Charting Your Pregnancy Since most women don't know the exact
date of conception, the standard method for charting a pregnancy
is by counting forward from the first day of your last menstrual
period (LMP). This method assumes that you ovulate 14 days after
your period begins (and that you'll remember the day your period
started!). These results give health care providers -- and you
-- a ballpark estimate for your baby's due date. Your First
Ultrasound For more accurate pregnancy dating, health care
providers can request an ultrasound. Careful measurements taken
in the first trimester are even more accurate at predicting an
embryo's age than ultrasounds performed later in pregnancy.
Using these measurements, a sonographer can pinpoint a baby's
age to within a few days. As the baby-to-be grows larger, these
measurements are less reliable at predicting a baby's age
because of varying growth rates. Just like kids come in
different shapes and sizes, in utero babies can grow at
different rates, too. Along with figu