But early ultrasound due dates have a margin of error of roughly 1.2 weeks, so doctors will usually keep the original due date (the one generated by the date of your last menstrual period) if the ultrasound due date is within that margin of error.If your first ultrasound gives you a due date that is more than 1.2 weeks away from what was expected, there is a good chance that everything is still fine.A small percentage of cases can be linked to genetic disorders, but a recent major study of twins supports earlier studies in concluding that environmental exposures during or shortly after gestation cause a majority of autism cases. During brain development, cells form and migrate to the cerebral cortex.
There are different levels of severity and combinations of symptoms in autism.
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).
Your doctor might want to repeat the ultrasound to make sure that your pregnancy is developing as it should.
An image of your fetus will appear on an accompanying computer screen and while looking at this image, the technician will take some standard measurements from different angles and listen for a heartbeat.
Don't worry: This type of exam is painless and risk-free, and seeing your baby for the first time will likely be an enjoyable experience.