Pregnant woman holding a gender reveal card

What are the Chances of Having a Boy vs Girl

Published on March 19th, 2021 and Updated on January 12th, 2024

Check out SneakPeek Gender Test to find out your baby's gender as early as 6 weeks at over 99% accuracy1!

It’s generally understood that the chances of having a boy or a girl boil down to 50/50 odds—essentially a coin toss. Heads for boys, tails for girls! If you really want to test those odds, check out our Gender Quiz or explore the ancient tradition of the chinese gender predictor method!

But are the chances of having a boy or girl really as simple as a flip of the coin?

Nope! They’re actually much more interesting.

Not Quite 50/50: Understanding the Odds of Having a Boy or a Girl

According to the World Health Organization, for every 105 boys born globally, there are about 100 girls born. This is called the sex ratio at birth. Sex ratio at birth is a term used in studies to describe the ratio of boys to girls (always in that order) in a population when they’re born.

So really, that coinflip is a little bit more weighted in favor of having a baby boy.

  • What are the chances of having a boy? – If you’ve got your fingers crossed for a sweet baby boy, the odds are just ever so slightly in your favor. You have about a 51% chance of having a boy.
  • What are the chances of having a girl? – If you’re hoping for a bright-eyed baby girl, your chances are still very good at around 49%.

However, these numbers are based on a global sex ratio at birth—it doesn’t account for the many variables that could specifically impact your chances of having a boy or a girl.

If you’re wondering, “Can you pick the gender of your baby?”, the answer is generally no. However, factors such as paternal influence from a physiological perspective (more on this later), times of crisis, parental age, and geographic location can sway whether you will be having a sweet little girl or an adorable little boy.

Factors that Affect Sex Ratio at Birth

The 50/50 chance is a “close enough” metric when you’re speaking in generalities about the global sex ratio at birth. However, scientists, anthropologists, and sociologists are finding compelling data that the ratio can be swayed in one direction or the other in specific locations or instances.

Paternal Influence

Dad’s genetic contributions are responsible for plenty about your little bundle of joy to-be, including one of your child’s most foundational characteristics—gender.

  • The background – On a molecular level, a baby starts as two different reproductive cells—an egg cell contributed by Mom and a sperm cell contributed by Dad. During conception, these reproductive cells fuse together and create an embryo, the cellular start of your future child.

Each cell brings its own unique set of genetic material to the table. When it comes to the baby’s gender, a male sperm cell can carry either a Y or an X chromosome, while the egg always carries an X chromosome. When a Y-carrying sperm meets an egg, they create a male embryo. When an X-carrying sperm meets an egg, they create a female embryo.

  • Ratio of Y-sperm to X-sperm – Yup, Dad’s cells are the ones that determine the gender of your child (but don’t worry, a baby gets plenty of unique traits from Mom). One thing that could tip the balance of the 50/50 ratio? If Dad doesn’t create equal amounts of Y-carrying sperm and X-carrying sperm.

Scientists are examining whether certain genes in a man’s DNA impact the Y/X ratio of his sperm. DNA is like your body’s technical manual—it tells cells how to make all the parts that make you you. So it’s possible that under the “Sperm Production” section of that manual, there are clear instructions for the sperm-making systems of a dad’s body to always produce a 3:1 ratio in favor of Y-carrying sperm, increasing your chances for a male child substantially.

However, no specific gene has been isolated (yet). But scientists do have another way to examine the paternal genetic predisposition for having boys or girls—family trees.

  • A genetic link through siblings Researchers in England conducted a study to determine whether there was more to Dad’s genetic contribution to a baby’s sex. They looked at over 927 family trees dating back to 1600. They discovered that the sex ratio tended to follow the dad’s side of the family.

For example, if a dad had more brothers, he was more likely to have boys himself. But, if a dad had more sisters, then his children were more likely to be girls.

More studies need to be done to understand Dad’s genetic role in your chances of having a boy or a girl, but if you’re wondering how to have a baby boy, a good look at your partner’s family tree couldn’t hurt!

Times of Crisis

We all face little crises every day, from hitting “reply all” to a company email to forgetting a parent’s anniversary. These are typical issues we conquer daily and don’t create lasting biological impacts.

But what about big crises? Ones that drastically impact day-to-day life for an entire population?

Multiple studies show that war, famine, and environmental phenomenon like earthquakes impact sex ratio at birth—in favor of girls.

  • Iran-Iraq War, 1980 Prior to the Iran-Iraq war, the Iranian sex ratio at birth was in line with the global ratio, 105 boys for every 100 girls. However, during the first year of the Iran-Iraq War, the ratio dropped significantly. Instead of an extra 5 male births, the ratio decreased down to an even 50/50.
  • Zakynthos Earthquakes, 2006 – In 2005, the sex ratio on the island of Zakynthos was 1.1:1. So for every 11 boys born on the island, 10 girls were born. But in 2006, moderate earthquakes shook Zakynthos, an island of Greece, for an entire month. Researchers found that in the year after the month that shook the world, the sex ratio decreased 50% from the previous year. Instead of 11 boys for every 10 girls, only 6 boys were born for every 10 girls.

Why do times of crisis have such a big impact on the gender ratio? History, psychology, and biology offer an answer:

  • Stress and gender determination Scientists have recently found a connection between a mom-to-be’s stress levels and the likelihood of having a boy or a girl baby. Biologists discovered that moms who are carrying boys eat higher-calorie diets. But during times of crisis, there may not be enough calories to go around.

Could there be an element of self-preservation at play during conception? Scientists have found evidence that the woman’s egg plays a more active role in the fertilization process, even suggesting that eggs may have sway on which sperm becomes part of the embryo. So in times of crisis, could the egg choose a female sperm that will conserve resources for Mom in the long run? Maybe. Researchers certainly have a lot more research to do when it comes to how to have a baby girl!

Paternal Age

We’ve all heard about the “biological clock.” You know, the one that tells you hey, it’s quarter past baby-making o’clock! But when you decide to heed the call of the clock may have an impact on your chances of having a son or a daughter.

One study in Denmark sought to help illuminate that not-quite 50:50 ratio of boys to girls. They studied the births of children between 1980 and 1993, over 800,000 babies in all. They examined multiple births, gender ratios of siblings, birth order, and location. One of the most interesting connections they found was between paternal age and a child’s sex:

  • Younger dads were more likely to have boys.
  • Older dads were more likely to have girls.

Fathers who were younger than 25 years old were often in line with the birth ratio of the country, with a 51.6% chance of having boys. However, fathers over 40 had just a 51% chance of having a boy.

The decrease is slight, but half a percentage point can make a big difference in a population. However, further studies on how age impacts the sex-at-birth ratio are needed before we can say how old you are makes a difference in your chances of having a boy or a girl.

Geographic Location

Where you live in the world may affect your chances of choosing blue paint or pink for your baby room. For example, in Azerbaijan, the sex ratio is 111 boys born for every 100 girls, but in Zimbabwe, it’s only 102 boys born for every 100 girls!

Why such a difference? All the reasons we listed above can come together to impact a nation’s sex ratio at birth. For instance:

  • Countries that have been through recent wars may experience a decrease in their sex ratio, in favor of girls.
  • Nations where parents start having children at younger ages may have a higher sex ratio, in favor of boys.

After all, a country is its people. A multitude of demographic, environmental, and cultural factors may come together to influence the odds of having a boy or a girl in unique ways.

Girl Or Boy? Find Out Sooner with SneakPeek!

Even if your partner is the only boy in a family full of girls, or you’re living through something stressful like… a global pandemic, it’s hard to know precisely how that gender coin-toss will land for your child.

The good news? You won’t have to wait too long to find out, thanks to the SneakPeek Early Gender DNA Test.

The SneakPeek Early Gender DNA test lets you discover your child’s gender as early as 6 weeks7 weeks into pregnancy. Our simple DNA gender prediction test comes with easy-to-follow instructions and prepaid packaging so you can test, ship, and find out your baby’s gender seamlessly.

Find your answers sooner than ever before, with SneakPeek!

 

This post has been reviewed for accuracy by the following medical professional:

Katie Smith, MSN, APRN, CNM

Katie Smith is a seasoned Certified Nurse Midwife and a nurturing mother to six children, offering a unique blend of professional expertise and personal experience. She is the founder of Birth Your Way Midwifery and Women’s Wellness Center in Bay County, Florida. Katie's comprehensive approach to care is informed by her hands-on experience in motherhood and her passion for empowering women through their birthing journey. Her dedication extends beyond her center as she actively engages in community wellness and family health education.

Sources:

Pregnant woman holding a gender reveal card

Subscribe for Updates

Related Posts

January 20, 2024
Depending on who you ask, you might hear that being pregnant with twins is a unique experience. But the truth is that every...
January 15, 2024
Genetic testing has become an accessible healthcare option anyone can use to better understand both individual and family needs. But...
December 28, 2023
For as long as humans have been procreating, cultures around the world have developed imaginative rituals for predicting gender to...


SneakPeek aims to provide the most accurate and up-to-date information to help our readers make informed decisions regarding their health before, during, and after pregnancy. This article was written based upon trusted scientific research studies and/or articles. Credible information sources for this article are cited and hyperlinked.

What is the return policy for kits bought in a store?
Why is SneakPeek priced lower in stores vs. online?
Where can I buy SneakPeek in store?
How quickly can I receive my results with the clinical test?
How much does the clinical test cost?
Where can I find the closest clinic near me?
What should I do if my blood test result differs from my ultrasound?
Does a previous miscarriage affect my pregnancy test results?
How early can the gender prediction blood test be taken?
Is the gender prediction blood test safe?
How reliable is the gender prediction blood test?
What are other ways doctors can determine my due date?
How is the due date calculated if I conceived through IVF or fertility treatments?
Can I use a pregnancy calculator if I have irregular periods?
I Used the Pregnancy Calculator… Now What?
Can the baby hear the Fetal Doppler?
Can I use the Fetal Doppler if I have twins or multiples?
Are there any risks of using the Fetal Doppler frequently?
Is gel necessary for using the Fetal Doppler?
Are any specific preparations needed before visiting the clinic for a gender blood test?
Is there a difference in accuracy between home kits and clinical tests?
Why are blood tests used for early gender determination?
Why choose a clinical setting for an early gender test?
Why would a sample result be inconclusive?
What if my sample results are inconclusive?
Can FedEx pick up my SneakPeek FastTrack sample?
Is SneakPeek Clinical accurate at 6 weeks into pregnancy?
When can I use a Fetal Doppler?
What is the difference between Refer a Friend and Affiliate Program?
What do I do if the blood sample does not coat the test tube and mix with the preservative?
How do I dispose of the SneakPeek Snap device?
What is the maximum amount of time I should leave SneakPeek Snap on my arm if I’m not collecting enough blood?
Can my SneakPeek Snap helper be male?
What do I do if no blood at all is collected with SneakPeek Snap?
How does the microneedle part of SneakPeek Snap work?
Can I use SneakPeek Snap on my leg instead?
Will tattoos affect my blood sample and results with SneakPeek Snap?
I didn’t get enough blood the first time, can I try it again with the same SneakPeek Snap device?
Can I have a helper for using SneakPeek Snap?
What if I can’t hear my baby’s heartbeat with a Fetal Doppler?
Is it safe to use a Fetal Doppler?
How does a Fetal Doppler work?
I used last menstrual period (LMP) to calculate 6 weeks into pregnancy. Are my test results reliable?
If I can’t enter a post office due to social distancing or limited hours, are there other ways to return?
Are SneakPeek products safe from COVID-19?
How do I activate my SneakPeek At-Home test kit?
Can I buy the SneakPeek test kit now and use it later?
How do I become a SneakPeek Influencer?
Is SneakPeek a pregnancy test?
My blood sample was taken at a participating location. What is the status of my results?
Is shipping free?
Does taking progesterone or other hormones affect my results?
Do blood thinners affect my results?
Do you ship to APO/FPO/DPO addresses?
I’ve seen gender predictor tests that use urine samples. How is SneakPeek different?
What is the difference between SneakPeek Gender At-Home and SneakPeek Gender Clinical?
Can I take the SneakPeek Test if I’m breastfeeding?
Do hormone disorders such as PCOS affect my results?
What are SneakPeek’s privacy practices?
Is the test safe?
How quickly will I receive my refund?
When is SneakPeek Customer Care available?
What do I do if I have a question about my order?
I’m having twins. Can SneakPeek determine the gender of each one?
What is SneakPeek’s guarantee?
I’ve previously had a boy. Will that affect my test result?
How do I ensure an accurate test result?
I can’t find my results email, what do I do?
When will I receive my results?
How are my results given to me?
How will I know you received my sample?
I don’t want my gender results to be sent to my email address. Can I have them sent to someone else?
What email address should I provide during checkout?
Can I track my sample?
What is the shipping timeline?
How long does my sample stay stable after collection? How long can it stay stable during shipping?
What is the difference between SneakPeek Standard and SneakPeek FastTrack?
Can I use SneakPeek if I am having a multiple-birth pregnancy?
How is the DNA blood sample taken?
How accurate is the SneakPeek Early Gender DNA Test?
When can I use the SneakPeek test?
When in my pregnancy can I take the SneakPeek Test?
Do you have a pregnancy calculator that tells me when I can take the test?
How does the SneakPeek Test work?
done