OB 5 PP (Prolonged Pregnancy).pdf

Obstetrics: Prolonged Pregnancy PP Dr. Ishraq | Lecture 5 2012

The Spikings | Page | 1

Prolonged Pregnancy Pregnancies of 294 days duration or more are defined as prolonged, post-date ,post

Term.

Prolonged pregnancy is associated with an increase in perinatal mortality &morbidity in

pregnancy which appear to be otherwise low risk.

Incidence of PP

If we depend on LMP, the incidence of PP is 10%.

If we depend on first trimester U/S, the incidence will decrease to 6%.

PP is increase in first pregnancies, but it is not related to maternal age &the median

duration of pregnancy is 2 days longer in nulliparae compared with multiparas.

Women with body mass index of greater than 30 are at increased risk of PP.

Aetiology of PP

1- It is likely that the majority of PP. represent the upper range of a normal distribution.

2- Genetic factor might regulate the onset of labor.

3- previos PP .The risk of PP is twice in women with previous PP compared to women with no

history of PP .

4- 4Women with male fetus has an increased risk of PP.

5- Low vaginal level of fetal fibronectin at 39 weeks are predictive of an increase likelihood of

PP, this is associated with long cervix.

6- PP could result from variation in the CRH system during pregnancy, such as alteration in

the number or expression of myometrial receptor subtypes.

Risks Associated with PP

1- Perinatal mortality: there is 6 folds increase in the PMR.

2- There is a 4 folds increase in intra-partum fetal death.

3- There is an increase in early neonatal death.

4- There is an increase in the perinatal morbidity: meconium staining liquor, meconium

aspiration syndrome, neonatal seizures, neonatal sepsis, and brachial plexus injury.

5- There is an increase in birth trauma &shoulder dystocia.



Matertnal Risks

1- Increase incidence of dystocia (prolonged labor).

2- Increase incidence of operative interventions i.e. caesarean section was significantly more

common with PP. The increase was equally due to failure to progress &fetal distress.

3- Increase incidence of birth trauma &shoulder dystocia which in turn lead to increased

incidence of perineal injury &post partum haemorrhage.

Antenatal Test in PP

No single test is effective so combination of methods should be used.

1- U/S assessment of amniotic fluid: by measuring the largest vertical pool of amniotic fluid

&used as a 1 cm pool depth as the cut off for intervention. This was subsequently modified

to 2 cm to improve detection of growth retarded infant. I have been found that maximum

pool depth performed better than AFI in predicting adverse outcome in post-term

pregnancy.

However, this test has poor sensitivity &specificity.

2- Biophysical profile :no sufficient data to show that the biophysical profile is better than any

other form of fetal monitoring .The more complex method of monitoring , the more likely to

yield an abnormal result, but doesn't improve pregnancy outcome.

3- 3Cardiotocography: studies have reported very low rates of perinatal loss in high risk

pregnancies monitored in this way.

4- Fetal movement counting: this test does not reduce the incidence of intrauterine fetal death

in late pregnancy.

5- Doppler velocimetry: no benefit.

Management

1- 1-U/S to establish accurate gestational age:

This is to reduce the cases of PP .First trimester U/S is associated with lowest rate of PP.

2- Active management: induction of labor. Routine induction at 40 weeks would not considered

a realistic option for prevention of post-term pregnancy. Women with uncomplicated

pregnancy should be offered induction of labor beyond 41 weeks. Women with risk factors

should be offered induction at 40 weeks.

Women should informed that there is a small increase in risk associated with continuing

pregnancy beyond 41 weeks. Vaginal examination is performed &this could be accompanied by



sweeping of the membranes, provided women are warned about the discomfort associated with

this & are agreeable to proceed.Membrane sweeping reduces the need for formal induction of

labor .The vaginal examination allows the obstetrician to inform the women of the likely ease

&success of induction of labor. For women who have previously delivered vaginally & for

women with favorable cervix, induction of labor is unlikely to be a difficult process. Those with

unfavorable cervix, ripening with prostaglandin should be done.

For a patient with a previous caesarean section ,induction of labor is not contraindicated

but associated with increased risk of scar dehiscence compared with a spontaneous onset of

labor especially with prostaglandins are used.

3- CONSERVATIVE MANAGEMNET

From 42 weeks, women who decline induction of labor should be offered increase

antenatal monitoring, consisting of a twice weekly CTG &U/S estimation of maximum

amniotic pool depth.

Effects of induction of labor on the risk of caesarean section

Induction of labor for post-term pregnancy does not increase the caesarean section rate ,

irrespective of parity , cervical ripeness , method of induction .

THE END

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OB 5 PP (Prolonged Pregnancy).pdf