the bill defines gestational age as "calculated from the first day of the last menstrual period of the pregnant woman," which would move the beginning of a pregnancy up two weeks prior to conception.
Elizabeth Nash, states issues manager for Guttmacher Institute, a reproductive health research organization in Washington, said the definition corresponds with how doctors typically determine gestational age. She said since the exact date of conception cannot be pinpointed, doctors use the day of the woman's last menstrual period to gauge the duration of a pregnancy.
