The Britain's Got Talent judge, who is also celebrating her 35th birthday today, took to Twitter to announce the joyful news, calling her daughter "the best present in the world".
"My baby girl Azura Sienna was born last week!!! I'm elated and over the moon :) x x x x x x x x x x x x x x x x x x x x x," wrote Alesha.
The pop singer then explained what may have seemed like a sudden arrival to her fans, posting, "It seems quick because I was hiding it for so long!!! I was in my 6 month of pregnancy at the Britain's Got Talent final! :) xxx."
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The newborn is the first child for Alesha and her dancer boyfriend Azuka Ononye, who she met in 2006 when he worked as part of her backing team.
Friends say that Nigerian-born Azuka helped the songstress to get over her heartache, after Alesha found out that her then-husband, MC Harvey, had cheated on her. Alesha divorced the rapper that same year.
A spokesperson for the former X Factor star confirmed Alesha's pregnancy in June, after rumours emerged that she was expecting when she made two toasts "drinking water instead of wine".