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, techniques such as the Shettles method and 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, baby development starts with 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 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?

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.

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.

Signs Your Having a Boy or Girl

Let’s explore some old wives’ tales about pregnancy and gender prediction. While these pregnancy myths may not be backed by science, they offer a playful way for you and your family to guess whether you’ll be welcoming a boy or a girl.

Boy Signs:

• Carrying low
• Craving salty/savory foods
• Glowing skin
• Rapid fetal heartbeat

Girl Signs:

• Carrying high
• Craving sweets
• Morning sickness
• Slow fetal heartbeat

However, these are just myths – there’s no scientific evidence behind most of these outdated gender predictions. Just a fun way to get excited about your upcoming bundle of joy! Remember, the real answer will come in due time, so enjoy the anticipation and the playful guesses along the way.

Scientific Gender Predictions

After indulging in the fun of old wives’ tales, let’s shift our focus to more scientific methods of gender prediction. These approaches rely on medical technology and genetic testing to provide accurate information about your baby’s biological sex. Here’s how they work:

• Ultrasound Evidence: At around 18-20 weeks, a sonographer can often determine a baby’s biological sex by visually examining anatomy during an ultrasound scan.
• Genetic Testing: Non-invasive prenatal testing (NIPT) can reliably detect a baby’s sex chromosomes (XX or XY) from a blood sample as early as 9 weeks.

Shifting from old wives’ tales to scientific methods shows just how much medical technology has evolved, allowing expectant parents to find out their baby’s gender with great accuracy. If you’re interested in knowing whether you’re having a boy or a girl sooner rather than later, SneakPeek’s reliable tests can give you a clear answer early on.

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.

So, how early can you find out the gender? 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 weeks into pregnancy. Our simple DNA at home gender 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!