Before 2000, evidence on the optimal mode of delivery for breech presentation at term gestation was restricted to information from nonexperimental studies and small, randomized studies.1–4 This situation changed after the publication of the Term Breech Trial,5 which showed that perinatal mortality and serious neonatal morbidity rates were significantly lower after planned cesarean delivery compared with planned vaginal delivery. Despite numerous commentaries, criticisms, and misunderstandings related to trial design and conduct,6–11 the publication of the Term Breech Trial led to an immediate and sustained decline in vaginal breech delivery in many countries.12,13 The American College of Obstetricians and Gynecologists (the College) and the Royal College of Obstetricians and Gynaecologists (RCOG) guidelines published in 2001 recommended planned cesarean delivery as the safest delivery option for breech presentation at term gestation.14,15
In 2004, the 2-year follow-up of children from the Term Breech Trial showed no difference in death or neurodevelopmental delay between the planned vaginal delivery and planned cesarean delivery management algorithms.16 The Premoda study from France and Belgium appeared in 2006 and this large nonexperimental study revealed that perinatal mortality rates, and composite perinatal mortality and serious neonatal morbidity rates, were no different between planned vaginal delivery and planned cesarean delivery groups.17 In response to these developments, the College and the RCOG in 2006 and the Society of Obstetricians and Gynaecologists of Canada in 2009 revised their previous guidelines and recommended that planned vaginal delivery was a reasonable option for breech presentation at term (albeit with strict criteria including informed consent, appropriate patient selection, adherence to intrapartum management guidelines, and with delivery conducted by a skilled clinician).18–20
Despite these remarkable changes in the recommended management of breech presentation at term gestation, no recent North American study has examined the practices and outcomes associated with breech presentation at term gestation. We, therefore, carried out a study to quantify recent temporal changes in the mode of delivery for breech presentation in Canada and to examine outcomes after delivery of breech presentation at term gestation.
MATERIALS AND METHODS
We carried out a cohort study of all women who delivered a singleton fetus in breech presentation at term gestation in Canada (excluding Quebec) between the years 2003 and 2011 using data from the Discharge Abstract Database of the Canadian Institute for Health Information. This database contains information on all hospital discharges in Canada (excluding Quebec, which maintains its own database). Previous studies have shown that the database includes 98% of births in Canada (excluding Quebec) and that information in the database is valid.21,22 Diagnoses and procedures associated with hospital admission were entered in the database by trained health records personnel using the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10CA) and the Canadian Classification of Interventions codes. The study period was confined to between April 1, 2003, and March 31, 2011 when ICD-10 codes were used exclusively (hereafter referred to as years 2003–2011).
Our study focused on nonanomalous, singleton breech deliveries at term (37 weeks of gestation or greater) gestation that resulted in a live birth (ie, multiple births, births with congenital malformations, preterm births, and stillbirths were excluded). Temporal changes in the frequency of such term deliveries in breech presentation were examined by year. Temporal trends in the frequency of the different modes of delivery were also quantified with the mode of delivery classified as vaginal delivery, cesarean delivery with labor, and cesarean delivery without labor. Women who had a cesarean delivery in labor were identified using a previously described algorithm based on diagnosis codes indicating the presence of labor.23,24 We assumed that most women who delivered by cesarean without labor were women who had planned a cesarean delivery, whereas most women who delivered vaginally would have had a planned vaginal delivery. Women in the cesarean delivery with labor group could have belonged to the planned vaginal delivery group (and developed complications in labor), the planned cesarean delivery group (labor onset occurred before scheduled cesarean delivery), or could have had their breech presentation diagnosed in labor (see additional analyses subsequently).
The primary outcome of interest was composite neonatal mortality and serious neonatal morbidity. This included neonatal death, assisted ventilation, convulsions, and specific birth injury. Specific birth injury (potentially attributable to the mode of delivery) included intracranial laceration and hemorrhage resulting from birth injury; other birth injury to the central nervous system; birth injury to the skeleton; birth injury to the peripheral nervous system causing Erb's, Klumpke's, or phrenic nerve paralysis or other brachial plexus injury; or injury to the external genitalia. We also studied any birth injury, which included all the previously mentioned injuries and in addition included birth injury to the scalp, birth injury to other parts of the peripheral nervous system, and other birth injury (to the liver, spleen, sternomastoid, eye, subcutaneous fat, and other specified or unspecified birth injury).
The frequency of adverse neonatal outcomes among all breech deliveries was first contrasted with the frequency of adverse neonatal outcomes among all nonbreech deliveries. Neonatal mortality and morbidity rates among breech deliveries were then estimated by mode of delivery among women delivering vaginally, by cesarean delivery in labor, and cesarean delivery before labor onset (reference category). Logistic regression analyses were used to examine the independent effects of mode of delivery after controlling for potential differences in maternal age (younger than 20, 20–24, 25–29, 30–34, and 35 years or older), parity (zero, one, two to three, and four or more) and obesity as defined by ICD-10CA coding (yes or no). Odds ratios from logistic models were assumed to approximate proportion type rate ratios as the outcomes of interest were rare. Analyses were repeated among women at 40 weeks of gestation or greater to better identify women with planned cesarean delivery and planned vaginal deliveries. This reasoning was predicated on the assumption that women with a planned cesarean delivery would have the elective cesarean delivery scheduled at 39 weeks of gestation. Hence, women delivering by the vaginal route at 40 weeks of gestation or greater (and women presenting in labor at 40 weeks of gestation or greater) would more likely include women with a planned vaginal delivery.
Two-sided P<.05 was considered statistically significant and used to guide inference. All analyses were carried out using SAS 9.2. The data used for this study were a denominalized version prepared under strict confidentiality guidelines by the Canadian Institute for Health Information and accessible at the Public Health Agency of Canada. Individual consent was not obtained from the patients whose data were contained in the database, and approval from an ethics review board was not required by either the Canadian Institute for Health Information or the Public Health Agency of Canada.
Between 2003 and 2011, there were 1,995,379 nonanomalous, singleton deliveries at term gestation in Canada (excluding Quebec). Of these deliveries, 4.5% were to women younger than 20 years of age, 18.5% were to women 35 years or older, 34.0% were to nulliparous women, and 2.3% were to women of parity four or greater. The frequency of breech presentation at term gestation was 2.6% (52,671 deliveries). Among these breech deliveries, the proportion to women younger than 20 years was 2.5%, the proportion to women 35 years or older was 23.1%, 45.4% of breech deliveries were to nulliparous women, and 1.5% had a parity of four or greater.
Table 1 shows the rate of adverse neonatal outcomes among nonanomalous singletons with breech and nonbreech presentation at term gestation. The neonatal death rate among all breech neonates (irrespective of the mode of delivery) was 0.13 per 1,000 live births and not significantly different from the neonatal death rate of 0.15 per 1,000 live births among nonbreech neonates (rate ratio 0.87, 95% confidence interval [CI] 0.38–1.89). However, composite neonatal mortality and morbidity (neonatal death, assisted ventilation, convulsions, and specific birth injury) rates were significantly lower among breech neonates (rate ratio 0.87, 95% CI 0.79–0.96). Significant differences in specific neonatal morbidity included higher rates of assisted ventilation (including continuous positive airway pressure) among breech neonates and lower rates of intrapartum or birth asphyxia, specific birth injury, and any birth injury (Table 1).
The proportion of vaginal deliveries among singletons in breech presentation at term gestation increased from 2.7% in 2003 to 3.9% in 2011 (P for linear trend<.001). In fact there appeared to be a nonlinear trend in vaginal delivery rates with an increase in frequency after 2007 (Fig. 1A). Restriction to women 40 weeks of gestation or greater also showed a significantly increasing trend in vaginal deliveries from 3.0% in 2003 to 8.2% in 2011 (P for trend<.001; Fig. 1A). A similar increasing trend was also observed among breech deliveries that followed cesarean delivery in labor (from 8.7% in 2003 to 9.8% in 2011 among deliveries at 37 weeks of gestation or greater and from 12.4% in 2003 to 15.8% in 2011 among deliveries at 40 weeks of gestation or greater; both P for trend<.001; Fig. 1B). The proportion of vaginal deliveries varied by region, ranging from 1% to 2% in Prince Edward Island, Newfoundland, and Labrador and New Brunswick to 5.7% in Saskatchewan and 7.1% in Manitoba.
Table 2 presents rates and rate ratio contrasting neonatal mortality and morbidity rates among women who had a vaginal delivery, a cesarean delivery in labor, or a cesarean delivery without labor. Neonatal mortality rates were not significantly different among the three groups. However, rates of composite neonatal mortality and morbidity were significantly higher for vaginal delivery (adjusted rate ratio [RR] 3.60, 95% CI 2.52–5.15; adjusted rate difference 15.8/1,000 deliveries, 95% CI 9.2–25.2) and the cesarean in labor group (adjusted RR 2.79, 95% CI 2.18–3.58; adjusted rate difference 10.9/1,000 deliveries, 95% CI 7.2–15.7) compared with the cesarean delivery without labor group. Specific rates are provided in Table 2. Differences between the vaginal delivery and cesarean delivery without labor groups included significantly higher rates of assisted ventilation, intrapartum or birth asphyxia, specific birth injury, and any birth injury in the former group. Among women delivering after a cesarean delivery in labor, the rates of neonatal convulsions, assisted ventilation, intrapartum or birth asphyxia, specific birth injury, and any birth injury were significantly higher than in the cesarean delivery without labor group (Table 2).
Similar results were obtained among women delivering at 40 weeks of gestation and beyond, although RRs were slightly larger indicating higher neonatal morbidity associated with vaginal delivery and cesarean delivery in labor (Table 3). Women delivering vaginally had significantly higher rates of composite neonatal mortality and morbidity compared with women who had a cesarean delivery without labor (adjusted RR 5.39, 95% CI 2.68–10.8; adjusted rate difference 24.1/1,000 deliveries, 95% CI 9.2–53.8). Similarly, women who delivered by cesarean in labor had significantly higher rates of composite neonatal mortality and morbidity compared with women who had a cesarean delivery without labor (adjusted RR 4.63, 95% CI 2.74–7.84; adjusted rate difference 19.9/1,000 deliveries, 95% CI 9.6–37.5). Compared with women who delivered by cesarean without labor, women who delivered vaginally had significantly higher rates of assisted ventilation, intrapartum or birth asphyxia, specific birth injury, and any birth injury, whereas women delivering after a cesarean delivery in labor had significantly higher rates of assisted ventilation, convulsions, intrapartum or birth asphyxia, and specific birth injury (Table 3).
Rates of birth injury among nonanomalous singleton term neonates with breech presentation are presented by mode of delivery in Table 4. Among breech deliveries, rates of peripheral nervous system injuries and other birth injuries were significantly higher among live births after cesarean delivery in labor compared with cesarean delivery without labor. Rates of birth injuries to the scalp and other birth injuries were significantly higher among vaginal deliveries compared with deliveries after cesarean without labor (Table 4).
Table 4 also shows rates of birth injury among nonanomalous, singletons at term gestation who did not present as breech. Overall rates of any birth injury were significantly lower among breech live births (7.65/1,000 live births) compared with nonbreech live births (17.3/1,000 live births; Table 1). Rates of birth injury to the scalp, skeleton, and peripheral nervous system were significantly lower among breech compared with nonbreech deliveries, whereas other birth injuries were significantly higher among neonates who presented as breech (data not shown). Analyses stratified by mode of delivery showed that breech neonates born after cesarean delivery without labor had significantly lower rates of birth injury to the scalp and significantly higher rates of birth injury to the skeleton and other birth injuries compared with nonbreech neonates born after cesarean delivery without labor. Breech neonates born after cesarean delivery with labor and those born vaginally had significantly lower rates of birth injury to the scalp and significantly higher rates of other birth injuries compared with nonbreech neonates delivered similarly (Table 4).
Our study showed that the rate of neonatal death among term, nonanomalous singletons in breech presentation was not significantly different from nonbreech neonates, although rates of assisted ventilation were higher and rates of asphyxia and birth injury were lower among breech neonates. Among breech singletons, the frequency of vaginal delivery and cesarean delivery in labor increased from 2003 to 2011. Rates of composite neonatal mortality and morbidity were significantly higher among neonates who delivered vaginally and after cesarean delivery in labor compared with cesarean delivery without labor; among women who delivered at 40 weeks of gestation or greater, these differences were substantial, being five- to sixfold higher among those who delivered vaginally and by cesarean delivery in labor. The excess rates translate into a number needed to harm of 41 for the vaginal delivery group and a number needed to harm 50 for the cesarean delivery in the labor group.
After the Term Breech Trial,5 women with breech presentation were strongly recommended a planned cesarean delivery.14,15 As a consequence, obstetric residents and junior obstetricians have had few opportunities to acquire skills in delivering fetuses in breech presentation vaginally, thereby increasing risks associated with this mode of delivery. On the other hand, selection of candidates for vaginal delivery has become far more rigorous, leading to an expectation of better outcomes among women choosing a planned vaginal delivery. The increasing trend in vaginal deliveries appeared to be more pronounced after the change in College and RCOG guidelines in 2006. Nevertheless, our study showed that rates of composite neonatal mortality and morbidity were substantially higher among women who delivered by the vaginal route and those who delivered after cesarean in labor.
A comparison of our study's results with those from the Netherlands and Denmark after the Term Breech Trial provides some interesting contrasts.12,13,25 In both the Netherlands and Denmark, planned vaginal delivery was associated with a significantly higher rate of perinatal death compared with planned cesarean delivery. The rate of low 5-minute Apgar scores was significantly elevated in the planned vaginal delivery group in the Netherlands, but birth trauma rates were not.12 In Denmark, low 5-minute Apgar scores, neonatal intensive care unit admissions, and neonatal death rates were significantly higher in the planned vaginal delivery group.13
Besides the effect of delivery mode given breech presentation at term, our study also highlighted two other phenomena of import. First, rates of vaginal breech delivery increased between 2003 and 2011. Also, we observed significantly lower rates of serious neonatal morbidity among breech deliveries compared with nonbreech deliveries (Table 1). One potential explanation for this preliminary finding is the very high rate of cesarean delivery without labor for breech presentation compared with nonbreech presentation (88% compared with 11%).
Our study has some strengths and weaknesses. We included all hospital deliveries in Canada (excluding Quebec) and focused on the population of nonanomalous singletons in breech presentation at term gestation. The limitations of our study included an inability to directly identify planned vaginal and planned cesarean delivery groups. Some women in the vaginal delivery group could have planned to have a cesarean delivery but were thwarted by precipitous labor or other circumstance. Women who delivered after cesarean delivery in labor included a mixed group including those who planned a vaginal delivery but had complications in labor, women who had planned a cesarean delivery but went into labor before their scheduled cesarean delivery, and women whose breech presentation was diagnosed in labor. We used diagnosis codes based on a previously defined algorithm to identify labor and to distinguish the (with labor and without labor) subtypes of cesarean delivery. Nevertheless, we acknowledge that this likely resulted in some misclassification; previous analyses have shown that approximately 16–17% of women in the cesarean delivery without labor group would have experienced labor.26 Other study limitations included an inability to assess effects on intrapartum stillbirths, significant underestimation of obesity rates (obtained from ICD-10 diagnosis codes), and a significant proportion of missing values for parity (23%), two variables controlled in the regression analysis. Analyses without adjustment for obesity yielded similar results.
In conclusion, more women delivered vaginally for breech presentation at term gestation in recent years, at least partly the result of changes in recent guidelines. Composite neonatal mortality and morbidity rates were significantly higher after a vaginally delivery and after cesarean delivery in labor as compared with cesarean delivery before labor onset. The risks associated with vaginal and cesarean delivery should be carefully considered by women contemplating a singleton breech delivery at term gestation and by their physicians.
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