Journal club 21Jan2008 cervical cerclage

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Is cervical cerclage indicated for the prevention of preterm labour due to cervical incompetence? : 

Is cervical cerclage indicated for the prevention of preterm labour due to cervical incompetence? by Samir Dawlatly GP VTS ST1 21 Jan 2008

Summary of talk : 

Summary of talk Aims and objectives The Clinical Question (PICO) Literature Search and Guidelines Citation Details Flow chart of study Important results GATE Frame Analysis and Evaluation (RAAMbo) Evidence Summary (CATmaker) Conclusions and Issues raised Further slides regarding recent meta-analysis

Aims and Objectives : 

Aims and Objectives AIM To determine if cervical cerclage is effective for the prevention of preterm birth due to cervical incompetence OBJECTIVES To search for literature relevant to the question presented To select a useful paper to appraise To determine the validity of the paper & to identify if the results are reliable enough to help answer the question & subsequently use in clinical practice

Case presentation : 

Case presentation Not had opportunity to meet a patient being considered for cervical cerclage Topic suggested by senior colleague

The Clinical Question : 

The Clinical Question Population Women at increased risk of preterm birth due to cervical incompetence Intervention Use of transvaginal cervical cerclage in the second trimester Comparison Bed rest or monitoring Outcome Primary Decreased preterm delivery Secondary Reduced neonatal mortality and morbidity Reduced maternal morbidity

Literature search : 

Literature search Search terms Cervical AND Cerclage AND Randomised Controlled Trial Resources searched PubMed

Guidelines 1 : 

Guidelines 1 NICE August 2007 Guidelines available regarding laparascopic abdominal cerclage for prevention of recurrent miscarriage Uncertainty about efficacy of ALL cervical cerclage techniques Evidence about safety and efficacy of laparascopic cerclage is limited

Guidelines 2 : 

Guidelines 2 RCOG May 2003 Green top guideline No.17 “The investigation and treatment of couples with recurrent miscarriage” Only consider in women likely to benefit Abdominal cerclage may be associated with better perinatal outcomes but at a higher risk of serious operative complications Cochrane Review 2003 The use of a cervical stitch should not be offered to women at low or medium risk of mid trimester loss, regardless of cervical length by ultrasound. The role of cervical cerclage for women who have short cervix on ultrasound remains uncertain. BWH No comment in orange book or on U-drive

Paper selected : 

Paper selected To MS, et al (2004). Cervical cerclage for the prevention of preterm delivery in women with short cervix: randomised controlled trial. Lancet 363: 1849-53. on behalf of the Fetal Medicine Foundation Second Trimester Screening Group

Flow chart of the study : 

Flow chart of the study A multi-centre randomised controlled study, 1998- 2002 (12 hospitals in UK, Brazil, S Africa, Slovenia, Greece & Chile) 47,123 women screened at 22-24 weeks with transvaginal scan 470 eligible for trial (all singleton pregnancies) 253 women with cervix length <15 mm detected randomised Cervical cerclage versus expectant management Patients underwent transvaginal cervical cerclage under spinal anaesthesia. Suture removed at 37/40. All given steroids at 26-28/40. Control and experimental groups were compared for epidemiologic characteristics, delivery before 33 weeks, birthweight, stillbirth, perinatal death, major adverse outcome and maternal morbidity.

Characteristics of women at randomisation : 

Characteristics of women at randomisation

Primary outcome – delivery before 33 weeks : 

Primary outcome – delivery before 33 weeks Study powered to have 90% chance of detecting reduction in early preterm delivery from 30% to 10% (based on n=160). Two interim analyses.

Birthweight, stillbirth, perinatal death : 

Birthweight, stillbirth, perinatal death

Major adverse perinatal morbidity : 

Major adverse perinatal morbidity * Not including still births and one lost to F/U

Maternal morbidity : 

Maternal morbidity

GATE Frame analysis for primary outcome : 

GATE Frame analysis for primary outcome Participants Source population present absent Eligible population Participants 47,123 470 253 Delivery <33/40

Slide 17: 

The Evidence (taken from CATmaker) Control event rate = 0.262 Intervention event rate = 0.220 RRR 16% (95% CI: -24% to 56%) ARR is 0.042 (95% CI: -0.063 to 0.147) NNT is 24 (7 to inf)

RAAMbo : 

RAAMbo Representative Source population, number eligible & no. of participants are stated. Multi centre ?correct ethnic mix for Birmingham Only 253 of 470 eligible participated – selection bias Short cervix not always routinely screened for. High risk patients for recurrent preterm labour not targeted Allocation Details Yes – by telephone from trials office Accounted Yes – see “Trial Profile” Measured Blinded – not possible (or ethical) with surgical intervention Objective – Yes – outcomes objective

Summary : 

Summary Routine transvaginal USS may identify a group of patients at risk of preterm delivery, but insertion of a transvaginal suture does not conclusively decrease the risk of prematurity in these patients.

Evaluation 1 : 

Evaluation 1 A number of important discussion points Selection bias (253/470) What happened to those that declined randomisation? How many declined screening? No p-values for baseline characteristics Identification of those at risk Study states cerclage suture removed at 37/40 – was suture really Shirodkar as stated?

Evaluation 2 : 

Evaluation 2 Concordance with Cochrane Review 2003 Recent IPD meta-analysis comes to similar conclusions (see additional slides) Were cerclage sutures placed too late on in pregnancy? There are more questions than answers…

More questions… : 

More questions… How does one identify patients at risk of preterm labour due to cervical incompetence? Obstetric history vs. USS and role of screening Primary (prophylactic) vs. secondary vs. tertiary (rescue) cerclage Pre-pregnancy cerclage vs. no cerclage Transabdominal vs. transvaginal methods Shirodkar vs. McDonald technique (Odibo et al 2007)

…than answers… : 

…than answers… Single stitch vs. double stitch Lap. transabdominal cerclage vs. open Elective vs. emergency cerclage Emergency (rescue cerclage) vs. no cerclage or bed rest Elective cerclage vs. other treatments What outcome should be measured? What else contributes to cervical “malfunction”?

Conclusions : 

Conclusions Further research is required to be able to provide conclusive advice with regard to the benefits of using cervical cerclage to improve neonatal outcome Women should be advised to of the possible increased risk of maternal pyrexia Research into the role of the cervical plug is ongoing (see BJOG May 2007 issue)

Thank you for listening : 

Thank you for listening Any comments or questions? More slides on Jorgensen et al, 2007 to follow if time permits…

Cervical cerclage: IPD meta-analysis. Jorgensen et al (2007). BJOG 114:1460-1476 : 

Cervical cerclage: IPD meta-analysis. Jorgensen et al (2007). BJOG 114:1460-1476 Slightly different clinical question: Does cervical cerclage prevent pregnancy loss compared with expectant management in women with confirmed or suspected cervical insufficiency? IPD used due to heterogeneity of studies included in Cochrane Review 2003

Cervical cerclage: IPD meta-analysis. Jorgensen et al (2007). BJOG 114:1460-1476 : 

Cervical cerclage: IPD meta-analysis. Jorgensen et al (2007). BJOG 114:1460-1476 Identified 17 potentially eligible studies 16 studies retrieved Excluded cerclage vs. pessary study studies with women already in other studies Study where patients not randomised Study where control patients subsequently received cerclage Study comparing inpatient vs outpatient cerclage Studies for whom individual patient data unavailable 7 studies included Data standardised and patients treated as though they were in one large study

Cervical cerclage: IPD meta-analysis. Jorgensen et al (2007). BJOG 114:1460-1476 : 

Cervical cerclage: IPD meta-analysis. Jorgensen et al (2007). BJOG 114:1460-1476 Primary outcome of 7 studies “Pregnancy loss or death before discharge from hospital”

GATE Frame for:Cervical cerclage: IPD meta-analysis. Jorgensen et al (2007). BJOG 114:1460-1476 : 

GATE Frame for:Cervical cerclage: IPD meta-analysis. Jorgensen et al (2007). BJOG 114:1460-1476 Participants Source and eligible population not stated present absent Participants Pregnancy loss/neonatal death 2091

Cervical cerclage: IPD meta-analysis. Jorgensen et al (2007). BJOG 114:1460-1476 : 

Cervical cerclage: IPD meta-analysis. Jorgensen et al (2007). BJOG 114:1460-1476 No difference for singleton pregnancies in: Baby healthy at discharge Maternal morbidity with spontaneous labour Maternal morbidity: chorioamnionitis Preterm prelabour rupture of membranes Induced labour or need for C-section Cerclage has worse outcome for: Maternal pyrexia Multiple pregnancies

Slide 32: 

Comparison of Evidence (CATmaker)

Thank you : 

Thank you

Extra slides : 

Extra slides Shirodkar images McDonald images Double stitch UK stillbirth and perinatal death rates Definition of cervical incompetence Other causes of preterm labour MRC/RCOG trial 1993 Why might cerclage not work

Shirodkar : 

Shirodkar

Double stitch : 

Double stitch

McDonald : 

McDonald

UK Stillbirth Perinatal mortality 2002 : 

UK Stillbirth Perinatal mortality 2002 Still births 5.6 per 1000 births Perinatal mortality 8.2 per 1000 Preterm birth rates 50-100 per 1000 in developed world

Definition of cervical incompetence 1 : 

Definition of cervical incompetence 1 May be due to previous obstetric or gynaecological trauma or due to congenital weakness of the cervix “characterised by painless dilatation of the cervix in the second or third trimester, followed by premature rupture of the membranes and preterm delivery or miscarriage”

Definition of cervical incompetence 2 : 

Definition of cervical incompetence 2 “recurrent second or early third trimester losses caused by the inability of the cervix to retain a pregnancy to term”

Other causes of preterm labour : 

Other causes of preterm labour Low socio-economic status Young age Black race (in USA) Previous preterm birth Smoking Drug use Multiple gestation Polyhydramnios Uterine anomalies Infection

MRC/RCOG trial 1993 : 

MRC/RCOG trial 1993 1292 women between 1981 and 1988 Obstetricians unsure of whether to use cerclage Different types of transvaginal suture Preterm delivery overall 28% Difference in preterm delivery (<33 weeks) 13% vs 17% p=0.03 (NNT = 25 or 25% reduction?) Powered to have 80% chance of detected 33% reduction in preterm labour No significant difference in perinatal mortality

Why might cerclage not work? : 

Why might cerclage not work? The technique is not effective Stitch is placed incorrectly Selection of patients is incorrect Cervix is so weak that it can’t be corrected by a suture Failure of the protective mechanism of the cervical plug

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