after delivery. Risk factors include previous back pain, previous pregnancy-related pain, high physical workload, and psychological factors.
What Actually Helps
Physical therapy has the best evidence. Exercises that strengthen the core, pelvic floor, and hip muscles can improve stability and reduce pain. Working with a physical therapist experienced in pregnancy-related conditions is ideal.
Support belts (sacroiliac belts, pregnancy support bands) may help some women by providing external stability. The evidence is mixed, but many women find them useful.
Activity modification: Avoiding prolonged standing, heavy lifting, and asymmetric activities (like standing on one leg) can reduce symptoms.
Pain management: Acetaminophen is considered the safest analgesic during pregnancy. NSAIDs (ibuprofen, naproxen) should generally be avoided, especially in the third trimester, due to risks to fetal kidney function and premature closure of the ductus arteriosus.
“Pregnancy Brain”: It’s Real, But Not What You Think
If you’ve felt foggy, forgetful, or mentally slower during pregnancy, you’re not imagining it. A 2025 systematic review of 31 studies confirmed that “pregnancy brain” involves measurable changes.
A meta-analysis found that memory, executive function, and overall cognitive functioning were significantly poorer in pregnant women compared to controls, particularly in the third trimester. The differences develop primarily in the first trimester and persist into the postpartum period.
MRI studies show actual structural changes: gray matter volume decreases during pregnancy—by an average of 4.9%—particularly in areas involved in social cognition. A 2024 study confirmed these changes cover 94% of the brain.
But here’s the crucial reframe: this isn’t damage. It appears to be adaptive brain remodeling.
The areas that change most are involved in social cognition, empathy, and detecting emotional cues—skills essential for maternal bonding and infant care. Studies show that mothers with greater gray matter reduction showed stronger attachment to their infants.
The “fog” you experience may reflect a brain that’s reprioritizing. Functions related to caregiving are being enhanced at the (temporary) expense of things like remembering where you put your keys.
What Actually Helps
Reduce cognitive load. Use lists, calendars, reminders, and routines. Write things down rather than relying on memory. This isn’t a crutch—it’s adapting to temporary changes.
Prioritize sleep. Sleep deprivation worsens cognitive function for everyone. The fragmented sleep of pregnancy compounds existing hormonal effects on cognition.
Self-compassion. Understanding that these changes are normal, temporary, and possibly adaptive reduces the stress and self-criticism that make cognitive symptoms worse.
Don’t catastrophize. Pregnancy brain is not permanent cognitive decline. Studies show that long-term, pregnancy may actually protect against age-related cognitive decline. Mothers show better cognitive outcomes in older age compared to women who haven’t given birth.
The Bottom Line
Pregnancy is a hormonal transformation unlike anything else your body will experience. Understanding what’s happening—and that most of it serves an important purpose—can make the symptoms more tolerable.
A few key points:
Nausea has a biological cause. GDF15 from the fetus triggers it. This isn’t psychological, and severe cases deserve real treatment. Ginger, vitamin B6, doxylamine, and antiemetics are all safe and effective options.
Progesterone is a double-edged sword. It keeps you pregnant (essential), but also makes you tired, slows your digestion, and contributes to heartburn. Lifestyle modifications work for mild symptoms; safe medications are available for more severe cases.
Your brain is remodeling, not declining. The forgetfulness and fog are real, but they’re part of preparing for motherhood—not signs of permanent impairment.
Evidence should guide treatment. Too often, pregnant women are told to “just deal with it” or given outdated advice to avoid all medications. Many treatments are well-studied and safe. Don’t suffer unnecessarily.
Your body is doing something remarkable. These hormones, as uncomfortable as their effects can be, are building another human being. The discomfort is temporary. The payoff is permanent.
References:
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