Curve spine

hi momsh. need ur opinions po. im in my 37th week of pregnancy. with my last ultrasound.. na noticed n doc na parang nag cu curve spine n baby.. so sabi nya baka lng din sa position nya. And nagkaroon ng issue regarding with my amniotic fluid..its low normal (7.8) so the doctor advised me to drink plenty of water about 3 liters a day. I did. and with my next ultrasound just this day. naging okay na ang water so no need for me to worry. And when I ask regarding sa spine if okay na.. she said shes not sure so she ask me to take a doppler ultrasound test. does anyone of you here have the same situation with mine? Nag dadalwang isip kc ako if i really need to have the test pa since feeling ko nag cu curve lng naman dahil sa position nya siguro and also knowing na mahal yung test.. ilang ulit na din kasi akong nag ultrasound so sobrang gastos na talaga. im really not sure. can anyone help me pls thanks