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Specialized antenatal clinics for women with a pregnancy at high risk of preterm birth (excluding multiple pregnancy) to improve maternal and infant outcomes

RHL Commentary by Oloyede O.A.O

1. INTRODUCTION

Preterm birth, defined as a birth before 37 completed weeks of pregnancy, is a significant contributor to morbidity and mortality in the perinatal, neonatal and childhood periods.. Worldwide, preterm birth is reported to occur in about one in 6–10 pregnancies. The average incidence is 9.7% in the USA, 11% overall in North America, and 5.4% in Europe. In Africa, incidence rates vary from 20.3% in Malawi to 8.5% in Nigeria (1, 2, 3, 4). Women of African ethnicity are at a higher risk of delivering preterm compared with women of other ethnic origins.

Preterm birth is associated with health, economic and emotional consequences. The severity of its impact on fetal outcome depends on gestational age, being highest at the lowest gestational ages at birth. Preterm birth accounts for about half of perinatal and neonatal deaths and contributes to severe immediate and long-term morbidity (5, 6, 7). In terms of economic cost, major infant and paediatric cost savings could be realized by preventing preterm birth (8). The declining health and socioeconomic indices in less developed countries are pointers to a gloomier picture of preterm birth and a justification for intervention.

A rational approach to achieving improved outcome in preterm birth is based on effective screening and application of interventional measures. The traditional screening method for preterm birth relies most on history of previous preterm birth. More recent options include measuring levels of cervical fibronectin secretions and cervical length by ultrasound. Interventional measures are more likely to produce favourable outcomes if these indicators of preterm birth are closely monitored in specialized antenatal clinics. This Cochrane review (9) assessed the benefits of monitoring and caring for women at high-risk of preterm delivery in specialized antenatal clinics compared with the care in "standard" antenatal clinics.

2. METHODS OF THE REVIEW

All published, unpublished and ongoing randomized controlled trials (including cluster and quasi-randomized control trial) were identified from the Cochrane Pregnancy and Childbirth Group’s Trials Register by the Trial´s Search Coordinator. Two independent reviewers using predetermined criteria assessed for inclusion all the identified studies as result of the serach. Whenever necessary, the reviewers consulted the trial authors to clarify discrepancies, thus allowing for objectivity and reliability of review outcome. The reviewer rejected some of the randomized control trials because of lack of clarity about allocation concealment and blinding. The findings and data were clearly summarized and presented using appropriate statistical methods.

3. RESULTS OF THE REVIEW

Three trials conducted in the USA met the inclusion criteria. These included a total of 3400 women carrying singleton pregnancies, considered at high risk of preterm birth (based on previous preterm birth). The interventions in these trials were not similar. The trials had evaluated primary and secondary outcomes related to perinatal death, extreme preterm birth, pregnancy and delivery complications in the mother, infant morbidity and cost implication of care. No single trial evaluated all the outcomes.

Gestational age of 28 weeks was used in the trials to define extreme prematurity, which does not uniformly apply in many under-resourced settings, especially in Africa. Similarly, preterm prelabour rupture of membranes and preterm labour are etiological factors and should not have been classified as secondary outcomes.

With regard to primary outcomes studied, there was no difference in risk of perinatal death (one trial, 302 infants) and extreme preterm birth (defined as <28 weeks gestation; one trial, 376 women) between the treatment and control groups.

Secondary outcomes studied included antenatal complications, preterm birth (birth before 37 weeks gestation), and very preterm birth. Antenatal complications were reviewed in one study, which showed no difference between the treatment and control groups. There was also no statistically significant difference in preterm and very preterm births between the groups. In fact, there were more preterm births in the control group rather than the treatment group (3 trials, 3400 women). No differences were also found for other secondary outcomes, namely gestational age at birth, caesarean section or neonatal intensive care utilization.

The cost of care for women (two trials) was not significantly different between the intervention and control groups, although one study had considered only 10% of population for this outcome and the second had not made a correction for the effect of cluster design used. The number of antenatal visits could influence the cost difference: the number visits was lower (mean 4.9) in control group compared with the experimental group (mean 6.6).

4. DISCUSSION

4.1. Applicability of results

Specialized antenatal clinics for women at high risk of preterm birth are now accepted as part of care in many countries (9). However, there is no firm evidence that specialized clinics reduce the number of preterm births and mitigate their outcomes. The trials included in this review were conducted in the USA, where maternal parity is low and health-care facilities are expected to be optimal. In such settings, previous preterm birth may not be an effective indicator of risk, as about 50% of women affected by preterm birth are primigravida, without a history of preterm birth (10). Specialized clinics may therefore not have the desired impact. However, the use of specialized antenatal clinics may be justifiable in under-resourced settings, where factors such as high parity, cervical injury and infection predominate. More women are likely to screen positive for higher risk of preterm birth, which entails more severe adverse consequences in under-resourced settings. There are, however, some arguments that can be made against specialized clinics. The use of standard antenatal clinics is low owing to economic, sociocultural and literacy reasons. Traditional antenatal clinics and specialists physicians are concentrated in urban areas and are scarcely adequate to take care of the large number of pregnant women in the rural areas, where the majority of preterm birth occur.

4.2. Implementation of the intervention

In the light of the available evidence is not recommended the implementation of specialized antenatal clinics for women at high risk of preterm birth, particularly in under resourced settings.

4.3. Implications for research

Further studies should focus on the specific antenatal care needs of women in under-resourced settings. Future research should examine the parameters similar to those evaluated in the studies included in this review, but should also include other screening methods such as cervical length measurement and fibronectin test. The studies should focus as well on the role and expected impact of involving traditional midwives in the prediction and care of preterm birth using routine risk factors. The costs and benefits of reducing the magnitude of preterm birth and care of preterm babies through specialized clinics should also be examined.

Sources of support: None

Acknowledgements: The advice of Dr OT Oladapo is the preparation of manuscript is well appreciated.

References

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This document should be cited as: Oloyede O.A.O. Specialized antenatal clinics for women with a pregnancy at high risk of preterm birth (excluding multiple pregnancy) to improve maternal and infant outcomes: RHL commentary (last revised: 1 April 2012). The WHO Reproductive Health Library; Geneva: World Health Organization.