Postmaturity also known as dysmaturity is used to describe babies born after 42 weeks. The normal length of pregnancy is 37 to 41 weeks. Early term is 37 to 38 weeks and 6 days. Full term is 39 weeks to 40 weeks and 6 days. Late term is 41 weeks to 41 weeks and 6 days. Very few babies are born at 42 weeks or later. Other terms used to describe these births include post-term, postmaturity, prolonged pregnancy and post-date pregnancy.
Causes of postmaturity in the newborn
It is not known why some pregnancies last longer than others. Sometimes the pregnancy may be off because the mother is not sure of her last menstrual period. Getting the date wrong will mean the baby will be born earlier or later than expected. The most accurate way to tell the date of a pregnancy is through an ultrasound in the first trimester unless the date of conception is specifically known such as an in vitro fertilization.