Beli Prenatals are HSA/FSA eligible!

Can you influence whether you have a boy or a girl? Here is what the science says!

Science tells us that dad’s sperm determines whether a baby will be a boy or a girl. About half of his sperm will make a boy and half a girl. The sex of the baby depends on which sperm gets to the egg first. In a perfect world, it would all be up to chance. Both types of sperm would have an equal chance of reaching the egg first. And once fertilized, each type of egg would have an equal chance of developing fully into a baby.

But as you know, the world is not perfect. There is always genetics and environmental factors at play. Science now tells us that certain environmental factors can influence the sex of the child, including the egg's receptivity to the male's chromosomes. A number of studies have suggested that factors like nutrition and how the parents live can affect the odds of having a boy or a girl.  

As many people know (or have heard), the sperm that carry male chromosomes (which will make a boy) can swim faster because they carry less genetic material and are lighter. So though male and female sperm have equal muscular power in their flippers, the lighter ones will travel faster (just like a smaller cyclist will go faster than a larger one, if all other things are equal, because there's less mass to move).

But even if the male sperm outrace the female sperm, the male sperm will die off if the egg isn't in proper position for fertilization, leaving the female sperm clear for landing. Although male sperm are faster, female sperm are like tortoises; they keep pushing ahead slowly, hanging out, and waiting a few days. To have a boy, having sex around ovulation is critical, or the female sperm will win.

A recent Newcastle University study involving thousands of families is also helping prospective parents work out whether they are likely to have sons or daughters.

The work by Corry Gellatly, a research scientist at the university, has shown that men inherit a tendency to have more sons or more daughters from their parents. This means that a man with many brothers is more likely to have sons, while a man with many sisters is more likely to have daughters.

The research involved a study of 927 family trees containing information on 556,387 people from North America and Europe going back to 1600.

"The family tree study showed that whether you’re likely to have a boy or a girl is inherited. We now know that men are more likely to have sons if they have more brothers but are more likely to have daughters if they have more sisters. However, in women, you just can’t predict it," Mr. Gellatly explains.

Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother’s X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother’s to make a boy (XY).

The Newcastle University study suggests that an as-yet undiscovered gene controls whether a man’s sperm contains more X or more Y chromosomes, which affects the sex of his children. On a larger scale, the number of men with more X sperm compared to the number of men with more Y sperm affects the sex ratio of children born each year.

Sons or daughters?

A gene consists of two parts, known as alleles, one inherited from each parent. In his paper, Mr. Gellatly demonstrates that it is likely men carry two different types of allele, which results in three possible combinations in a gene that controls the ratio of X and Y sperm;

  • Men with the first combination, known as mm, produce more Y sperm and have more sons.
  • The second, known as mf, produce a roughly equal number of X and Y sperm and have an approximately equal number of sons and daughters.
  • The third, known as ff produce more X sperm and have more daughters.

“The gene that is passed on from both parents, which causes some men to have more sons and some to have more daughters, may explain why we see the number of men and women roughly balanced in a population. If there are too many males in the population, for example, females will more easily find a mate, so men who have more daughters will pass on more of their genes, causing more females to be born in later generations,” says Newcastle University researcher Mr. Gellatly.

Journal Reference: Note: Content may be edited for style and length.

Gellatly et al. Trends in Population Sex Ratios May be Explained by Changes in the Frequencies of Polymorphic Alleles of a Sex Ratio GeneEvolutionary Biology, Dec 11, 2008; DOI: 10.1007/s11692-008-9046-3 

Newcastle University

Stanford University

Additional Resources

There’s a lot of chatter when it comes to male masturbation and what it says about a man’s fertility or whether it’s an issue when a couple is actively trying to conceive. And in the interest of clearing up the confusion, we’re taking a facts-based approach to the topic of men, masturbation and fertility.

Read More

For many of us, our twenties and even thirties are a time when the focus is on pregnancy prevention. And that’s okay! But even when the idea of motherhood is miles away there is tremendous value in understanding your fertility health and what you can do to support it during these young, carefree days.

Read More

We’re thrilled to introduce Beli Women Preconception, a complementary fertility supplement designed to support fertility health by promoting egg quality, supporting ovulation, balancing hormones, regulating your cycle and helping to manage symptoms of both PCOS and PMS.

Read More

Once a month, PMS symptoms make their unpleasant presence known. And while knowing what’s happening won’t make PMS magically disappear, it can help you manage symptoms by balancing hormones and supporting your reproductive health. Let’s review.

Read More

Raise your hand if you already know that you have a biological clock. From age 35 and beyond, there is a natural decline in testosterone and sperm quality. Just as people lose muscle strength, flexibility and endurance with age, sperm also tend to lose their "fitness" over the life cycle. But what does that mean—and does it really matter?

Read More

It’s an easy assumption, but you’re much better off thinking that every prenatal vitamin is wildly different in terms of composition, nutrient quality and, importantly, nutrient amount. Not only is that actually true, it puts you in the smart consumer mindset of understanding what matters in a prenatal vitamin—and why.

Read More

If you have endometriosis, you can already recite its lengthy list of pretty terrible symptoms. And the standard options for managing those symptoms — medications, hormone therapy, hormonal birth control, estrogen blockers, surgery —  aren’t always great. But there is evidence that a so-called “endometriosis diet” can help.

Read More

Men really do benefit from specialized nutrition in the form of a prenatal vitamin that’s formulated to support sperm health. Here’s what that looks like, and how specific nutrients can impact a man’s fertility health before fatherhood.

Read More

Shilajit is finally getting the credit it’s due, and we’re proud to point out that our proprietary formula was the very first to include this powerful Ayurvedic compound. Here’s why shilajit is rapidly becoming the darling of the male fertility world–and what you’re missing if you’re skipping it.

Read More

Ever wondered why men produce so much darn sperm, especially if only one of them will ultimately fertilize the egg? There are millions of sperm in normal ejaculate because it increases the likelihood that one will reach the egg and seal the deal. It begs the question, what exactly happens on the journey to the egg?

Read More

Optimal nutrition plays a pivotal role in enhancing fertility and supporting a healthy pregnancy. A diet rich in essential nutrients, such as vitamins, minerals, antioxidants, and healthy fats, lays the foundation for reproductive health.

Read More

Is there anything unsexier than scheduled, pressure-ridden, trying-like-hell-to-conceive sex? But good news. We’ve found handy workarounds and tricks of the trade, so forget the basal temperature chart for a second and read on for four ways to keep things hot when you’re TTC.

Read More

Just as women’s bodies need to be prepared for pregnancy, men’s bodies need to be ready to contribute healthy sperm for conception. Nutrients are the foundation that support the normal structure and function of sperm and men's fertility health. Taking Beli’s male prenatal supplement is a proactive way to strategically fuel your body to optimize fertility contributing to your overall chances of conceiving and supporting a healthy pregnancy.  

Read More

Diet has been suggested to have an influence on the quality and function of human sperm. More specifically, the results of a randomised trial have shown that including nuts as a component of a regular diet improved the quality and function of human sperm.

Read More

A shot to the balls may be played for laughs on screen, but testicular impacts really aren’t a joke. Worse case scenario, getting hit in the balls can affect fertility thanks to complications like sexual dysfunction, low testosterone and other issues. Let's discuss.

Read More

With the New Year upon us, there are all kinds of articles and videos making the rounds with predictions of the Zodiac signs most likely to get pregnant in 2024. But here at Beli, we take a much more scientific approach to conception. Here are the top eight things people will do to get pregnant in 2024.

Read More

Research shows that the overall health of both biological parents during the preconception window plays a huge role in everything from conception to pregnancy health to the lifetime health of their baby. Luckily, there are simple steps you can both take to improve your health together.

Read More

When it comes to becoming parents, good habits really will take you where you want to go. Now, new science is giving us insight into exactly how long it takes to form those good habits. We're breaking down all the ways you can build healthy habits to boost your chances of conception. Think of it as life-hacking, but for grown-ups.

Read More

Preparing for a baby means doing everything in your power to nourish your fertility health. If you’re totally on board but wondering what that actually means, we’re breaking down the do’s and don’ts for planning a pregnancy.

Read More

Somewhere between the “let’s have a baby!” conversation and seeing those two pink lines, you’re going to end up researching prenatal vitamins. And trust us when we say you’re going to have a ton of options to wade through. Consider this your handy guide to the best prenatal vitamins for men and women in 2024.

Read More

Here at Beli, we’re working hard to raise awareness of the important role men play in the baby-making equation, which brings us to today’s topic of men’s preconception health and specifically, sperm health. Knowing what you’re working with can save you a lot of time, but is at-home sperm testing considered an important part of men’s preconception health? Let’s break it down.

Read More

Most births occur between June and early November. Count back nine months, and you’ll see that places most conceptions in the fall and winter. So what’s the deal? Is it the cold weather, all the festivities, or something else driving us between the sheets? That ugly sweater is pretty cute, but you can chalk this up to reproductive seasonality. Here’s what that means, why it matters, and what to do to use it to your advantage.

Read More

There’s a certain magic to the holiday season, whether you’re all-in on the decorations and the family time or a self-proclaimed Scrooge from mid-November to the New Year. But when you’re trying to conceive, it can be a challenging time.  We’re sharing five tips for managing the holidays when you’re trying to conceive.

Read More

Everyone knows that alcohol and pregnancy don’t mix. But what about before you’re pregnant, during the trying-to-conceive stage? There’s no evidence that the occasional drink—i.e. one or two a week—is going to torpedo your chances of parenthood. But it is true that the more you drink, the greater the likelihood it will have an effect on your health. Here’s what the research says about alcohol and your fertility.

Read More

You’re clear on the mechanics of making a baby, but how much do you really know about conception and fertility? There are a lot of wild stories, downright falsehoods and notions that are actually rooted in a kernel of truth out there. In the interest of sticking to the facts, we’re debunking 15 of the most common myths about conception and fertility.

Read More

When you’re knocking boots in an effort to get knocked up, timing is everything. Your best chance of conceiving is during the most fertile time of your menstrual cycle—when you ovulate. The key is figuring out exactly when that happens. Fortunately, you have a few ways of detecting ovulation. Here’s what to know about understanding ovulation and timing sex for pregnancy.

Read More

You have big plans for parenthood in 2024, which means this is the time to start laying the groundwork for everything to come. While so much of conception is beyond our control, there are actionable steps you and your partner can take right now to support and nourish your fertility.

Read More

Is there anything worse than the two-week wait? All the listicles out there sensibly advise keeping busy and journaling and talking it out, but we’re sharing more specific recommendations collected from the Beli community. Read on for seven tips for surviving the two-week wait without losing your mind.

Read More

Heard the one about ice baths and testosterone? Spoiler: there's little to no research behind that idea. Here’s what to know about cold plunges and male fertility, according to the research, plus where you should really focus your efforts if you’re trying to improve sperm health.

Read More

As a society, we’re an impatient bunch, and that applies to pregnancy, too. The second you decide it’s time to try for a baby, you’re ready to see those two pink lines. If you’ve recently tossed the birth control and you’re wondering how long it should take to get pregnant, here's what to know.

Read More

Jimmy Fallon. Hugh Jackman. Mark Zuckerberg. Keith Urban. Gordon Ramsey. Kyle Busch. Besides immediate name recognition, what else do these men have in common? They’ve all struggled with infertility issues—and it’s something they’re all talking about publicly. Here's why that matters.

Read More

There’s a persistent misconception that a woman’s egg quality is largely untouchable—you get what you get, and the rest is out of your hands. But for women actively planning on becoming mothers, there are a handful of best practices that can go a very long way. So, can you improve egg quality in 90 days?

Read More

Can weight loss improve your fertility? That depends on what you read. In today’s post, we’re running through all the latest data on weight loss and fertility, and clarifying why the focus should be less on pounds lost and more on prioritizing habits that support your health as a whole.

Read More