Are the protein supplement powders beneficial during pregnancy to the mother and unborn baby?

Probably not. Typically a healthy diet is sufficient and protein powders aren't needed.
Unnecessary/ okay. Your typical balanced nutrition augmented by prenatal vitamins is enough to build a healthy baby. The babies system draws from the proteins and other nutrients circulating in your blood.If you are not eating right, baby will take proteins from your muscle mass & calcium from your bones,etc. Supplemental proteins might make it to baby, but when not needed will be converted over time to carbs & fat.