Beyoncé Knowles-Carter announced on Instagram Wednesday that she's pregnant with twins - the news came on the heels of mega-producer Pharrell Williams' announcement Tuesday that he's now the proud father of triplets.

The internet immediately erupted with speculation about whether Knowles used fertility treatments to help her conceive this second time around, since in vitro fertility (IVF) treatments in recent years may have played a part in increasing a woman's likelihood of getting pregnant with multiples.

Salacious rumors about the pop icon's reproductive health have been circulating since she gave birth to her daughter Blue Ivy in 2012. But regardless of the singer's private and personal choices, the science of having twins is remarkably complex.  

About one in every 75 women will naturally become pregnant with twins, according to Dr. Kristin Bendikson of the University of Southern California Fertility Clinic. Even with the help of technology and medical treatments, twins account for just 3 percent of American births. However, the rate is slightly higher, 4 percent, among black women, according to a 2014 report by the Centers for Disease Control and Prevention.

A woman's age and genetics both influence whether she is likely to get pregnant with twins.

"As a woman gets older, her chances of getting pregnant with twins goes up by 25 or 30 percent," Bendikson told ATTN:. "As a woman ages, her hormones change. And the hormone that is responsible for making an egg grow increases... you ovulate one egg a month, unless your hormones change and then you can ovulate two eggs. The ovary is responding to what the brain is telling it to do." The chemical is called a follicle-stimulating hormone, and it's found in both male and female brains. 

For those with ovaries, the fluke that allows two eggs to slip through instead of just one is what leads to fraternal twins. Another way someone can become pregnant with multiple children at once is for an egg to split, which creates identical twins or triplets. There are also genetic factors that increase a woman's propensity for naturally conceiving twins.

"There is a genetic link and, again, it's more likely with fraternal twins as opposed to identical twins," Bendikson said. "If you have a sister who has twins, you are twice as likely to have twins... but that type of research is still in its infancy." 

The "Lemonade" singer hasn't released any statements about whether her twins are fraternal or identical, or whether there are other sets of twins in her family tree.

Women pregnant with twins have higher chances of complications during pregnancy and during the birth - in addition to having a higher risk of experiencing severe postpartum depression. The babies themselves are more likely to be born prematurely, as well. Bendikson said twins are born an average of three weeks earlier than children who have the womb all to themselves. However, Bey is likely well equipped with the support she needs to face these challenges head on.