Preterm labour/rupture of membranes

Question 1

Definition of preterm labour

Answer 1

Labour before a gestational age of 37+0 completed weeks of gestation

Question 2

Definition of preterm birth

Answer 2

Birth of a baby between 24-37 weeks of gestation

Question 3

Definition of preterm premature rupture of membranes (PPROM)

Answer 3

Rupture of membranes at less than 37 weeks gestation, prior to the onset of
labour

Question 4

Definition of threatened preterm labour (TPTL)

Answer 4

A woman presenting with

contractions within weeks 24-37

Question 5

Epidemiology of preterm birth in Australia

Answer 5

8% nationwide (13% in ATSI mothers)

Question 6

Major risk factors for preterm labour (10)

Answer 6

Obstetric:
- past history of preterm birth/PPROM
- Antepartum hemorrhage
- multiple pregnancy
Maternal medical conditions
- systemic infections
- genital tract infections
Anatomic factors:
- congenital uterine abnormalities
- cervical insufficiency
Social factors:
- ATSI status
Foetal factors:
- IUGR
- congenital anomalies

Question 7

Primary processes responsible for spontaenous preterm labour and delivery (4)

Answer 7

1. activation of maternal or foetal HPA axis due to maternal anxiety/depression or foetal stress
2. Infection
3. Decidual haemorrhage
4. Pathological uterine distention

Question 8

Common indications for iatrogenic preterm delivery (5)

Answer 8

Preterm premature rupture of membranes
Preeclampsia/eclampsia/HELLP syndrome
Intrauterine growth restriction
Placental abruption
Placenta praevia

Question 9

What is foetal fibronectin and what is its significance

Answer 9

A glycoprotein which promotes adhesion between foetal chorion and maternal decidua

Should be absent from cervicovaginal secretions 24-36 weeks GA, becomes detectable as term approaches

Levels >50ng/mL in cervicocaginal secretions 24-36w associated with increased risk of preterm birth within next 7-10 days

Question 10

How to obtain fFN sample

Answer 10

Sterile speculum examination WITH ONLY STERILE WATER AS LUBRICANT with no blood or amniotic fluid seen
Collect from the posterior fornix of the vagina

Question 11

Causes of false positives in fFN

Answer 11

Blood
Semen (recent coitus)
Digital vaginal examination or transvaginal USS

Question 12

Causes of false negative results in fFN

Answer 12

Intravaginal lubricants or disinfectants

Question 13

Presentation of premature labour

Answer 13

Regular uterine contractions + cervical dilatation and/or effacement at less than 37 weeks GA

Question 14

Cervical length parameters in premature labour assessment

Answer 14

Over 3cm = low risk of premature birth
2-3cm = increased risk of preterm birth (most will still deliver at term) - test fFN in this group to determine risk
under 2cm = high risk of preterm birth despite fFN result (therefore fFN not required)

Question 15

Signs of chorioamnionitis

Answer 15

Maternal fever higher than 38 + any 2 of the following:

• raised WCC
• Maternal tachycardia
• Foetal tachycardia
• Uterine tenderness
• Offensive smelling vaginal discharge
• CRP greater than 40

Question 16

Investigations in preterm labour

Answer 16

Investigate for infection or concealed haemorrhage
CRP daily for 3 days
CBE daily for 3 days
Low and high vaginal swab MCS
Midstream urine MCS

Question 17

Confirmatory tests for PPROM

Answer 17

AmniSure: measurement of placental alpha macroglobulin-1 protein assay
Actime PROM: measurement of ILGF binding protein 1
Nitrazine test: measurement of pH (vaginal = 4.5, amniotic fluid = 7.0-7.3)

Question 18

Primary prevention of preterm labour

Answer 18

Smoking cessation
Avoid iatrogenic preterm delivery in absence of medical indications
Limiting number of embryos returned to uterus in assisted conception
Cerclage in women with previous preterm and cervical insufficiency
Progesterone supplementation in women with previous preterm birth or short cervix (less than 2cm)

Question 19

What is cervical cerclage?

Answer 19

Stitching cervix closed during pregnancy to prevent cervical insufficiency from leading to preterm birth

Question 20

Progesterone supplementation to prevent preterm birth

Answer 20

Indicated in women with previous preterm birth or short cervix (2cm)
Begin mid pregnancy (20w) if scan shows short cervix until 34 weeks gestation
90mg intravaginal gel or 100-200mg pessary

Question 21

Management of chorioamnionitis

Answer 21

Triple antibiotics IV

Amoxycillin, gentamicin, metronidazole

Question 22

Management of preterm premature rupture or membranes without high risk of imminent delivery

Answer 22

Inpatient monitoring
Corticosteroid administration
Antibiotics
Iatrogenic delivery in setting of chorioamnionitis or if older than 34w GA

Question 23

Evidence of high risk of imminent delivery in woman presenting with ?preterm labour

Answer 23

Regular contractions, cervical dilatation or a positive fFN

Question 24

Antibiotics contraindicated in preterm labour

Answer 24

Augmentin duo forte, associated with increased risk of necrotising enterocolitis

Question 25

Management of women at high risk of imminent preterm delivery

Answer 25

Corticosteroid administration
Tocolysis (if no contraindications)
IV Benzylpenicillin (unless chorioamnionitis, triple therapy)

Question 26

Rationale for corticosteroid administration in preterm labour

Answer 26

Prevents adverse perinatal outcomes, most notably respiratory distress syndrome, increases likelihood of neonatal survival
(assists foetal lung maturity)
Dexamethasone also associated with lower rates of intraventricular haemorrhage

Question 27

Corticosteroid regimes for preterm labour

Answer 27

Given if woman likely to deliver between 23-35 weeks
IM betamethasone 2 doses 11.4mg 24 hours apart
OR
IM dexamethasone 2 doses 12mg 24 hours apart
then weekly dose until 32+0 or delivery

Question 28

Contraindications to tocolytics (10)

Answer 28

Gestation over 34w
Labour too advanced
Intrauterine foetal death
Lethal foetal anomaly
Suspected foetal compromise
Maternal SBP less than 90mmHg
Maternal cardiac disease
Maternal hyperthyroidism
Placental abruption
Chorioamnionitis

Question 29

Rationale for tocolysis in preterm labour

Answer 29

may delay birth by 2-7 days and reduce occurrence of preterm birth (useful for short term to administer corticosteroids and transfer to hospital with NICU)

Question 30

Groups of tocolytics

Answer 30

Calcium channel blockers (nifedipine)
Oxytocin antagonists (Atosiban)
Beta-blockers (salbutamol)

Question 31

Dosing of nifedipine for tocolysis

Answer 31

20mg oral stat
2nd dose of 20mg if contractions persist after 30minutes
No more until 3 hours after 2nd dose
20mg PRN every 3 hours up to max of 160mg in 24 hours

Question 32

Prostaglandin synthesis inhibitors in preterm labour

Answer 32

i.e. indomethacin - MOST POTENT INHIBITORS OF UTERINE CONTRACTILITY CURRENTLY AVAILABLE
Potential adverse foetal and neonatal effects, thus indications restricted to:
- GA less than 28
- failure to achieve tocolysis with other regimens
- contraindications to other tocolytics (e.g. cardiac disease)

Question 33

Indications for magnesium sulphate in preterm labour

Answer 33

For neuroprotection of foetus
(reduced risk of CP)
Give to women at risk of preterm birth 24-30w GA
Give when birth is anticipated within 24 hours, as close to 4 hours before expected delivery as possible

Question 34

Post-delivery investigations for preterm neonate

Answer 34

Cord blood (arterial and venous blood gas)
Placenta: histopathology, microbiology (?chorioamnionitis)