If your cycle lengths vary a lot, your results might not be accurate. All rights reserved. Expert Jan Steward, who is director of Ultrasound Direct and Babybond, agrees that early scans carry a much greater risk of inaccuracy. The process by which your baby becomes a boy or a girl, according to what's written in his or her genetic code, is awe-inspiring. Ultrasonography dating in the second trimester typically is based on regression formulas that incorporate variables such as. The accuracy of determining the due date using LMP depends on regular cycles. Clinical Considerations in the Second Trimester Using a single ultrasound examination in the second trimester to assist in determining the gestational age enables simultaneous fetal anatomic evaluation.
Your week scan will be far more accurate.
How Precise is an Ultrasound for Determining the Exact Age of a Baby?
You may have simply conceived earlier or later than you thought you did which can happen if your cycle is at all irregular or if you remembered your last menstrual period date incorrectly. Watch it all unfold. The ultrasound combined with the hormone levels and the date of the woman's last period give an accurate estimation, especially if all of the methods give a similar time frame. More in Your Baby. Early ultrasound has a negligible margin of error while determining the due date. Your most fertile time to conceive is within the day or two after a positive result.