How accurate are early ultrasounds in dating pregnancy
It's helpful to know about twins early on, as it's easier to see whether or not they share a placenta.
Finding out about having twins early in pregnancy also gives you more time to prepare for the birth and for your doctor or midwife to plan your care.
However, you can use various factors and knowledge about reproduction to help narrow down the date to within one to five days if your cycles are regular.
The accuracy of estimating your date of conception depends on several factors about your menstrual cycle and ovulation, as well as facts about the egg and the sperm.
The LMP is used because most women know when their last period was, but may not know when they actually conceived.