small fetus

Mga mommies may naka-experience po ba sa inyo na mas maliit ang baby kaysa sa tunay nyang gestational age? At meron din ako placenta previa. I'm 37 weeks and so worried. My OB told me that I have constitutional small fetus. His 37 weeks but measures only 32 weeks. I had Doppler ultrasound results saying that his blood flow is normal. Please can share with me your experience.