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Flaws In Recent Home Birth Research May Mislead Parents, Providers

September 26th, 2013 by avatar

by Wendy Gordon, CPM, LM, MPH, MANA Division of Research, Assistant Professor, Bastyr University Dept of Midwifery

Midwife Wendy Gordon shares with Science & Sensibility readers why the recent home birth research using 5 minute Apgar scores does not produce reliable data that consumers can use to make a decision on where they would like to give birth.  Have you had a chance to read the study?  What were your conclusions? See if you agree with Wendy or had some different thoughts.  Share your opinion and thoughts with us in the comments section.  Thank you Wendy for providing information that can help us to assess the study and understand it better. Sharon Muza, Science & Sensibility Community Manager

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A recent press release by the authors of a new study raised alarming headlines in a few media outlets, suggesting that babies born at home had a 10-fold higher death rate than babies born in the hospital. I’ve written previously about reliability concerns with the use of birth certificates in this study. In this post, we’ll go more in-depth with some of its other flaws. Let’s start with the fact that the authors did not examine stillbirths.

Apgar scores and stillbirth

The new study by Grunebaum et al. (2013), in press with the American Journal of Obstetrics & Gynecology, examined birth certificate data for almost 14 million births between 2007 and 2010 looking for differences in outcomes between home and hospital births. They did not look at “stillbirths,” perinatal, intrapartum or neonatal deaths. They looked at 5-minute Apgar scores of zero, and led the readers of their press release to believe that this meant that the babies died during or shortly after labor, due entirely to their choice of birthing at home.

When we examine a little more closely what it means to have a 5-minute Apgar score of zero, we might find that it does include some babies who died shortly after birth. We might also find a number of babies who had lethal congenital anomalies, who would not have survived no matter where they were born or who attended the birth; there may be important differences between home and hospital populations with regard to whether these anomalies were detected prenatally and whether parents changed their birth plans because of it. There may also be some babies who were successfully resuscitated after the 5-minute Apgar score was assessed. While the authors conceded in the study that their analysis could have included these births, as well as babies who died before labor even began, the terminology used in their press release is highly misleading.

A rigorous study that actually examined deaths would have excluded births with outcomes that had nothing to do with place of birth or attendant. Several well-designed studies have done just that and have found no differences in mortality rates between planned home and hospital births, and often fewer low 5-minute Apgar scores among planned home births attended by midwives (Ackermann-Liebrich et al., 1996; Olsen, 1997; Janssen et al., 2002; Hutton et al., 2009; Janssen et al., 2009). Grunebaum does not mention that their findings are actually the opposite of what several rigorous studies have already determined.

Absolute vs relative risk

I’ve also written previously about the dangers of reporting relative risks (“ten times higher!”) without acknowledging that the absolute risk of the complication is actually very, very low. Even if Grunebaum’s study had appropriately excluded outcomes that had nothing to do with place of birth, and even if their source of data was reliably accurate — no one is served by omitting the fact that 5-minute Apgar scores of zero are exceedingly rare.

Some of the raw numbers that Grunebaum reports in the study are so low — less than a dozen events within tens of thousands of births, in some cases — that it is hard to imagine how practitioners could use this information to draw any meaningful conclusions whatsoever about clinical practice.

Even with all of the flaws in this study, the rate of zero Apgars in the “home midwife” category in this study was 1.6/1000. This is a very low number. If these results were valid, it would be these absolute risks that mothers and families should be informed about, and honest discussions should be had regarding why there might be a higher risk in the home setting so that families can make the best decisions for themselves about all of the risks and benefits that come with location of birth.

Transfers not accounted for in “planned” home births

A concern that is often raised by anti-homebirth activists is that births that start out as planned home births but transfer to the hospital in labor are actually counted as hospital statistics in birth certificate data. To be fair, these births likely do have worse outcomes. Although most transfers are for non-urgent reasons such as stalled labor or desire for pain relief (Johnson & Daviss, 2005), some transfers occur because medical assistance is needed and the appropriate place to be is in the hospital.

But let’s look at the real impact of these transports. U.S. data shows that about 10% of planned home births result in transport to the hospital during labor (Johnson & Daviss, 2005). Even if Grunebaum was able to accurately capture planned home births and that number truly was 67,429, we could reasonably assume that about 10% of those babies (6743) were born in the hospital. Those babies account for less than 0.05% of the 14 million babies born in the hospital. Even if every single one of those babies had a 5-minute Apgar score of zero, Grunebaum’s rate of zero Apgars in the hospital would increase from 0.25/1000 to 0.49/1000. In reality, only a very small proportion of home birth transports actually do result in such an adverse outcome, and thus essentially have a negligible effect on hospital outcomes.

On the other hand, even a small percentage of misclassified outcomes in the home birth category have a dramatic impact. Because the number of home births in the U.S. is small, the inclusion of prenatal stillbirths, congenital anomalies and unplanned, unattended home births in the “home midwife” category is likely to have an appreciable effect on the negative outcomes examined here. Furthermore, the 10% of home birthers who transport to the hospital and have positive outcomes there are not appropriately attributed to the planned home birth group either. The truth about the safety of home birth simply cannot be determined in this way.

Reliability of birth certificates

I wrote my initial reaction to Grunebaum et al’s study last week when their press release came out. I expressed concerns about the low reliability and validity of birth certificates for drawing conclusions about rare outcomes. Grunebaum’s own data shows that over 10% of “home midwife” deliveries had no information on the birth certificate about the mother’s parity and had to be excluded from their calculations, while only 0.2-0.5% of hospital or birth center deliveries were missing parity data; this strongly suggests that something is amiss with the “home midwife” data.

Epidemiologists and birth certificate scholars have made their concerns about reliability and validity exceedingly clear in an enormous body of literature over the last few decades, and in fact, expressed these concerns directly to Frank Chervenak (co-author on this study) earlier this year when he presented this very data at the Institute of Medicine’s workshop on Research Issues in the Assessment of Birth Settings (IOM & NRC, 2013, p.143). The fact that these authors were clearly warned about the low quality of their data regarding both low Apgar scores — and especially seizures — but chose to push ahead with publication without addressing them, suggests other motivations.

Summary

Families deserve to have the best possible information with which to make decisions about where to have their babies. Grunebaum and co-authors miss the mark by a wide margin with the methodology and conclusions of this study.

To learn more about existing, well-designed home birth studies, 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.

References:

Ackermann-Liebrich, U., Voegeli, T., Gunter-Witt, K., Kunz, I., Zullig, M., Schindler, C., Maurer, M. & Zurich Study Team. (1996). Home versus hospital deliveries: follow up study of matched pairs for procedures and outcome. BMJ 313:1313-1318.

Declercq, E., MacDorman, M. F., Menacker, F., & Stotland, N. (2010). Characteristics of planned and unplanned home births in 19 states. Obstetrics & Gynecology 116(1):93-99.

Grunebaum, A., McCullough, L. B., Sapra, K. J., Brent, R. L., Levene, M. I., Arabin, B., & Chervenak, F. A. (2013). Apgar score of 0 at 5 minutes and neonatal seizures or serious neurologic dysfunction in relation to birth setting. Am J Obstet Gynecol, 209:x-ex x-ex.

Hutton, E. K., Reitsma, A. 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.

IOM (Institute of Medicine) and NRC (National Research Council). (2013). An Update on Research Issues in the Assessment of Birth Settings: Workshop Summary. Washington, DC: The National Academies Press.

Janssen, P. A., Lee, S. K., Ryan, E. M., Etches, D. J., Farquharson, D. F., Peacock, D., & Klein, M. C. (2002). Outcomes of planned home births versus planned hospital births after regulation of midwifery in British Columbia. CMAJ 166(3):315-323.

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.

Johnson, K. C. & Daviss, B. A. (2005). Outcomes of planned home births with certified professional midwives: large prospective study in North America. BMJ 330:1416-

Olsen, O. (1997). Meta-analysis of the safety of home birth. BIRTH 24(1):4-13.

About Wendy Gordon

Wendy Gordon, LM, CPM, MPH is a midwife, mother and educator in the Seattle area.  She helped to build a busy, blended homebirth practice of nurse-midwives and direct-entry midwives in Portland, Oregon for eight years before recently transitioning to Seattle.  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.

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  1. avatar
    Wendy Gordon, LM, CPM, MPH
    October 1st, 2013 at 19:09 | #1

    MomOfMore :
    There are definitely weaknesses in the Grunebaum study, but I do not see how those weaknesses add up to a 10x different relative risk, and the research by Judith Rooks showing similar increased risks further confirms my unease. The magnitude of difference is too high. By the way, Judith Rooks’s sample size is admittedly small for the home birth population, but would it be fair to use her computation of in hospital perinatal mortality rates, albeit knowing that they do not remove infants with congenital anomalies? The rate she gave was .6/1000, which is roughly the same as the average of midwife attended and MD attended in hospital perinatal death in the Canadian study.

    To clarify, neither Judith Rooks nor the State of Oregon conducted “research” — they reported data. As you can see in Ms. Rooks’ analysis, she used an estimate of hospital death rates, which unfortunately was vastly lower than the state’s actual hospital data. While I hear that some folks here are really wanting to stick with Ms. Rooks’ analysis, I think that we would all be better served in our search for understanding if we used actual data rather than estimates. The Oregon State data does not correlate with Grunebaum’s data; nothing does. This Apgar study is out in left field all by itself, and in fact is exactly the opposite of what many other well-designed studies have found (citations listed in my article above).
    Another issue that can be confusing when trying to compare absolute numbers from studies is that different studies use different definitions of death rates. Readers have to be very careful to make sure that the rates they are comparing are actually apples and apples. For example, the de Jonge (2009) Netherlands study reports an intrapartum (IP) death rate, an IP + neonatal death rate in the first 24 hours of life, and an IP + neonatal death rate for the first 7 days of life. Johnson & Daviss (2005) report an IP + neonatal death rate in the first 28 days of life. Janssen (2002 & 2009) report a perinatal death rate that covers deaths from 20 weeks of pregnancy through the first 7 days of life. The Birthplace in England study (2011) reports a neonatal death rate in the first 7 days and a perinatal death rate that is defined similarly to Janssen. Kennare (2009) reports a perinatal death rate of 20 weeks of pregnancy through 28 days of life. Some studies included higher-risk births such as preterm, post-term, breech, twins and VBACs. Some don’t. So when trying to make sense of the numbers, we have to look very closely at what the numbers really mean, how they were derived and who they are talking about.
    The Oregon State report used an unusual definition: term fetal deaths (>37 weeks) and term early neonatal deaths (first 6 days of life). Honestly, I’m not sure how to advise that you use these data to make comparisons with other studies; it doesn’t really correlate with the definitions that most studies have used. I can’t be certain how Ms. Rooks examined her data; she doesn’t define this in her letter to the Oregon state legislature. It appears that she used the state’s “term fetal deaths + early neonatal deaths” data for the out-of-hospital group, but for the hospital group, she used her estimate of intrapartum deaths (which was interestingly… zero) plus early neonatal deaths for the hospital group. I think it’s hard to make honest comparisons between two groups when you use different criteria for each of them. And when we broaden that out to look at different studies and different countries and healthcare systems… there are a lot of factors to consider. But what seems to be clear, time and time again in the most rigorous studies on homebirth safety, is that for women with healthy low-risk pregnancies, there is no increased risk of death (however that is defined in those studies) between planned home and planned hospital births — and that risk is very low — with much lower rates of interventions at home with midwives. When we include unplanned and/or unattended home births (Pang, Wax, Malloy) or women with higher-risk pregnancies (Kennare and others), some differences start to sift out. We have to be very careful about how we evaluate this information; there are many varieties of apples and oranges.

  2. avatar
    Kim Lane, CPM, LM
    October 1st, 2013 at 21:05 | #2

    @Another Liz

    I completely agree with you, Liz!

  3. avatar
    Kim Lane, CPM, LM
    October 1st, 2013 at 21:07 | #3

    @Sarita

    Amen… & … Awomen! ;)

  4. avatar
    Siri Dennis
    October 2nd, 2013 at 02:48 | #4

    Yes, it IS interesting that the OOH intrapartum death rate is zero. Could this be because homebirth midwives are incapable of diagnosing intrapartum death? We read so many birth stories where ‘fetal heart tones were good’ until the baby dropped dead into the midwife’s hands. Or fatally compromised, destined to die in hospital and be counted in hospital statistics. @Wendy Gordon, LM, CPM, MPH

  5. avatar
    Wendy Gordon, LM, CPM, MPH
    October 2nd, 2013 at 06:49 | #5

    @Siri Dennis, you may want to re-read the letters, articles and comments that you’re responding to before you hit the send button.

  6. avatar
    Siri Dennis
    October 2nd, 2013 at 13:12 | #6

    Touche! I was too hasty that time…my bad.

  7. avatar
    Siri Dennis
    October 2nd, 2013 at 13:19 | #7

    Though I’d still appreciate an explanation of exactly how delayed cord clamping saves babies’ lives and brain function… how does it improve Apgar scores, reduce admission to NICU etc?

  8. avatar
    deena chamlee
    October 4th, 2013 at 08:48 | #8

    @Wendy Gordon, LM, CPM, MPH
    Wendy,

    I worked with the Oregon Affiliate and with Judith. I also practiced in Portland at OHSU and Kaiser. Not to base ones opions on transports only, however, the climate was hostile because of the morbidity and mortality regarding high risk ooh births.

    I have never experienced anything like it in my entire career. Groups called MAD AS HELL MOMS which consisted of mothers who lost babies. Protest rallies by families who had lost babies at homebirths, pictures on signs of their dead babies. I mean 20- 30 families.
    Lawsuits by cpms against the regulatory direct entry board when disipline was attempted. Lawsuits by cpm owned birth center against OHSU when an attempt to address morbidity and mortality was made.

    I was contacted on Facebook by moth ers wanting to tell me their traumatic homebirth loss stories. Lawsuits against the state of Oregon by a mother whose baby siffered significant encelphalopathy from hypoxia at a cpm attended birth. And it goes on and on.

    I don’t care about the numbers debate I lived it! Trust me we have major issues to address nationally.

  9. avatar
    M Sonntag
    October 5th, 2013 at 14:34 | #9

    @deena chamlee

    There are also mothers in Oregon who have lost a baby at a home birth who do not agree that home births are more risky, are not members of Mad as Hell Moms, and in fact are attacked online and silenced by those groups. It’s a highly polarized debate, but the loudest voices are not always in the right – sometimes they are just louder. That’s why we NEED numbers. We can’t base policy on whomever is shouting the loudest (witness the current state of the American government).

  10. avatar
    deena chamlee
    October 5th, 2013 at 16:03 | #10

    @M Sonntag
    @M Sonntag

    As I said, I have never and I mean never be exposed to anything as sad. I have never experienced a complete and total consuming feeling of total depression as I did back in May of 2011.

    The numbers are needed and I am working on writing a paper. The birth data by state may be limited to only those states who collect outcomes on home births.Thus, limiting over all sample size.

    The CDC Wonder isn’t the best but I do feel that querring the database could possibly assist with understanding what in the world is occuring and why.

    Gestaltly, I feel outcomes are directly related to educational standards, state regulations and inclusion and exclusion criteria.

    In hospital providers also must take some responsibility for not offering informed choice at in hospital settings. And for not supporting midwifery led services so informed choice can be offered.

    Multifactorial, complex and heartbreaking. I am telling you the mortality and morbidity rate in Oregon was horrific. If it wasn’t I certainly would not have experienced such a hostile environment. And it was unfathomable.

  11. October 9th, 2013 at 05:05 | #11

    Siri, I am not a midwife but I am a HypnoBirthing childbirth educator. Cord clamping has become a big deal. Studies have been done on small animals which have had the cords clamped immediately and during autopsies, they have found that their brains (specifically frontal lobes)showed contusions- this would be the same result in a human who was strangled to death. The part of the brain does not get enough oxygen and small parts begin to die. Is it any wonder there is a 47% increase in learning disabilities with standard cord clamping? When baby is born, 30%-50% of it’s blood is still in the placenta and cord. If baby does not get all or more of that blood, its little body is going to have a very hard time filling up those flappy little lungs to start working. If baby can’t draw blood from other areas of its body fast enough to fill up the lung tissues, then it will experience “respiratory distress” and be taken away, missing out on optimal bonding time with its parents. The cord is there as a secondary oxygen source while baby learns to breathe on its own- this is a new experience for baby and does not come immediately. Babies transition into breathing as much as everything else.It might only take 20 seconds but those are some important 20 seconds!

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