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access or satisfaction with services) were identified but excluded from our review.
All included studies in the review were therefore assessed using quantitative
checklist criteria (in the case of two economic evaluations, we were able to assess
the quality of the empirical trial and separately use economic evaluation checklists).
Almost a third (31 percent) of the included quantitative studies were identified as
‘low quality’ by the team which meant both external and internal validity were
scored as (-) low. Our causal chain analyses are restricted to medium- and highquality
items only. We assessed item quality after completion of the searches, and
to avoid exclusion of potentially valid items, quality was not part of the inclusion
criteria. Of particular note was the lack of clarity or depth surrounding the ethical
conduct of research that involved human subjects.
Out of 114 studies, 21 were identified as high quality (++/++) and 14 medium quality
(either ++/+ or +/++). For those high- or medium-quality studies which included
specific interventions with clearly identified outcomes, we considered whether the
study could be potentially included for meta-analysis. We obtained nine items of
high quality and 8 of medium quality that met these criteria.
Meta-analysis is particularly common in the analysis of studies which include clinical
trials when the samples and results of individual studies are not conclusive enough to
be able to generalise the overall results. It is also commonly used to remove bias
from the conclusions as it combines the results of many trials and allows more
transparency in the interpretation of the results. Despite the many advantages, it
needs careful coding of the studies as well a careful evaluation of the quality of the
papers. One of the key requirements above all for meta-analysis is a complete,
unbiased collection of all the original studies of acceptable quality that examine the
same therapeutic question (Crombie and Davies, 2009). This systematic review
aimed for breadth rather than depth, given the lack of studies in the field.
In Table 3.3, we show the distribution of the high-quality papers which were suitable
for meta-analysis. The overall number of studies was nine, although in a few
instances more than one outcome was included in the analysis.
Table 3.3: Distribution of items coded as ‘high quality’ and suitable for metadata
by outcome and focus
Intervention
outcome
Clinical Non-clinical
Maternal mortality Dumont et al. (2005)
Neonatal mortality Darmstadt et
al. (2008)
Kaestel et al.
(2005)
Infant mortality Darmstadt et
al. (2008)
Kuhn et al.
(2008)
Martins et al.
(2008)
Dumont et al. (2006)
Jakobsen et al. (2008)
Mbori-Ngacha et al. (2001)
What are the effects of different models of delivery for improving maternal and infant health
outcomes for poor people in urban areas in low income and lower middle income countries? 27