It isn’t meant as a statement of the usual of care. It does not clarify all the proper therapies or methods of care. Cartilage for the limbs, arms, and feet begin to form but won’t harden into bones for a few weeks. But when the date of the LMP is uncertain, an ultrasound exammay be carried out in the course of the first trimester to estimate the due date. If you have had in vitro fertilization , the EDD is set by the age of the embryo and the date that the embryo is transferred to the uterus. Second and third youngsters arrive 5 to six days early.