Preterm labour/rupture of membranes Flashcards
Definition of preterm labour
Labour before a gestational age of 37+0 completed weeks of gestation
Definition of preterm birth
Birth of a baby between 24-37 weeks of gestation
Definition of preterm premature rupture of membranes (PPROM)
Rupture of membranes at less than 37 weeks gestation, prior to the onset of
labour
Definition of threatened preterm labour (TPTL)
A woman presenting with
contractions within weeks 24-37
Epidemiology of preterm birth in Australia
8% nationwide (13% in ATSI mothers)
Major risk factors for preterm labour (10)
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
Primary processes responsible for spontaenous preterm labour and delivery (4)
- activation of maternal or foetal HPA axis due to maternal anxiety/depression or foetal stress
- Infection
- Decidual haemorrhage
- Pathological uterine distention
Common indications for iatrogenic preterm delivery (5)
Preterm premature rupture of membranes Preeclampsia/eclampsia/HELLP syndrome Intrauterine growth restriction Placental abruption Placenta praevia
What is foetal fibronectin and what is its significance
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
How to obtain fFN sample
Sterile speculum examination WITH ONLY STERILE WATER AS LUBRICANT with no blood or amniotic fluid seen
Collect from the posterior fornix of the vagina
Causes of false positives in fFN
Blood
Semen (recent coitus)
Digital vaginal examination or transvaginal USS
Causes of false negative results in fFN
Intravaginal lubricants or disinfectants
Presentation of premature labour
Regular uterine contractions + cervical dilatation and/or effacement at less than 37 weeks GA
Cervical length parameters in premature labour assessment
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)
Signs of chorioamnionitis
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
Investigations in preterm labour
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
Confirmatory tests for PPROM
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)
Primary prevention of preterm labour
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)
What is cervical cerclage?
Stitching cervix closed during pregnancy to prevent cervical insufficiency from leading to preterm birth
Progesterone supplementation to prevent preterm birth
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
Management of chorioamnionitis
Triple antibiotics IV
Amoxycillin, gentamicin, metronidazole
Management of preterm premature rupture or membranes without high risk of imminent delivery
Inpatient monitoring
Corticosteroid administration
Antibiotics
Iatrogenic delivery in setting of chorioamnionitis or if older than 34w GA
Evidence of high risk of imminent delivery in woman presenting with ?preterm labour
Regular contractions, cervical dilatation or a positive fFN
Antibiotics contraindicated in preterm labour
Augmentin duo forte, associated with increased risk of necrotising enterocolitis
Management of women at high risk of imminent preterm delivery
Corticosteroid administration
Tocolysis (if no contraindications)
IV Benzylpenicillin (unless chorioamnionitis, triple therapy)
Rationale for corticosteroid administration in preterm labour
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
Corticosteroid regimes for preterm labour
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
Contraindications to tocolytics (10)
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
Rationale for tocolysis in preterm labour
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)
Groups of tocolytics
Calcium channel blockers (nifedipine) Oxytocin antagonists (Atosiban) Beta-blockers (salbutamol)
Dosing of nifedipine for tocolysis
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
Prostaglandin synthesis inhibitors in preterm labour
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)
Indications for magnesium sulphate in preterm labour
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
Post-delivery investigations for preterm neonate
Cord blood (arterial and venous blood gas) Placenta: histopathology, microbiology (?chorioamnionitis)
