When is the first week of pregnancy is it from the last period date or is it ovuluation day?

Pregnancy can be calculated two ways. The most common way is to start counting from the first day (when you started bleeding) of your last period. Most OBGYN offices use this and will give you your EDD(estimated due date) from this.

The less common way is to start counting from the day you ovulated. So few women know the exact date they ovulate that this is not a widely used method. This is usually reserved for women how have undergone medical treatments to become pregnant.