[4] Mboma also won the event at the 2021 World Under-20 Championships and Diamond League final, improving her record mark to 21.78 seconds.

[5] In 2021, the 18-year-old set an unratified world under-20 and African senior record of 48.54 s in the 400 metres, which made her the seventh-fastest woman of all time at the event.

[6] Prior to the Tokyo Games, World Athletics had announced that Mboma and fellow Namibian sprinter Beatrice Masilingi would not be allowed to compete under the female classification in events between 400 metres and one mile due to its regulations on testosterone levels for athletes with XY disorders of sex development.

Her father abandoned her as a baby, and her mother, Patricia, died in 2016 while giving birth, leaving Christine to take care of her younger siblings.

[12] In May 2019, 16-year-old[A] Mboma won the 800 and 1500 metres events at the school's Cossasa Games in Manzini, Eswatini (no WA recognition, its database shows 2m 18.68s in the 800 m on 18 May in Windhoek, Namibia).

[22][23][6] She was withdrawn from the 400 metres race at the delayed 2020 Tokyo Olympics; the Namibian athletics federation announced that she would compete in the 200 m event for which she also qualified.

[29] In July 2021, the Namibian National Olympic Committee announced that Mboma and fellow Namibian sprinter Beatrice Masilingi would not be allowed to compete in the 400 m competition at the Tokyo Olympics,[7][30] due to World Athletics rules requiring that athletes with certain DSDs participating in women's running events from 400 metres to one mile cannot have blood testosterone levels above 5 nmol/L.

[31][9] Mboma and Masilingi had undergone a medical assessment at a training camp in Italy in early 2021, at which they tested positive for elevated testosterone levels due to a naturally occurring genetic condition.