This document discusses post-term pregnancy, which is defined as pregnancy extending beyond 42 weeks from the last menstrual period. Risks to the fetus include doubling of perinatal mortality and risks to the mother include increased risk of labor abnormalities and cesarean delivery. The preferred course of management is induction of labor between 41-42 weeks, as this is supported by evidence of reduced perinatal mortality, morbidity and cesarean section rates. Membrane sweeping can also be used to prevent post-term pregnancy by reducing the percentage of patients going past term.

1. POST-TERM PREGNANCYPOST-TERM PREGNANCY
Dr Max Mongelli
Women & Childrens’ Health
Nepean Hospital
Sydney, Australia
Max Mongelli 2011

2. DefinitionsDefinitions
Pregnancy has extended to or beyond 42
weeks from LMP
“Post-dates” applies to pregnancy over 40
and less than 42 weeks
Critically dependent on accurate pregnancy
dating
Max Mongelli 2011

3. PrevalencePrevalence
Prevalence of post-term pregnancy highly
dependent on local policies for induction.
preterm delivery rates, complicated
pregnancy rates
In the USA about 6% of pregnancies are
post-term
Using 1st
trimester scans for dating results in
only 2% of pregnancies going post-term
Max Mongelli 2011

4. Risk FactorsRisk Factors
Primigravidity
Previous post-term pregnancy
Genetic factors
Male fetus
Maternal obesity
Fetal anencephaly
Max Mongelli 2011

5. PathophysiologyPathophysiology
Deterioration in placental function
Increased placental apoptosis
Increased cord blood erythropoetin
Max Mongelli 2011

6. Risks to the FetusRisks to the Fetus
Doubling of perinatal mortality
Asphyxia, meconium aspiration,
intrauterine sepsis
Fetal macrosomia
Fetal dysmaturity syndrome
Max Mongelli 2011

7. Max Mongelli 2011

8. Risks to the MotherRisks to the Mother
Increased risk of labor abnormalities
Third and fourth degree perineal tears
Increased risk of cesarean delivery
Max Mongelli 2011

9. ManagementManagement
Induction of labor
Membrane sweeping
Conservative management
Max Mongelli 2011

10. Induction of LaborInduction of Labor
This is the preferred course of management
Most units induce labor from 41 weeks
onwards
Strong evidence from meta-analysis to
support reduced perinatal mortality,
morbidity and cesarean section rates
Shown to be cost-effective
Max Mongelli 2011

11. Membrane SweepingMembrane Sweeping
Membrane sweeping (or “stripping”) may
be used to prevent post-term pregnancy
Reduces the percentage of patients going
postterm from 41% to 23%
Can be repeated if required
Max Mongelli 2011

12. Conservative ManagementConservative Management
 Reserved for women who decline induction or
labor or have a contraindication
 Optimal gestational age for beginning monitoring
is unknown, usually 41-42 weeks
 Monitoring should include amniotic fluid
assessment, CTG’s
 Immediate delivery if these become abnormal
Max Mongelli 2011

13. Intrapartum ManagementIntrapartum Management
Continuous electronic fetal monitoring is
required
Greater risk of fetal distress or meconium
aspiration
Max Mongelli 2011

14. PrognosisPrognosis
No detectable differences in children born
postterm regarding IQ, physical milestones
or intercurrent illnesses, when tested at 1-2
years of age.
Max Mongelli 2011

15. Further ReadingFurther Reading
Williams’ Obstetrics
Max Mongelli 2011