The grandson of former president Nelson Mandela posted a picture yesterday of two positive home pregnancy tests, showing two bright pink lines.
The image was captioned "ALHAMDULILLAH", which is a saying used by Muslims to express praise to God.
Messages of congratulations soon started to flood Mandela's timeline.
One Instagram user said it wasn't the most appropriate way of breaking the news.
"This is NOT how you break our news though. Kanti you are how??? A cute baby bootie or a baby dummy so much cuter, not a pee stick," media personality Bridget Masinga said.
Mandela responded: "Just something to get the day started Queen @bridgetmasinga I've got something coming soon soon."
This was followed yesterday afternoon by a statement, issued with their traditional Mvezo titles - Nkosi Zwelivelile and Nkosikazi Nosekeni Rabia Mandela.
"We are excited beyond words today to be celebrating not only our first wedding anniversary but also the fact that we are expecting our first bundle of joy (in transit)," they said, using emoticons to describe their love.
"Mvezo Komkhulu will once again experience the pitter-patter of a young Mandela's feet.
Today marks a year since Mandela and Rabia Clarke tied the knot in a traditional Muslim Nikah ceremony. A month later Clarke was officially welcomed into the Mandela family and given the traditional name of Nkosikazi Nosekeni Rabia Mandela.
This was the Mveso chief's fourth marriage.
At the time of their wedding, Mandela said: "Although Rabia and I were raised in different cultural and religious traditions, our coming together reflects what we have in common: We are South Africans."
He is still legally married to his first wife, Tando Mabunu-Mandela, although they are estranged and embroiled in bitter court battles. Mandela's second and third marriages were annulled.
- Additional reporting TMG Digital
Just R20 for the first month. Support independent journalism by subscribing to our digital news package. 
