1. 5
Preterm labour
and preterm
rupture of the
membranes
Before you begin this unit, please take the PRETERM LABOUR AND
corresponding test at the end of the book to
assess your knowledge of the subject matter. You PRETERM RUPTURE OF
should redo the test after you’ve worked through THE MEMBRANES
the unit, to evaluate what you have learned.
Objectives 5-1 What is preterm labour?
Preterm labour is diagnosed when there are
When you have completed this unit you regular uterine contractions before 37 weeks of
should be able to: pregnancy, together with either of the following:
• Define preterm labour and preterm 1. Cervical effacement and/or dilatation.
rupture of the membranes. 2. Rupture of the membranes.
• Understand why these conditions are
very important. 5-2 What is preterm rupture
• Understand the role of infection in of the membranes?
causing preterm labour and preterm Preterm rupture of the membranes is
rupture of the membranes. diagnosed when the membranes rupture before
• List which patients are at increased risk 37 weeks, in the absence of uterine contractions.
of these conditions and what preventive
measures should be taken. 5-3 What is prelabour rupture
of the membranes?
• Diagnose preterm labour and preterm
rupture of the membranes. Prelabour rupture of the membranes is defined
• Initiate the correct management and as rupture of the membranes for at least one hour
before the onset of labour in a term pregnancy.
appropriate referral of patients.

2. PRETERM LABOUR AND PRETERM RUPTURE OF THE MEMBRANES 97
5-4 How should you diagnose preterm membranes and placenta. Later these bacteria
labour if the gestational age is unknown? may colonise the liquor, from where they may
infect the fetus.
Preterm labour is diagnosed if the estimated
fetal weight is below 2500 g. The symphysis- Infection of the membranes and placenta
fundus height will be less than 35 cm.
(chorioamnionitis) may occur with either intact
or ruptured membranes.
5-5 Why are preterm labour and preterm
rupture of the membranes important?
5-8 What is the clinical presentation
Preterm labour and preterm rupture of the
of chorioamnionitis?
membranes are major causes of perinatal
death because: Usually chorioamnionitis is asymptomatic
(subclinical chorioamnionitis) and, therefore,
1. Preterm delivery, especially before 34 weeks,
the clinical diagnosis is often not made.
commonly results in the birth of an infant
However, the following signs may be present:
who develops hyaline membrane disease
and other complications of prematurity. 1. Fetal tachycardia.
2. Preterm labour and preterm rupture of 2. Maternal pyrexia and/or tachycardia.
the membranes are often accompanied by 3. Tenderness of the uterus.
bacterial infection of the membranes and 4. Drainage of offensive liquor, if the
placenta, that may cause complications for membranes have ruptured.
both the mother and the fetus. The mother
If any of the above signs are present, a diagnosis
and fetus may develop severe infection,
of clinical chorioamnionitis must be made.
which is life threatening.
5-9 What factors may predispose
5-6 What is the commonest known
to chorioamnionitis?
cause of preterm labour and preterm
rupture of the membranes? 1. Rupture of the membranes.
2. Exposure of the membranes due to
In many cases the cause is unknown, but
dilatation of the cervix.
increasing evidence points to infection of the
3. Coitus during the second half of
membranes and placenta as the commonest
pregnancy.
known cause of both preterm labour and
preterm rupture of the membranes. However, in many cases, the factors that result
in chorioamnionitis are not known.
Infection of the membranes and placenta is the
commonest recognised cause of preterm labour 5-10 Can chorioamnionitis cause
and preterm rupture of the membranes. complications during the puerperium?
Yes, it can cause serious problems.
5-7 What is infection of the 1. Bacteria that have colonised the amniotic
membranes and placenta? fluid, may infect the fetus and the infant
Infection of the membranes and placenta may present with signs of infection
causes an acute inflammation of the placenta, (congenital pneumonia or septicaemia) at
membranes and decidua. This condition is or soon after birth.
called chorioamnionitis. It may occur with 2. Chorioamnionitis may cause infection of
intact or ruptured membranes. the genital tract (puerperal sepsis) which,
if not treated correctly, may result in
Bacteria from the cervix and vagina spread
septicaemia, the need for hysterectomy,
through the endocervical canal to infect the
and possibly in maternal death. These

3. 98 PRIMAR Y MATERNAL CARE
complications can usually be prevented 7. Have any of the maternal, fetal or placental
by starting a course of broad-spectrum factors listed above.
antibiotics (e.g. intravenous ampicillin plus
metronidazole), as soon as the diagnosis of The most important risk factor for preterm
clinical chorioamnionitis is made. labour is a previous history of preterm delivery.
5-11 What factors other than
5-13 What can be done to decrease the
chorioamnionitis can lead to
incidence of these complications?
preterm labour and preterm
rupture of the membranes? 1. Take measures to ensure that all pregnant
women receive antenatal care.
The following maternal, fetal and placental
2. Identify patients with a past history of
factors may be associated with preterm labour
preterm labour.
and/or preterm rupture of the membranes:
3. Give advice about the dangers of smoking,
1. Maternal factors: alcohol and the use of habit-forming drugs.
• Pyrexia, as the result of an acute 4. Advise against coitus during the late 2nd
infection other than chorioamnionitis, and in the 3rd trimester in pregnancies at
e.g. acute pyelonephritis or malaria. high risk for preterm labour or preterm
• Uterine abnormalities, such as rupture of the membranes. If coitus occurs
congenital uterine malformations during pregnancy in these patients, the use
(e.g. septate or bicornuate uterus) and of condoms must be recommended as this
uterine myomas (fibroids). may reduce the risk of chorioamnionitis.
• Incompetence of the internal cervical 5. Insert a McDonald suture at 14–16 weeks,
os (‘cervical incompetence’). in patients with a proven incompetent
2. Fetal factors: internal cervical os.
• A multiple pregnancy. 6. Prevent teenage pregnancies.
• Polyhydramnios 7. Improve the socio-economic and
• Congenital malformations of the fetus. nutritional status of poor communities.
• Syphilis. 8. Arrange that the workload of women,
3. Placental factors: who have to do heavy manual labour, is
• Placenta praevia. decreased when they are pregnant and
• Abruptio placentae. that an opportunity to rest during working
hours is allowed.
5-12 Which patients are at an increased
risk of preterm labour or preterm 5-14 How should you manage a patient
rupture of the membranes? at increased risk of preterm labour or
preterm rupture of the membranes?
Both preterm labour and preterm rupture of
membranes are more common in patients who: 1. Patients at increased risk must have 2
weekly vaginal examinations from 24
1. Have a past history of preterm labour.
weeks, in order to make an early diagnosis
2. Have no antenatal care.
of preterm cervical effacement and/or
3. Live in poor socio-economic
dilatation.
circumstances.
2. In all women with cervical effacement or
4. Smoke, use alcohol or abuse habit-forming
dilatation before 34 weeks, the following
drugs.
preventive measures can then be taken:
5. Are underweight due to undernutrition.
• Bed rest. This can be at home, except
6. Have coitus in the 2nd half of pregnancy,
when the home circumstances are poor,
when they are at an increased risk of
preterm labour or infections.

4. PRETERM LABOUR AND PRETERM RUPTURE OF THE MEMBRANES 99
in which case the patient should be DIAGNOSIS OF
referred to the hospital for admission.
• Sick leave must be arranged for PRETERM LABOUR AND
working patients. PRETERM RUPTURE OF
• Coitus must be forbidden.
• Advice must be given to report THE MEMBRANES
immediately, if contractions or rupture
of the membranes occur.
• Women with preterm labour or preterm 5-16 How should you distinguish
rupture of the membranes must be seen between Braxton Hicks contractions and
as soon as possible, and the correct the contractions of preterm labour?
measures taken to prevent the delivery Braxton Hicks contractions:
of a severely preterm infant.
1. Are irregular.
All patients should be told to immediately 2. May cause discomfort but are not painful.
report preterm labour or preterm rupture of the 3. Do not increase in duration or frequency.
4. Do not cause cervical effacement or
membranes.
dilatation.
The duration of contractions cannot be used
5-15 What should you do if a patient as Braxton Hicks contractions may last up to
threatens to deliver a preterm infant? 60 seconds.
1. Infants born between 34 and 36 weeks can In contrast, the contractions of preterm or
usually be cared for in a level 1 hospital. early labour:
2. However, women who threaten to deliver
between 28 and 33 weeks, should be 1. Are regular, at least one per 10 minutes.
referred to a level 2 or 3 hospital with a 2. Are painful.
neonatal intensive care unit. 3. Increase in frequency and duration.
3. If the birth of a preterm baby cannot be 4. Cause effacement and dilatation of the
prevented, it must be remembered that the cervix.
best incubator for transporting an infant
is the mother’s uterus. Even if the delivery 5-17 How should you confirm the
is inevitable, an attempt to suppress labour diagnosis of preterm labour?
should be made, so that the patient can be
Both of the following will be present in a
transferred before the infant is born.
patient of less than 37 weeks gestation:
4. The better the condition of the infant on
arrival at the neonatal intensive care unit, 1. Regular uterine contractions, palpable on
the better is the prognosis. abdominal examination, of at least one
per 10 minutes.
2. A history of rupture of the membranes, or
cervical effacement and/or dilatation on
vaginal examination.
5-18 How can you diagnose preterm
rupture of the membranes?
1. A patient of less than 37 weeks gestation
will give a history of sudden drainage
of liquor followed by a continual leak

5. 100 PRIMAR Y MATERNAL CARE
of smaller amounts, without associated indicating that the membranes have
uterine contractions. ruptured. If blue litmus is used, it will
2. A sterile speculum examination will remain blue with rupture of membranes or
confirm the diagnosis of ruptured change to red if the membranes are intact.
membranes.
3. A digital vaginal examination must not be 5-21 How should you manage
done as it is of little value in diagnosing patients with preterm labour,
rupture of the membranes and may preterm rupture of membranes and
increase the risk of infection. prelabour rupture of membranes?
A digital vaginal examination must not be done 1. If the gestational age is less than 36 weeks,
in preterm rupture of the membranes. these patients should be referred to a level
I hospital for admission. If the gestational
age is less than 34 weeks, she must be
5-19 What is the value of a sterile referred to a level 2 hospital.
speculum examination when preterm 2. If the gestational age is 36 weeks of more,
rupture of the membranes is suspected? patients can safely be delivered in a midwife
obstetric unit (MOU) or district hospital.
1. The danger of ascending infection is not
At a gestational age of 36 weeks babies will
increased by this procedure.
not develop the complications of preterm
2. Observing drainage of liquor from the
infants and could be discharged 6 hours
cervical os confirms the diagnosis of
following delivery with their mothers.
ruptured membranes.
3. If no drainage of liquor is observed,
drainage can sometimes be seen if the 5-22 How will you decide that a patient
patient is asked to cough. is less than 36 weeks pregnant if the
4. If no drainage of liquor is seen, a smear duration of the pregnancy is unknown?
should be taken from the posterior This is done by measuring the symphysis-
vaginal fornix with a wooden spatula to fundus height and by doing a complete
determine the pH. abdominal examination. An estimated fetal
5. The possibility of cord prolapse can be weight of less than 2500 g, suggests a gestational
excluded or confirmed. age of less than 36 weeks. The symphysis-fundus
6. It is also important to see whether the height measurement will be less than 34 cm.
cervix is long and closed, or whether
there is already clear evidence of cervical 5-23 What should be done if preterm
effacement and/or dilatation. labour has been diagnosed and the
7. A patient with a profuse vaginal discharge patient is less than 34 weeks pregnant?
or stress incontinence (leaking urine
when coughing or laughing) may think Contractions should be suppressed with
that she is draining liquor. A speculum nifedipine (Adalat). The patient must then
examination will help to confirm or rule be transferred as an urgent transferal to a
out this possibility. level 2 hospital. If nifedipine is not available
salbutamol (Ventolin) can be used. This
5-20 How should you test the vaginal pH? measure will:
1. The pH of the vagina is acid but the pH of 1. Improve the chance of successful
liquor is alkaline. suppression of preterm labour at the
2. Red litmus paper is pressed against the hospital.
moist spatula. If the red litmus changes to 2. Reduce the risk of a delivery before arrival
blue, then liquor is present in the vagina, at the hospital or clinic.

6. PRETERM LABOUR AND PRETERM RUPTURE OF THE MEMBRANES 101
Infants born before 34 weeks are at increased 5-28 What are the contraindications to the
risk of developing complications. Therefore, use of salmotamol in suppressing labour?
suppression of contractions to allow
1. Heart valve disease. The use of salmutamol
continuation of pregnancy is important in
(or another beta2 stimulant), can endanger
these cases. The earlier the suppression of
the patient’s life, especially if she has a
contractions is started the better the chance of
narrowed heart valve, e.g. mitral stenosis.
successful suppression will be.
2. A shocked patient.
3. A patient with a tachycardia, e.g. as the
5-24 How would you decide that a patient result of an acute infection.
is less than 34 weeks pregnant if the
duration of the pregnancy is uknown?
5-29 What advice should you
This is done by measuring the symphysis- give to a woman who has
fundus height and by doing a complete delivered a preterm infant?
abdominal examination.
1. She should be seen at a level 2 hospital
Labour must be suppressed if the estimated before her next pregnancy to be assessed for
fetal weight is less than 2000 g as this suggests possible causes, e.g. cervical incompetence.
an estimated gestational age of less than 2. She must book early in any future
34 weeks. The symphysis-fundus height pregnancy.
measurement will be less than 33 cm.
5-25 How should you give nifedipine for CASE STUDY 1
the suppression of preterm labour?
Three nifedipine (Adalat) 10 mg capsules (total A patient, 32 weeks pregnant, presents with
30 mg) should be taken by mouth. If there regular painful uterine contractions. She
are still contractions with cervical dilatation is apyrexial and appears clinically well. On
and effacement 3 hours after the initial dose, a vaginal examination, the cervix is 4 cm dilated.
follow-up dose of 20 mg must be given. The fetal heart rate is 138 beats per minute
with no decelerations.
5-26 What are the contraindications to the
use of nifedipine in suppressing labour? 1. Is the patient in true or false labour?
Give the reasons for your diagnosis.
Nifedipine (Adalat) cannot be used for the
suppression of preterm labour if patients have She is in true labour because she is getting
hypertension, e.g. suffering from any of the regular painful contractions and her cervix is
hypertensive disorders of pregnancy. 4 cm dilated.
5-27 How should you use salmutamol 2. What signs exclude a diagnosis
for the suppression of preterm labour? of clinical chorioamnionitis?
1. A half an ampoule (0.5 ml = 250 μg) of The patient is apyrexial, clinically well and has
salbutamol (Ventolin) is diluted with 9.5 ml a normal fetal heart rate.
of sterile water in a 10 ml syringe and
administered slowly intravenously (0.5 ml 3. Why could chorioamnionitis still be
per minute) while the maternal heart rate is the cause of her preterm labour?
carefully monitored for a tachycardia. Because chorioamnionitis is often
2. The patient must be warned that salbutamol asymptomatic (subclinical chorio-amnionitis).
causes tachycardia (palpitations).

7. 102 PRIMAR Y MATERNAL CARE
4. Would you allow labour to continue 4. Is this patient at high risk of having
or would you suppress labour prior to or developing chorioamnionitis?
referring the patient to the hospital?
Yes. The preterm prelabour rupture of
Labour should be suppressed because the the membranes may have been caused by
pregnancy is of less than 34 weeks duration. chorioamnionitis. In addition, all patients with
ruptured membranes are at an increased risk
5. How should labour be suppressed? of developing chorioamnionitis.
Labour must be suppressed using nifedipine
5. Should the patient be referred to
(Adalat) or salbutamol (Ventolin).
a level I (district hospital/MOU) or
level II hospital? Give your reasons.
CASE STUDY 2 She is 36 weeks pregnant and there are no
signs of chorio-amnionitis. She should be
A patient, who is 36 weeks pregnant, reports referred to a level I hospital or MOU.
that she has been draining liquor since earlier
that day. The patient appears well, with normal
observations, no uterine contractions and the CASE STUDY 3
fetal heart rate is normal.
An unbooked patient presents at a primary
1. Would you diagnose rupture care clinic with a 5 day history of ruptured
of the membranes on the history membranes. She is pyrexial with lower
given by the patient? abdominal tenderness and is draining
offensive liquor. She is uncertain of her dates
No, other causes of fluid draining from the but abdominal examination suggests that she
vagina may cause confusion, e.g. a vaginitis or is at term. Treatment has been started with
stress incontinence. oral ampicillin.
2. How would you confirm 1. What signs of clinical chorioamnionitis
rupture of the membranes? does the patient have?
A sterile speculum examination should be She is pyrexial, with lower abdominal
done. If there is no clear evidence of liquor tenderness and she has offensive liquor.
draining, the vaginal pH must be determined
with Litmus paper to identify liquor.
2. How should the patient be managed?
3. Why should you not perform a digital There is danger of spreading infection in
vaginal examination to assess whether both the mother and fetus if the infant is not
the cervix is dilated or effaced? delivered. The patient must be referred to the
next level of care as an urgent case.
A digital vaginal examination is contra-
indicated in the presence of rupture of the
3. Is oral ampicillin the correct initial
membranes if the patient is not already in
treatment while waiting for the
labour, because of the risk of introducing
transfer? Give your reasons.
infection.
Chorioamnionitis may result in a severe
infection of the genital tract that may cause
a maternal death. These complications can
usually be prevented by starting broad-
spectrum antibiotics (ampicillin and

8. PRETERM LABOUR AND PRETERM RUPTURE OF THE MEMBRANES 103
metronidazole) as early as possible. The
ampicillin must be given intravenously.
4. Why is the infant at increased risk
for neonatal complications?
The chorioamnionitis has already spread to the
liquor as this is offensive. Therefore, the fetus
may also be infected and may present with
congenital pneumonia or septicaemia at birth.