It's common to tell your mum on your own, for the sake of female solidarity, the whole generation-to-generation thing, and because at times like this you also need to be made a fuss of, like the little girl you once were. Going back in time and reflecting on your own childhood will also give you strength and guidance for motherhood.
When you tell your mum you're pregnant you can bet on lots of reassurance and good advice from one who knows! In many civilisaitons (particularly African ones) there's a lot of emphasis on female support and solidarity through pregnancy and motherhood, and it's very true. Many young mums want their own mum to be present at the birth.
Telling your dad
Telling your dad you're pregant isn't as easy and women often struggle to find the right words. Telling your dad you're pregnant is like revealing your sexuality to him, which isn't always easy! If you're struggling, why not make telling him a family occasion with your mum and your partner both there too?