Sex Recorded at Birth

What is sex recorded at birth (sex assigned at birth)?

Your sex recorded at birth — sometimes called sex assigned at birth — has to do with your genitals. When a baby enters the world, a doctor or midwife inspects their genitals. If they see a penis, it means a male baby. It’s a boy! A vagina means a female baby. It’s a girl! And just like that, a baby is assigned a sex.

Then there’s the “recorded” part. In the U.S., sex is recorded on your birth certificate and in your medical records. Although an ultrasound can usually show the beginnings of a vulva or penis at 20 weeks, it’s not until you’re born that sex becomes a matter of public record.

As you grow, those around you may abandon the more formal-sounding labels. For example, a baby assigned female at birth may grow into labels like young lady, woman, mom and grandma. These labels are less about your genitals at birth and more about how others view or relate to you. The way you view yourself may match these expectations, or it may not. Your experience of your body and how others perceive it, as well as your assigned sex, all matter to your health.

This is why it’s essential to understand what your sex recorded at birth may — and may not mean — for your care.

What determines sex?

Your assigned sex (M or F) keeps the biology simple. But in reality, sex isn’t just penises and vaginas. The science is more complex. Sex is the genetic instructions that tell an embryo which sexual organs to form. It’s the presence of hormones that act on sexual parts and even non-sexual ones. It’s things like your:

• Chromosomal sex. Chromosomes contain the instructions that tell your body how to develop. Humans have 23 pairs of chromosomes. The 23rd pair determines your chromosomal sex. Males are XY and females are XX.
• Gonadal sex. Your gonads are your primary reproductive organs. The presence of ovaries means female, while testicles means male. These parts are important because they make the sex cells (eggs and sperm) that allow reproduction to happen. They also produce sex hormones, like estrogen and testosterone.
• Phenotypic sex. Phenotypic sex includes all parts involved in male and female sexual anatomy. It also includes secondary sex characteristics that develop during puberty, like facial hair (males) and breasts (females). These changes happen thanks to a surge in sex hormones.

For most people, chromosomes, gonads and phenotype all match up as either male or female. But in every 1 in 1,000 to 4,500 births, these indicators of sex don’t align. Currently, there are 60 different known variations where genitals, chromosomes and hormones don’t clearly match up as either male or female.

In that case, a healthcare provider delivering a baby may not be able to easily classify them as male or female. Or, genitals may look typically female or male but internal organs or chromosomes don’t match the outside. Sometimes, there are hormone differences that affect phenotypic sex that don’t show up until puberty.

How does sex recorded at birth relate to your health?

Although the language we use to talk about sex isn’t always the best at describing diverse human biology, it can still be useful. Depending on how it’s used, sex can help doctors talk about disease and wellness in general ways that can help you care for your body.

Still, you should always discuss your individual care plan — tailored to your unique needs and biology — with your medical team.

Specialty care

The specialty care you need may depend on your sex. For example, obstetricians and gynecologists specialize in female sexual and reproductive health. Urologists, on the other hand, treat urinary conditions in everyone and sexual and reproductive issues in males, specifically. Among other things, endocrinologists help with issues related to sex hormones like testosterone and estrogen.

Health screenings

The screenings you need depend largely on your anatomy. For example, getting your first Pap, HPV test or mammogram is a rite of passage for most females. For males, that rite is often their first testicular or prostate exam.

It’s important to know how your anatomy relates to your disease risk. That way, you can schedule screenings that make early diagnosis and treatment possible.

Conditions

Several conditions are sex-related. Both benign (noncancerous) conditions and cancer can affect your reproductive organs. This is why screenings are a must.

With some conditions, the connection to sex is less obvious. For example, some genetic disorders that involve problems related to the X chromosome can affect you differently based on your chromosomal sex. These X-linked conditions often cause males (XY) to develop the disease (or the worst effects of it) while females (XX) experience less severe effects or just carry the gene for the disease. This is the case with conditions like Duchenne muscular dystrophy, hemophilia A and red-green color blindness.

In this case, your sex at the cell level not only matters to your health, but it also influences how likely it is that you’ll pass the condition along to your biological children. You may need to seek genetic counseling before trying to have a baby.

Some sex-related differences may increase or decrease your disease risk. For example, body composition (the distribution of fat and muscle) and hormones likely play a role in why males are at greater risk of heart disease. After menopause, when estrogen levels drop, females are about as likely to develop heart disease as males.

And then there are conditions that seem to relate to sex, but scientists don’t know why. For instance, it’s unclear why females are more likely to get diagnosed with an autoimmune disease, while males are more likely to develop Parkinson’s disease or ALS.

Symptoms

Even when doctors don’t completely know why a condition is different based on your sex, it’s still useful to know about it. This can help you recognize symptoms as potentially serious. It can give you that nudge to call your healthcare provider.

This is especially the case when your experience of a condition depends on your sex. Probably the most well-known example is heart attack symptoms. If you’re male, a heart attack often feels like chest pain or indigestion. If you’re female, it’s more likely to feel like shortness of breath, fatigue or pain in places other than your chest.

Knowing how you may experience a condition based on your sex can keep you from dismissing a symptom as minor. It can potentially save your life.

Diagnostics and test results

Most tests report normal results as falling within a range. This accounts for natural variations among individuals. But the ranges may be sex-specific if the values relate to things like sex hormones or your body size. Both of these things relate to your gonadal sex (ovaries or testicles) and sexual development during puberty.

Two common values on routine blood work where there are sex differences are:

• Hemoglobin. The normal ranges of (the key ingredient in your red blood cells) vary slightly based on whether you are male or female.
• Creatinine. What’s considered a healthy range for creatinine varies by sex. Creatinine levels provide clues about your kidney health.

These are just two examples — there are many more.

Wellness

The advice that you get from your primary healthcare physician about how to stay healthy from day to day may include recommendations related to sex. Differences relate to things like your:

• Nutritional needs. How many calories you need per day and recommended nutrients may vary based on sex. And needs change depending on life events, like pregnancy and menopause.
• Exercise routine. While most adults need roughly the same amount of exercise daily, bodies respond differently to exercise, in part, because of your sex. For example, it’s generally easier for males to build muscle mass, thanks to high testosterone levels. The benefits of exercise also differ based on age.
• Alcohol consumption. Females have less of an enzyme that breaks down alcohol, which means they tolerate less of it than males. This is partly why recommendations for limiting alcohol intake differ by sex.

It’s important to remember, though, that sex is only one small factor that may guide your wellness routine. After all, your health goals likely tell you more about your nutritional needs than your sex. The way you’d like to feel in your body likely matters more to your exercise regimen than your sex organs do.

What sex recorded at birth can’t tell you about your health

Your sex can provide guidance on essential things, but there’s much that it can’t tell you. For example, most wellness advice, like how much sleep adults need each night, applies to everyone. And most diseases don’t seem to discriminate based on sex. Research shows that there may be connections among things like sex chromosomes, immune system function, and cancer risk and severity. But more research is needed to understand these relationships.

It’s also difficult to tell how disease risk relates to your sex versus your environment. For instance, throat cancer is more common in males. But the primary risk factor for throat cancer is smoking. Since men smoke more than women, it’s possible that it’s the behavior and not the biology that leads to throat cancer.

Finally, sex can’t tell you the complete story about how your health relates to your experience of identity. If you’re having trouble sleeping at a time in your life when you’re caring for an aging parent, being female likely matters less than the stress you’re carrying. Your experience isn’t completely separate from sex, especially if one of the labels you grew into was loving child or devoted daughter. Research shows females are more likely to experience insomnia. But your genitals as a baby matter much less than your experience as a tired adult and loving caregiver.

This is why it’s important to speak frankly with your healthcare provider about all the factors that matter to your health. A designation of male or female on your birth certificate provides a starting place to talk about the care you may need. The conversation should continue to address things like your unique biology, experience and health goals. It all matters when it comes to your health.