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Premature infant
Last reviewed: 08.07.2025
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A post-term baby is a baby born after 42 weeks of gestation.
The reasons for a baby being overdue are usually unknown. Very rarely, it may be due to abnormalities that affect the fetal pituitary-adrenal system (such as anencephaly or adrenal agenesis).
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What happens during a post-term pregnancy?
In postmaturity, the placenta involution occurs, and multiple infarcts and degeneration of the villi lead to the development of placental insufficiency syndrome. In this syndrome, the fetus does not receive sufficient nutrients from the mother, which leads to soft tissue hypotrophy. During labor, postmature infants are susceptible to asphyxia; meconium aspiration syndrome, which can be unusually severe due to the reduced volume of amniotic fluid with postmaturity and, consequently, aspiration of less dilute meconium; neonatal hypoglycemia due to insufficient glycogen stores at birth. Since the anaerobic pathway of glucose metabolism quickly uses up the remaining glycogen stores, hypoglycemia is exacerbated if perinatal asphyxia occurs.
Symptoms of a Post-Term Baby
A post-term baby is active and appears mature, but has a reduced layer of subcutaneous fat. The skin may hang loosely on the limbs, and dryness and flaking are common. Fingernails and toenails are long. The nails and umbilical cord may be stained with meconium passed in utero. Diagnosis is based on clinical examination and the estimated date of birth.
What is the prognosis for a post-term baby?
The post-term infant has a variable prognosis, which depends on prompt treatment and associated complications. Infants with meconium aspiration may develop chronic respiratory failure and secondary pulmonary hypertension if untreated; surfactant replacement therapy is often helpful.