The new Australian homebirth study shows what???

Andrew Pesce, president of the Australian Medical Association, has emphasized that his opposition to homebirth is based on the scientific evidence. Indeed, he promised in late November:

There is an article to be published soon in the Medical Journal of Australia which is a 15-year review of 1150 home births and it shows there is a seven times higher risk of a baby dying during home birth than a hospital birth … We feel that if we’re not listened to then the safety of the maternity system can be fundamentally compromised.

The paper, Planned home and hospital births in South Australia, 1991–2006: differences in outcomes by Kennare et al., was published this week and if Dr. Pesce is hanging his case against homebirth on this paper, he better head back to the drawing board. The paper does not show that homebirth increases the risk of neonatal death. In fact, the paper is so poorly done that it doesn’t show much of anything.

Let’s take a moment to consider what a well designed study would look like. When comparing homebirth to hospital birth:

The groups should be created by “intention to treat.” In other words, it does not matter where the patient ultimately delivered. The most important criterion is where the patient intended to deliver at the start of labor.

Like must be compared to like. The hospital group should contain only low risk women, since the homebirth group presumably contains only low risk women.

Unfortunately, the Kennare paper fails to meet either requirement, and a few more besides.

The authors explain how they created the groups for comparison:

Of 300 011 births during the period 1991–2006 (consisting of all livebirths as well as stillbirths of at least 400 g birthweight or 20 weeks’ gestation), 461 that were terminations of pregnancy and 1217 with no antenatal care were excluded. The remaining 298 333 were divided into 297 192 planned hospital births and 1141 (0.38%) planned home births. The latter were defined as any birth that, at the time of antenatal booking, was intended to occur at home. Of these, 792 (69.4%) did occur at home and 349 occurred in hospital after transfer.

Right away there is a problem. The groups were not defined by intention to treat at the start of labor, but rather by intention to treat at the start of prenatal care. So any woman who developed complications during pregnancy and was appropriately transferred to hospital care long before labor began was included in the homebirth group.

Moreover, instead of comparing the homebirth group to comparable risk women who gave birth in the hospital, the authors compared the homebirth group to all women who gave birth in the hospital including premature births, and those with serious complications.

What did they find?

The rate of neonatal death in the homebirth group was 7.9 per 1000 births, compared with 8.2 per 1000 births for planned hospital births. In other words, there was NO difference between the planned homebirth group and the planned hospital group. Oops! That wasn’t what the authors were hoping to find.

So the authors take a different tack:

One third of deaths (3 of 9) among planned home births were due to intrapartum asphyxia compared with 3.6% among planned hospital births. Both intrapartum deaths and deaths attributed to intrapartum asphyxia were considerably more frequent in the home birth group than in the hospital birth group.

And proudly conclude:

In our study of births and perinatal deaths in SA during the period 1991–2006, planned home births had a perinatal mortality rate similar to that of planned hospital births, but had a sevenfold higher risk of intrapartum death and a 27-fold higher risk of death from intrapartum asphyxia.

To which I say: So what? Dead is dead. It it hardly a ringing endorsement of hospital birth to claim that all the dead babies died AFTER birth instead of during birth.

So the study does not show that homebirth increases the risk of neonatal death. What does it show? In my judgment, it doesn’t show anything because it is poorly done. The authors should go back and reanalyze their data. First they should create the groups by intention to treat at the start of labor. Second, they should remove high risk women from the hospital group. Only then is there a chance of obtaining valid, useful results.

If the intention of the authors was to bolster the case against homebirth, it has certainly back fired. Instead, they’ve given Australian homebirth advocates a gift. Homebirth advocates be able to point to this study as showing that homebirth doesn’t increase the risk of neonatal death. Perhaps more importantly, though, homebirth advocates will be able to point to this study as evidence that opponents of homebirth disingenuously sliced and diced the data to make hospital birth look good on at least one criterion. And that criterion, the fact that the homebirth babies died during labor instead of after labor, is absurd.