That’s a really good question! When my wife was expecting with one of our children and went for a check-up in the hospital, she recalls that some of the secular Israeli doctors wished her “mazel tov”, which always felt wrong to her as well. Mazel tov is a term which is more suitable for congratulating a mother after giving birth, and saying it to a pregnant woman is jumping the gun and might make her feel uncomfortable.
Therefore, the customary term for wishing her an easy pregnancy and healthy birth is “besha’ah tova”. This literally means “in good time”, although I admit that it doesn’t seem to translate all that well.
One reason I’ve heard for this phrase of well-wishing is that it means that you hope she will give birth at the proper time, and not prematurely. In addition, “in a good time” conveys the message that you hope that she will be feeling healthy and in good spirits whenever it is that she gives birth. And, hopefully, that she will feel well throughout her pregnancy and give birth to a completely healthy child.
Of course, besides this brief Hebrew greeting, you can put into your own words whatever good wishes and hopes you have for her and her baby, and express yourself to her in any way you choose that everything should go well
