We cannot rely on the findings of a recent meta-analysis on safety of home birth
Mayor reports (News, 2 July 2010) a meta-analysis(1) has linked
planned home births with a twofold higher rate of neonatal mortality
compared with hospital births. Closer inspection calls this finding into
1. The quality of studies in any meta-analysis is critical but no
assessment was reported. Studies were observational and many were not
matched adequately for confounding risk factors.
2. Misclassification errors are also a concern. Neonatal mortality
data came mainly from small studies, with most weight from one larger
retrospective study on birth registry data for Washington State(2). Here,
some unplanned home births, more likely to have poor outcomes, may have
been misclassified as planned home births as birth certificates did not
distinguish between these.
3. Differences arising from relatively small numbers should be
interpreted with caution as lack of statistical power can give rise to
systematic errors. Differences in neonatal mortality were based on 32
deaths in 16,500 planned home births and 32 in 33,302 hospital births(1).
This lacks the power recommended by the GRADE quality assessment tool(3)
(being phased in by NICE) which suggests 200-400 events are needed. In
contrast, perinatal mortality was based on 229 deaths amongst 331,666
planned home births and 140 among 175,443 hospital births, thus no
Unfortunately Wax and BMJ chose to focus on the neonatal mortality
findings. Outcomes given less prominence were no significant differences
in perinatal mortality, and in neonatal deaths with planned home births
attended by certified midwives. Mothers planning a home birth were
significantly less likely to have a preterm or low birthweight baby. All
the outcomes should be viewed within the overall poor quality of the meta-
analysis, however. Professional journals have a responsibility to report
the findings of studies in a balanced way, highlighting methodological
1. Wax JR et al. Maternal and newborn outcomes in planned home birth
vs planned hospital births: a metaanalysis. American Journal of Obstetrics
and Gynecology 2010;203:x.ex-x.ex.
2. Pang JWY et al. Outcomes of planned home births in Washington
State: 1989-1996. Obstetrics and Gynecology 2002;100:253-9.
3. GRADE Working Group. Grading quality of evidence and strength of
recommendations. BMJ 2004;328:1490-1494.
Competing interests: No competing interests