Australian fans will first see the feisty matriarch next week, while UK viewers will have to wait until November.
Francesca, portrayed by actress Carmelina di Guglielmo, will be shocked when she discovers that her daughter has become pregnant out of wedlock.
She will initially presume that the baby's father Lucas is Vanessa's landlord, reports TV Week.
Vanessa believes that she has kept her baby bump from sight until Francesca overhears Chris discussing her daughter's pregnancy.
Alin Sumarwata, who plays Vanessa, teased: "Vanessa planned to turn up on her mum's doorstep after the baby was born.
"So that all the shame, blame and judgement about getting pregnant before marriage would just dissolve when the family saw the baby.
"This way she has a lot of explaining to do."