As one of my students pointed out to me recently, there are many ways to express the idea of being pregnant in English!
For example, rather than saying that someone “is pregnant,” you can also say that the person “is expecting.” This may seem vague (expecting what?), but it will be understood to mean that the person is pregnant, even without an object. For example, someone gossiping at work might ask “Did you hear that Vivian is expecting?”
An older way of saying this (which you might hear in movies or read books) is to say that someone “is with child.” This phrase sounds rather old-fashioned today, so I don’t recommend using it in conversation.
More modern and useful phrases include “to have a baby on the way” or the rather informal “to have a bun in the oven” (some people may consider this impolite).
To talk about when a baby is expected to “be born,” you can use the phrase “is due,” as in “When is the baby due?” A baby can “be due,” but a mother can also “be due,” so it’s also OK to ask a question like “When is your wife due?” This is a short form of asking “When is the baby due to be born?” or “When is the mother due to give birth?” (“due” means “expected”).
Another way to say that a baby “is born” is to say that the child “comes into the/this world,” as in “Our daughter came into the world on a snowy December night.” Perhaps it sounds more poetic than simply saying “Our baby was born on a snowy December night.”
Finally, another way to say that a mother “gives birth (to a baby)” is to simply use the phrase “to have a baby.” You can say either “She gave birth to a pair of beautiful baby girls” or “She had a pair of beautiful baby girls.”