Obstetrics Simplified - Diaa M. EI-Mowafi
Post-term Pregnancy
Definition
A pregnancy that persists for 42 weeks or more from the onset of the last menstrual period. Sometimes called postmaturity or postdate.
Incidence
5-10%. It is more common in primigravidae.
Aetiology
Unknown, but hereditary, hormonal and non-engagement of the presenting part are suspected factors.
Risk of Post-term
- Placental insufficiency: which may lead to foetal hypoxia or even death.
- Oligohydramnios: with its sequelae particularly cord compression during labour.
- Obstructed labour: due to;
- oversized baby,
- no moulding of the skull due to more calcification.
- Increased incidence of operative delivery.
Diagnosis
Antenatal
- History: calculation of gestational age (see later).
- Examination: larger baby size.
- X-ray: large ossification center in the upper end of the tibia.
- Ultrasonography: can detect,
- Biparietal diameter more than 9.6 cm.
- Increased foetal weight.
- Oligohydramnios.
- Increased placental calcification.
- Tests for placental function.
Postnatal
- Baby length: more than 54 cm.
- Baby weight: more than 4.5 kg.
- Skull: well ossified with smaller fontanelles.
- Finger nails: project beyond finger tips.
Management
Termination of labour is indicated which may be by:
- Induction of labour if the condition is favourable for vaginal delivery
using:
- amniotomy ± oxytocin, or
- prostaglandins ± oxytocin.
- Caesarean section: if conditions are not favourable for vaginal delivery, or if induction of labour failed.
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Edited by Aldo Campana,