Pregnancy causes a woman's blood volume to increase by up to 50%

Every organ in a mother's body changes during pregnancy

There's limited real estate inside a mother's body; as the uterus grows both up and out, it shifts other organs to make space. A pregnant woman's body produces hormones to loosen muscles to allow for this expansion. Pregnancy also triggers other changes, including faster breathing to compensate for decreased diaphragm range.

A pregnant woman's brain sheds gray matter, perhaps explaining 'baby brain'

The brain areas involved in processing information and emotions decrease by an average of almost 5% during pregnancy. Researchers discovered in a 2025 study that this mostly temporary change—the brain hadn't fully returned to its normal size six months after pregnancy—seems to be associated with self-reported improved bonding and less hostility toward the child postpartum.

How women grow tiny humans inside of them

Pregnancy is a complex biological journey, lasting about 40 weeks. When a sperm fertilizes an egg, that event triggers intricate cellular and hormonal processes, driven by hardwired cellular instructions, which lead to cell division, differentiation, and development—ultimately culminating in the birth of a baby.

Pregnancy makes someone more attractive to the mosquito species that transmits malaria

Research suggests that hormonal levels can affect mosquito attraction. Pregnancy, in particular, is associated with significantly increased interest from Anopheles mosquitoes, which boosts pregnant women's malaria risk.

Nasal congestion is a common side effect of pregnancy, called pregnancy rhinitis

In one recent study, almost 100% of pregnant women experienced this condition in their third trimester. The congestion is likely due to hormonal changes and neurophysiological factors, and it may also worsen at night due to circadian factors and gravitational redistribution when lying down. Treatments include saline nasal irrigation and the use of nasal strips to widen the nasal valve area.

Modern pregnancy tests detect a specific hormone in a woman's urine or blood

They pick up human chorionic gonadotropin, in either blood or urine. The hormone is produced by a woman's reproductive tissues during pregnancy.

Blood leaves the heart at speeds around 12-16 miles per hour

Blood is pumped around the body through the circulatory system, aka the cardiovascular system. This system comprises the heart, arteries, veins, and capillaries. This video is the first in a multi-part series on the circulatory system, focusing on the role of the heart, the pump that powers the entire system.

Gestational diabetes occurs when the body can't produce insulin during pregnancy

Globally, pregnant people are increasingly at risk to develop gestational diabetes due to rising maternal ages and obesity rates. The condition is associated with heavier fetal weight, congenital abnormalities, and perinatal mortality, which includes stillbirths and deaths of babies younger than 7 days old.

Explore this week-by-week visualization of pregnancy

This graphic illustrates how development proceeds during each week of pregnancy, tracking what shifts and milestones typically occur during each stage of the process. It also includes typical weights of the fetus throughout.

Only about 0.0001% of sperm, on average, successfully reach the uterine cavity

We've evolved to make pregnancy a complex and difficult process. From the initial development of the blastocyst, to the energy and nutrients needed to grow a new human, our bodies are both fighting and supporting fetal development.

Chagas disease can be transmitted to a fetus during pregnancy

Researchers estimate that 63 to 315 cases of congenital Chagas disease occur annually in the US. Roughly 20 to 30 percent of all Chagas disease cases will progress to cardiac or gastrointestinal disease.

Exercise helps make your arteries more elastic

Regular aerobic exercise releases nitric oxide, a key molecule that relaxes blood vessel walls and improves vascular function. These exercise-induced adaptations make the heart work more efficiently and blood vessels become more elastic, leading to improved circulation and lowered cardiovascular risk.

Stress-induced adrenaline can trigger a 'hysterical strength' response

The stress response is a powerful ancient mechanism designed to maximize human survival—it can even result in superhuman strength. The adrenal glands are located just above the kidneys, and stress-induced adrenaline release causes more blood (and therefore more oxygen) to flow to your muscles, increasing performance.

Pulsatile tinnitus is when you hear thumping synchronized with your heartbeat

This rare type of tinnitus, which sounds like rhythmic thumping or whooshing, is often linked to blood vessel conditions or high blood pressure. Lowering blood pressure through exercise and food choices can help reduce the severity of this condition.

Certain medications that affect blood flow or mood boost the risk of heatstroke

Drugs that narrow blood vessels, beta blockers that regulate blood pressure, diuretics, antidepressants, and antipsychotics can all affect the body's ability to regulate its internal body temperature, and so individuals taking these medications need to take special care in extreme heat and when exercising in hot conditions.

Heart attack risk jumps to 21 times its norm on the day of a loved one's death

Research published in 2012 suggests that the intense emotional burden of suffering a loved one's death can escalate heart rate, blood pressure, and clot risks—culminating in elevated heart attack risk. The increased heart attack risk remains after that first day, remaining eight times above normal during the first week, and then dropping down over the course of a month. (Some users may encounter a paywall.)

Menstruation, which occurs monthly, is the release of an unfertilized egg

This routine vaginal bleeding is part of a woman's hormonal cycle and occurs after an egg is released by an ovary during ovulation and isn't fertilized. Also known as periods, this monthly occurrence can cause symptoms including cramping, fatigue, and mood changes.

A look at the concentrations of water in the human body and various organs

When we're born, about three-quarters of our bodies are composed of water, dropping to an average of 55-60% for the average adult. The lungs are over 80% water, the kidneys and spleen about 80%, and the heart and brain are approximately three-quarters composed of water—about the same moisture as a banana.

The hidden effects of March Madness

March Madness isn’t just a major sporting event—it’s also peak season for vasectomies. Urologists report a 50% increase during the tournament, as patients use recovery time as an excuse to watch nonstop basketball. Meanwhile, workplace distractions from bracket pools and game streaming are estimated to cost US businesses $17 billion.

How to repair a baby’s broken heart

A rare disorder that prevents some babies from getting enough oxygen to their organs can be repaired through a series of three intricate surgeries. This article and graphic explain the process behind correcting single-ventricle defects, also known as SVDs.This disorder happens when one of the heart's lower chambers doesn't work correctly, resulting in deoxygenated and oxygenated blood circulating the body rather than just the latter.

Increases in atmospheric carbon dioxide lead plants to produce more pollen

Pollen issues are emerging earlier in the year and lasting longer as rising levels of carbon dioxide in the atmosphere boost plants’ pollen production and also simultaneously extend warmer, pollen-producing seasons.

Dozens of US women in labor turned away from hospital between 2022 and 2024

An Associated Press analysis of federal hospital investigation data concluded that more than 100 pregnant women in medical distress were turned away from emergency rooms or treated negligently since 2022.

Women typically have more robust immune responses than men

This difference helps women better combat infectious diseases, but this more turbo-charged response may also make women more vulnerable to autoimmune diseases by potentially priming their immune systems to overreact to their own cells and tissues and label them as invaders that must be destroyed. Roughly 80% of American women have autoimmune conditions.

Rapid intensification can cause hurricanes to increase by two categories in 24 hours

Rapid intensification is a 35 mph or more increase in a hurricane's sustained wind speed within 24 hours. The phenomenon is expected to become more common, resulting in more storms becoming life-threatening faster than people can modify their preparations for the increased intensity.

The syncytiotrophoblast is the outer layer of the placenta and the largest human cell, spanning an area about twice that of a king-sized bedsheet.

Why don't giraffes get hypertension?

The average blood pressure of a giraffe is about double that of a human, yet they don't suffer from the symptoms of high blood pressure that humans do: stiffening of the left heart ventricle, shortness of breath, fatigue, or swollen legs and ankles. This article explains how giraffes have evolved to have the "biological equivalent of support stockings."

Scientists testing how climate change affects plants found, in a years-long simulation study, that poison ivy grew 70% faster with the resulting extra carbon dioxide.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

Ebola infects and disables immune cells, triggering a cascade of events that leads to small blood clots throughout the body, weakening blood vessels and interrupting blood flow to key organs.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Fireworks-related ER visits are on the rise—in 2024, they increased by 52% as compared to the prior year.

Use this calculator to find the dollar value of your mental load, from meal planning to coordinating after-school care for your children.

US consumers collectively owe more than $1T to credit card companies—almost as much as they owe in auto loans.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

Human-to-human transmission of hantavirus remains extremely rare, so the 2026 hantavirus cruise ship outbreak doesn't mean we're facing a COVID-style pandemic risk.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

The price of gas is a composite made up of several different factors, with the federal gas tax making up less than 20% of what drivers pay at the pump.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

A pickleball's loud 'pop' sound can reach 120 decibels, which is equivalent to a hammer hitting a nail

To reduce wrinkles in clothing, research recommends gentle wash cycles with more water and tumble drying with smaller loads and longer times.

The power and influence of the American presidency have expanded significantly over time—far beyond what the founders envisioned.

When caught in the mouths of cardinal fish, seed shrimp release glowing, bioluminescent chemicals, which alert predators of the cardinal fish, prompting the shrimp's ejection.

Explore fun facts from the USPS, including unique post office buildings, a stamp that traveled past Pluto, and more.

Animal phobias are likely the most common type of phobias, followed by an extreme fear of heights.

Dozens of S&P 500 stocks, including Coca-Cola and Walmart—known as the dividend aristocrats—have increased dividends every year for 25 years

Venture capital is a form of funding provided to early-stage companies with high growth potential, typically in exchange for an equity (or ownership) stake

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.