Comparing Neonatal Mortality Rates for CNMs and Other Midwives
I’ve been following with interest the discussion of homebirth midwife education at The Skeptical OB.
In her post, Dr. Tuteur repeats her oft-made claim that direct-entry midwives (DEMs) are poorly trained and incompetent compared with MDs, certified nurse-midwives (CNMs) and midwives in other wealthy countries.
Many claims for the safety of CPM-attended homebirth are the frequently cited Johnson & Daviss study, in which the authors concluded that planned homebirth with a CPM had intrapartum and neonatal mortality rates comparable to hospital birth (and which Dr. Tuteur has critiqued), but I was curious to see if there was any other evidence.
I took a closer look at the CDC’s so-called WONDER Database (cited in my recent post on the ACNM), which contains information on births and deaths of infants born in the U.S. between 1995 and 2005, querying the database for early neonatal mortality rates among different providers for low-risk women.
I hadn’t planned on posting about it, but what I found was so startling that I thought I would offer it up for discussion.
In every case, mortality rates for the “other midwife” category is considerably worse than for other categories. When compared with those for CNMs (the group with patients most closely matched for risk level), other midwives’ mortality rates are at least three times higher.
In an attempt to eliminate neonatal deaths due to issues not generally related to quality of obstetrical care, I used the following parameters:
- Early neonatal deaths = < 1 hour to 6 days of age
- White women, ages 20-44
- 37+ weeks gestation
- Singleton pregnancy
- Prenatal care beginning in months 1-6
- Birth weight 2500+ grams
- Deaths due to “certain conditions originating in the perinatal period”
To eliminate (insofar as possible) unassisted births, I also eliminated births within the following parameters:
- Place of birth listed as “unknown or not stated”
- Medical attendant listed as “unknown or not stated” or “other”
Note: I did not query the database for 1995-1998 because it does not allow queries by attendant type, and uses ICD-9 codes for cause of death, which may not match up with later ICD-10 codes. The CDC separates databases for 1999-2002 and 2003-2005 because the latter group includes additional categories for maternal race.
I have denoted with an * where the numerators are <20, and the morality rate does not meet National Center for Healthcare Statistics standards for reliability or precision.
|CDC WONDER 1999-2002: Early neonatal deaths—low risk women—perinatal causes|
|CDC WONDER 2003-2005: Early neonatal deaths—low risk women—perinatal causes|
One claim frequently made by proponents of midwifery and out-of-hospital birth is that physicians and CNMs who practice in hospitals are too quick to induce postdates babies, so I also calculated rates for neonates born at 41+ weeks gestation.
Mortality rates for postdates neonates were significantly higher for non-CNM midwives than for any other attendants.
|CDC WONDER 1999-2002: Early neonatal deaths–perinatal causes–41+ weeks gestation (otherwise low-risk)|
|CDC WONDER 2003-2005: Early neonatal deaths–perinatal causes–41+ weeks gestation (otherwise low-risk)|
For a wide variety of reasons , this data cannot be used to draw valid conclusions about the competence of any group of providers.
One particularly important caveat is that the numbers for the “other midwife” category are so small that a single death can disproportionately influence the mortality rate.
Nevertheless, I find it interesting that the numbers consistently point to poorer outcomes for non CNM-midwives (I ran several additional queries using other parameters that revealed similar results, but chose not to include them here because they included factors that either placed the mothers at higher risk, or causes of death largely unrelated to birth.)
What it suggests is not necessarily that non-CNM midwives are incompetent, but that it is incumbent upon the organizations that advocate for them to conduct or sponsor additional, high-quality research into potential disparities in quality of care, both among differently-trained midwives, and between non-CNM midwives and other providers.
- 1. This is raw data, and can’t be compared with a meticulously designed and conducted study for a wide variety of reasons, including:
- It is based on birth and death certificate information, which can be unreliable, particularly with regard to cause of death.
- It contains only information about actual place of birth rather than intended place of birth, which would be important in determining which deaths were due to unintended out-of-hospital birth, and which deaths occurred in hospital after transfer from homebirth or other out-of-hospital settings.
- It provides fairly simple parameters with which to eliminate potential confounding factors.
- The “other midwife” category includes all non-CNM midwives, from CPMs to lay midwives.
- Finally, and most importantly, this is based on my own review of the database. I am not a scientist, and have little formal education in statistics. Anything I say here should be taken as nothing more than the observations of an interested lay person.