Inaccurate dating of the pregnancy
From that day, 40-weeks of pregnancy is officially counted, and your doc or midwife busts out the red pen and marks your due date on the calendar. However, many pregnancies are confirmed by a Doppler heartbeat monitor, not an ultrasound.
If this was you, that could be why your doctor’s original timing was off.
For transvaginal ultrasound you can have an empty bladder Dating scans are usually recommended if there is doubt about the validity of the last menstrual period.
For example if you a tiny sac can be seen in the uterus, but the baby and its heart beat may not be detected yet.
5 ½ weeks gestation means 5 ½ weeks from the first day of the last menstrual period, which is usually about 3 ½ weeks from the date of conception (confusing, isn’t it!
If the difference between the two is less than a week apart, she’ll generally go with the date calculated from your last period.the baby and its heart beat can be detected relatively easily with trans-abdominal and trans-vaginal examination.This is presuming that the pregnancy is actually at this stage of development.There are basically seven different ultrasound exams, but the principle process is the same.The different types of procedures include: Transvaginal Scans – Specially designed probe transducers are used inside the vagina to generate sonogram images.