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

The ancient Egyptians developed the first pregnancy test—and scientists tested it in the 1960s and discovered it was accurate about 70% of the time.

Read the 1963 study testing out an ancient Egyptian pregnancy urine test.

Premarin, the hormone medication derived from pregnant horses, is 'PREgnant MARes urINe'

Scientists in the late 1920s and early 1930s discovered estrogens could be extracted from human placenta, and then isolated it from the urine of pregnant women. But researchers discovered the urine of pregnant horses had similar substances and the horse product was much easier to collect in significant amounts—leading to Premarin.

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

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

Heightened sense of smell during pregnancy is not yet well understood

Boosted smell powers and strong reactions to them are often reported beginning around the six-week mark of pregnancy. Researchers say hormonal changes likely play a role, but the change remains poorly understood.

Many of the new prenatal genetic tests for rare genetic conditions are inaccurate

Established screening tests for Down syndrome in utero are reliable and accurate. But a New York Times investigation into expanded prenatal genetic tests for very rare diseases—much rarer than Down syndrome—found that more than 80 percent of the positive test results turned out to be wrong based on follow-up testing. These expanded tests for rare diseases are performed from a blood draw at 10 weeks of pregnancy and aim to detect chromosomal abnormalities linked to rare diseases. Companies that offer these controversial tests counter that it's only a screening test—not a diagnosis—picking up true positives and noting that patients can and should be counseled about what the findings mean. (Some users may encounter a paywall.)

Every organ in a mother's body changes during pregnancy as her body produces hormones that relax muscles, allowing for the needed expansion.

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.

Hair loss after childbirth happens because pregnancy hormones paused the normal hair shedding process during pregnancy, so the hair loss is actually your hair cycle 'catching up' with its normal process several months postpartum.

Understand the complex, biological journey of pregnancy with this science explainer.

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 a number of symptoms, including cramping, fatigue, and mood changes.

Diabetes is a hormonal disorder that occurs when the pancreas does not produce enough of a hormone that regulates blood glucose, called insulin, or when the body cannot effectively use the insulin it produces.

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.

Menopause hormone therapy infuses the body with estrogen after the body's natural levels drop

The treatments can treat symptoms like hot flashes and vaginal dryness at varying doses. Progestogen, another hormone, is also typically prescribed with estrogen because estrogen alone can thicken the uterus lining, which elevates the risk of developing endometrial cancer.

The pregnancy test industry is worth roughly $769M

The inventor of the at-home pregnancy test, Margaret Crane, largely hasn't taken credit for her invention until recently.

Pregnancy at older ages increases the chances of fetal abnormalities

Chromosomal irregularities are more likely at older maternal ages so genetic testing for a fetus of mothers-to-be at age 35 and older is often recommended. Conditions that can be screened for in utero include cystic fibrosis, Tay-Sachs disease, sickle cell disease, Down syndrome, spina bifida, Duchenne muscular dystrophy, and more.

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

Explore how the placenta acts as lungs, kidneys, and more in the womb.

A baby's due date is calculated from the first day of the last menstrual period—not when sexual intercourse occurred.

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.

Humans have taste receptors throughout the body, including in the testes and lungs, but we don't taste what they detect because those areas lack taste buds.

Trials ongoing for a 99% accurate, AI-powered blood test

The UK's National Health Service has launched a trial for a blood test that can detect a dozen types of cancers with just ten drops of blood. An AI tool looks for genetic material known to be released by tumors, allowing for cancer detection before tumors are large enough to be imaged.

Plant hormones and growth regulators guide growth stages and responses in plants

Plants naturally produce hormones like auxin and gibberellins, while humans apply synthetic or extracted growth regulators to control plant development. These substances influence processes like flowering, root growth, dormancy, and ripening—even in very small doses.

Silicon Valley startups Orchid, Nucleus, and Genomic Prediction are selling so-called polygenic tests for prospective parents

These tests claim to show how at-risk a hypothetical baby would be for genetic syndromes. The newfound industry has prompted ethical and medical debates, with critics questioning their accuracy and highlighting the potential problems behind pursuing the perfect baby.

Testosterone therapy can cause infertility, and has been explored as a contraceptive.

A DNA paternity test will show a less than 1% probability if the tested man is not the actual father.

Babies taste food in the womb via amniotic fluid, and it may influence future taste buds.

Allergy tests identify antibodies, but not whether allergy symptoms may appear

Skin prick tests and blood tests, the two most common allergy tests, both detect the presence of allergen-specific antibodies. But just because the body has those antibodies doesn’t mean that a person is “allergic” to a substance or that they will develop symptoms of an allergy when encountering the substance. Allergists work with families to interpret the results and sometimes combine that data with approaches including exposure challenges—giving someone a tiny bit of the food or substance they may be allergic to—under medical supervision.

What happens during the first eight weeks of pregnancy?

The first weeks of embryonic development, known as embryogenesis, are one of the most critical phases during pregnancy. This simple breakdown from the Khan Academy illustrates what we know about how the complex process unfolds.

Health problems are being misdiagnosed as perimenopause symptoms

Symptoms of menopause and perimenopause (the premenopause period) can be varied enough that clinicians dismiss them in patients in their mid-30s and onward as just a symptom of hormone level change. In this story, a woman's itching was dismissed as a hormonal change, but after two years and 11 separate doctor consultations, was diagnosed as cancer. (Some users may experience a paywall.)

Postpartum depression typically starts in the weeks following childbirth, and the disorder can keep someone from performing tasks of daily living.

Mifepristone, approved in 2000, is used to end early pregnancies

The drug works by blocking progesterone, a hormone that is needed to support pregnancy. Mifepristone is typically used in combination with a second drug, misoprostol, because this regimen often causes less cramping and bleeding than just using misoprostol alone.

Fetal development, week by week

Gestation is the period of time between conception and birth when a baby grows inside the mother's womb. Changes occur constantly over the course of these 40 weeks. At week 17, for instance, the skeleton of a fetus begins changing from soft...

The ultrarare 'Er' blood type has been documented only about 40 times, and it can cause devastating pregnancy complications.

Polygenic scores aim to predict traits based on the contributions of many genes

These novel tests for multifactorial conditions evaluate the probability of traits like elevated blood pressure, diabetes, or high cholesterol based on what researchers currently know about different gene variants and their links to various traits. The tests are predictive, not definitive, partly because environmental factors influence the expression of genes. What's more, knowledge about cumulative effects from individual genes continues to evolve. The American Society for Reproductive Medicine states that these tests are too unreliable and nascent for clinical use.

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.

US regulators have approved an at-home genetic test looking for BRCA gene mutations

The direct-to-consumer genetic test, approved by US regulators in 2018, examines 3 out of the more than 1,000 known breast cancer-linked genetic mutations. It looks for genetic variations that can increase risk for breast, ovarian, and other cancers. These mutations are most commonly found among Jewish people with Eastern European ancestry.

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.

There are multiple HRT options to treat menopause and perimenopause symptoms including hot flashes, vaginal dryness, and mood swings.

Two dogs were able to detect prostate cancer in 98% of patients in one study

In this small study published in 2015, two highly trained German Shepherd dogs sniffed hundreds of urine samples and were able to accurately detect prostate cancer—sniffing out certain volatile organic compounds—in almost every single case. One dog was correct 98% of the time and the other correctly identified patients 100% of the time. (Some users may encounter a paywall.)

The word allergy is partly derived from the Greek word 'allos' for 'other'

For people with allergies, their immune systems recognize substances as a harmful "other"—cuing an inflammatory response. This podcast explores allergy details and related topics, including how scientists are interested in if the same allergic response mechanisms could underpin other health issues, including severe, painful symptoms around the time of menstrual cycles. Since estrogen acts on white blood cells called mast cells, which leads to the release of histamines—similar to what happens during allergic responses—an understudied question is whether the same process is fueling some of the uncomfortable symptoms around menstruation. An allergist guest notes this raises questions about if antihistamine medications like Pepsid might alleviate them, something that hasn't yet been explored in clinical trials.

A super-sniffer smelled her husband's Parkinson's disease years ahead of symptoms.

Genetic blood test offers an estimated clock on when Alzheimer's symptoms may appear

The 2026 research finding from researchers at Washington University School of Medicine in St. Louis—if validated in broader populations—suggests that an already available blood test could estimate when Alzheimer's symptoms may begin within a margin of several years. The test detects a protein called p-tau217 found in blood plasma and the researchers incorporated the findings from that blood test into a statistical model to come up with the symptom timeline predictions.

There's no definitive test for inflammation, or a baseline for what's considered normal

Existing tests can pick up proteins that indicate an immune response—in particular C-reactive protein, which the liver produces when the body's stressed—but that won't tell you why there's inflammation nor if it's chronic or acute inflammation. (Some users may experience a paywall.)

The first newborn screen for diseases was developed in 1961.

Selecting an embryo based on polygenic score is illegal in the UK, Israel, and swaths of Europe

Though their use for embryo selection is illegal in many locations, private clinics in the US may offer polygenic scores to inform embryo selection. The US Food and Drug Administration has not banned their use—instead the tests are regulated like supplements, meaning they are not regulated before they come to market but consumers can file complaints and then the agency may take action.

Your feet can expand—permanently—due to pregnancy.

Aurea is the first US baby born following polygenic analysis

The child, born in May 2020, was selected by her parents to optimize for certain health qualities based on an analysis of her multifactorial genes by a New Jersey-based company called Genomic Prediction. Her embryo was selected for implantation based on polygenic risk scores for heart disease, diabetes, and cancer.

Treatment-induced menopause is menopause induced by surgery or medicine

Chemotherapy and radiation, as well as oophorectomy (a surgical procedure to remove one or both ovaries) and a radical hysterectomy, can cause a woman to become menopausal. Women who go through medical menopause experience the same symptoms as women who go through menopause caused by natural hormonal cycles.