Premature birth: predicting the risk of early labour in first-time mothers

Published on 16 November 2010

What's the problem and who does it affect?

Many early births are unexpected

Pregnancy can be a time of great excitement and anticipation. Expectant parents hope for a normal pregnancy and a healthy baby. Sadly, however, things don’t always work out. About 50,000 babies are born prematurely each year in the UK, putting them at risk of death and disability.^5,6,c

Some premature births are planned – doctors decide to deliver the baby early because complications in the pregnancy are putting the health of mother or baby at risk. However, the majority of early births – around two thirds – are spontaneous, with the mother going into labour, or her waters breaking, too soon.7 Over half of these women are in their first pregnancy.⁸

Sadly, once a woman has gone into labour early, doctors can do little to stop her baby from being born too soon. The majority of women go into labour unexpectedly, without warning, and are totally unprepared for the early arrival of their baby.

To reduce the number of premature births, we need a way to screen first-time mothers and identify who’s at increased risk of giving birth early, so they can be referred for specialist care. Unfortunately, no suitable screening test is available.

What is the project trying to achieve?

Can markers of infection help predict risk of premature birth?

The researchers aim to find a way to identify first-time mothers who are at high risk of giving birth prematurely. They are drawing on evidence that suggests there is a strong link between infection and premature birth – many women who go into labour early, or whose waters break too soon, have infections.

The body responds to infection by releasing a wide variety of signalling molecules that stimulate the immune system. These signalling molecules can be thought of as markers of infection.

The researchers believe these markers of infection could have an important new use. They are developing a test which, they hope, will predict whether a pregnant woman is at increased risk of having her baby prematurely. The test will work by measuring the levels of markers of infection in vaginal secretions.

The researchers are focusing on 119 first-time mothers who gave birth prematurely – 77 who went into labour early and 42 whose waters broke too soon – and another 238 women who gave birth at full term. They are measuring the level of 28 different markers of infection, in vaginal swabs taken when the women were 20 weeks pregnant, and comparing the results in women who did, and did not, give birth early.

What are the researchers' credentials?

This highly experienced research team, based at King’s College London, comprises Dr Rachel Tribe, Professor Andrew Shennan and Professor Robyn North. Dr Tribe is an eminent scientist in the field of pregnancy research. She leads a flourishing research group, looking for better ways to prevent premature birth and predict who’s at risk. Professor Shennan is a leading expert in pregnancy and childbirth, particularly premature birth.

Professor North is the principle investigator of a global research project called the SCOPE study (www.scopestudy.net/). Around 10,000 women from around the world will take part in this ambitious study into health problems experienced by first-time mothers and their babies. The 357 women who are being studied in this project are volunteers from SCOPE.

The team is collaborating with Dr Paul Seed, a well-known statistician with a wealth of experience of developing ways to predict an individual’s risk of developing a particular disease.

The researchers are based at St Thomas’ Hospital, where they have access to state-of-the-art equipment. They are part of the Maternal and Fetal Research Unit of King’s College London, which is dedicated to improving outcomes for pregnant women and their babies.

Who stands to benefit from this research and how?

Identifying and helping women at risk

The researchers aim to help women in their first pregnancy. They are aiming to develop a new screening test, to give women the opportunity to find out if they are at increased risk of having their baby prematurely – of going into labour too soon or having their waters break early.

The researchers envisage that the test will work by measuring markers of infection in swabs taken from the vagina. It could be cheap and simple enough to be used to screen all first-time mothers early in pregnancy. It may also benefit women in subsequent pregnancies.

Women who are found to be at low risk of having their baby early – who represent the majority – might find the results reassuring. Women who are at high risk could be referred for specialist antenatal care at a preterm surveillance clinic. They could then be monitored regularly and if necessary given treatment, in an attempt to stop their baby from being born too soon.

Data from recent interventional trials suggest that this specialist care could prevent at least one premature birth for every six women treated.^9-11 By ensuring the right women have access to this care, the new screening test could help more babies escape premature birth.

References

1. Office for National Statistics. Health Statistics Quarterly 28 (Winter 2005), 32 (Winter 2006), 36 (Winter 2007)
2. Office for National Statistics. Infant and perinatal mortality in England and Wales by social and biological factors. Statistical Bulletin. 24 November 2009. http://www.statistics.gov.uk/pdfdir/ipm1109.pdf
3. General Register Office for Scotland, Vital Events Reference Tables 2009
4. Northern Ireland Statistics and Research Agency. Registrar General Annual Report 2008
5. Office for National Statistics. Health Statistics Quarterly 43 (Autumn 2009), Table 2.1 http://www.statistics.gov.uk/downloads/theme_health/HSQ43.pdf
6. The Information Centre, Community Health Statistics. NHS Maternity Statistics, England: 2006-07, 2007-08, 2008-09 http://www.ic.nhs.uk/statistics-and-data-collections/hospital-care/maternity/nhs-maternity-statistics-2008-09
7. Iams JD, Romero R, Culhane JF, Goldenberg RL. Preterm Birth 2. Primary, secondary, and tertiary interventions to reduce the morbidity and mortality of preterm birth. Lancet 2008; 371:164-75
8. Langhoff-Roos J, Kesmodel U, Jacobsson B, Rasmussen S, Vogel I. Spontaneous preterm delivery in primiparous women at low risk in Denmark: population basedstudy. BMJ 2006; 332:937-9. Epub 2006 Feb
9. Owen J, Hankins G, Iams JD, Berghella V, Sheffield JS, Perez-Delboy A, Egerman RS, Wing DA, Tomlinson M, Silver R, Ramin SM, Guzman ER, Gordon M, How HY, Knudtson EJ, Szychowski JM, Cliver S, Hauth JC. Multicenter randomized trial of cerclage for preterm birth prevention in high-risk women with shortened midtrimester cervical length. Am J Obstet Gynecol 2009; 201:375.e1-8.
10. Meis PJ, Klebanoff M, Thom E, Dombrowski MP, Sibai B, Moawad AH, Spong CY,Hauth JC, Miodovnik M, Varner MW, Leveno KJ, Caritis SN, Iams JD, Wapner RJ, Conway D, O'Sullivan MJ, Carpenter M, Mercer B, Ramin SM, Thorp JM, Peaceman AM, Gabbe S. National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network. Prevention of recurrent preterm delivery by 17 alpha-hydroxyprogesterone caproate. N Engl J Med 2003; 348:2379-85.
11. Fonseca EB, Celik E, Parra M, Singh M, Nicolaides KH; Fetal Medicine Foundation Second Trimester Screening Group. Progesterone and the risk of preterm birth among women with a short cervix. N Engl J Med 2007; 357:462-9
    
    
    a. For England and Wales, deaths listed as due to “immaturity related conditions”
    
    b. For Scotland and Northern Ireland, deaths listed as due to “disorders related to length of gestation and fetal growth”
    
    c. Calculation made by Action Medical Research based on figures in references 5 and 6 for the number of births a year in the UK and the number of preterm deliveries in England, respectively. Estimate assumes incidence of premature birth is the same for the UK overall as it is for England.