| disease | Premature Baby |
| alias | Overripe, Postterm Infant |
An infant born at or beyond 42 completed weeks of gestation (≥294 days) is called a postterm infant (also known as postmaturity). If the placental function is normal and intrauterine growth and development are good, with a birth weight ≥4000g, the infant is called a macrosomic baby. If the placenta is significantly aged and its function declines, leading to fetal nutritional disorders and stagnation of growth and development, it is called placental dysfunction syndrome.
bubble_chart Etiology
The exact cause remains unclear, but it is often associated with the following factors: ① excessive progesterone and insufficient estrogen in late pregnancy; ② frequent bed rest and insufficient physical activity; ③ abnormal fetal position and fetal malformations; ④ good nutritional status and excessive vitamin E; ⑤ genetic factors and individual constitution; ⑥ uterine inertia.
bubble_chart Pathological Changes
Post-term infants experience progressive hypoxia due to the placenta gradually aging, calcifying, and developing increased infarcted areas, resulting in reduced placental weight, narrowed intervillous spaces, thickened and occluded villous blood vessel walls, and decreased placental function. Additionally, the growing fetus compresses the uterus, slowing uterine blood flow and reducing uterine blood supply.
bubble_chart Clinical Manifestations
The post-term infant with good placental function appears clinically healthy. The eyes are alert, the skin is fair, resembling a newborn a few days after birth, with abundant subcutaneous fat, longer nails, coarser hair, disappearance of lanugo, and elastic auricular cartilage, with prominent nipples.
The post-term infant with placental insufficiency mainly manifests as the disappearance of vernix caseosa, progressive hypoxia, and fetal malnutrition in the uterus. It is classified by severity into the late stage [third stage];the vernix caseosa disappears, and the keratinized layer of the epidermis may become macerated due to the loss of vernix protection, drying after birth, becoming wrinkled, cracked, and desquamated.
On the basis of the initial stage [first stage], hypoxia progressively worsens, intestinal peristalsis accelerates, the anal sphincter relaxes, leading to the passage of meconium, thus staining the umbilical cord, amniotic membrane, and skin with meconium, and the respiratory tract may aspirate meconium-stained amniotic fluid.
In addition to the above symptoms, because the meconium has been in the amniotic fluid for a long time, the fetal nails, vernix caseosa, skin, and umbilical cord may all be stained yellow-green.
bubble_chart Treatment Measures
To prevent the dangers caused by placental insufficiency due to post-term pregnancy, timely termination of pregnancy must be considered. The gestational age and expected delivery date should be rechecked, and if confirmed as post-term, labor induction should be performed. Before delivery, preparations for neonatal asphyxia resuscitation should be made to ensure that the newborn can promptly receive endotracheal intubation, removal of airway obstructions, and pressurized oxygen administration. Always maintain airway patency. For those with amniotic fluid or meconium aspiration, oxygen should be administered early. If hypoxia persists, a ventilator can be used, along with correction of acidosis and energy supplementation to prevent hypoglycemia. Administer antibiotics to prevent infection.
Post-term infants with normal placental function have a good prognosis. Due to harder skull bones, smaller fontanels, and narrower cranial sutures, their heads have poor molding ability, making difficult delivery more likely. If placental function is insufficient, the morbidity and mortality rates are higher than usual. Especially for post-term infants in the intermediate stage [second stage], acute hypoxia and the inhalation of meconium-stained amniotic fluid can often lead to severe respiratory symptoms or hypoxic intracranial hemorrhage.
Conduct systematic prenatal check-ups, monitor the pregnant woman's weight, and consider terminating the pregnancy if continuous estriol measurements show a declining trend.
