OBJECTIVE: To assess the prognosis for vaginal delivery in women with entirely normal pregnancies who began spontaneous labor at term.I'm trying to fathom how only 37% of the women in this study had "normal" pregnancies that culminated in spontaneous labor (that is, without induction or a scheduled c-section). And I'm just failing. If you tally up all the women with prior cesareans, high blood pressure, gestational diabetes, placental abnormalities, and so on - do they really add up to nearly two-thirds of all pregnant women?
METHODS: Between January 1, 1988, and October 31, 2006, a total of 278,164 women delivered newborns at our hospital. A subset of women with uncomplicated pregnancies and spontaneous labor between 37 and 41 weeks of gestation then were identified for analysis of maternal and neonatal outcomes. The outcomes we studied included admission-to-delivery intervals, use of epidural analgesia, maternal perineal trauma, route of delivery, and several potential indices of neonatal condition at birth.
RESULTS: There were 103,526 (37%) women who delivered at our hospital during the study period who had normal term pregnancies and entered labor spontaneously. Overall, 96% of these women had vaginal deliveries, and adverse neonatal outcomes were rare. For example, perinatal deaths occurred in 0.3 of every 1,000 women.
CONCLUSION: Approximately one third of pregnant women have entirely normal pregnancies and enter spontaneous labor at term. Virtually all such women can anticipate safe vaginal deliveries for themselves and their infants.
[My emphasis. That's the entire abstract, but you can find it here. The full article is inObstetrics & Gynecology (April 2009, vol. 113): 812-816.]
Yeah, the authors appear to be making a case for the safety of vaginal childbirth. But they do so on the basis of such a small subset of women that their conclusions can't carry any real force. Skeptics looking at their findings can easily object that the safety of vaginal delivery only applies to the healthiest women.
I'd really, really like to know how the study's authors defined "normal." I tried to look at the full text of this article, but my university's library doesn't carry this journal at all anymore - apparently not even in the print version - presumably because it's too expensive.
At any rate, it's a seriously through-the-looking-glass world when "normal" childbirth is defined such that it's actually outside the norm - that is, abnormal.
Update, March 25, 2009, 2:30 p.m.: Commenter smk has kindly provided the full text of the study. Its definitions of "normal" and "uncomplicated" closely match my assumptions, except that I neglected to mention anticipated fetal abnormalities. The authors of the study may serve a higher-risk population than is typical. They write: "Parkland Hospital is a tax-supported institution serving Dallas County that has a neonatal intensive care unit adjacent to the labor and delivery units." Taxpayer support suggests they may serve a disproportionate number of poor women, and the NICU means that the hospital will draw a clientele with an above-average rate of fetal complications.
The authors cite CDC statistics that put 50% of all women into the uncomplicated category. Using the CDC numbers and assuming 25 to 30% fall into the complicated category due to a prior c-section, that would leave 20-25% with significant complications. Those numbers seem slightly less outlandish but still high.