MIDWIFE-LED BIRTH CENTERS: THE RESEARCH
There has been extensive research about the safety of birth centers, including two major studies of outcomes at US birth centers, along with a systematic review of 17 different studies of birth center safety in the US, a systematic review of 23 international studies of maternal outcomes in birth centers, and a large study of outcomes at a single US birth center.
This body of research suggests that outcomes for women who choose midwife-led birth centers are as good as those for low-risk women who choose hospital birth, including rates of neonatal and perinatal mortality.
Women who choose birth centers also have lower rates of interventions, including:
- cesarean birth
- induction and augmentation of labor
If you plan to give birth in a birth center, you need to be prepared for the possibility of transfer. The research studies show that 12 – 20% of women who labor in a birth center end up transferring to the hospital. Most transfers (about tw-thirds) are for failure to progress. Your likelihood of needing to transfer is higher if this is your first baby, and lower if you’ve already given birth. Fewer than 1% of women or newborns require emergency transfer in labor.
WHAT IS A MIDWIFE-LED BIRTH CENTER?
A midwife-led birth center is a freestanding birth center, or a birthing unit within a hospital that is separate from the labor & delivery unit. All Chicago-area birth centers are accredited by the Commission for the Accreditation of Birth Centers (CABC) applying the standards for the American Association of Birth Centers.
The standards for CABC accreditation include that:
1. FOR LOW-RISK WOMEN, OUTCOMES IN MIDWIFE-LED BIRTH CENTERS ARE AS GOOD AS IN THE HOSPITAL
The safety of midwife-led birth centers is not controversial. No major study has reported poorer outcomes for the babies of women who plan birth in accredited birth centers as compared to women of similar risk giving birth in the hospital.
The best available evidence on birth centers in the US comes from two major studies: the National Birth Center Study, 1985 to 1987 (“NBCS I”), Rooks, J. P., Weatherby, N. L., Ernst, E. K., Stapleton, S., Rosen, D., & Rosenfield, A. (1989). Outcomes of care in birth centers. the national birth center study. The New England Journal of Medicine, 321(26), 1804-1811; and the National Birth Center Study II, 2007 to 2010 (“NBCS II”), Stapleton, S. R., Osborne, C., & Illuzzi, J. (2013). Outcomes of care in birth centers: Demonstration of a durable model. Journal of Midwifery & Women’s Health, 58(1), 3-14. doi:10.1111/jmwh.12003.
NBCS I, published in 1989, followed the pregnancies of almost 18,000 women who planned to give birth in 84 birth centers around the country. Researchers found a combined rate of intrapartum mortality (babies dying during labor) and neonatal mortality (babies dying shortly after birth) of 0.7/1000 births. For comparison, the researchers looked at studies of comparably low-risk women giving birth in three major US hospitals during the same time period. Those studies reported combined intrapartum and neonatal mortality rates of 1.0 to 4.3/1000 hospital births. So the combined intrapartum and neonatal mortality rate for birth centers was lower than the rates in the comparison hospitals.
NBCS II, published in 2013, followed more than 15,000 women planning to give birth in accredited birth centers at the onset of labor. In this second study, the intrapartum mortality rate was 0.47 per 1000 and the neonatal mortality rate was 0.4/1000. Again, researchers concluded that the intrapartum and neonatal mortality rates in birth centers were comparable to rates for low-risk women planning to give birth in hospitals.
A third study—a 2018 systematic review of birth center outcomes—also found birth centers to be as safe as hospitals for the babies of low-risk women. Phillippi, J. C., Danhausen, K., Alliman, J., & Phillippi, R. D. (2018). Neonatal outcomes in the birth center setting: A systematic review. Journal of Midwifery & Women’s Health, 63(1), 68-89. doi:10.1111/jmwh.12701. The researchers looked at results from 17 different studies. They concluded that “no reviewed study found a statistically increased rate of neonatal mortality in birth centers compared to low-risk women giving birth in hospitals, nor did data suggest a trend toward higher neonatal mortality in birth centers.”
Finally, a 2016 systematic review found excellent maternal safety outcomes for women planning to give birth in birth centers. In the combined population of over 84,000 women included in the 23 quantitative studies examined, “[s]erious maternal outcomes were exceedingly rare, and no maternal deaths occurred following admission to the birth center in any of the studies.” Alliman J, Phillippi JC. (2016). Maternal Outcomes in Birth Centers: An Integrative Review of the Literature. Journal of Midwifery & Women’s Health, 61:21-51, doi:10.111/jmwh.12356.
So all four of the major studies found that US midwife-led birth centers are safe for low-risk women and their babies.
THINKING ABOUT SAFETY
To measure the safety of birth in one setting versus another, researchers typically look at outcomes like neonatal mortality, Apgar scores [a measure of the baby’s health right after birth], and admission to the Neonatal Intensive Care Unit (NICU). Unlike these outcomes, intervention rates (for instance, cesarean birth, induction and augmentation, epidural and episiotomy rates) are not generally considered measures of safety.
But when you want to answer the question “Is this setting safe for me?”, intervention rates may be as important as outcomes. For instance, after a cesarean birth—and especially after repeat C-sections—your risk of complications in future pregnancies goes up. So while a C-section is certainly an “intervention,” you might also consider it a safety outcome. Avoiding a cesarean birth in this pregnancy makes your future pregnancies safer.
So as you think about safety, keep in mind that the research on “outcomes” in different settings is just a starting place.
2. INTERVENTION RATES ARE SIGNIFICANTLY LOWER FOR WOMEN WHO CHOOSE BIRTH CENTERS
NBCS I reported a cesarean birth rate of 4.4% for women planning birth in a birth center, compared to 8.4% for low-risk women delivering in hospitals in 1980. (Hospital C-section rates for low-risk women are considerably higher now.)
While the NBCS II study did not compare birth center and hospital intervention rates, another group of researchers used data from the NBCS II study to make that comparison. Fullerton, J. T., & Severino, R. (1992). In-hospital care for low-risk childbirth. comparison with results from the national birth center study. Journal of Nurse-Midwifery, 37(5), 331-340. They found that intervention rates for women who planned to deliver in a birth center were lower for all interventions they examined:
- External electronic fetal monitoring (7% in the birth center group, 50% in the hospital group)
- IVs (8% in the birth center group, 24% in the hospital group)
- Artificial rupture of membranes (41% in the birth center group, 50% in the hospital group)
- More than four vaginal exams during labor (44% in the birth center group, 53% in the hospital group)
- No solid food (85% in the birth center group, 89% in the hospital group)
- No shower or bath (60% in the birth center group, 86% in the hospital group)
- Episiotomy (21% in the birth center group, 34% in the hospital group)
- Cesarean birth (4% in the birth center group, 9% in the hospital group)
The 2016 systematic review by Alliman and Phillippi had similar findings. Rates for cesarean birth, instrumental delivery, episiotomy, use of oxytocin, pain medication in labor were all lower in the birth center group.
Finally, one other major study also found lower intervention rates in birth centers. A 2003 study compared outcomes for 1,808 women who delivered at an independent birth center (the BirthPlace in San Diego) compared to 1,149 similarly low-risk women who delivered in the hospital. Jackson, D. J., Lang, J. M., Swartz, W. H., Ganiats, T. G., Fullerton, J., Ecker, J., & Nguyen, U. (2003). Outcomes, safety, and resource utilization in a collaborative care birth center program compared with traditional physician-based perinatal care. American Journal of Public Health, 93(6), 999-1006. Women who began labor in the birth center had a cesarean birth rate of 10.7%, compared to 19.1% for the planned hospital group. The birth center group had lower rates of technological interventions (oxytocin induction and augmentation, epidural use) and higher rates of non-technological techniques of labor support (walking and movement, tub or shower use, oral fluids). Id. Table 3. In addition, 23% fewer women in the birth center group had episiotomies.
3. TRANSFER RATES
The percentage of women who transferred to the hospital during labor in these studies ranged from 12% to almost 20%. NBCS I: 11.9%; Jackson et al.: 18.5 %; NBCS II: 16%.]
Women having their first baby were twice as likely to transfer to hospital care than women who had already given birth. Nguyen, Uyen-sa & J Rothman, Kenneth & Demissie, Serkalem & J Jackson, Debra & M Lang, Janet & L Ecker, Jeffrey. (2009). Transfers Among Women Intending A Birth Center Delivery in the San Diego Birth Center Study. Journal of midwifery & women’s health. 54. 104-10. 10.1016/j.jmwh.2008.11.002.
NBCS I reported an emergency transfer rate of 2.4%; NBCS II found that fewer than 1% required emergency transfer during labor.
Overall then, the majority of women planning to give birth in a birth centers were able to do so. For the minority or women or their newborns who required transfer to a hospital, very few transferred for an emergency.
SO WHAT DOES THIS ALL MEAN FOR YOU?
The eligibility criteria for delivering in a midwife-led birth center are quite strict. If you qualify for care, you can feel confident that any Chicago-area midwife-led birth center is as safe for you as a hospital, and you are much less likely to have interventions.
You should keep in mind that the likelihood that you will need to transfer to hospital care during labor is between 12 and 20%, but it will be higher if you are having your first baby. In either case, though, the likelihood that you will have to transfer for an emergency is only around 1–2%.