It is not uncommon for there to be a discrepancy between the estimated gestational age based on your last menstrual period (LMP) and the measurement obtained during an ultrasound. The LMP method assumes that ovulation and conception occur on day 14 of your cycle, which may not always be accurate. Additionally, variations in individual cycles can affect the accuracy of this calculation. Ultrasounds are considered more reliable for determining gestational age as they measure the size of the fetus directly. Factors such as irregular periods, late ovulation, or implantation bleeding can contribute to differences between LMP and ultrasound measurements. If you have concerns about your pregnancy or if there is a significant discrepancy between your LMP and ultrasound dates, it is best to consult with your healthcare provider for further evaluation and guidance.