More careful meta-analysis would have demonstrated home birth safety
The article by Tony Delamothe, “Throwing the baby back into the
bathwater,”(1) provides important observation about obstetric reaction to
home birth research. It follows the uncritical news report in the BMJ(2)
that highlighted a home birth meta-analysis(3) which fell short of the
accepted standards of analysis and presentation espoused by groups like
the Cochrane Collaboration. Delamothe recognizes the disconnect between
science and medical obstetric opinions on the home birth safety issue,
which vary, dependent on the country. Then he queries why the authors of
the American meta-analysis shifted focus from perinatal mortality to
neonatal mortality “despite having relevant data for these calculations on
only 9% of their total sample.”(1)
The answer to this question is the key in undoing the original
conclusions of the meta-analysis. The researchers included the very large
Dutch study in their meta-analysis of perinatal mortality, and found no
difference in outcomes between planned home and planned hospital births.
When the authors isolated the neonatal risk from the perinatal risk, they
chose to include only studies that looked at combined early (0-7 days) and
late (8-28 days) neonatal mortality (deaths in the first 28 days).
Conveniently, that allowed them to leave out the Dutch study because it
reported only on early (0-7 day) neonatal mortality. However, across
perinatal/neonatal studies in high resource countries, 2/3 to 4/5 of
neonatal deaths consistently occur in the first 7 days.(4)
The Dutch study represents over 90% of the home births in all the
studies summarized in the meta-analysis and there is no reason to expect
that the rate of later neonatal mortality would carry any difference in
safety had it simply been reported or requested. Thus, setting up the
methodology in this way and then running shamelessly with conclusions that
focus on less than 10% of the data, to suggest a twofold higher rate of
death with home births compared to hospital, is a form of cultural myopia
most politely described as academic oversight.
Of equal if not greater concern is that the exclusion of the high
quality Dutch study from the neonatal mortality analysis means that it has
been displaced by an American study by Pang et al., which consequently
becomes the largest contributing study to the neonatal risk estimate.
Based on birth certificates, this study does not meet the more
sophisticated approaches of home birth research that since the 1980s have
required home/hospital birth comparisons to stratify for whether the home
births in the studies were planned and had a midwife or physician in
attendance,(5) as the Dutch study does.
Leaving out the Pang study or including the Dutch study would have
meant that the authors could not have jumped to the conclusion that less
medical intervention or home birth creates higher neonatal risk. Rather,
the more accurate conclusion of the meta-analysis would read, “planned
home birth produces the same intrapartum and neonatal outcomes as planned
hospital birth with far less intervention.” Not so savory for the
international media, but fairer for birthing women.
(1) Delamothe T. Throwing the baby back into the bathwater. BMJ
341[c4292], 331. 14-8-2010.
(2) Mayor S. Planned home births are linked with higher rates of
neonatal mortality, study shows. BMJ 341[c3551], 69. 10-7-2010.
(3) Wax JR, Lucas FL, Lamont M, Pinette MG, Cartin A, Blackstone J.
Maternal and newborn outcomes in planned home birth vs planned hospital
births: a metaanalysis. Am J Obstet Gynecol 2010.
(4) World Health Organization. Neonatal and Perinatal Mortality.
Country, Regional and Global Estimates. 51. 2006. Geneva, Switzerland,
World Health Organization .
(5) Johnson KC, Daviss BA. Comment on:Outcomes of planned home
births in Washington State: 1989-1996. Obstet Gynecol 2003; 101(1):198-
Competing interests: No competing interests