There are few celebrities more adept at controlling their image than Beyoncé. She tells us only what she wants to tell us through the elusive mediums of music and photography. This power was in play during her announcement that she was pregnant with twins last week, which she made by releasing a Rococo meets Flemish photoshoot of herself cradling her belly and looking beatific.

Most of her fans were happy to celebrate the news and accompanying, otherworldly images. Still, others couldn’t help but puncture the elation with speculation as to whether the fact that she was having twins meant she and Jay-Z used in-vitro fertilization in order to conceive. It’s true that IVF results in a higher likelihood of multiple births: In 2013, the last year for which there is data, 41.1 percent of all IVF deliveries were multiples (though remember, IVF is responsible for just 1.6 percent of all infants born in the U.S.). Compare that to the natural occurrence of twins—just 2 percent of pregnancies—and you can see the reason for the rumor. But recent advancements in reproductive medicine make this explanation less likely today, particularly for a woman of Beyoncé’s wealth.

Until recently, doctors thought that couples would have a higher chance of pregnancy if they implanted more than one embryo. They did this because many embryos, conceived naturally or in the lab, are chromosomally abnormal—the exact percentage increases with age—and will likely miscarry. At the time, they thought implanting more embryos would lead to a higher chance that at least one would survive. Of course, it also meant that there were occasions in which multiple embryos survived. And while a multiple pregnancy carries more risks, for years, doctors didn’t worry about these risks as much as they focused on maximizing the likelihood of pregnancy.

Today that is changing, for two reasons. The biggest is the ongoing push in reproductive medicine towards single-embryo transfers, or putting in just one embryo at a time. Doctors are beginning to weigh the risks of having twins, which can lead to higher rates of pregnancy complications, miscarriage, preterm delivery, low birth weights, and hospitalization, with the benefits of multiple-embryo transfers, and coming out in favor of single-embryo transfer.

This preference has been bolstered by new research that suggests the multiple-embryo transfer strategy wasn’t as effective as many presumed. Studies released in the last few years have found that single-embryo transfers yield the same number of live birth rates as multiple-embryo transfers. Another recent one found that putting in a poor-quality embryo alongside a healthier one can actually make pregnancy less likely. Researchers believe this is because the body puts its energy into helping the weaker one survive instead of focusing on helping the healthier one safely implant.

This new research is solidifying a scientific preference for single-embryo implantation. Many countries have started to think that multiple transfers are not worth it, and in places like Sweden, the United Kingdom, and Japan, multiple-embryo transfers are becoming increasingly rare. The American Society for Reproductive Medicine recommends single-embryo implantation. Still, multiple-embryo transfers are common in American fertility clinics likely because many patients never hear about the alternative options or the potential risks involved. Fertility clinics tend to give patients a fair amount of control in choosing their course of treatment—due largely to the fact that these procedures are both elective and often not covered by insurance—but they don’t always provide them with all the relevant information to make the best decisions for themselves.

The other big shift making it more likely for doctors to recommend a single-embryo transfer is that they are now better able to create and identify healthy embryos, which increases the odds that any embryo placed in the womb will survive and decreases the necessity of implanting more than one. This is happening thanks to better technology in the embryology labs, and the increasingly popular preimplantation genetic screening, or PGS. PGS occurs before implantation, when doctors remove a small number of cells from 5- or 6- day-old embryos and send them to a lab where they are tested for chromosomal abnormalities and genetic diseases.

The frozen embryos are only thawed and transferred after the results come back. Patients who use PGS are twice as likely to do a single-embryo transfer, because they are more confident that the one being put in is likely to survive. And the biggest deterrent to PGS screening, for the patients who know about it, is the price tag. It can cost around $3,000–$5,000, on top of the already five-digit price tag for a basic course of IVF treatment.* If a woman or couple is paying for infertility treatment out-of-pocket, as most Americans do, they might be inclined to skip this extra expensive step.

The rich, on the other hand, have the ability to do all they can upfront to ensure the safest pregnancy and healthiest baby possible. It is also safe to assume that they would have access to the best, and most responsible, doctors and embryologists around. Today, that likely means someone who will recommend maximum screening and implanting just one embryo, which is what most doctors consider the current standard based on the best available science.

There are other reasons besides a multiple-embryo transfer that a 35-year-old woman like Beyoncé would be pregnant with twins. She could have dropped two eggs during ovulation, the odds of which rise with age. The embryo could have split into two shortly after fertilization, another natural, though less likely, means of conceiving twins. It’s also possible that she got pregnant with the help of Clomid, a drug which stimulates the ovaries to drop more than one egg during a monthly cycle to increase the chance of pregnancy (it also increases the chance of multiples by 10 percent ) .

We’ll likely never know because Beyoncé will, wisely, never feel obligated to tell us. But in 2017, the truth is that a wealthy, relatively older woman pregnant with twins is far less likely to have gotten there by way of IVF than she would have in the past. Future projections regarding the wombs of famous women should take this into account.

*Correction, Feb. 7, 2017: This piece originally misstated the cost of a basic course of IVF treatment. (Return.)