Threatened Pre Term Birth

Max Brinsmead MB BS PhD

December 2015

Pre term Birth Affects 5-9% births in Europe and 12-13% in

US Increasing in frequency in both 1:4 is induced labour for maternal and fetal

reasons Single most common cause of perinatal

mortality & morbidity Increases risk of cerebral palsy (80-fold @

28w compared to term) Is a particular challenge to those who work

with limited neonatal facilities

When confronted by possible Pre term Birth

There are 6 questions you need to ask yourself

And they need to be answered ASAP

Because time is of the essence

6 Questions about Pre term Birth

1 Is the baby premature?

2 Is it really labour?

3 Why is labour occurring now?

4 Should the labour be suppressed?

5 Can the labour be suppressed?

6 What else can be done?

Is this baby premature? Dates uncertain or unknown? Be the obstetric detective! The earliest ultrasound is best Measure uterine size and estimate fetal

weight But there is a problem with PROM! Use USS to measure biparietal diameter &

femur length Remember the baby that is mature before

its time

Is it Labour? Listen to what the patient is telling you Has it happened before? A warm hand is better than a

tocograph! Ruptured membranes - if it isn’t

obvious then it isn’t relevant Cervical assessment Observation over time

Fetal Fibronectin Easy to perform but not inexpensive

High negative predictive value of delivery within seven (7) days (particularly in women who present with contractions)

Poor positive predictive value and specificity– Overall ~50%

(Based on a 2003 BMJ meta analysis of 40 published studies)

Quantified bedside test preferred especially for asymptomatic women with a short cervix– <10 ng/ml has a high negative predictive value– >200 ng/ml positive (PPR 38%)

Ultrasound Measures of Cervical Length

Simple and safe

Expertise and equipment required

High negative predictive value if the cervix is >15 mm and there is no beaking of membranes with straining down

The positive predictive value and sensitivity is less certain

The appropriate intervention for a short cervix is also debatable

Why is Labour occurring now?

Underlying maternal problem? Is the baby normal? Antepartum haemorrhage Chorioamnionitis Ruptured membranes Cervical incompetence

Should Labour be suppressed?

Is the baby better off in or out? Will depend on your local resources At the limits of viability survival with

handicap is possibly the worse outcome

But you need to be aware of the wishes and resources of the family

Can the labour be suppressed?

In many cases the answer is YES

But

Advanced labour and ruptured membranes sometimes make it difficult

What is the best tocolytic to use? In general, use the one you know best I prefer IV Betamimetics

5 mg Ventolin in 500 ml and run until MPR >110 but <140 bpm. Rapidly effective but maternal side effects common

Oral Nifedipine has fewer side effects 2 crushed tablets (20 mg) stat and repeat in one hour if

required. Then 10 – 20 mg 6 – 8 hourly PRN Doses >60 mg over 48 hrs best avoided RCT comparisons with betamimetics suggest improved

neonatal outcomes Atobisan = an oxytocin blocker

As effective as Ca channel blocker in delaying delivery Questions arising from long term follow up of children

Gyceryl trinitrate - transdermal patch NSAIDs – use with caution

Problems include premature closure ductus and renal effects Rebound effects described after withdrawal at 32w

IV Mg sulphate - ? protects the fetal brain

What else can be done for the patient in premature

labour? Psychological care Administration of steroids

Doubles survival and halves all complications Can the patient be transferred?

Doubles survival and halves handicap What about MgSO4 to prevent brain

damage? Are antibiotics required? Optimal care in labour

Corticosteroids Effectively reduce the risk of:

– Hyaline membrane disease– Necrotising enterocolitis– Intracranial haemorrhage– Death and disability

Are safe in the short and long term Are effective at gestations 26w – 40w Effective for all clinical indications including:

– Idiopathic pre term labour– PROM– Maternal hypertensive diseases– Twins (maybe)

Must be given within 24 hrs and 7 days Repeat once if <34 weeks or still high risk Optimum formulation, dose & route – uncertain

I prefer IM Betamethasone 11.2 mg 24 hours apart

Mg suphate for Neuroprotection

Effectively reduces the risk of:– Periventricular leucomalacia– Cerebral palsy– Overall OR is 0.14 (CI 0.05 – 0.51)

Most data arises from use of MgSO4 for eclampsia prophylaxis

In this MgSO4 has been proven to be safe Recommended for gestations <30 weeks

– Planned preterm delivery– Inevitable preterm delivery

Must be given within 24 hrs of birth Consider repeating if <30 weeks and >24 hrs Dose is 4G IV loading over 20 – 30 min then 1

G/hour IV infusion for 24 hrs or until delivery

Infection and Prematurity Subclinical infection implicated in 40-70% of pre

term labour Also has a sinister role in the aetiology of cerebral

palsy The results of therapeutic trials of antibiotics in

preventing pre term birth are conflicting Vaginosis is a risk factor for prematurity

– But screening and treatment should be reserved for those at risk

– Most studies have focused on anaerobic BV but aerobic BV may be the more important

Erythromycin or Clindamycin is useful after PROM Do not use Amoxil (Increases the risk of NEC) Antibiotics with intact membranes may increase risk

of perinatal mortality (RR 1.52, CI 0.99-2.34) and increases the risk cerebral palsy (RR 1.18, CI 1.02-1.37)

Is the source of infection outside the genital tract?

Overall, uterine tocolysis: Prolongs gestation

– But the gains are modest

Buys time for perinatal transfer and administration of steroids

By themselves they have no effect on perinatal mortality and morbidity

Ineffective or impractical for long term use

Ca channel blockers are safer than betamimetics but sometimes slow and unpredictable

Optimal intrapartum care for the premature fetus

Delivery at the optimal site the most important

Avoid hypoxia and trauma Avoid sedatives and narcotics if

possible CS for the pre term breech? CS for the very premature?

Prediction and Prevention of Preterm Birth

Prior history of preterm birth the best predictor But also look out for overworked, stressed,

abused and smoking patient And those with other chronic diseases Multiple pregnancy The short & incompetent cervix continuum

– Monitor and plot on a scale against GA– Consider suture for cervix <15 mm

Endocrine predictors include the measurement of CRH, steroids, AFP etc

Progestational AgentsNEJM June 2003

– A DB PC RCT of weekly injections of 17hydroxyprogesterone caproate from 16-20w in 267 high risk women in several centres

– Reduced delivery at <37w from 55% to 36%– Reduced delivery at <32w from 20% to 11%

These results confirmed by a meta analysis that includes previous trials

ANDThey have now proven effective in a wide

range of patients at risk incl. twins

The best agent to use is vaginal Progesterone

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