Naomi Osaka graces InStyle cover, reveals details of complicated pregnancy, labor and delivery

Naomi Osaka is opening up about the nine months of her pregnancy—and the complications she suffered ahead and during her daughter Shai's birth in July—in a new, exclusive interview with InStyle magazine.

Gracing the cover of the magazine's December issue—the celebration issue, it says—Osaka revealed to InStyle writer Erika Hayasaki that she tested positive for Group B streptococcus during her pregnancy, a bacterial infection which can cause premature birth, sepsis, menegitis, and, in rare cases, stillbirth in newborn babies.

Later, a 12-hour labor resulted in only one centimeter of dialation, and Osaka reacted negatively to being given Pitocin, a drug which is meant to stimulate the process.

"I do remember feeling in that moment, 'This is the worst pain of my life,'” Osaka said "'And I know that if I get through this, then everything else will feel very easy.'"

Previously, in an interview with Japanese news outlet NHK last week, Osaka touched the surface of some of what she experienced, including morning sickness and weight gain. To InStyle, she revealed she consulted with 11-time Olympic medalist Allyson Felix, who experienced preeclampsia during her pregnancy with daughter Camryn, about her fears, and candidly shared she wrote a will.

“I don't think people know how hard pregnancy is; no one really talks about it as much,” she said. “Going into it, you kind of think: 'Oh, it's this beautiful journey.' But it's kind of rough.”

The feature also sees Osaka discuss the early months of motherhood, what it's been like to parent Shai with her boyfriend, rapper Cordae, and how motherhood has changed her approach to her tennis and entrepreneurial careers.