Kylie Mantz has perfectly bookended her first pregnancy. Just two weeks before her due date, the 24-year-old former BYU walk-on athlete stepped onto the track in Provo, Utah, and laid down an astonishing 5:26.2 mile at full effort.
The feat brings a full-circle conclusion to a pregnancy that quite literally began at maximum running velocity. Back on November 2, Mantz made her competitive marathon debut at the Two Cities Marathon in Fresno, California. Guided through all 26.2 miles by her husband—American marathon record holder Conner Mantz—she won the women’s field outright in an impressive 2:43:49. It wasn’t until a few weeks later that the couple discovered she had run the entire marathon while newly pregnant.
“We started this pregnancy with a marathon, we’re ending it with a mile,” Mantz shared on Instagram following her track effort.
The Breakdown of the “Preggo Mile”
Running at an altitude of roughly 4,600 feet in Provo, Mantz donned a custom racing bib reading “Kylie’s Preggo Mile” alongside the number 38—marking each week of her pregnancy. Laced up in Nike Alphafly 3 racing shoes, her pacing was a masterclass in controlled aggression.
A rotating group of training partners shared pacing duties to keep her on target. Fellow American marathoner Habtamu Cheney filmed the historic run, tracking her through these exact splits:
1.Opening Lap:0 to 400m.
Mantz went out hard, setting an aggressive tone with an opening lap of 77.6 seconds.
2.Holding Pace:400m to 800m.
She settled beautifully into her rhythm, locking in a steady second lap of 82.4 seconds.
3.The Hard Yards:800m to 1200m.
Maintaining her aerobic engine through the third lap, she crossed the 1200m mark with a 82.9-second split.
4.The Finish Line:1200m to 1600m.
Digging deep through the final turn, she closed the final 400m in 83.3 seconds to stop the clock at 5:26.2.
Due to the thin air in Provo, standard altitude conversions value her raw 5:26.2 time at approximately a 5:21 to 5:22 mile at sea level. “I took every lap as a win,” Mantz said after stepping off the track.
A Tradition Born in Utah
While track and field governing bodies do not officially ratify records for late-pregnancy time trials, Mantz’s run places her in elite company. The phenomenon has a strong history tied to BYU alumni. In October 2020, former BYU runner Makenna Myler went viral when she ran a 5:25 mile at nine months pregnant, later lowering that mark to an unbelievable 5:17 during her second pregnancy. Myler went on to place seventh at the 2024 U.S. Olympic Marathon Trials less than a year after giving birth.
Medical guidance from the American College of Obstetricians and Gynecologists (ACOG) firmly supports continuous aerobic exercise, including running, throughout uncomplicated pregnancies. For an elite athlete like Mantz, whose body is deeply adapted to high training volumes, the baseline is entirely different than for a casual jogger.
Looking to the Future
Mantz, who put competitive running on hold as a teenager before picking it back up after marrying Conner in 2022, has shown immense upside. Before her pregnancy, she ran a 34:57.36 10,000m at the Stanford Invitational and openly aimed for the 2:37:00 Olympic Trials Marathon qualifying standard.
Her performance drew swift praise from the vanguard of American distance running, with training partner Keira D’Amato, Jess McClain, and Sara Hall flooding her social media with congratulations.
With the track milestone officially in the books, Mantz turned her attention to the ultimate endurance event. When asked on the track when she expected the baby to arrive, she smiled. “We’re hoping hours now. That today’s the day.”
