CH11 Preterm Labor

Preterm LaborInternational

Preterm Labor


Objectives

• Definition and Incidence

• Etiology

• Diagnosis

• Management- Delaying delivery- Promoting fetal maturity- When to transfer- Delivery


Definition

• regular uterine contractions accompanied by progressive cervical dilatation and/or effacement at less than 37 weeks gestation

20 to 50% of PTL diagnosis is incorrect


Dilemma

• interventions to stop preterm labor are not particularly effective - especially when not instituted early

'Solution'

• diagnosis based on some degree of uterine activity combined with a single cervical exam suggesting early dilatation or effacement


Diagnosis

• establish dates

• history of contractions, risk factors

• abdominal exam for uterine activity

• cervical exam - serial if reasonable

• sterile speculum exam alone should be done in PPROM

• defer digital exam if there is undiagnosed vaginal bleeding until _______ of placenta is known


Establishing the EDD - LMP

• Naegele's Rule can be used in conjunction with the LMP if:- first day of last menses is known- period was 'normal'- cycle is regular and between 24 and 35 days- no recent hormonal contraception, lactation or

pregnancy (3 subsequent spontaneous periods)


Establishing the EDD - When ultrasound is available

• Ultrasound should be used when the LMP is unknown or criteria are not fulfilled for its use in calculating the EDD

• U/S dating accuracy decreases as gestational age increases- 7 - 12 weeks GA ± 5 days- 13 - 20 weeks GA ± 1 week- 21 - 30 weeks GA ± 2 weeks- > 30 weeks GA ± 3 weeks


Establishing the EDD

• please tell someone the EDD!- inform woman of EDD from LMP if appropriate and

reinforce at time of dating and/or 18 week ultrasound- document EDD on antenatal forms- document dates and findings of each ultrasound on

antenatal (include placental location)

• good dating is useless if no one but you knows the EDD and you are not available


Incidence

• preterm delivery occurs in about 7% of pregnancies

• there has been little change in this rate despite new technologies


Significance

• preterm birth accounts for 75% of perinatal mortality

• significant longterm neonatal/pediatric sequelae- CNS and neurodevelopmental- respiratory- blindness and deafness


Etiology• Idiopathic

• Antepartum haemorrhage

• Preterm prelabor rupture of membranes

• Chorioamnionitis

• Multiple pregnancy / Polyhydramnios

• Incompetent cervix / Uterine Anomaly

• Maternal disease

• Fetal anomaly


Management of Preterm Labor

Four Objectives:

1. Early diagnosis of preterm labor

2. Identify and treat the underlying cause of preterm labor if possible

3. Attempt to stop labor when appropriate

4. Minimize neonatal morbidity and mortality


Management - Prolongation of Pregnancy

less than 40% of patients in preterm labor will be candidates for tocolysis

Goal of Tocolytic Therapy

• Delay delivery when appropriate- gain 48 hours for corticosteroids- transport- optimize personnel


Management - Tocolysis Contraindicated

• contraindication to continuing pregnancy

e.g. severe pregnancy induced

hypertension, chonoamnionitis intra-

uterine fetal death

• contraindication to specific tocolytic agents


Tocolytics - No strong evidence for efficacy

• Fluid bolus - small trial (n=48), no detected effect

• Ethanol- small trials, no benefit over placebo- ritodrine more effective in comparative trials- concerns re: adverse effects

• Sedation - no evidence, concern re: adverse effects


Tocolytics - No strong evidence for efficacy

• Magnesium sulfate- small, poor quality trials; placebo and comparative- no benefit shown


Tocolytics - Good evidence for efficacy-sympathomimetics (ritodrine)

- highly effective for delaying delivery in the short term- no demonstrated effect on neonatal outcome

• PG synthetase inhibitors (indomethacin)- more effective than placebo in delaying delivery

>48 hours and beyond- no demonstrated positive effect on neonatal outcome- small trials, concern re: adverse effects

• Calcium channel blockers (e.g. nifedipine)


Side Effects of -mimetics• tachycardia - maternal and/or fetal

• headache and nasal congestion

• hyperglycemia / hypokalemia

• hypotension

• pulmonary edema- multiple gestation- other interventions- infection

• myocardial ischemia


Contraindications to -mimetics• Maternal cardiac disease - structural, ischemic, rhythm

• Significant antepartum haemorrhage

• Poorly controlled medical condition- type I diabetes mellitus- hyperthyroidism

• Contraindication to prolongation of pregnancy- preeclampsia or other medical indication- chorioamnionitis, suspected fetal compromise- mature fetus / imminent delivery / IUFD or anomaly


Minimizing Neonatal Adverse Outcomes

• Respiratory distress syndrome (RDS) is a major concern with preterm delivery

• Incidence of RDS has improved due to newer therapies

• RDS plays a role in several other conditions- intraventricular haemorrhage (IVH)- necrotising enterocolitis (NEC)- persistent pulmonary hypertension (PPHN)- other respiratory conditions


Meta-analysis of Antepartum Steroids

• 15 trials evaluating antenatal glucocorticoids for the reduction of RDS in preterm infants (>24 weeks and < 34 weeks)

• an incomplete course of steroids may still be beneficial

P. Crowley CCPC Review No. 02955


Effect of Corticosteroids on Neonatal Outcomes

RDS

IVH

NEC

Perinatal Infection

Neonatal Death

0.1 1 10Odds Ratio (95% Confidence Interval)

P. Crowley CCPC Review No. 02955


Recommendations

Which steroid ?

• betamethasone 12 mg IM q 24h x 2 doses (or q 12h)

• dexamethasone 6 mg IV q 12h x 4 doses (or q 6h)

Beware

• steroids in the presence of infection

• steroids in combination with tocolytics in multiple gestation or diabetes


Recommendations

When should steroid therapy be instituted?

• lower gestation limit 22 - 24 weeks

• upper gestation limit 34 - 36 weeks

• prophylactic administration depends on diagnosis and risk

• repeated administration unknown


Recommendations

Who is a candidate for antenatal steroid therapy?

Considerations

preterm labour YES cause

preterm PROM YES infection

hypertensives YES urgency

diabetics YES type, sugars

IUGR YES urgency

multiple gestation YES pulmonary edema


Decision to Transport• Available level of neonatal or obstetrical care

• Available transport and skilled personnel

• Travel time

• Risk of journey - maternal and fetal/neonatal well-being

• Risk of delivery en route- Parity, length of previous labour- State of cervix- Contractions- Response to tocolytics


Transport Plan

• Copies of antenatal forms, lab results, ultrasounds

• Communication- with patient and family- with receiving physician re: indication, stabilization,

optimization, mode of transport, E.T.A.

• Appropriate attendant

• IV access, indicated medications, appropriate equipment

• Assess patient immediately prior to transport


Preterm Delivery

• caesarean not indicated on basis of prematurity

• recommendation for C/S of breech < 31 weeks not based on good evidence

• prophylactic outlet forceps not indicated

• routine episiotomy not indicated

• personnel skilled in neonatal resuscitation present


Conclusion

• Prompt and accurate diagnosis

• Identify and treat underlying cause if possible

• Attempt to prolong pregnancy if appropriate

• Intervene to minimize neonatal mortality and morbidity- antenatal steroid therapy- maternal transport- optimize local resources if unable to transport


Prelabor Rupture of the Membranes (PROM)


Objectives

• Definition

• Diagnosis

• Management - Preterm and Term


Definition

• rupture of the membranes before the onset of labor– preterm - < 37 weeks gestation (PPROM)– term - 37 weeks gestation (TPROM)


Latent Period• time from rupture until onset of labor

• earlier the gestation the longer the latent period

• At term - 90% go into labor within 24 hours

• At 28 - 34 weeks– 50% go into labor within 24 hours– 80 - 90% go into labor within 1 week


Etiology of PROM• idiopathic

• infection (e.g. bacterial vaginosis)

• polyhydramnios

• cervical incompetence

• uterine abnormality

• following cervical cerclage or amniocentesis

• trauma


Diagnosis of PROM

• history

• sterile speculum exam ( avoid digital exam)– glistening, washed out vagina– fluid pooling in posterior fornix– free flow from cervix– pH testing of fluid (nitrazine paper) - non specific– ferning

• ultrasound - PROM less likely if normal fluid volume


Complications of PROM - Term

• fetal / neonatal infection

• maternal infection

• umbilical cord compression / prolapse

• failed induction resulting in cesarean section


Complications of PROM - Preterm• preterm labor and delivery

• fetal / neonatal infection

• maternal infection

• umbilical cord compression / prolapse

• failed induction resulting in cesarean section

• pulmonary hypoplasia (early, severe oligohydramnios)

• fetal deformation


Management - General• assess maternal and fetal well-being

• confirm diagnosis

• assess cervical status by speculum exam (sterile)

• avoid digital cervical exam

• assess for conditions requiring concurrent management

e.g. presence of temperature or maternal or

fetal tachycardia

• assess for indications for immediate delivery


Management - Term (> 37 weeks)


• assess for infection

• consider need for antibiotics if prolonged PROM

• expectant or active management depending on circumstances and patient preference


Management - Preterm (34-37 weeks)


• consider antenatal steroids

• intrapartum antibiotic prophylaxis

• surveillance for infection - clinical (monitor maternal

temperature and pulse, fetal heart rate)

• appropriate antibiotics for chorioamnionitis if develops


Management - Preterm (< 34weeks)• avoid digital cervical exam

• steroids

• antepartum and intrapartum antibiotics to mother

• surveillance for infection - clinical (monitor maternal pulse and temperature, fetal heart rate, presence of uterine irritability)

• appropriate antibiotics for chorioamnionitis if develops

• consider transfer to higher level of care center if appropriate

• expectant management (possibly outpatient)


Antibiotic options are:

Women with suspected chorioamnitonitis require broader range spectrum antibiotic coverage

Iv Penicillin G 5 million units q 4-6h preferred

or

Iv AmpiullinAmpiullin 2g followed by 1 g q 4h

or

IV ClindamyinClindamyin 600 ng q 8h

Documents

CH11 Preterm Labor