4,000 women are missing from the MANA statistics paper; where did they go?*

the missing piece

Geradine Simkins, President of the Midwives Alliance of North America, July 2008.

MANA estimates approximately 20,000 cases will be in the database by the end of 2008.

Peggy Garland, MANA Director of Research, November 2009:

I am pleased to announce the availability of data from the MANA Statistics Project. We have completed review of almost 13,000 records from late 2004 through the end of 2007…

… [W]e expect another 10,000 records will become available for research, spanning 2008-2009.

Melissa Cheyney, August 2011:

The MANA Stats project currently has over 600 active contributors … and our database contains over 27,000 records and counting …

MANA Stats webpage, now:

The MANA Statistics Registry (“MANA Stats”) has gathered has over 24,000 records in the initial (“2.0”) dataset (2004-2009) …

Here’s part of the explanation, accounting for approximately 4,000 women:

Development and Validation of a National Data Registry for Midwife-Led Births: The Midwives Alliance of North America Statistics Project 2.0 Dataset, January 2014:

In 2004, the Midwives Alliance of North America’s (MANA’s) Division of Research developed a Web-based data collection system to gather information on the practices and outcomes associated with midwife-led births in the United States…

The 2004 to 2009 MANA Stats 2.0 dataset includes data from a total of 24,848 courses of care. The sample for the analyses reported here is restricted to 20,893 pregnancies in which women were planning a home or birth center birth at the onset of labor. These pregnancies included 66 sets of twins for a total sample of 20,959 newborns. Excluded from our sample are 521 women who were not planning a home or birth center birth at the onset of labor, 3434 women who transferred care to another provider prior to the onset of labor for either medical (eg, a complication requiring obstetric specialty care) or nonmedical (eg, woman moved during pregnancy) reasons…

The geographic distribution of the births included 35.7% in the Pacific states (Alaska, California, Hawaii, Oregon, Washington); 23.4% in the West (Arizona, Colorado, Idaho, Montana, Nevada, New Mexico, Oklahoma, Texas, Utah, Wyoming); 14.8% in the Midwest (Illinois, Iowa, Indiana, Kansas, Michigan, Minnesota, Missouri, North Dakota, Nebraska, Ohio, South Dakota, Wisconsin); 10.8% in the Southeast (Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, Kentucky, South Carolina, Tennessee, Virginia, West Virginia); 10.0% in the North Atlantic states (Delaware, New Jersey, New York, Maryland, Pennsylvania, Washington, DC); and 5.3% in New England (Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island, Vermont). [my emphasis]

Outcomes of Care for 16,924 Planned Home Births in the United States: The Midwives Alliance of North America Statistics Project, 2004 to 2009, January 2014:

The complete November 2004 through December 2009 MANA Stats 2.0 dataset (N = 24,848) includes records from all women receiving at least some prenatal care from contributor midwives. For the purposes of this analysis, we excluded women who transferred care to another provider prior to the onset of labor, women who at the onset of labor had a planned birth location other than home, and women who did not live in the United States. Thus, our final sample for this analysis consisted of all planned home births (N = 16,924).

We already know from the companion paper that 20,959 newborns were left after excluding 521 women who were not planning a home or birth center birth at the onset of labor and 3434 women who transferred care to another provider prior to the onset of labor. Moreover, according to the companion paper, 100% of the women in the studies lived in the US. How, then, could nearly 4000 additional women be excluded for not living in the US?

Unless MANA accidentally misrepresented the number of women in the study or the number of women excluded, they appear to have left out nearly 20% of the patients in their database.


And what would that data show if it were included?


* A commentor pointed out that the difference may be that the first paper includes birth center births, while the second paper excluded them. That would make sense. However, it doesn’t explain why they claim to have excluded women who lived outside the US even though the first paper indicates that all the women lived in the US.

If the women excluded from the second study were women who gave birth at birth centers, a comparison between outcomes would have been useful. It’s curious that they didn’t include it.