Background and aims
Maternal mortality is the health indicator that shows the greatest differential between developing and industrialised countries. The lifetime risk of death as a result of pregnancy or childbirth is estimated at one in 23 for women in some countries in Africa, compared with about one in 7000 for women in Northern Europe. Less reliable information exists on levels of serious morbidity related to pregnancy and childbirth, and on differentials between developed and developing countries. However, it is clear that those conditions that can lead to maternal mortality occur much more commonly in developing countries, and/or give rise to far higher case fatality rates.
Whether antenatal care can prevent or contribute to the prevention of maternal mortality and serious morbidity is a difficult question to answer definitively. Although systematic antenatal care was first introduced in the early 1900s in Europe and North America, and is now almost universal in developed countries, questions related to its effectiveness have only begun to be tackled comparatively recently. In 1972, Cochrane wrote: ‘By some curious chance, antenatal care has escaped the critical assessment to which most screening procedures have been subjected’. He further recommended that ‘the emotive atmosphere should be removed and the subject treated like any other medical activity and investigated by randomised controlled trials’.1 Current knowledge, doubts and recommendations for antenatal care have been explored in Effective Care in Pregnancy and Childbirth,2 in Caring for Our Future: the Content of Prenatal Care3 and in the articles by Villar and Bergsjø.4,5 These publications, however, largely deal with populations with low maternal mortality, and examine the effectiveness and potential of care in pregnancy to improve perinatal and infant mortality, and the general wellbeing of the family rather than maternal mortality and serious morbidity.
The role that pregnancy care, as distinct from delivery care, has played in this dramatic decline in maternal mortality in the developed world is not clear.6–9 Reviews on improving the status of women, providing family planning programmes, provision of safe abortion services, strengthening antenatal care, improving emergency obstetric services, training traditional birth attendants (TBA) and community mobilisation have provided optimistic10,11 and pessimistic9,12,13 views of the potential of antenatal care to reduce maternal mortality. There is, however, a notable lack of comprehensive and critical reviews of the effectiveness of antenatal care programmes and/or of individual interventions during pregnancy to avert maternal death or severe morbidity. An article challenging aspects of routine care that do, or could improve maternal survival14 provoked responses from many parts of the world.15–20 Solutions were suggested but no firm evidence put forward for the most pressing local problems, which included anaemia, hypertensive diseases of pregnancy (HDP) and unwanted pregnancy.
There is a widespread desire to improve maternity care services and make optimum use of women’s contact with the health services. If considerable resources are to be devoted to providing antenatal care, then it is important to identify which interventions are effective and how best to deliver them. The primary aims of the document are as follows:
• to identify those interventions in pregnancy that have been proved to be effective in terms of reducing major maternal morbidity and mortality;
• to identify promising but unproven interventions to be assessed;
• to define research priorities.
It should be noted that some interventions may not be effective in reducing maternal mortality or morbidity, but are effective in either improving general or perinatal health and, for these reasons, should also be included in antenatal care programmes. The present article updates a review first published by the World Health Organization (WHO) in 1992.21
Scope, sources and definitions
This overview draws together available information on how antenatal care could be used to reduce serious morbidity and maternal mortality, especially in areas where high levels of morbidity and maternal mortality currently arise. In deciding which interventions to include, the overview begins with the main causes of maternal mortality.
The causes of maternal deaths are often multifactorial and involve complex interactions of several medical, obstetric, health service and social factors. Attribution of deaths to a given underlying cause may be an artefact of classification when infection caused by unclean delivery leads to secondary postpartum haemorrhage, or pre-eclampsia to placental abruption, and women do not receive the necessary emergency care.22,23 Nevertheless, haemorrhage, infection (including HIV), obstructed labour, HDP and unsafe abortion are estimated together to account for at least two-thirds of all maternal deaths in developing countries.24 Although the available data on maternal mortality from developing countries are incomplete and not completely reliable, there is general agreement that they are the most important issues to tackle for preventing maternal mortality. From this basis, the overview identifies the antecedents in pregnancy and all the diagnostic, prophylactic and therapeutic interventions that might be employed at various stages to detect, prevent or treat the conditions outlined above.
For descriptive purposes, the WHO defines antenatal care as a dichotomous variable, having one or more visits with a trained person during the preg-nancy, or none. However, it may be taken to mean only the care that is routinely provided for all pregnant women at the primary care level, or every aspect of care from screening to intensive life support provided to any woman while pregnant and up to delivery. Because what is provided at the primary or secondary level varies widely even within developing countries and because effective care for one condition may involve a coordinated series of interventions at different levels, this overview does not use primary or referral level to define antenatal care. Primary care level and first referral level are used here to refer to services that are or should be available to all pregnant women, and to services that are or should be provided to women referred because of complications of pregnancy.
Evidence for the 1992 review21 was sought through searches of the published literature, and from unpublished reports provided by the WHO and several research groups working in the field of maternal health. Extensive searches of Medline and Popline on CD-ROM covering from 1982 to 1992 were carried out using as key words all the conditions and interventions considered, as well as more inclusive terms, such as ‘maternal health care’, ‘prenatal care’ and ‘maternal mortality’, to identify original research studies and reviews. The reference collections on maternal health held by the Maternal and Child Epidemiology Unit at the London School of Hygiene and Tropical Medicine (LSHTM) and by the Family Health Division of the WHO, which include many unpublished or unindexed reports, were systematically searched. Several international groups provided extensive reports of health-care and research projects on maternal health in developing countries that they had carried out, supported or evaluated (see Acknowledgements). Bibliographies and reference lists of papers from all these sources were used to identify important earlier writings. The Oxford Data Base of Perinatal Trials (ODPT) was also searched to identify randomised controlled trials (RCT) and systematic reviews of several interventions. These reviews include pooled estimates of the effects of interventions from meta-analyses of methodologically sound trials.25,26
For the present updated review, new search strategies were developed. Sources searched included the following:
• PubMed, which provides access to the PubMed database of bibliographic information, drawn primarily from MEDLINE and PREMEDLINE. In addition, for participating journals that are indexed selectively for MEDLINE, PubMed includes all articles from that journal, and not just those that are included in MEDLINE. The file contains approximately 9 million records that date back to 1966. Coverage is worldwide, but most records are from English-language sources or have English abstracts. The searches were carried out using as key words all the conditions and interventions considered, as well as more inclusive terms, such as ‘maternal health care’, ‘prenatal care’ and ‘maternal mortality’, to identify original research studies and reviews covering the period from 1966 to December 1999.
• The Cochrane Database of Systematic Reviews (CDSR) 2000, disk issue 2.
• The Cochrane Pregnancy and Childbirth Database (CCPC) 1995, disk issue 4.
• The Cochrane Controlled Trials Register (CCTR) 2000, disk issue 2.
Electronic searches of Medline and CCTR were also performed to identify trials that might have been published after the most recent update of the relevant systematic review, and for interventions where no systematic reviews were available.
In many cases, conclusions from studies in industrialised countries can be generalised to treatment of the same conditions in developing countries. For example, a drug found to be effective in controlling blood pressure in severe pre-eclampsia from trials in Europe and North America is likely to have the same effect on pre-eclampsia in Africa. However, other issues may have to be addressed before treatments are transferred, such as drug safety and the level of supervision required. In addition, it may not be possible to generalise the results because of differences in health patterns.
In this overview, the effectiveness of each intervention is considered in terms of what it is intended to achieve. Thus, for a screening test, this may be defined as its ability to discriminate between those with and without the condition in question; in contrast, a treatment’s effectiveness may be judged by its ability to prevent, cure or prevent progression of a condition or reduce case fatality. Where possible, the evidence that any type of intervention reduces mortality from a given cause is assessed. The main emphasis is on biological effectiveness or efficacy. Once the biological effectiveness is demonstrated, the effectiveness of an intervention in normal practice or as part of a programme can be explored, including operational questions of how best to deliver the treatment in the various situations encountered in developing countries.
The reliability of evidence on effectiveness could be ranked according to The Levels of Evidence and Grades of Recommendations.27 The ‘gold standard’ in assessing the effectiveness of any preventive or therapeutic intervention is the systematic review (SR) of RCTs, followed by a single RCT. When properly conducted, random, concealed allocation to a treatment group eliminates the possibility that differences in outcome between treatment groups are caused by systematic differences in underlying risk between the groups. There are treatments with such dramatic and enor-mous benefit that their efficacy is obvious without the need for a formal trial; for example, the introduction of penicillin to treat puerperal fever in the 1940s. However, most if not all interventions in obstetrics have much smaller effects and an RCT is the only way to obtain a true, unbiased estimate of their efficacy.25 However, RCTs have not been carried out on all interventions of interest. Evidence from other types of epidemiological studies on the effectiveness of interventions has been assessed for this review and the evidence extracted is ranked accordingly.
Although numerous assessments of various aspects of antenatal care in developing countries were identified, many of these did not provide any useful information on the effectiveness of the care being provided. There are several reasons for this. Some studies only set out to measure the process (availability, uptake, number of visits, etc.) of the services and not health outcomes. Others measured various aspects of ‘quality’, including the percentage of attendees who received particular tests or treatment, or who were seen before a given point in their pregnancies. While this information is obviously useful for management of services, the value of those services in terms of improved health cannot be assumed until the effects of the individual interventions or the package on the outcome for mother and infant have been demonstrated. The scale of many studies is too small, so they lack the statistical power to show an effect on important outcomes. Adverse maternal outcomes are uncommon events, and results from many centres may need to be pooled to obtain a clear answer. This can only be done when the studies are similar in several aspects and is best achieved by a planned, multicentre study. In many published reports, insufficient information is given to know whether data can be pooled. Unclear objectives and poor study design often mean that only a portion of the information needed to judge effectiveness is collected. For example, several studies of the risk approach report the percentage of women seen for antenatal care who are judged to be at high risk, or the percentage of those delivering in hospital who are at high risk, but they do not give data on outcome for high- and low-risk groups, either in terms of process (such as percentage delivering where recommended) or health (such as percentage with obstructed labour, incidence of morbidity or mortality). Few studies provide adequate details of the catchment population or possible biases in self- or health service selection for attendance at the antenatal clinic or delivery in hospital. Studies that are sufficiently large, carefully designed and executed, with clear objectives, are needed to establish the efficacy of antenatal care. Rigorous peer review of proposals and publications is needed to ensure the quality of future research.