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Effect of first trimester crown rump length measurement on rates of induction of labour for postdates.
ISRCTN ISRCTN16877725
ClinicalTrials.gov identifier
Public title Effect of first trimester crown rump length measurement on rates of induction of labour for postdates.
Scientific title
Acronym N/A
Serial number at source SPGS 757
Study hypothesis The project is an RCT of the effect of first trimester ultrasound on rates of induction of labour for postdates. Currently it is widespread practice in most obstetric units in the United Kingdom to induce labour 14 days after the estimated date of delivery (EDD). While this has been shown to have a beneficial effect on perinatal outcome, it may cause consumer dissatisfaction as it is perceived to be a painful intervention in an otherwise normal pregnancy. Measurement of the biparietal diameter at 20 weeks gestation has been shown to improve the accuracy of gestational age assessment, and this should lead to a reduction in rates of induction of labour for postdates. Gestational age assessment using CRL in the 1st trimester is more accurate than the biparietal diameter and may further reduce the numbers requiring induction for postdates. There is an increasing shift to perform prenatal diagnosis in the first trimester. Those providing antenatal care may have to choose the best time at which a routine scan in pregnancy can be offered. If a first trimester ultrasound scan is shown to improve the customisation and therefore the appropriateness of obstetric care this would provide further evidence to justify its introduction as well as its use in screening for Down's syndrome, either with nuchal fold or as an adjunct to serum screening.
The objective is to determine whether an ultrasound scan in the first trimester of pregnancy will lead to more accurate assessment of gestational age and consequently lead to a reduction in the number of pregnancies induced at term and fourteen days. If this is the case then there will be cost savings for the NHS, as well as the reduction in unnecessary and potentially painful interventions.
Lay summary
Ethics approval Not provided at time of registration
Study design Randomised controlled trial
Countries of recruitment United Kingdom
Disease/condition/study domain Pregnancy and childbirth: Childbirth
Participants - inclusion criteria Women in the first trimester of pregnancy who do not require a first trimester ultrasound for any other clinical indication.
Participants - exclusion criteria Women will be excluded if there is a clinical indication for a first trimester ultrasound scan or if they refuse consent. Examples of the former would be if there was vaginal bleeding, uncertainty about viability of the pregnancy or the possibility of an ectopic pregnancy.
Anticipated start date 01/02/1999
Anticipated end date 30/09/2002
Status of trial Completed
Patient information material
Target number of participants Added December 2008: 800 intended
Interventions The control group will continue with routine antenatal care with ultrasound performed for the usual indications.
The intervention group will have an ultrasound scan between 8 and 12 weeks gestation to measure the crown-rump length (CRL) and if there is a discrepancy of greater than 5 days between the estimated date of delivery (EDD) calculated form the last menstrual period and that by CRL the EDD will be revised to that derived by scan. The EDD will be entered in the patient's obstetric notes and all subsequent management decisions will be based on this assessment of gestational age.
Primary outcome measure(s) Rates of induction of labour for postdates
Secondary outcome measure(s) 1. The characteristics of labour with respect to the length of labour, the mode of delivery, the immediate perinatal outcome, analgesic requirements for labour and the overall client satisfaction with labour
2. Rates of gestation dependent events in pregnancy - false positive and negative outcomes from maternal serum screening
3. The management of early pregnancy complications
Sources of funding NHS Executive South East (UK)
Trial website
Publications 2006 results of uncompleted trial on http://www.ncbi.nlm.nih.gov/pubmed/16411994
Contact name Mr  I  Mackenzie
  Address Nuffield Department of Obstetrics and Gynaecology
John Radcliffe Hospital
  City/town Oxford
  Zip/Postcode OX3 9DU
  Country United Kingdom
Sponsor NHS R&D Regional Programme Register - Department of Health (UK)
  Address The Department of Health
Richmond House
79 Whitehall
  City/town London
  Zip/Postcode SW1A 2NL
  Country United Kingdom
  Tel +44 (0)20 7307 2622
  Fax +44 (0)20 7307 2623
  Email dhmail@doh.gsi.org.uk
  Sponsor website: http://www.doh.gov.uk
Date applied 23/01/2004
Last edited 03/12/2008
Date ISRCTN assigned 23/01/2004
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