Prolonged Pregnancy and Disorders of Uterine Action

Chapter 20 Prolonged Pregnancy and Disorders of Uterine Action



Post-term or prolonged pregnancy




Risks and clinical implications of post-term pregnancy




image Post-term pregnancy is one that is in excess of 287 days (although 42 weeks is often considered acceptable).


image Accurate dating of a pregnancy is essential, as incorrect diagnosis that a pregnancy has gone beyond term may lead to inappropriate or unnecessary intervention.


image Post-term pregnancy is associated with an increase in perinatal mortality and neonatal morbidity rates.


image Possible fetal consequences include macrosomia or fetal compromise due to placental demise.


image Prolonged pregnancy is the largest single indication for induction of labour.



Management of post-term pregnancy


Two forms of care are offered:



image Expectant management with fetal surveillance.


image Elective induction of labour after 41 weeks of gestation.



Antenatal surveillance




image Biophysical profile. A combined ultrasound assessment of fetal breathing, fetal movement, fetal tone, reactivity of the heart rate and amniotic fluid volume is used to predict fetal wellbeing in a high-risk pregnancy. A total score of 8–10 indicates the fetus is in good condition.


image Doppler ultrasound of umbilical artery.


image Twice weekly cardiotocography (CTG), also known as non-stress testing (NST).


image Amniotic fluid measurement.



Induction of labour




Indications for induction


Induction is indicated when the benefits to the mother or the fetus outweigh those of continuing the pregnancy. It is associated with the maternal and fetal factors described in Box 20.1.



Box 20.1 Indications for induction of labour



Maternal




• Prolonged or post-term pregnancy


• Hypertension, including pre-eclampsia


• Diabetes


• Medical problems, e.g. renal, respiratory or cardiac disease


• Placental abruption


• Obstetric history, such as previous stillbirth or previous caesarean section


• Prelabour rupture of membranes


• Maternal request



Fetal




• Suspected fetal compromise


• Multiple pregnancy


• Intrauterine death


• Some breech presentations



Contraindications to induction


These include:



image placenta praevia


image transverse or compound fetal presentation


image cord presentation or cord prolapse


image cephalopelvic disproportion


image severe fetal compromise


image active genital herpes.


If delivery is imperative, it should be effected by caesarean section.



Cervical ripening



Structural changes in ripening


Successful induction occurs when the cervix is favourable or so-called ‘ripe’. The cervix is then more compliant, offering less soft tissue resistance to the actions of the myometrium and the presenting part.



Prostaglandins


Pre-induction prostaglandin can be used to prime or mature the cervix for induction. A low-dose prostaglandin is administered to bring about effacement and dilatation without stimulating contractions.



Methods of inducing labour



Prostaglandins and induction


Prior to prescribing prostaglandin, the cervix is assessed using the Bishop’s score (Table 20.1). PGE2 preparations are available in gels, tablets or controlled-release pessary form; they are inserted close to the cervix within the posterior fornix of the vagina. Fetal heart rate and uterine contractions should be monitored continuously for 30–60 minutes thereafter. The mother remains recumbent or resting for 1 hour. Changes in the cervix can be assessed by an increase in the Bishop’s score.



Table 20.1 Modified Bishop’s pre-induction pelvic scoring system

image

Recommended prescribed doses of PGE2 are shown in Table 20.2.


Table 20.2 Recommended prescribed doses of prostaglandin E2



















Form Dose
Slow-release pessary One dose (10 mg of dinoprostone), string left accessible, removed after 24 hours
Tablets 3 mg 6–8 hourly, maximum dose 6 mg
Gels Nulliparous women with an unfavourable cervix: 2 mg (maximum 4 mg)
All other women: 1 mg (maximum 3 mg)
Repeat doses of 1–2 mg 6 hourly may be given


Sweeping or stripping of membranes


Sweeping the membranes can be an effective method of inducing labour where there is an uncomplicated pregnancy. During a vaginal examination the clinician inserts a finger through the cervical os, and using a sweeping or circular movement releases the fetal membranes from the lower uterine segment. The woman should be made aware that it may cause some discomfort and bleeding.



Amniotomy


Amniotomy is the artificial rupture of the fetal membranes (ARM), resulting in drainage of liquor. It is performed to induce labour when the cervix is favourable or during labour to augment contractions. ARM may also be carried out to visualise the colour of the liquor or to attach a fetal scalp electrode for the purposes of continuous electronic monitoring of the fetal heart rate. A well-fitting presenting part is essential to prevent cord prolapse.


ARM is carried out using an amnihook or an amnicot. Procedures are shown in Box 20.2.



Box 20.2 Amniotomy procedures



Prior to intervention




• Informed maternal consent is obtained


• The reason for the amniotomy is clearly stated in the records


• Presentation and degree of engagement of the presenting part are confirmed by abdominal palpation


• The fetal heart rate is auscultated


• The presence of a low-lying placenta or cord is excluded



Following intervention




• Note the colour and quantity of liquor


• Check the presentation, position and station of the fetus


• Ensure no cord has prolapsed


• Auscultate the fetal heart rate



Hazards of ARM


These include:



image intrauterine infection


image early decelerations of the fetal heart


image cord prolapse


image bleeding from fetal vessels in the membranes (vasa praevia); friable vessels in the cervix; or placenta praevia.



Oxytocin


Oxytocin is used in conjunction with amniotomy and may be commenced at the same time as ARM or after a delay of several hours.



Administration of oxytocin to induce labour




image Oxytocin is used intravenously, diluted in an isotonic solution such as normal saline.


image The infusion should be controlled through a pump to enable accurate assessment of volume and rate.


image Dosage should be recorded in milliunits per minute, with the suggested dilution being 30 IU in 500 ml of normal saline. (Note: 1 ml per hour delivers 1 milliunit per minute.) The midwife should aim to administer the lowest dose required to maintain effective, well-spaced uterine contractions, with a maximum of 3–4 contractions every 10 minutes (Table 20.3).


image Oxytocin should not be started within 6 hours of the administration of prostaglandins.

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Related posts:

  1. The Placenta
  2. Trauma During Birth, Haemorrhage and Convulsions
  3. Obstetric Emergencies
  4. Problems of Pregnancy

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Jul 11, 2016 | Posted by in MIDWIFERY | Comments Off on Prolonged Pregnancy and Disorders of Uterine Action

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