New Study Shows Excellent Outcomes in Birth Centers

By Rachel Walden |

More than 9 out of 10 women (94%) who entered labor planning a birth center birth achieved a vaginal birth

According to the CDC, in 2009, 98.9 percent of all U.S. births were in hospitals, while only 1.1 percent took place elsewhere.

Many women, however, wish to give birth in an environment that is more homelike, or want to reduce their likelihood of experiencing many of the interventions that have become very common in hospitals, such as continuous electronic fetal monitoring, induction of labor, and cesarean section.

Of the non-hospital births documented in 2009, 27.6 percent (just over 12,000 births) took place in freestanding birth centers — an option for women interested in giving birth with trained professionals outside of hospital obstetrics units. At birth centers, midwives generally provided prenatal, birth and postpartum care.

Now, there’s a large new study showing that birth centers are a safe option for both mothers and babies, reaffirming safety findings from previous research.

The study, published in the Journal of Midwifery & Women’s Health, looked at data from U.S. birth centers to assess outcomes for women and babies, including the need for a hospital transfer, mode of birth, complications, and deaths from 2007 through 2010.

The study is referred to as the National Birth Study II (NBSII); the research is an update of the National Birth Center Study conducted by Judith Rooks and colleagues and published in 1989.

The study gathered data from member organizations of the American Association of Birth Centers; 79 birth centers took part, with 59 of those sending data for the complete study period. The analysis included 15,574 women who planned and were eligible for a birth center birth at the onset of labor.

What does “eligible” mean in this context? Pregnancies considered medically low-risk: single-baby deliveries; pregnancies that went to full-term; and no breeches or medical/obstetric risk factors that required cesarean, continuous electronic fetal monitory, or labor induction.

Among the findings:

  • Of the women admitted to the birth center in labor, 87.6 percent did give birth there. The rest (12.4 percent) were transferred to the hospital. Most of the transfers were considered non-emergencies and occurred because of prolonged labor or arrest of labor. Just 1.9 percent of women or newborns required emergency transfer. Women who had never given birth before accounted for most (81.6 percent) of the transfers.
  • A few women (4.5 percent) planned to give birth at a center but were not able to, for issues such as breech, premature membrane rupture, or the woman’s choice.
  • Most of the births (92.3 percent) for all women who planned a birth center birth were head-first, spontaneous vaginal births. The mode of birth data includes women who transferred to a hospital as well — 1.2 percent ended up with an assisted vacuum or forceps birth, and 6.1 percent ended up having a cesarean birth.
  • There were no maternal deaths.
  • Women can mostly expect care from Certified Nurse-Midwives at AABC birth centers. Most of the care providers in the study were CNMs (80 percent, in 63 of the birth centers); Certified Professional Midwives or Licensed Midwives provided care in 11 of the centers (14 percent). In five of the centers, care was delivered by mixed teams of these providers.

There are some things the study can’t tell us, such as the outcomes at non-AABC birth centers and at AABC centers that don’t report their data to the AABC registry, and outcomes for women attempting vaginal birth after a prior cesarean (because most birth centers do not support it).

The NBSII study found a rate of 6.1 percent for cesareans. The authors looked at the cost savings related to reducing cesareans, and conclude, “Had this same group of 15,574 low-risk women been cared for in a hospital, an additional 2,934 cesarean births could be expected.”

They base this comparison on national rates of cesareans in low-risk women, currently reported at 26.5 percent (derived from data reported on birth certificates).

“Given the increased payments for facility services for cesarean birth compared with vaginal birth in the hospital,” the researchers wrote, “the lower cesarean birth rate potentially saved an additional $4,487,524. In total, one could expect a potential savings in costs for facility services of more than $30 million for these 15,574 births.”

I had some questions about whether the 26.5 percent figure was the best comparison group (versus older data with a lower rate), so I emailed the study authors, who responded: “It is not a perfect comparison, because this pool of low-risk women from birth certificate data may not be as stringently selected as women screened for birth center eligibility. But it is the best estimate we have for low-risk women being cared for in hospitals.” [We can discuss this issue in more detail in the comments if anyone is interested.]

Without a perfect comparison, we can still safely assume that the rate of cesarean is pretty low for women who qualify for AABC birth center births. It’s also fair to assume that very few women at AABC birth centers require emergency transfer to a hospital, and that the vast majority (almost 80 percent) of women who qualify for birth center care do end up giving birth there and being discharged to home.

There were no maternal deaths recorded in the study, and low fetal/neonatal death rates — the researchers found an intrapartum fetal mortality rate for women who were admitted to the birth center in labor of 0.47/1,000, and a neonatal mortality rate excluding lethal anomalies of 0.40/1,000. From this, we can conclude that AABC birth centers are a reasonably safe choice for low-risk women.

On Feb. 13, the American Association of Birth Centers and the American College of Nurse-Midwives are holding a Congressional briefing focused on the role of midwives and birth centers in potentially affecting health care costs and outcomes (such as cesarean rates). More information and registration are available here.

For more information, here a Q&A about the study. Visit Science & Sensibility for an interview with one of the study’s authors.

Plus: “It took more than two decades of labor,” writes Julie Deardorff in the Chicago Tribune, “but Illinois is finally poised to permit its first free-standing birth center, an alternative model of care for low-risk pregnant women who want to deliver in a homey environment with a reduced chance of medical interventions.”

Read about the pilot program and steps supporters took, along with the Illinois Department of Public Health, to negotiate with hospitals and doctors.

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3 Comments

  1. As you point out, we must take into account that women choose to deliver in a birth center are a self-selected group who differ markedly from the general population. They are more likely to be white, married and well educated and they are far less likely to smoke, drink alcohol or be obese.

    What is the appropriate comparison group? It’s women who choose to deliver in the hospital with a CNM. There are a number of studies performed in the past 2 decades that look at outcomes for women who delivered with CNMs in a hospital. The C-section rate in that group ranges from 4-8%. Moreover, women who give birth in the hospital have access to pain relief, something that most women want.

    There is no particular benefit to delivering in a birth center with a CNM as compared to delivering in a hospital with a CNM. There’s no decrease in C-section rate, and no savings from C-sections that were avoided.

    So while this paper makes an excellent argument for the safety of accredited birth centers that employ strict eligibility criteria, it does NOT show that birth centers reduce the C-section rate or save money by doing so.

  2. Great blog, OBOS! thanks for writing about our newly-published study. I would just like to correct one of your points:

    While the majority of midwives who participated in this study were CNMs, the results were equally excellent for both types of midwives, CNMs and CPMs. CPMs and other Licensed Midwives now own the majority of birth centers in the US and we are pleased to report that CPM-owned and -staffed birth centers are joining AABC in record numbers. A new phenomenon we are noticing is the growing number of joint CNM-CPM birth centers. AABC views itself as an organization where all health professionals who believe in the midwife-led birth center model of care can come together as equals.

  3. Liz says:

    This is the first post I’ve found regarding the birth center study that actually takes a critical look at it. You don’t know how happy this makes me! I am a huge midwifery supporter and aspiring midwife myself, but I’m not so much a fan of misrepresenting the truth.

    My love for OBOS has grown! If that’s even possible.

    It’s pretty clear that one of the objectives of this study was to promote midwifery, and reimbursement for midwifery care. And the comparison between c-section rates was used to emphasize a potential cost savings.

    I haven’t heard that hospital-based CNM practices have c-section rates as low as mentioned in a previous comment. But the ACNM tracks c-section rates for CNMs, and in 2010 found a c-section rate of 8-10%. I do think this would have been a more appropriate comparison.

    I’m also concerned about promoting “birth centers” without the caveat that these results are only applicable in centers where the strict risk-out criteria is observe.

    Thank you OBOS. I have been a fan for longer than you’ve been on the internet. This astute post only elevates the respect I have for you.