What's the best way to know baby's birth day?

Hello, I have 37 weeks of gestation, I had my first ultrasound (transvaginal) in pregnancy when I was 6 weeks old, the ultrasound date was correct with the last menstrual period, the second was 21 weeks and the third was 33 weeks and the dates always hit. However, I changed my doctor in my last visit (09.10) to Dr. said that because of my uterine height, she thought I had less getacional time (even with the previous ultrasound in hand) or that my amniotic fluid might be low and requested another obstetrical ultrasonography. Would you like to know what is more reliable in my case, to keep the correct DPP, the first ultrasonography, or the measurement of uterine height?
Expert answer:

The first ultrasound is certainly often more reliable than the uterine height. An ultrasound performed in the first trimester of gestation is the most reliable way to know when Baby is born.