While some methods almost guarantee results, others rival old wives' tales. We had a doctor explain exactly how it all works.

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If you're the kind of person who has been planning your perfect family unit since your Barbie Dream House days, there is a way to guarantee it.

Whether your idea of familial perfection is one boy and one girl, in that order, or you've got some other mix in mind, you don't have to leave it up to chance. 

Dr. Shayne M. Plosker, professor and director for the University of South Florida's Division of IVF and Reproductive Endocrinology, explained each method for Care.com.

First, there is in vitro fertilization, or IVF -- the only scientifically sound way to guarantee results, according to Plosker.

"There are several methods, but the only method by far that truly, truly is accurate at predicting sex is in vitro fertilization, followed by a biopsy of the embryo to determine the embryo's sex," Plosker said.

Genetic testing for sex associated with this method was discovered in Europe in the 1990s, when it was used to prevent passing hereditary diseases like hemophilia in families where boys would suffer from the disease but girls would only carry the trait.

Families can still use the method for this purpose, but it can now also be used by parents who prefer one sex over the other.

It's a complex process that requires up to three months of planning and multiple visits to your doctor during the final weeks.


Here's how it works... 

1. Women must first go through a process called "egg retrieval." While the patient is under mild anesthesia, her doctor uses a needle to pull eggs from her ovaries.

2. The eggs are fertilized.

3. A few days later, tissue from the fertilized eggs are sent off for testing. As scientists check for any abnormalities, they can also check for X and Y chromosomes that determine sex.

4. If mom and dad definitely want a girl or a boy, all the eggs of the opposite sex can be removed. 

From here, parents can start planning for the little girl or boy they chose. But, of course, there is a catch.

While the sex of the baby is 100 percent, what is not guaranteed is that the woman going through this process will get pregnant.

"IVF, although it's wonderful and highly successful in 2017, it doesn't work for everybody," Plosker said. "The success rate of IVF really starts to drop quite a bit as you get older. It will very accurately detect the gender of your embryo that you're going to put back inside your uterus but you have to remember that there isn't a guarantee that you're going to get pregnant."

And when the cost associated with it is in the range of $22,000, most families may be priced out of considering this method. But as your budget drops, so does your guarantee.


Other ways to choose the sex of your child... 

Other theories may cost less but are also considerably less likely to work, Plosker said.

The Shettles Method is hinged on a woman's ovulation cycle and the belief that male sperm move faster than female sperm.

Under the Shettles Method, couples hoping to have a girl are encouraged to have intercourse two to three days before the woman ovulates and hold off after that. The idea is that the male sperm will die off first and the female sperm will still be around to fertilize the egg by the time the woman ovulates.

If you want a boy, have intercourse at the height of ovulation and the speedy male sperm will be the first to make it to the egg.

"At the end of the day, (this method) didn't prove to be helpful," Plosker said. "It proved to be very theoretical and ultimately proved to be (difficult to reproduce.)"

Plosker said these methods only raise your chances of having a baby of your desired sex slightly above 50/50, which is where you are if it's just left up to nature.

Fertility medication fares slightly better for couples seeking to have a girl. Scientists can't explain why just yet, but people who use fertility drugs are slightly more likely to have girls, and those who choose artificial insemination are slightly more likely to have boys. 

The only method that comes close to the success rates of IVF is the Ericsson Method, which scientists use to separate male or female sperm before insemination.

"But it's only 70 to 80 percent," Polsker said. "You're looking at a 50/50 chance when you try it on your own versus 70/30 or 80/20 at best. There have been people who have said this works, but when other labs and other clinics try to replicate what they say is going on, they aren't able to do it."

So, even in the best possible scenarios, there is still a possibility you'll be bringing home a boy when you had your heart set on a girl.

"At the end of the day, coming back, the really, truly only accurate way of doing this is with the IVF and the preimplantation genetic testing," Plosker concluded.

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