Being pregnant doesn’t mean you have to stop kicking as*

Serena Williams just puts me to shame. No, not my pathetic serve. With one powerful wallop, she illustrated just how much I underestimate my body’s abilities. Williams recently revealed that she is having a baby in the fall, which means she won the 2017 Australian Open while two months pregnant. The 35-year-old played seven matches over two weeks, winning each one in straight sets and clinching the final in 31°C heat.

Now I’ve been pregnant twice, and good luck to you if you ever told me—during either nine-month saga—not to do something. I biked 22 kilometres along the Niagara River. I painted my hallway and installed a laminate floor, with my giant belly resting on my knees as I clicked the boards together. But I still bagged out of a mini-triathlon in the early weeks of my second pregnancy. I fell for traditional assumptions instead of checking the facts: Despite mounting evidence that activity—even some extreme stuff—is both safe and beneficial during pregnancy, we’re still utterly googly-eyed about elite performance in women who are expecting.

The triathlon plan—which I hatched with a group of girlfriends who also had toddlers and busy careers—was meant to be a test of what women could accomplish. The mini-triathlon, which involves distances of less than half of a regular triathlon, was set for mid-summer, so I added short runs to my usual routine of swimming laps and biking for transportation. On my holiday, I did two practice triathlons, complete with power swims in the lake. My legs burned and I napped a lot, but I felt ready.

Back home, on my bike again, I caught myself gagging. Sure enough, I was pregnant with child number two. I immediately pulled out of the mini-triathlon to a chorus of “Oh, of course, congrats,” got some anti-nausea meds and had a good nap while my friends hit the course.

“We still have very conservative thoughts about pregnancy and what we believe women can and can’t do,” says Elin Raymond, an OB/GYN at Toronto’s Michael Garron Hospital. (Hence, we follow the time-worn tradition of snatching heavy boxes from the arms of women with baby bumps.) “I think it’s fear because early pregnancy loss is so common, and people like to find a reason for that,” says Raymond. We want to do everything we can to prevent it, so we treat ourselves as though we’re made of glass.

Out of fear, we default to the view that women’s plumbing can’t withstand jolts and bumps. This ancient theory is elegantly explained by a 19th-century German doctor who wrote that “violent movements of the body can cause a shift in the position and a loosening of the uterus, as well as prolapse and bleeding.” When I was in public school in the early 1980s, girls were forbidden from doing triple jump for unspoken reasons we assumed were gynaecological. (What even is triple jump?)

Competitive distance running events bought into the same claptrap and only allowed women starting in the 1970s and ’80s. Kathrine Switzer ran the Boston Marathon in 1967 by registering with her initials instead of her first name. She got tackled by an official for doing so but eventually finished. She reprised her run in 2017 at the age of 70, proving twice over that women—and their uteruses—defy our dated assumptions.

But such assumptions still pepper medical recommendations. Women have been under-represented in scientific research, and pregnant women—who require extra-careful protocols—even more so. In the 18th century, when fitness wasn’t a priority, doctors in England told pregnant women to avoid dancing. In 1949, the U.S. Children’s Bureau said pregnant women could do housework, garden and walk up to a mile but should avoid all sports. It wasn’t until the 1990s that there was enough research done on intense exercise during pregnancy to reliably conclude that it was safe.

Today’s rules give the green light to a whole lot more activity. The 2015 guidelines from the American Congress of Obstetricians and Gynecologists include a list of exercises that women can safely do during pregnancy, such as modified yoga and Pilates, racquet sports, running and jogging. They warn against hot yoga, skydiving, contact sports and anything that poses a risk of falling, such as skiing. Canadian guidelines, published in 2003, include a handy chart that suggests heart rate target zones for pregnant woman. In your 30s? Keep it between 130 and 145 beats per minute.

But there has been “an explosion in the literature in the past 15 years” in this previously understudied area, says Margie Davenport, an assistant professor in the faculty of physical education and recreation at the University of Alberta. This includes emerging research on elite athletes. She is heading an update of the new guidelines for the Society of Obstetricians and Gynaecologists of Canada by doing a major systematic review of the medical literature. They will likely come out in 2018.

Hopefully, this evidence-based document will help quash old assumptions for good. The next on-the-cusp-of-triathloning pregnant woman will get the reassurance she needs to go for it or clear reasons why she shouldn’t. Accurate, bias-free information about our bodies also fends off guilt when something goes wrong with an unborn baby. We can’t all be Serena and win a major championship in a finely tuned body with a team of professionals behind us. But when we compete, play and move with the best facts possible to fuel us, everybody wins.

Read more: How to exercise when you’re pregnant Exercise during pregnancy is safe, so why all the fuss? 4 myths about sex after baby