All About Baby
You may not have conceived yet, but your body is still preparing for a potential pregnancy. Every time you ovulate, the lining of the uterus thickens. If no fertilized egg is implanted in the uterus, the lining sheds (menstruation). When you do conceive, your healthcare provider will ask for the date of your last menstrual period (LMP) to calculate your due date.
Physicians factor in the two weeks before conception into your delivery date. That means you get a two-week bonus toward your pregnancy—so if you're sure you know when you're baby was conceived and your healthcare provider puts the pregnancy start date a couple weeks before, not to worry, you're both right!