Kylie Mantz, 38 weeks pregnant with her first child, ran a mile at full effort on the BYU track in Provo, Utah, last week, clocking 5:26.2 while a rotating group of women shared the pacing and a bib reading “Kylie’s Preggo Mile” was pinned to her top.
The 24-year-old, who is married to American marathon record holder Conner Mantz, announced the run on Instagram. Her bib number was 38, one for each week of the pregnancy. Provo sits at roughly 4,600 feet, and by her own conversion the time is worth about 5:21 at sea level.
She went out in 77.6 for the opening 400m, then settled into laps of 82.4, 82.9 and 83.3 seconds to the finish, wearing Nike’s Alphafly 3 racing shoes. Habtamu Cheney, an American marathoner who ran 2:15:43 to place 22nd at the 2024 U.S. Olympic Marathon Trials, filmed the effort.
“I took every lap as a win,” Mantz said afterward.
“We started this pregnancy with a marathon, we’re ending it with a mile,” she wrote in the accompanying post.
The marathon in question was her debut. Mantz won the Two Cities Marathon in Fresno, California, on Nov. 2 in 2:43:49, with Conner pacing her through all 26.2 miles, only to learn a few weeks later that she had raced while pregnant. The couple announced the pregnancy on Valentine’s Day. Her win came three weeks after Conner ran 2:04:43 in Chicago to break Khalid Khannouchi’s 23-year-old American marathon record; he also holds the American half-marathon record of 59:17, set in Houston in 2025.
A latecomer to the sport, Kylie Mantz quit running as a teenager in Clovis and took it up again after her 2022 marriage to Conner, eventually walking on to BYU’s cross-country and track teams. By April 2025 she had a 34:57 10,000m to her name from the Stanford Invitational. Before the pregnancy she was open about chasing the 2:37:00 Olympic Trials qualifying standard, writing on Strava after Fresno that “I think if I can figure out fueling, the OTQ is pretty obtainable.”
No governing body ratifies miles run in late pregnancy, but the event has a lineage, and much of it runs through BYU. Makenna Myler, also a former BYU runner, ran 5:25 at nine months pregnant in October 2020 after her husband bet her $100 she could not break eight minutes, a video that drew millions of views. Sixteen months later, pregnant with her second child, she lowered the mark to 5:17. Myler went on to finish seventh at the 2024 U.S. Olympic Marathon Trials in a personal-best 2:26:14, 10 months after her second child was born. Mantz’s raw time sits a second outside Myler’s first run; her converted one splits the pair. The trend has reached the roads too: Calli Hauger-Thackery ran 2:43:58 at the Boston Marathon while 22 weeks pregnant.
Guidance from the American College of Obstetricians and Gynecologists supports aerobic exercise, running included, through uncomplicated pregnancies; Myler ran her 2020 mile after clearance from two doctors.
The comments under the post filled with congratulations from some of the biggest names in American women’s distance running: Keira D’Amato, the former American marathon record holder who now trains in Utah in Ed Eyestone’s group alongside Conner; Jess McClain, the top American at the Boston Marathon in April; and Sara Hall.
As for the baby, Mantz is not planning on a long wait. “We’re hoping hours now,” she said after the mile. “That today’s the day.”
RunClub
Get more running stories — join RunClub
Daily running news, a community of 300,000+ runners, free training plans for every distance, and a daily running game. Free to join — no card.
Already a member? Log in →
Start the conversation