Maggie Ruderman, Boston University and Kimberly Zayhowski, Boston University

Gender reveal parties are best known as celebrations involving pink and blue, cake and confetti, and the occasional wildfire. Along with being social media hits, gender reveals are a testament to how society is squeezing children into one of two predetermined gender boxes before they are even born.

These parties are often based on the 18- to 20-week ultrasound, otherwise known as the anatomy scan. This is the point during fetal development when the genitals are typically observed and the word “boy” or “girl” can be secretly written on a piece of paper and placed into an envelope for the planned reveal.

Now there is a new player in the gender reveal game: genetic screening.

Advancements in genetic research have led to the development of a simple blood test called cell-free DNA prenatal screening that screens for whether a baby has extra or missing pieces of genetic information – chromosomes – as early as 10 weeks into pregnancy. Included in this test are the sex chromosomes, otherwise known as X and Y, that play a role in the development and function of the body.

This blood test is more informally called noninvasive prenatal testing, or NIPT. Many people refer to it as “the gender test.” But this blood test cannot determine gender.

As genetic counselors and clinical researchers working to improve genetic services for gender-diverse and intersex people, we emphasize the significance of using precise and accurate language when discussing genetic testing. This is critical for providing affirming counseling to any patient seeking pregnancy-related genetic testing and resisting the erasure of transgender and intersex people in health care.

Distinguishing sex and sex chromosomes

Sex and gender are often used interchangeably, but they represent entirely different concepts.

Typically when people think of sex, they think of the categories female or male. Most commonly, sex is assigned by health care providers at birth based on the genitals they observe on the newborn. Sex may also be assigned based on the X and Y chromosomes found on a genetic test. Commonly, people with XX chromosomes are assigned female at birth, and people with XY chromosomes are assigned male. Since cell-free DNA, or cfDNA, prenatal screening can report on sex chromosomes months before birth, babies are receiving sex assignments much sooner than previously possible.

While cfDNA prenatal screening can offer insights into what sex chromosomes an infant may have, sex determination is much more complicated than just X's and Y's.

For one, sex chromosomes don't exactly determine someone's sex. Other chromosomes, hormone receptors, neural pathways, reproductive organs and environmental factors contribute to sex determination as well, not unlike an orchestra with its ensemble of instruments. Each cello, flute, tympani and violin plays a crucial role in the performance of the final musical score. There is no single instrument that defines the entirety of the symphony.

Intersex people, or those with variations in sex characteristics that deviate from societal norms of binary sex, exemplify the complexities of sex. These variations can manifest in various ways beyond X and Y chromosomes, such as differences in hormone levels, genitalia or secondary sexual characteristics.

The oversimplification of sex based on societal norms has led many to believe that there are only two discrete sexes. The binary framework of sex excludes intersex people and perpetuates their erasure and mistreatment within both health care and society at large.

For instance, many intersex individuals face unnecessary surgeries, such as nonconsensual genital procedures, to conform to binary norms, violating their bodily autonomy.

Where gender comes in

While sex typically describes someone's anatomical characteristics, gender is an umbrella term that encompasses the way someone views and presents themselves to the world. Countless aspects influence how someone defines their own gender and how the world views their gender, including clothing, haircuts and voice tone. Similar to how Western cultures have historically confined sex to two buckets, it has also created two gender categories: man and woman.

Gender is not dependent on anatomical parts or chromosomes. People are not math equations, and having certain combinations of biological parts does not equal someone's gender. For example, some people may be transgender, meaning their assigned sex is not congruent with their socially or self-defined gender. Nonbinary people do not identify exclusively with either of the two genders in the binary, regardless of their assigned sex.

Just like sex diversity, gender diversity is not rare. A 2022 Pew Research Center analysis found that approximately 5% of adults in the U.S. under the age of 30 are transgender or nonbinary.

These estimates will likely increase as societal awareness and acceptance of gender-diverse individuals increases. Anti-transgender legislation often oversimplifies gender as strictly binary, conflating it solely with sex assigned at birth.

Intersex and gender-diverse people show that sex and gender are both multidimensional. Gender is not solely determined by biology, and it is erroneous to define someone's gender by their sex, much less by their sex chromosomes.

Challenging sex and gender norms

The idea that biology plays the largest role in determining who an individual is, or bioessentialism, has governed misconceptions about sex and gender for many years. This concept is used to confine people to buckets and limit their self-determination.

For instance, societal norms dictate that women should be nurturing and gentle, while men are expected to be protective and assertive. Such rigid gender roles, often enforced through the lens of biology, serve to uphold notions of evolutionary destiny and a purported natural order.

Marketing strategies for children's toys often adhere strictly to gender roles, steering girls toward dolls and domestic play sets while steering boys toward action figures and construction sets.

Educational systems often reinforce gender norms by directing girls toward subjects such as literature and arts while steering boys toward science and mathematics. This perpetuates the notion that certain traits and interests are inherently linked to one's sex and gender, thereby reinforcing societal norms and sustaining inequality.

Upholding binary constructs of sex and gender does not allow for individuality and gender fluidity. Categorizing people from the time their chromosomes are analyzed or the moment their genitals are observed at birth restricts their autonomy and authenticity. These simple assumptions set expectations that can be harmful.

Letting children define themselves

If you're a parent offered cfDNA prenatal screening during pregnancy, remember that it is commenting only on one instrument in the orchestra of sex. It cannot examine all of the other factors that determine sex as a whole. And it most certainly cannot determine gender, which is an entirely different concert.

In recent years, Jenna Karvunidis, the mother considered the inventor of gender reveal parties, shared her regrets for starting the trend and noted that her views on sex and gender have shifted. In a 2019 Facebook post, Karvunidis wrote, “PLOT TWIST. The world's first gender reveal party baby is a girl who wears suits!” She had also gone on to say, “Celebrate the baby … Let's just have a cake.”

When the envelope is opened, the balloons are popped and the crafty cake is cut, consider how these practices perpetuate social confinements and a gendered destiny for your little bundle of joy. Perhaps opt simply for a celebration that leaves space for your child to one day define who they are.

Maggie Ruderman, Assistant Professor of Medicine, Boston University and Kimberly Zayhowski, Assistant Professor, Boston University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Natalie C. Tronson, University of Michigan

More than 85% of women – and more than 300 million people worldwide at any given time – use hormonal contraceptives for at least five years of their life. Although primarily taken for birth control, many people also use hormonal contraceptives to manage a variety of symptoms related to menstruation, from cramps and acne to mood swings.

For up to 10% of women, however, hormone contraceptives can increase their risk of depression. Hormones, including estrogen and progesterone, are crucial for brain health. So, how does modifying hormone levels with hormone contraceptives affect mental health?

I am a researcher studying the neuroscience of stress and emotion-related processes. I also study sex differences in vulnerability and resilience to mental health disorders. Understanding how hormone contraceptives affect mood can help researchers predict who will experience positive or negative effects.

How do hormone contraceptives work?

In the U.S. and other western countries, the most common form of hormonal contraceptive is “the pill” – a combination of a synthetic estrogen and a synthetic progesterone, two hormones involved in regulation of the menstrual cycle, ovulation and pregnancy. Estrogen coordinates the timed release of other hormones, and progesterone maintains a pregnancy.

This may seem counterintuitive – why do naturally occurring hormones required for pregnancy also prevent pregnancy? And why does taking a hormone reduce the levels of that same hormone?

Hormone cycles are tightly controlled by the hormones themselves. When progesterone levels increase, it activates processes in cells that shut off production of more progesterone. This is called a negative feedback loop.

Estrogen and progesterone from the daily pill, or other common forms of contraceptives such as implants or vaginal rings, cause the body to decrease production of those hormones, reducing them to levels observed outside the fertile window of the cycle. This disrupts the tightly orchestrated hormonal cycle required for ovulation, menstruation and pregnancy.

Brain effects of hormonal contraceptives

Hormonal contraceptives affect more than just the ovaries and uterus.

The brain, specifically an area called the hypothalamus, controls the synchronization of ovarian hormone levels. Although they're called “ovarian hormones,” estrogen and progesterone receptors are also present throughout the brain.

Estrogen and progesterone have broad effects on neurons and cellular processes that have nothing to do with reproduction. For example, estrogen plays a role in processes that control memory formation and protect the brain against damage. Progesterone helps regulate emotion.

By changing the levels of these hormones in the brain and the body, hormonal contraceptives may modulate mood – for better or for worse.

Hormonal contraceptives interact with stress

Estrogen and progesterone also regulate the stress response – the body's “fight-or-flight” reaction to physical or psychological challenges.

The main hormone involved in the stress response – cortisol in humans and corticosterone in rodents, both abbreviated to CORT – is primarily a metabolic hormone, meaning that increasing blood levels of these hormones during stressful conditions results in more energy mobilized from fat stores. The interplay between stress systems and reproductive hormones is a crucial link between mood and hormone contraceptives, as energy regulation is extremely important during pregnancy.

So what happens to someone's stress response when they're on hormonal contraceptives?

When exposed to a mild stressor – sticking an arm in cold water, for example, or standing to give a public speech – women using hormone contraceptives show a smaller increase in CORT than people not on hormone contraceptives.

Researchers saw the same effect in rats and mice – when treated daily with a combination of hormones that mimic the pill, female rats and mice also show a suppression of the stress response.

Hormonal contraceptives and depression

Do hormonal contraceptives increase depression risk? The short answer is it varies from person to person. But for most people, probably not.

It's important to note that neither increased nor decreased stress responses are directly related to risk for or resilience against depression. But stress is closely related to mood, and chronic stress substantially increases risk for depression. By modifying stress responses, hormone contraceptives change the risk for depression after stress, leading to “protection” against depression for many people and “increased risk” for a minority of people. More than 9 out of 10 people who use hormonal contraceptives will not experience decreased mood or depression symptoms, and many will experience improved mood.

But researchers don't yet know who will experience increased risk. Genetic factors and previous stress exposures increase risk for depression, and it seems that similar factors contribute to mood changes related to hormone contraception.

Currently, hormone contraceptives are usually prescribed by trial and error – if one type causes side effects in a patient, another with a different dose, delivery method or formulation might be better. But the process of “try-and-see” is inefficient and frustrating, and many people give up instead of switching to a different option. Identifying the specific factors that increase depression risk and better communicating the benefits of hormone contraception beyond birth control can help patients make more informed health care decisions.

Natalie C. Tronson, Associate Professor of Psychology, University of Michigan

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Nicole Granucci, Quinnipiac University

Curious Kids is a series for children of all ages. If you have a question you'd like an expert to answer, send it to curiouskidsus@theconversation.com.

Why do some planets have moons and some don't? – Siddharth, age 6, Texas

On Earth, you can look up at night and see the Moon shining bright from hundreds of thousands of miles away. But if you went to Venus, that wouldn't be the case. Not every planet has a moon – so why do some planets have several moons, while others have none?

I'm a physics instructor who has followed the current theories that describe why some planets have moons and some don't.

First, a moon is called a natural satellite. Astronomers refer to satellites as objects in space that orbit larger bodies. Since a moon isn't human-made, it's a natural satellite.

Currently, there are two main theories for why some planets have moons. Moons are either gravitationally captured if they are within what's called a planet's Hill sphere radius, or they're formed along with a solar system.

The Hill sphere radius

Objects exert a gravitational force of attraction on other nearby objects. The larger the object is, the greater the force of attraction.

This gravitational force is the reason we all stay grounded to Earth instead of floating away.

The solar system is dominated by the Sun's large gravitational force, which keeps all of the planets in orbit. The Sun is the most massive object in our solar system, which means it has the most gravitational influence on objects such as planets.

In order for a satellite to orbit a planet, it has to be close enough for the planet to exert enough force to keep it in orbit. The minimum distance for a planet to keep a satellite in orbit is called the Hill sphere radius.

The Hill sphere radius is based on the mass of both the larger object and the smaller object. The Moon orbiting Earth is a good example of how the Hill sphere radius works. The Earth orbits around the Sun, but the Moon is close enough to Earth that Earth's gravitational pull captures it. The moon orbits around the Earth, rather than the Sun, because it is within Earth's Hill sphere radius.

Small planets like Mercury and Venus have a tiny Hill sphere radius, since they can't exert a large gravitational pull. Any potential moons would likely get pulled in by the Sun instead.

Many scientists are still looking to see whether these planets may have had small moons in the past. Back during the formation of the solar system, they may have had moons that got knocked away by collisions with other space objects.

Mars has two moons, Phobos and Deimos. Scientists still debate whether these came from asteroids that passed close into Mars' Hill sphere radius and got captured by the planet, or if they were formed at the same time as the solar system. More evidence supports the first theory, because Mars is close to the asteroid belt.

Jupiter, Saturn, Uranus and Neptune have larger Hill sphere radii, because they are much larger than Earth, Mars, Mercury and Venus and they're farther from the Sun. Their gravitational pulls can attract and keep more natural satellites such as moons in orbit. For example, Jupiter has 95 moons, while Saturn has 146.

Moons forming with a solar system

Another theory suggests that some moons formed at the same time as their solar system.

Solar systems start out with a big disk of gas rotating around a sun. As the gas rotates around the sun, it condenses into planets and moons that rotate around them. The planets and moons then all rotate in the same direction.

But only a few moons in our solar system were likely created this way. Scientists predict that Jupiter's and Saturn's inner moons formed during the emergence of our solar system because they're so old. The rest of the moons in our solar system, including Jupiter's and Saturn's outer moons, were probably gravitationally captured by their planets.

Earth's Moon is special because it likely formed in a different way. Scientists believe that long ago, a large, Mars-sized object collided with the Earth. During that collision, a big chunk flew off the Earth and into its orbit and became the Moon.

Scientists guess that the Moon formed this way because they've found a type of rock called basalt in soil on the Moon's surface. The Moon's basalt looks the same as basalt found inside the Earth.

Ultimately, the question of why some planets have moons is still widely debated, but factors such as a planet's size, gravitational pull, Hill sphere radius and how its solar system formed may play a role.

Hello, curious kids! Do you have a question you'd like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you're wondering, too. We won't be able to answer every question, but we will do our best.

Nicole Granucci, Instructor of Physics, Quinnipiac University

This article is republished from The Conversation under a Creative Commons license. Read the original article.