by Wendy Gordon, CPM, LM, MPH, member of the Coordinating Council of the MANA Division of Research
Yesterday, a press release was issued drawing new attention to the American Journal of Obstetrics and Gynecology’s not yet published research that finds that babies born at home are “roughly 10 times as likely to be stillborn and almost four times as likely to have neonatal seizures or serious neurologic dysfunction when compared to babies born in hospitals.”
First, it is vitally important to note that this study did not actually examine rates of stillbirth, but rather 5-minute Apgar scores. The press release is completely misleading and inaccurate on this point. We will return to this issue below.
This research stands in sharp contrast to a large and growing body of research that shows that, for low-risk women with a skilled midwife in attendance, home birth is a safe option for newborns with lower rates of interventions and complications for mothers. In addition, it opposes the enormous amount of research regarding the usefulness of birth certificate data to draw conclusions about rare outcomes.
Haven’t we seen this guy before?
These claims - and these co-authors - are not unfamiliar to home birth scholars. The first glimpse of this study’s results was seen at the Institute of Medicine’s “Research Issues in the Assessment of Birth Settings” workshop earlier this year.
The early findings were presented at the IOM workshop by Dr. Frank Chervenak, a co-author of the study - whom you may remember from the notorious “recrudescence” article, where he argued that physicians have a professional responsibility to advise against home birth (read responses from consumers here and here and an analysis of the science behind it here.)
During Chervenak’s presentation of this data at the IOM workshop, serious concerns about the methodology were raised - none of which appear to have been addressed in this final article. So now that the full study is seeing the light of day, what are the concerns? And what does this research tell us?
What are the limitations of birth certificate data for this kind of research?
This research, which claims to be the largest study of its kind, relies on data from birth certificates (known as “vital records”). What we know about using information drawn from birth certificates is that they are pretty good for capturing information about things like mother’s age and whether she is carrying twins. They are not very accurate when it comes to rare outcomes like very low Apgar scores, seizures, or deaths (Northam & Knapp, 2006). Fortunately, these outcomes are extremely rare events, regardless of place of birth, but their rarity makes them quite difficult to study - especially when using a source of data that is known to be unreliable. With rare events, even a small number of miscounted events can distort findings and produce misleading interpretations.
A second, deep concern is that birth certificates in almost half of U.S. states still do not adequately capture intendedplace of birth. This has been a fatal flaw in the few studies that have shown adverse outcomes with home birth, and it is a fatal flaw in this study as well. In recent well-designed studies that captured planned place of birth andused better sources of data, there were no differences in 5-minute Apgar scores between home and hospital settings (Hutton et al, 2009; Janssen et al, 2009; van der Kooy et al, 2011).
The fact that vital statistics data can’t tell us much about the safety of home birth has been well-established by birth certificate scholars and epidemiologists. At the IOM workshop, Marian MacDorman, Senior Statistician at the National Center for Health Statistics, CDC, clarified how to interpret the this type of data. In response to Chervenak’s presentation on the data in this study, she pointed out that regarding low Apgar scores, “the absolute risk is low; that’s all you can say with vital data.” She also made clear that data from birth certificates cannot be used to make comparisons between settings or providers.
What about equating low 5-minute Apgars with stillbirth?
One assumes that the press release was perhaps not carefully reviewed by the authors of the study, as they did not actually examine data about stillbirths. They analyzed the rare occurrence of 5-minute Apgar scores of zero, which may be indicative of a number of possible events which may or may not have been related to the time, location or care provider at the birth. The authors note that stillbirths may have occurred in the third trimester, may have been due to lethal congenital anomalies, and other possibilities that are captured in a 5-minute Apgar score of zero. We cannot draw any conclusions about safety when looking at this piece of data in isolation.
We will examine this issue and other methodological concerns more in depth in a later blog post, as will many home birth scholars, undoubtedly. However, if we are committed to providing women and their families with useful information about birth safety, our media materials need to correspond to the actual research conducted.
Concerns that birth in any given setting may pose a risk to mothers or babies need to be taken seriously and examined closely. However, when the underlying data source is flawed, it is difficult to draw meaningful conclusions from the analysis of the data.
To learn more about existing, well-designed home birth data, read here. To learn more about the MANA Stats Project, which provides researchers with a dataset of more than 24,000 planned home birth and birth center births, read here. And watch for new research based on the MANA Stats dataset 2004-2009. Two articles are in press and two more are under review in peer-reviewed journals.
Wendy Gordon, LM, CPM, MPH is a midwife, mother and educator in the Seattle area. She has practiced for several years in both home and birth center settings with nurse-midwives and direct-entry midwives. She is a Coordinating Council member of the Midwives Alliance Division of Research, a board member of the Association of Midwifery Educators, and teaches at the Bastyr University Department of Midwifery.
Hutton, E. K., Reitsma, E. H., & Kaufman, K. (2009). Outcomes associated with planned home and planned hospital births in low-risk women attended by midwives in Ontario, Canada, 2003-2006: A retrospective cohort study. BIRTH 36(3):180-189.
Janssen, P. A., Saxell, L., Page, L. A., Klein, M. C., Liston, R. M., & Lee, S. K. (2009). Outcomes of planned home birth with registered midwife versus planned hospital birth with midwife or physician. CMAJ 181(6-7):377-383.
Northam, S., & Knapp, T. R. (2006). The reliability and validity of birth certificates. JOGNN 35(1):3-12.
van der Kooy, J., Poeran, J., de Graaf, J. P., Birnie, E., Denktas, S., Steegers, E. A. P., & Bonsel, G. J. (2011). Planned home compared with planned hospital births in the Netherlands: Intrapartum and early neonatal death in low-risk pregnancies. Obstetrics & Gynecology 118(5):1037-1046.
Photo credit: Jason Lander on Flickr