post dates fetus
Post dates fetus or post-term pregnancy is when the gestation has extended 2 weeks beyond the expected date of delivery (>42 weeks gestation).
Epidemiology
The reported prevalence is 7 % of pregnancies .
Pathology
The etiology of post-term pregnancy is still unknown.
Research has shown that the synthesis of corticotrophin releasing hormone (CRH) by the placenta is increased in late pregnancy and peaks at the time of labor and this fact is related to the length of gestation. However, the exponential rise of CRH production is slower in women who deliver post-term. Some risk factors have been identified such as:
Maternal factors:
- primiparity
- obesity
- history of prior post-term pregnancy: the risk increase from 27% with one prior prolonged pregnancy to 39% with 2 prior prolonged pregnancies.
- hormonal factors
- genetic predisposition: the risk is higher for women who were themselves products of prolonged pregnancy.
Fetal-placental factors:
- anencephaly: decreased production of 16α-hydroxydehydroepiandrosterone beta-sulfate a precursor of estriol
- fetal adrenal hypoplasia: decreased the production of estriol precursors
- placental sulfatase deficiency: prevents placenta conversion of sulfated estrogen precursors
Radiographic findings
Obstetric ultrasound commonly shows oligohydramnios (81.8%), macrosomia, andplacenta grade 2 or 3.
Complications
Fetal complications
- fetal macrosomia: which in turn can cause added complications such as
- prolonged labor
- cephalopelvic disproportion
- shoulder dystocia
- dismaturity syndrome
- higher rate of meconium aspiration
- neonatal acidemia
- higher rate of neonatal encephalopathy
- increased risk of placental insufficiency
- duplicates the rate of stillbirth and early neonatal death
Maternal complications
- increased risk of severe perineal injury.
- labor dystocia
- increased risk of endometritis
- chorioamnionitis
- cesarean delivery
- postpartum hemorrhage
Treatment
- elective induction of labor
- expectant management +/-
- antenatal testing
Differential diagnosis
Inaccurate dating
Siehe auch:
Assoziationen und Differentialdiagnosen zu post dates fetus: