The diagnosis of postterm pregnancy may be erroneous if the gestational age was not determined correctly. Nowadays an erroneous diagnosis is made very seldom due to the use of sonofetometry in the first and second trimesters.
Postterm pregnancy is marked by an exponential increase of complications in the mother, fetus and newborn as the gestational age advances.
The major cause of the rise of maternal complications is the cesarean section as it increases the risk of postpartum infection, hypotonic hemorrhage, septic and embolic complications. The rate of cesarean section after 42 weeks is 2 times higher than at 38-40 weeks gestation. Maternal complications also include injury due to giving a vaginal birth to a macrosomic fetus (rupture of the cervix, vaginal walls, third-degree perineal rupture). These complications can result in urine retention, fistula, hemorrhage, infection, postpartum ulcer. Postterm infants show greater morbidity and mortality compared with term infants.
Neonatal complications encompass chronic hypoxia, birth trauma (due to mac-rosomia), meconium aspiration.
23.1. DEFINITION
A pregnancy is described as postterm if it extends to 42 and more weeks beyond the gestational (menstrual, obstetric) age. The birth following this pregnancy is described as postterm.
An infant born of such pregnancy quite often (but not always!) shows signs of postmaturity. Postterm pregnancy can end in a birth of neonate without signs of postmaturity; on the other hand, a term birth producing a postmature infant is a possibility, too.
23.2. HISTORICAL ASPECT
The scientific approach to postterm pregnancy was first defined by 1902 when Ballantyne, and then Runge (1948) described the signs of postmaturity in a neonate. In 1954 Clifford described a syndrome encountered at a rate of 10% in true post-term pregnancy.