She ended the tweet with an Arabic expression of relief meaning 'praise be to God.'
The Rhythm Nation singer married Wissam Al Mana, a Qatari business magnate back in 2012.
Jackson's ability to keep her pregnancy secret until the second trimester emphasised how skilled the singer is at deceiving the media.
After denying months of rumours in 2013 the couple were already married, Jackson finally came clean and told Entertainment Tonight they "were married in a quiet, private and beautiful ceremony" and their "wedding gifts to one another were contributions to our respective children's charities."
Al Mana and Janet started dating shortly after the singer split from long-time boyfriend Jermaine Dupri in 2009,Wissam is Jackson's third husband.
It's believed the baby is due any day now but considering Jackson's secret keeping ability, she might already be a mother.