The app itself gives you an estimated baby weight range. As long as you measure well, your baby should be in the ranges given. Several sites will also give you a week to week range. You will never be able to tell your child's true weight until you have them, this can be an issue for some women as the bigger the baby, the harder labor is. If your doctor starts to feel concerned about your baby's weight/size then they may suggest a c-section as a larger baby in regular delivery can be extremely stressful.
they have trouble telling no matter what so it's nothing to stress about. The best thing to do is limit the amount of newborn size diapers you get And only have about a weeks worth of newborn clothes. This way there is no investment if baby gets bigger faster
Im 30w and I asked my doc the same thing. They start measuring your stomach every 2 weeks starting at 28 weeks. If you measure bigger than normal then they will send you for an ultrasound to find out weight. Also if you are past due and such depending on your doctor they will give you an ultrasound to see how much the baby weighs. Once you get into your second trimester they will not tell you weight because it is based off certain measurements of the baby they have to look for and it's not necessary.
I was always told how much my baby weighed. If the doc says he/she is healthy than trust him. I just loved being able to hear how much my baby had grown compared to my last vist. The babys weight is just an estimate based off their measurements. I would just ask. Im sure they have the measurements in your file