Australian and New Zealand Journal of Obstetrics and Gynaecology 2014
DOI: 10.1111/ajo.12220
Original Article
The timing of elective caesarean deliveries and early neonatal outcomes in singleton infants born 37–41 weeks’ gestation Emily DOAN,1 Kristen GIBBONS2,3 and David TUDEHOPE1,3 1
School of Medicine, The University of Queensland, Brisbane, 2Mater Research Office, Mater Research, and 3Mothers and Babies Research, Mater Research, South Brisbane, Qld, Australia
Background: Births by elective caesarean section (CS) are rising, particularly before 39 weeks’ gestation, which may be associated with unacceptably high risk of adverse neonatal outcomes. The optimal timing of these deliveries needs to be determined with recent recommendations to delay births by elective CS until 39 weeks. Aims: To evaluate the association between gestational age (GA) at delivery and neonatal outcomes after elective CS between 37 and 416 weeks. Materials and Methods: Retrospective cohort study of viable singleton neonates delivered by elective CS at Mater Mothers’ Hospitals (1998–2009). Neonates were stratified into two GA groups with early term (ET, 37–386 weeks) compared with the reference group of full and late term (FLT, 39–416 weeks). The primary outcome examined was serious respiratory morbidity; secondary outcomes included depression at birth, nursery admission and assisted ventilation. Results: Fourteen thousand and four hundred and forty-seven mother–baby pairs were included (59.9% delivered before 39 weeks). There was a significantly decreasing risk of adverse neonatal outcomes with increasing GA. Compared to FLT, delivery at ET almost tripled the risk of the primary outcome (AOR 2.74; 95% CI 1.79–4.21). Rates of most secondary outcomes were at least doubled. Conclusion: Elective CS performed at 37–386 weeks is associated with poorer neonatal outcomes compared to those delivered at 39–416 weeks. This study supports recent recommendations to delay delivery by elective CS until week 39 if possible. Key words: caesarean section, elective, infant, morbidity, neonatal mortality, newborn, surgical procedures.
Introduction Birth by elective (prelabour) caesarean section (CS) increased in Australia from 14.3% in 2001 to 18.6% in 2010.1 This increase has been ascribed to many factors, including increasing maternal age, fetal monitoring, assisted reproductive technology (ART), maternal request and breech delivery.2,3 However, it can be predominantly attributed to rising rates of first time, or primary CS, which leads to a repeat CS in 90% of cases.1–5 Studies have examined the impact of this mode of delivery on a limited number of short-term neonatal outcomes, particularly when compared to vaginal birth (VB).6–12 They report a decreased risk of adverse neonatal outcomes with increasing gestational age (GA), even once term is reached at 37 weeks.6–15 These findings
Correspondence: Professor David Tudehope, Mater Research, Level 3, Aubigny Place, Raymond Terrace, South Brisbane, QLD 4101, Australia. Email: [email protected] Received 7 November 2013; accepted 18 April 2014.
challenge the traditional definition of ‘term’, as the risk of adverse outcomes continues to decrease with each additional week, until week 39,6,14–17 culminating in guidelines advocating delaying elective CS in low-risk pregnancies until at least 39 weeks.18–20 Furthermore, a recent working group has recommended that ‘term’ be subclassified into early term (ET, 37–386 weeks), full term (FT, 39–406 weeks) and late term (LT, 41– 416 weeks), to reflect these findings.21 With the recent trend of increasing elective CS rates, it is important to confirm and quantify the impact on neonatal outcomes. The aim of this study was to report the effect of the timing of elective CS deliveries at term on early neonatal outcomes. The results will provide further evidence to guide policy on the optimal timing of these deliveries.
Materials and Methods Patients and methods This study evaluated the short-term neonatal outcomes of singleton babies born by elective CS between 37 and 41
© 2014 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists The Australian and New Zealand Journal of Obstetrics and Gynaecology
1
E. Doan et al.
completed weeks of gestation at Mater Mothers’ Hospitals (MMH) over a 12-year period (1998–2009). MMH is one of two large perinatal referral centres in South East Queensland and is a co-located public and private facility. This retrospective cohort study was performed using prospectively entered, routinely collected de-identified data from the MMH obstetric and neonatal databases. Elective CS was defined as a CS performed before the onset of labour. Women with prepregnancy conditions (HIV/AIDS, autoimmune disease, hypertension, diabetes) were excluded, as were babies who were stillborn or had major congenital anomalies diagnosed antenatally. The first day of the mother’s last menstrual period (either with or without ultrasound confirmation) was used to calculate GA. This study was approved by the Mater Health Services Human Research Ethics Committee. Maternal demographics extracted and examined were as follows: age, body mass index (BMI), marital status, socio-economic status (as measured by the Socioeconomic Index for Areas (SEIFA) quintiles), ethnicity, insurance status (public/private), parity, use of ART, smoking at booking and ultrasound validation of GA. Maternal pregnancy characteristics extracted included antenatal complications and comorbidities (gestational diabetes mellitus (GDM), antepartum haemorrhage ≥20 weeks (APH), hypertension), and labour and delivery details (indication for CS, primary/repeat CS, presentation, use of general anaesthesia). Neonatal birth characteristics extracted and examined were as follows: gender, birth weight and GA at birth.
Statistical analysis This study analysed two GA groups by comparing ET (weeks 37–386) with the reference group of full- and lateterm births (FLT; FT weeks 39–406 and LT weeks 41– 416). Bivariate analysis comparing demographic, pregnancy and birth characteristics across the two GA groups was undertaken to identify potential confounders for multivariate analysis. Means and standard deviations are presented for continuous data when normally distributed, medians and interquartile ranges when nonnormally distributed, and counts and percentages for categorical data. Independent t-test, Mann–Whitney Utest or chi-squared tests were used to undertake the bivariate analyses. Statistically or clinically significant confounders were included in the multivariate logistic regression to determine whether the rate of neonatal morbidity varied by GA group; these confounders were year of birth, maternal age, parity, smoking, insurance status, ethnicity (Caucasian/other), use of ART and presence of antenatal comorbidities (GDM, APH and/or hypertension during pregnancy). Rare outcomes (NND, low Apgar, depression at birth, HIE, PPHN, pneumothorax) were not further investigated using multivariate analysis. There was minimal missing data, except for maternal BMI, and this is listed as ‘unknown’. Adjusted odds ratios (AOR) and 95% confidence intervals (CI) are presented. Statistical significance was accepted at the 0.05 level. Data were analysed using StataSE 10.1 (StataCorp, College Station, TX, USA).
Study outcomes
Results
Neonatal outcomes were based on diagnoses made by treating clinicians and recorded in the electronic databases. The primary outcome was serious respiratory morbidity, defined as admission to the Neonatal Critical Care Unit (NCCU), either intensive or special care, with respiratory morbidity and receiving assisted ventilation via mechanical ventilation and/or continuous positive airway pressure (CPAP) for ≥4 h. Secondary outcomes examined were as follows: neonatal death (NND), low Apgar score (five-minute Apgar
DOI: 10.1111/ajo.12220
Original Article
The timing of elective caesarean deliveries and early neonatal outcomes in singleton infants born 37–41 weeks’ gestation Emily DOAN,1 Kristen GIBBONS2,3 and David TUDEHOPE1,3 1
School of Medicine, The University of Queensland, Brisbane, 2Mater Research Office, Mater Research, and 3Mothers and Babies Research, Mater Research, South Brisbane, Qld, Australia
Background: Births by elective caesarean section (CS) are rising, particularly before 39 weeks’ gestation, which may be associated with unacceptably high risk of adverse neonatal outcomes. The optimal timing of these deliveries needs to be determined with recent recommendations to delay births by elective CS until 39 weeks. Aims: To evaluate the association between gestational age (GA) at delivery and neonatal outcomes after elective CS between 37 and 416 weeks. Materials and Methods: Retrospective cohort study of viable singleton neonates delivered by elective CS at Mater Mothers’ Hospitals (1998–2009). Neonates were stratified into two GA groups with early term (ET, 37–386 weeks) compared with the reference group of full and late term (FLT, 39–416 weeks). The primary outcome examined was serious respiratory morbidity; secondary outcomes included depression at birth, nursery admission and assisted ventilation. Results: Fourteen thousand and four hundred and forty-seven mother–baby pairs were included (59.9% delivered before 39 weeks). There was a significantly decreasing risk of adverse neonatal outcomes with increasing GA. Compared to FLT, delivery at ET almost tripled the risk of the primary outcome (AOR 2.74; 95% CI 1.79–4.21). Rates of most secondary outcomes were at least doubled. Conclusion: Elective CS performed at 37–386 weeks is associated with poorer neonatal outcomes compared to those delivered at 39–416 weeks. This study supports recent recommendations to delay delivery by elective CS until week 39 if possible. Key words: caesarean section, elective, infant, morbidity, neonatal mortality, newborn, surgical procedures.
Introduction Birth by elective (prelabour) caesarean section (CS) increased in Australia from 14.3% in 2001 to 18.6% in 2010.1 This increase has been ascribed to many factors, including increasing maternal age, fetal monitoring, assisted reproductive technology (ART), maternal request and breech delivery.2,3 However, it can be predominantly attributed to rising rates of first time, or primary CS, which leads to a repeat CS in 90% of cases.1–5 Studies have examined the impact of this mode of delivery on a limited number of short-term neonatal outcomes, particularly when compared to vaginal birth (VB).6–12 They report a decreased risk of adverse neonatal outcomes with increasing gestational age (GA), even once term is reached at 37 weeks.6–15 These findings
Correspondence: Professor David Tudehope, Mater Research, Level 3, Aubigny Place, Raymond Terrace, South Brisbane, QLD 4101, Australia. Email: [email protected] Received 7 November 2013; accepted 18 April 2014.
challenge the traditional definition of ‘term’, as the risk of adverse outcomes continues to decrease with each additional week, until week 39,6,14–17 culminating in guidelines advocating delaying elective CS in low-risk pregnancies until at least 39 weeks.18–20 Furthermore, a recent working group has recommended that ‘term’ be subclassified into early term (ET, 37–386 weeks), full term (FT, 39–406 weeks) and late term (LT, 41– 416 weeks), to reflect these findings.21 With the recent trend of increasing elective CS rates, it is important to confirm and quantify the impact on neonatal outcomes. The aim of this study was to report the effect of the timing of elective CS deliveries at term on early neonatal outcomes. The results will provide further evidence to guide policy on the optimal timing of these deliveries.
Materials and Methods Patients and methods This study evaluated the short-term neonatal outcomes of singleton babies born by elective CS between 37 and 41
© 2014 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists The Australian and New Zealand Journal of Obstetrics and Gynaecology
1
E. Doan et al.
completed weeks of gestation at Mater Mothers’ Hospitals (MMH) over a 12-year period (1998–2009). MMH is one of two large perinatal referral centres in South East Queensland and is a co-located public and private facility. This retrospective cohort study was performed using prospectively entered, routinely collected de-identified data from the MMH obstetric and neonatal databases. Elective CS was defined as a CS performed before the onset of labour. Women with prepregnancy conditions (HIV/AIDS, autoimmune disease, hypertension, diabetes) were excluded, as were babies who were stillborn or had major congenital anomalies diagnosed antenatally. The first day of the mother’s last menstrual period (either with or without ultrasound confirmation) was used to calculate GA. This study was approved by the Mater Health Services Human Research Ethics Committee. Maternal demographics extracted and examined were as follows: age, body mass index (BMI), marital status, socio-economic status (as measured by the Socioeconomic Index for Areas (SEIFA) quintiles), ethnicity, insurance status (public/private), parity, use of ART, smoking at booking and ultrasound validation of GA. Maternal pregnancy characteristics extracted included antenatal complications and comorbidities (gestational diabetes mellitus (GDM), antepartum haemorrhage ≥20 weeks (APH), hypertension), and labour and delivery details (indication for CS, primary/repeat CS, presentation, use of general anaesthesia). Neonatal birth characteristics extracted and examined were as follows: gender, birth weight and GA at birth.
Statistical analysis This study analysed two GA groups by comparing ET (weeks 37–386) with the reference group of full- and lateterm births (FLT; FT weeks 39–406 and LT weeks 41– 416). Bivariate analysis comparing demographic, pregnancy and birth characteristics across the two GA groups was undertaken to identify potential confounders for multivariate analysis. Means and standard deviations are presented for continuous data when normally distributed, medians and interquartile ranges when nonnormally distributed, and counts and percentages for categorical data. Independent t-test, Mann–Whitney Utest or chi-squared tests were used to undertake the bivariate analyses. Statistically or clinically significant confounders were included in the multivariate logistic regression to determine whether the rate of neonatal morbidity varied by GA group; these confounders were year of birth, maternal age, parity, smoking, insurance status, ethnicity (Caucasian/other), use of ART and presence of antenatal comorbidities (GDM, APH and/or hypertension during pregnancy). Rare outcomes (NND, low Apgar, depression at birth, HIE, PPHN, pneumothorax) were not further investigated using multivariate analysis. There was minimal missing data, except for maternal BMI, and this is listed as ‘unknown’. Adjusted odds ratios (AOR) and 95% confidence intervals (CI) are presented. Statistical significance was accepted at the 0.05 level. Data were analysed using StataSE 10.1 (StataCorp, College Station, TX, USA).
Study outcomes
Results
Neonatal outcomes were based on diagnoses made by treating clinicians and recorded in the electronic databases. The primary outcome was serious respiratory morbidity, defined as admission to the Neonatal Critical Care Unit (NCCU), either intensive or special care, with respiratory morbidity and receiving assisted ventilation via mechanical ventilation and/or continuous positive airway pressure (CPAP) for ≥4 h. Secondary outcomes examined were as follows: neonatal death (NND), low Apgar score (five-minute Apgar
