After you see those two pink lines on a pregnancy test, it can feel like forever until you find out your baby’s sex. Some What to Expect Community moms in search of early clues are turning to the ovary gender test method for predictions. This buzzy theory suggests that the side you ovulate on might hold the secret to whether you're having a boy or a girl.
"I read about a theory today that states that the ovary you ovulate from can also influence sex," a WTE Community mom shared with her birth month club. While the ovary gender test has Community moms speculating, here's what science has to say about this theory.
- The ovulation gender theory proposes that if you ovulate from your right side, you're more likely to have a baby boy; if you ovulate on the left side, you're more likely to have a girl.
- There isn't enough scientific evidence to support this theory. In actuality, the sex chromosomes in sperm determine a baby's sex.
- A better way to find out whether you're having a boy or girl is through noninvasive prenatal testing (NIPT) or at an anatomy scan later in pregnancy.
What is the ovulation gender theory?
The ovulation gender theory proposes that the side you ovulated on correlates to your baby's sex. Specifically, if you ovulate from your right side, you're more likely to have a boy, and from your left, a girl.
Some moms in the What to Expect Community have found that this was true for them. "I have ovulated on the right side [three times] and have three boys," one wrote. "A friend of mine who only has her right ovary has four boys."
However, doctors do not have enough research-based evidence to confirm this theory. This is what they do know: Every month, hormones from the brain signal the right or left ovary to start preparing an egg for ovulation, says Jessica Ryniec, M.D., an OB/GYN and reproductive endocrinology and infertility specialist at CCRM Fertility in Boston. The brain then sends out a final signal triggering the release of the egg from the ovary into the fallopian tube, where sperm can fertilize it. From there, the fertilized egg makes its way down to the uterus.[1]
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How to know which side you ovulated on
You might know which side you ovulated on if you experience ovulation cramps (also called Mittelschmerz) mid-cycle, says Dr. Ryniec. If you're working with doctors to conceive, it's likely that they performed an ultrasound mid-cycle, when you can see which ovary will produce the egg, notes Dr. Ryniec. The follicle containing the egg that will ovulate will look bigger than the rest to a trained eye.
Otherwise, the only way to know for sure which side you ovulated on is during an early ultrasound (usually before week 10) when you can still see the corpus luteum in your ovary, she says.[2]
The corpus luteum is the collection of cells that contain the egg while it grows and develops in your ovary, says Anupama Kathiresan, M.D., an OB/GYN and reproductive endocrinologist at Kindbody Santa Monica in California. The corpus luteum produces progesterone, the hormone that prepares the uterus for implantation. If you can see the corpus luteum in one of the ovaries, you can infer which side a person ovulated on, she explains.
If you're past this point in your pregnancy, ask your doctor if it's on a previous ultrasound report. The technician would note which side the corpus luteum was on and how big it was.
Does the ovulation gender theory really work?
The ovulation gender theory is not a good tool to help plan for a specific gender, say you want to have a girl, when trying to conceive. "There's no way to predict which ovary will ovulate each cycle, and it does not necessarily go back and forth — left, right, left, right — as many people believe," Dr. Ryniec says. In other words, you can't use an ovulation pattern to predict or plan your baby's sex.
But does it work to help predict the gender after fertilization? There isn't a ton of research to prove this, but a 2022 study found that a "significantly higher frequency" of boys were conceived after the women had three consecutive ovulations that followed a left-left-right pattern.[3] Meanwhile, three ovulations on the left side had a higher chance of leading to a baby girl.
While this might sound like ovulating on the left side could mean you're more likely to have a girl, there just isn't enough evidence to support this theory scientifically. Observational studies like this one typically offer a low-quality level of evidence, because they can only show associations and not a cause and effect, Dr. Ryniec says. "There could be other factors leading to the results," she explains.
In this case, researchers only observed three menstrual cycles of women undergoing intrauterine insemination (IUI) and/or in-vitro fertilization (IVF). The results could have been related to chance, Dr. Ryniec says.
Remember, there is always a 50-50 chance you will conceive a boy or a girl. And as with any gender prediction method — including old wives' tales like the ring gender test and the baking soda gender test — this prediction method has a 50% likelihood of (coincidentally) being right.
Ultimately, both she and Dr. Kathiresan emphasize that a baby's sex has nothing to do with ovulation.
"Biologically, the sex of a pregnancy is determined by the sex chromosomes," explains Dr. Kathiresan. "Females have two X chromosomes (XX), and males have one X and one Y chromosome (XY)." The mom always contributes an X chromosome to the future offspring, while the dad could contribute an X or Y chromosome. It's this chromosome given by the male that determines the baby's sex.
Better ways to determine your baby's sex
If you want to know whether you're having a boy or girl before meeting your baby at birth, you'll want to use a more reliable, high-tech way to find out during pregnancy:
- Noninvasive prenatal testing (NIPT): This simple blood test can happen as early as nine weeks into your pregnancy. The NIPT accurately predicts a baby's sex more than 99% of the time, and it also provides information on a child's risk of chromosomal abnormalities including trisomy 21 (Down syndrome), trisomy 18 (Edwards syndrome) and trisomy 13 (Patau syndrome).[4]
- Chorionic villus sampling (CVS) and amniocentesis: These diagnostic tests primarily screen for chromosomal abnormalities, but they can also reveal a baby's sex. Since they're more invasive than the NIPT, your care provider might recommend one if your pregnancy is at higher risk. "CVS is a procedure performed at around 10 to 13 weeks that involves taking a sampling of tissue from the placenta, and an amniocentesis involves taking a sampling of amniotic fluid that is usually performed between 15 and 18 weeks of pregnancy," says Dr. Kathiresan.
- Anatomy scan: Done between 18 and 20 weeks, this second trimester ultrasound takes an in-depth look at your baby's anatomy. At this point, your baby's genitals are more readily visible, so your care team can likely confirm your baby's sex.
The bottom line: You might be eager to learn as much as you can about your baby as soon as possible, but while the ovulation gender test sounds good in theory, it's not the most accurate way to know whether you're having a boy or girl. Thankfully, whether you use the results of a science-backed test or you choose to wait until delivery day, you'll discover your baby's sex soon enough.
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