Aim: To determine the association between the mode of delivery and selected neonatal and maternal morbidities and outcomes in NSW, during 1998-2008. Methods: This study is a retrospective review of NSW Midwives Data Collection (MDC) of 981,178 deliveries during 1998-2008. Maternal condition and neonatal outcomes were compared for different modes of delivery. Results: The annual rate of caesarean section has steadily increased from 19% to 31.1% with a mean of 25.9% during the study period. The risk of neonatal death was higher for forceps-assisted delivery compared to vacuum-assisted delivery (adjusted odds ratio 0.85%, 95% CI 0.52 - 1.37), caesarean section (adjusted odds ratio 1.14%, 95% CI 1.01 - 1.3) and normal vaginal delivery. Operative vaginal delivery and caesarean section had significantly increased risk for maternal mortality compared to normal vaginal delivery. Conclusions: There is an association between maternal and neonatal outcome and mode of delivery. Mothers and babies with normal vaginal delivery achieved better outcomes in this community. Caesarean section and operative vaginal delivery are associated with significant maternal and neonatal risk. Breech vaginal delivery carries a significant neonatal risk. More future prospective analyses, such as multicentre controlled studies, should be designed to determine whether and how much the adverse pregnancy outcomes were caused by unnecessary surgical and operative vaginal delivery.
A frequent dilemma for obstetricians is to determine the best mode of delivery in order to optimize pregnancy outcome for both the mother and the neonate. If all independently significant parameters can be used to construct a predictive model, it would be possible to identify the most appropriate mode of delivery. Controversy exists as to whether the increase of intervention such as operative vaginal delivery and caesarean delivery improve obstetric outcomes.
There is a concern about the dramatically rising rates of caesarean delivery worldwide [1]. In NSW, between 1998-2008, the caesarean section rate increased while the rate of instrumental delivery remained stable [2,3]. One of the major reasons attributed to the overall increase in caesarean delivery is a reluctance to attempt a vaginal birth after a previous caesarean delivery. However, this is not the only factor because the increase in primary caesarean delivery parallels the total caesarean delivery rate [4].
Unnecessary caesarean sections may be associated with increased maternal and perinatal morbidity [5]. Operative vaginal deliveries (forceps and vacuum-assisted delivery) whilst carrying their own attendant risk [6] can often facilitate child birth in the second stage of labour, thus avoiding caesarean section and its associated morbidities. Although several authors have reported the relative safety of operative vaginal delivery [7,8], many obstetricians have abandoned the use of these interventions. The complications associated with operative vaginal delivery are dependant on case selection and the level of the experience of the obstetrician [9]. The sequential use of instruments during operative vaginal delivery and difficult instrumental delivery carry an even greater risk for the neonate [10,11]. There are no published randomized clinical trials on which to base a choice between Caesarean and operative vaginal delivery in managing complications in second stage of labour [12].
This current study was undertaken to compare the influence of the mode of delivery on selected neonatal and maternal morbidities and outcomes in NSW over a period of 1998-2008, during which 981,178 babies were born.
2. METHODS
The New South Wales Midwives Data Collection (MDC) is a population-based surveillance system covering all births in NSW Australia public and private hospitals, as well as home births [2] and is a reliable system of collecting clinical information regarding obstetrics performance of women and clinical outcomes. A validation study of the MDC by staff of NSW Health Department showed low rates of missing data and generally high levels of agreement between MDC data reported to the NSW Health Department and information obtained directly from the medical record. Most data items on the new MDC form were highly reliable [13].
The MCD includes demographic details, and information of maternal health, pregnancy, labour, delivery and perinatal outcomes. The accuracy of the data is dependant on the attending midwife or doctor to complete the standardised notification form when the birth occurs [3]. The period of the data used in this study was between 1998 and 2008. The total number of birth during this period of 11 years was 981,178. The data were analysed using the SPSS package (SPSS Inc., Chicago, IL, USA). Pregnancy and perinatal data from the MDC was used and univariate analysis was done to compare maternal conditions and neonatal outcomes in different modes of delivery, including normal vaginal delivery, forcepsassisted delivery, vacuum-assisted delivery, caesarean section and breech vaginal delivery. Further multiplevariate analyses were conducted on deliveries to compare selected maternal conditions and neonatal outcomes adjusted for maternal age, parity, maternal hypertension, pregnancy induced hypertension, maternal diabetes and gestational age. All models were checked for effect modifications. Results are presented as odds ratios (ORs) with the associated 95% confidence interval (95% CI). Multiple logistic regression analysis was used to determine the differences in probability of pregnancy outcome and maternal condition variables for different modes of delivery.
This study has been approved by South-western Sydney Area Health Service Ethics Committee.
3. RESULTS
Of all 981,178 births during the study period, 62.9% were normal vaginal deliveries, 10.4% were operative vaginal deliveries, including 3.8% and 6.6% for forceps and vacuum-assisted deliveries respectively, and 25.9% of the births were by caesarean section. There was a 0.7% rate of vaginal breech delivery in the study population.
Figure 1 provides information on the trend of modes of delivery in NSW over the study period. It shows that the normal vaginal delivery rate has decreased from 1998 to 2008, whilst the caesarean section rate has increased. The operative vaginal delivery rate has remained constant, however the vacuum delivery rate has increased and the forceps delivery rate has decreased.
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