showed the singer looking bronzed and beautiful, baring her growing baby bump.
Celebrity trainer Alex also shared the video on his own Instagram page and said: "Fine Family just got bigger, heart just got Fuller, light just got brighter.
"So blessed to be a dad to the best little girl and husband to the best wife."
When did Cassie and Alex Fine start dating?
Cassie and Alex confirmed their relationship in December 2018.
It followed Cassie's 11-year relationship with rapper and music mogul P Diddy.
Cassie, 34, and Alex, 27, married in September last year in an intimate ceremony.
Alex's proposal to Cassie took place on a rustic ranch, with the personal trainer riding a horse into the moment, eight months after she split from her former flame.
"Congratulations @Cassie and Alex," Diddy, 49, wrote on Instagram after the announcement was made.
"I wish you all nothing but love and happiness. God bless," he continued.
Do the couple have other children?
Cassie and Alex share one-year-old daughter Frankie together, who they welcomed on December 6, 2019.
Their eldest daughter played a starring role in the announcement of their newest addition, as Cassie also posted a video of Frankie smiling away as she listened to the heartbeat of her baby brother or sister through a sonogram machine.
The touching footage was captioned with the words: "Coming soon…"