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Ob/gyns with even a little gray hair have witnessed an extraordinary evolution in our collective thinking about cesarean delivery (CD) over the past three decades. I believe that a variety of factors are behind high CD rates in the United States, and that continued increases are inevitable.
Ob/gyns with even a little gray hair have witnessed an extraordinary evolution in our collective thinking about cesarean delivery (CD) over the past three decades. I believe that a variety of factors are behind high CD rates in the United States, and that continued increases are inevitable. I'll address the epidemiology of CD now; and in coming months, we'll look at managing the logjam of CDs on L&D floors and the looming specter of elective CD.
CD rates began rising in the 1970s, when about 5% of all deliveries were by cesarean section. In the early 1980s, ob/gyns were sincerely alarmed at a seemingly precipitous and unjustifiable increase in the CD rate, which we thought threatened women's health and our financial well-being. The result, some said, was premature acceptance of the safety and efficacy of trials of labor after a prior CD. And so rates of vaginal birth after cesarean (VBAC) peaked in the mid-1990s. After a brief dip between 1989 and 1996, fueled by our national "experiment" with VBACs, CD rates have resumed their climb from 20.7% to 26.1%the highest rate ever recorded, with an increase of 7% in 2002 alone.1
The decline in VBACs is unquestionably the single greatest factor fueling our rising cesarean rates. Since 1996, VBAC rates have fallen a staggering 55%, dropping 23% in the past reporting year alone.1 The principal cause is the realization that such trials of labor are associated with more perinatal morbidity and mortality than we first thought, particularly when cervical ripening with pitocin and/or prostaglandin is involved.2
But that does not fully explain the continuing rise in the CD rate, since primary cesarean accounted for a record 18% of deliveries in 2002, a 7% increase in 1 year and a 23% increase since 1996.1 And the trend does not change when the analysis is restricted to "low-risk" womenthose with term, singleton, vertex presentations. The rise is even more remarkable considering that teenage pregnancies have declined 30% since 1991 and midwife-attended deliveries have increased from 1% in 1975 to 8.1% in 2002, an all-time record.
Why the increase in the primary CD rate? There are several factors, the first of which is the impact of increasing maternal age. The average age of women at delivery in the US has now reached 25 years and 8.3% of births are to women older than age 40long known to be a major risk factor for CD.1 Women over 40 have a 76.7% higher rate of CD than those younger than 30.1 One reason is the increasing frequency of preconceptional medical illnesses, such as hypertension, diabetes, cardiovascular, renal, and autoimmune disease, with advancing age.1,3,4 The current epidemic of obesity, which increases with age, has not helped. Since 1991, the percentage of women who gain more than 40 lb during pregnancy has increased 27%, from 15.1% to 19.2%.1 It's not surprising, then, that the incidence of gestational diabetes has increased 40% since 1989, with 3.1% of pregnancies now affected.1 So, the observed increase in CD in older women can be partially explained by medical complications.5
Advanced maternal age also may be an intrinsic cause of labor abnormalities. Oxytocin use, duration of second-stage labor, CD for failure to progress, and operative vaginal delivery rates are all significantly increased with advancing maternal age.6 Because the prevalence of macrosomia has dropped more than 20% over the past two decades,1 the association between increased CD rates and advanced maternal age may reflect abnormalities in uterine activity or pelvic floor compliance. Regardless of the precise etiology for increases in CD among older parturients, the national trend toward increasing maternal age is likely to be exacerbated in the next few decades.
A second explanation for the rising CD rate is the corresponding rise in labor induction, which has increased 129%, from 9% in 1989 to 20.6% in 2002.1 Legitimate reasons for labor inductionsome of which have been validated by large clinical trialsinclude preeclampsia, diabetes, premature rupture of the membranes at term, chorioamnionitis, fetal growth restriction, and postterm pregnancy. True, many of these disorders have been on the increase in the last 10 years, but the incidence has not doubled. Two major but questionable indications for induction are "impending macrosomia" and "patient choice." The former does not reduce CD rates and the latter appears to increase them by 50% (9.9% vs. 6.5%).7,8
Another putative contributor to the rising CD rate is the steady decline in operative vaginal deliveries. Over the past decade, forceps and vacuum-assisted vaginal deliveries have declined by 61%, from 9.5% in 1994 to 5.9% in 2002.1 In my opinion, abandoning vaginal delivery for term singleton fetuses in breech presentation is appropriate, but it has contributed another percentage point or so to our collective CD rate.9 The rise in multiple gestations is also forcing rates up, since twins are associated with at least a twofold higher rate in CD, and higher-order multiples, though rarer, are almost always delivered by CD. The national "twinning" rate has increased 38% since 1990 and 65% since 1980.1,10 I doubt that rates of multifetal pregnancy will decline, given increasing maternal age and availability of ever more ART services.
Finally, there is the "elephant in the room"the unspoken, unquantifiable, yet unquestionable effect that the professional liability crisis is having on CD rates. Nonreassuring fetal heart rate tracings that once might have been tolerated or would have prompted a fetal scalp pH are now grounds for CD. The onset of chorioamnionitis, which we formerly managed with acetaminophen and antibiotics, is now a clarion call for CD. Operative vaginal delivery is rapidly becoming a lost art and VBACs, I believe, will all but disappear in the next few years.
And so, I fully expect CD rates to continue upward for the next few years. Barring concerted societal pressure to lower the rates and tort reform, I predict that our national CD rate will peak at around one third to one half of all deliveries by the end of the decade. The immediate effect will be intense pressure on L&D operating room capacity. The latter may lead to quality assurance issues if emergent CDs cannot be done quickly enough because operating rooms and/or anesthesiologists are not available. How to manage this "traffic-control" nightmare will be the topic of next month's editorial. In Part 3 of this series, we'll talk about the potential for an explosion in requests for elective CDs, given the growing perception that CD lessens risk of pelvic floor damage and optimizes fetal outcome. The result could be national CD rates well above 50%, which already are a reality in several Latin American countries.
1. CDC National Vital Statistics Report. Vol 52. No. 10. December 17, 2003.
2. Lockwood CJ. Into the vortex. Contemporary OB/GYN. 2001;(46)8:8-12.
3. Hollander D, Breen JL. Pregnancy in the older gravida: how old is old? Obstet Gynecol Surv. 1990;45:106-112.
4. Edge V, Laros RK Jr. Pregnancy outcome in nulliparous women aged 35 or older. Am J Obstet Gynecol. 1993;168:1881-1885.
5. Gilbert WM, Nesbitt TS, Danielsen B. Childbearing beyond age 40: pregnancy outcome in 24,032 cases. Obstet Gynecol. 1999;93:9-14.
6. Main DM, Main EK, Moore DH 2nd. The relationship between maternal age and uterine dysfunction: a continuous effect throughout reproductive life. Am J Obstet Gynecol. 2000;182:1312-1320.
7. Gonen O, Rosen DJ, Dolfin Z, et al. Induction of labor versus expectant management in macrosomia: a randomized study. Obstet Gynecol. 1997;89:913-917.
8. Cammu H, Martens G, Ruyssinck G, et al. Outcome after elective labor induction in nulliparous women: a matched cohort study. Am J Obstet Gynecol. 2002;186:240-244.
9. Lockwood CJ. The end of term breech delivery. Contemporary OB/GYN. 2001;(46)9:10-13.
10. Lockwood CJ. It's time for a rational approach to ART. Contemporary OB/GYN. 2004;(49)2:9-10.
Charles J. Lockwood, MD
P.S. Don't miss Joe Leigh Simpson's article on the cystic fibrosis screening guidelines, "Making sense of the CF screening guidelines" and Janet Serwint and colleagues' article on contraception and breastfeeding, "Offering breastfeeding mothers advice on contraception."
Charles Lockwood. Editorial: Why the CD rate is on the rise (Part 1).
Oct. 1, 2004;49:8.