08 - preterm labor

Preterm labor is the presence of contractions of sufficient strength and frequency to effect progressive effacement and dilation of the cervix between 20 and 37 weeks' gestation

WHO

Incidence : 6- 10%

Spontaneous : 40-50%

PROM : 25-40%

Obstetrically indicated : 20-25%

Most mortality and

morbidity is

experienced by babies

born before 34 weeks.

Death Respiratory distress syndrome Hypothermia Hypoglycaemia Necrotising enterocolitis Jaundice Infection Retinopathy of prematurity

Goldenberg , Obstetrics &Gynecology 11-2002

Can preterm labor be predicted?

1. Assessment of risk factors 2. Vaginal examination to

assess the cervical status 3. Ultrasound visualization of

cervical length and dilatation 4. Detection of foetal

fibronectin in cervicovaginal secretions

While the exact cause of preterm labor is often unknown, there is strong evidence that intrauterine infection may play a role in very early preterm labor. ACOG NEWS RELEASE November 2002

Bacterial vaginosis increased the risk of preterm delivery >2-fold .

Risks were higher for those screened at <16 weeks (odds ratio, 7.55; 95% CI, 1.80-31.65) than those at <20 weeks of gestation (odds ratio, 4.20; 95% CI, 2.11-8.39).

Leitich et al Am J Obstet Gynecol. 2003 Jul;189(1):139 ( Meta-Analysis)

1-Risk Factors

Multiple pregnancy: risk >50%

Previous preterm delivery: risk 20-

40%

Cigarette smoking: risk 20-30%

Cervical incompetence

Uterine abnormalities

MOH Sing. Guideline Grade C Recommendation 2001

1-Risk Factors

Young age of mother - less than 16 years of age.•Lower socioeconomic class.Reduced body mass index (BMI) - BMI less than 19.0.Antiphosphlipid syndrome. Obstetric complications, including hypertension in pregnancy,antepartum haemorrhage, infection, polyhydramnios, foetalabnormalities.

MOH Sing. Guideline Grade C Recommendation 2001

1-Risk Factors

Digital examination is the traditional method used to detect cervical maturation, but quantifying these changes is often difficult.

Vaginal ultrasonography

allows a more objective

approach to examination

of the cervix.


Outcome Sensitivity specificity

Delivery <37

Delivery <34

52%

53%

85%

89%

Delivery within 1 Week



Leitich & Kaider ,BJOG. 2003 Apr;110 , 20:66-70. Meta-Analysis 40 studies

71%

67%

59% 92%

89%

89%

4-Fibronectin Test

Prevention

Women at increased risk of preterm delivery may be identified by various risk factors in the obstetric history and treated.

American Academy of Pediatrician & ACOG 1997

Prophylactic use of 17 hydroxy progesterone caproate to prevent preterm labor revealed a significant decrease in preterm birth .

However, it has not successfully inhibited active preterm labor.

Meis et al. N Engl J Med. 2003 Jun 12;348(24):2379-85.RCT (19 centers )

Keirse. Br J Obstet Gynaecol 1990;97:149-54. Meta-anlysis of 6RCTs.

Treatment of asymptomatic abnormal vaginal flora and bacterial vaginosis with oral clindamycin early in the 2nd trimester significantly reduces the rate of late miscarriage and spontaneous preterm birth.

Ugwumadu et al. Lancet. 2003 Mar 22;361:983-8. ) RCT

Diagnosis

3 criteria to document PTL(20-

37w)

1-Regular uterine contractions

occur at 4/20 min. or 8/60 min.

Plus: progressive change in the

cervix. 2- Cervical dilatation > 1 cm 3- Effacement _ 80%.

American Academy of Pediatrician & ACOG 1997

>

Suspected preterm labor with no cervical changes :

Negative fetal fibronectin + Cervical length > 30 mm the likelihood of delivering in the next

week is less than 1%. Thus most women with a negative test can

safely be sent home without treatment.


Inhibition of labor Corticosteroid Antibiotics Others.

Bed rest :DVTHydration &sedation

Tocolytics

Until effective strategies are found, efforts should be aimed at preventing newborn complications by :

Corticosteroids Antibiotics against group B strep Avoiding traumatic deliveries. Delivery in a center with experienced

resuscitation teams and neonatal intensive care

ACOG NEWS RELEASE: November 2002

Intravenous hydration does not seem to be beneficial, even during the period of evaluation soon after admission,

Women with evidence of dehydration may, however, benefit from the intervention.

Stan et al (Cochrane Review 2000). In: The Cochrane Library, Issue 1 2003. Oxford

It is reasonable not to use tocolytic drugs, as there is no clear evidence that they improve outcome. However, tocolysis should be considered if the few days gained would be put to good use, such as completing a course of corticosteroids, or in utero transfer

RCOG Guideline Grade A recommendation 2002 (Valid:2005)

Most authorities do not recommend use of tocolytics at or after 34 weeks' .

There is no consensus on a lower gestational age limit for the use of tocolytic agents.


Nifedipine = EpilateAtosiban= Tractocile

B –Sympathomimetic (Ritodrine)

Magnesium sulphate

Indomethacin

Use of beta-agonists should be restricted to the management of preterm labour between 20 and 35 completed weeks, including women with ruptured membranes. (Grade A)

RCOG Guideline Grade A recommendation 1997

There is insufficient evidence for any firm conclusions about whether or not maintenance tocolytic therapy following threatened preterm labor is worthwhile. Therefore maintenance therapy cannot be recommended for routine practice.

RCOG Guideline Grade A recommendation 2002 (Valid:2005)

Antenatal corticosteroids are associated

with a significant reduction in rates of

RDS, neonatal death and

intraventricular haemorrhage,

although the numbers needed to treat

increase significantly after 34 weeks'

gestation.

RCOG Guidelines : Grade A Recommendation

The optimal treatment-

delivery interval for

administration of antenatal

corticosteroids is after 24

hours but < 7 days after the

start of treatment. RCOG Guidelines : Grade A Recommendation

Two 12 mg doses of betamethasone

given IM 24 hours apart, Or

Four 6 mg doses of dexamethasone

given IM 12 hours apart (I-A).

There is no proof of efficacy for any

other regimen.

SOGC Recommendation Jan. 2003

There is no evidence of clear overall benefit from prophylactic antibiotics for preterm labour with intact membranes on neonatal outcomes. King & Flenady (Cochrane Review August 2002). In: The

Cochrane Library, Issue 1 2003. Oxford: Update Software.

ACOG Advises Screening All Pregnant Women for Group B Strep. ACOG NEWS RELEASE November 2002

All patients in preterm labor are considered at high risk for neonatal GBS sepsis and should receive prophylactic antibiotics regardless of culture status.


The goal of this strategy is to prevent neonatal sepsis, and not to prevent preterm birth.


Have not been shown to significantly prevent periventricular haemorrhages in preterm infants.

Goldenberg , May 2003

Crowther & Henderson-Smart (Cochrane Review May 2003 ) In:The Cochrane Library, Issue 1 2003. Oxford: Update Software

Crowther & Henderson-Smart (Cochrane Review Novemb. 2000 ) In:The Cochrane Library, Issue 1 2003. Oxford: Update Software

Various strategies that have been used to prevent or treat preterm labor, haven't proven effective.

Tocolysis should be considered only for 2 days- if needed - for corticosteroids thereby , or in utero transfer to a tertiary center .

If a tocolytic drug is used, ritodrine no longer seems the best choice.

Other drugs with fewer adverse effects and

comparable effectiveness are now

recommended

Atosiban or nifedipine have been

recommended by RCOG

endomethacin may be used as a 2nd line

tocolytic or if there is polyhydramnous

Maintenance tocolytic therapy has no proven effect.

It cannot be recommended for routine practice.

Thank You

Thank You

08 - preterm labor

Documents