Diabetes during pregnancy and method of birth : a population study of women giving birth in New South Wales, Australia

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Background and aims: Diabetes during pregnancy – including pre-existing diabetes and gestational diabetes mellitus (GDM) – is an increasing public health problem worldwide. The objective of this thesis is to investigate the association between method of birth and the perinatal outcomes of women with diabetes during pregnancy. It aims to: • identify the main contributors to caesarean section amongst women with diabetes using the Robson classification for caesarean section • determine neonatal outcomes for babies born to women with diabetes by method of birth • compare the rate of obstetric anal sphincter injuries (OASIs) for women with and without GDM and investigate the association between combining episiotomy with method of birth and the risk of OASIs • compare the perinatal outcomes for women giving birth with diabetes by public and private hospital sector. Materials and method: Four population-based studies were conducted using the New South Wales (NSW) Perinatal Data Collection. The study population comprised 1,103,380 women who gave birth in NSW between 2002 and 2013 and their babies. Of these women 7,200 (0.7%) had pre-existing diabetes, 57,822 (5.2%) had GDM and 1,038,358 (94.1%) had no diabetes. Women were stratified by onset of labour, method of birth, and birthweight. Neonatal outcomes included perinatal death, five minutes Apgar score, admission to neonatal intensive care and/or special care nursery and neonatal resuscitation. The primary maternal outcome was OASI. Results: The total caesarean section rate was higher among women with pre-existing diabetes (53.6%) and women with GDM (36.8%) compared to women without diabetes (28.5%). Robson group five (multiparity with a history of caesarean section) was the main predictor of the total caesarean section rates in all women. Of the 39,625 women with diabetes who laboured, 32.1% had instrumental or caesarean births that were associated with poorer outcomes. Women with GDM who had an instrumental vaginal birth and gave birth to babies with birthweights ≥4000g had a significant increase in the odds of OASIs compared to women without diabetes. Combining episiotomy and forceps was a protective factor on OASIs. Similar proportions of no labour caesarean section were observed among women with pre-existing diabetes in private and public hospitals. Proportions of induction of labour were similar among women with GDM in private and public hospitals. Conclusion: The Robson classification can be used to benchmark and monitor method of birth for women with diabetes. Information, education and counselling on the risks and complications associated with different methods of birth, should routinely be provided for women with diabetes antenatally.
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