Friday, July 13, 2012

The Wax study has serious flaws

I've been crunching the numbers myself for years. I've never been in any doubt about them, but it's nice to see confirmation in the literature. The largest homebirth study ever done shows that homebirth triples the rate of neonatal death.

Maternal and newborn outcomes in planned homebirth: a meta-analysis will be published in the September issue of the American Journal of Obstetrics and Gynecology. I was fortunate to obtain an advance copy. More than 342,000 homebirths were compared to more than 207,000 hospital births. The data was obtained by pooling 12 major studies from a variety of countries. These studies include the recent DeJonge study from The Netherlands and the Janssen study from Canada. There are also studies from the US, the UK, Australia and Sweden.

The 12 studies were culled from a search of the scientific literature comparing planned homebirth to hospital birth. Only those studies that used the intended place of birth, as opposed to the actual place of birth, are included. That's important because many homebirth studies look at actual place of birth and thereby include homebirth transfers in the hospital group, skewing the results.

Not surprisingly, the rate of interventions was lower in the homebirth group:

Planned home births experienced significantly fewer medical interventions including epidural analgesia, electronic fetal heart rate monitoring, episiotomy, and operative vaginal and cesarean deliveries. Likewise, women intending home deliveries hadfewer infections, 3-degree lacerations [or greater], perineal and vaginal lacerations, hemorrhages, and retained placentas.
Unfortunately, that lower rate of interventions resulted in a higher rate of neonatal death:
... the overall neonatal death rate was almost twice as high in planned home vs planned hospital births, and almost tripled among nonanomalous neonates. Importantly, these latter observations were consistent across all studies examining
neonatal mortality, regardless of the covered time period...
These findings are troubling:
Of concern, this investigation identified a doubling and tripling of the neonatal mortality rate overall and among nonanomalous offspring, respectively, in planned home compared to planned hospital births. This finding is particularly robust considering the homogeneity of the observation across studies. It is especially striking as women planning home births were of similar and often lower obstetric risk than those planning hospital births. The planned home delivery group commonly exhibited fewer obstetric risk factors such as excessive body mass index, nulliparity, prior cesarean, and previous pregnancy complications.
Why was the neonatal death rate higher in the planned homebirth group?
... 2 cohort studies implicated intrapartum asphyxia in 31% and 52% of planned home delivery perinatal deaths. The past 2 decades have seen a significant decrease in such deaths, with evidence suggesting fewer fetuses experiencing intrapartum anoxia. Speculative explanations for the trend include more liberal use of ultrasound, electronic fetal heart rate monitoring, fetal acid-base assessment, labor induction, and cesarean delivery. Our findings, considered in light of these observations, raise the question of a link between the increased neonatal mortality among planned home births and the decreased obstetric intervention in this group.
I'd like to tell you that this study is rock solid, since it confirms what I have been writing for years. Unfortunately, the study has some serious flaws. First, it includes some data collected more than two decades ago. Second, it includes some papers that looked at very small numbers of births. Third, while it found a dramatically increased risk of neonatal mortality, it found no difference in perinatal mortality. This is not what we would expect if the excess deaths were due to intrapartum stillbirths or failed resuscitations.

The meta-analysis include two large studies from The Netherlands and Canada, both of which showed no difference in perinatal and neonatal mortality rates. The other 10 studies (from the US, the UK, Sweden and Australia) did show increased rates of perinatal and neonatal death. It seems to me that the take home message of the study is not that homebirth is unsafe, but that homebirth can only be safe when practiced by highly trained midwives, fully integrated into the hospital system in countries with strict criteria for homebirth and dedicated transport systems for emergencies. In other words, homebirth is safe in The Netherlands and Canada, but no where else.

This piece first appeared on The Skeptical OB in July 2010.

No comments:

Post a Comment