Obstetrics and Gynaecology · MU Sofia

19. Post-term pregnancy. The post-mature infant

Explains what counts as a post-term pregnancy and how often it occurs, then lists causes and risk factors, including the rare hormonal ones. A table sets out the risks to the fetus and to the mother. It describes postmaturity syndrome in the newborn and its complications, then covers management: confirming dates, offering induction from 41 weeks, monitoring if induction is declined, and choosing an induction method. A Bishop score table with its interpretation closes the note.

Inside: 5 sections · 2 tables · 16 flashcards · 2 min

Topic 19 of 61 in the MU Sofia syllabus for Obstetrics and Gynaecology (Dental Medicine, Year 4). The free AceMed note covers it in 5 sections, about 213 words (2 min of reading), with 16 flashcards.

In this note

  1. Introduction
  2. Causes and risk factors
  3. Risks
  4. The post-mature infant
  5. Management

Introduction

A post-term (prolonged) pregnancy is one that reaches 42⁺⁰ weeks or more. About 5–10% of pregnancies go beyond 41 weeks. Accurate early dating removes many apparent cases.

Causes and risk factors

  • Wrong dates (most common), first pregnancy, previous post-term pregnancy, obesity, male fetus.
  • Rarely, low oestrogen production: anencephaly, placental sulphatase deficiency.

The post-mature infant

Some post-term babies show postmaturity (dysmaturity) syndrome: long thin body with loss of subcutaneous fat, dry peeling skin, long nails, abundant hair, alert open eyes, and meconium staining of the skin, nails and cord. They are at risk of hypoglycaemia, polycythaemia and meconium aspiration.

Management

  1. Confirm the dates (first-trimester ultrasound).
  2. Offer induction of labour from 41⁺⁰ weeks (and by 42 weeks): it reduces perinatal death without increasing caesarean section.
  3. If she declines, monitor from 41–42 weeks: CTG and amniotic fluid measurement (deepest pocket) about twice a week.
  4. Induction method depends on the cervix (Bishop score): prostaglandins or a balloon catheter for an unripe cervix, then amniotomy and oxytocin.
  5. Continuous CTG in labour; be ready for meconium and shoulder dystocia.

Bishop score

A score of 8 or more means a ripe cervix and a high chance of successful induction; 6 or less means the cervix needs ripening first.

After 41 weeks the placenta ages and the stillbirth risk rises, so induction is offered rather than waiting for 42.

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