Trends in the Distribution of Gestational Age and Contribution of Planned Births in New South Wales, Australia

Abstract

BackgroundThere is concern that the rate of planned births (by pre-labour caesarean section or induction of labour) is increasing and that the gestation at which they are being conducted is decreasing. The aim of this study was to describe trends in the distribution of gestational age, and assess the contribution of planned birth to any such changes.MethodsWe utilised the New South Wales (NSW) Perinatal Data Collection to undertake a population-based study of all births in NSW, Australia 1994–2009. Trends in gestational age were determined by year, labour onset and plurality of birth.ResultsFrom 1994–2009, there was a gradual and steady left-shift in overall distribution of gestational age at birth, with a decline in the modal gestational age from 40 to 39 weeks. For singletons, there was a steady but significant reduction in the proportion of spontaneous births. Labour inductions increased in the proportion performed, with a gradual and changing shift in the distribution from a majority at 40 weeks to an increase at both 37–39 weeks and 41 weeks gestation. The proportion of pre-labour caesareans also increased steadily at each gestational age and doubled since 1994, with most performed at 39 weeks in 2009 compared with 38 weeks up to 2001.ConclusionsFindings suggest a changing pattern towards births at earlier gestations, fewer births commencing spontaneously and increasing planned births. Factors associated with changing clinical practice and long-term implications on the health and well-being of mothers and babies should be assessed.

Women’s views about the timing of birth

“…In NSW, there has been a gradual left shift in the gestational age at birth, with the modal gestational age declining from 40 to 39 weeks gestation and over 50% of women giving birth before their EDB. 17 It is possible that women are accepting that birth before the EDB is 'normal' or common, perhaps informed by their own past experiences or those of family and friends. Another potential explanation may relate to how the EDB is interpreted.…”

Why do women in the private sector have shorter pregnancies in Brazil? Left shift of gestational age, caesarean section and inversion of the expected disparity

“…The duration of pregnancy is the main neonatal health predictor and is usually reported in completed weeks 1 . The calculation of weeks of pregnancy is done by several methods, the most common being the onset of the last menstrual period (LMP) or by ultrasonography (USG).…”

“…The ideal period for birth is classically defi ned as being between 37 weeks and 41 6/7. However, in the last decade, an international consensus emerged, fi nding this defi nition inadequate, since it was established based on the understanding that the perinatal outcomes of this group would 1 be uniform, when in fact, this supposed uniformity does not exist 1,5,6 .…”

“…Several studies have focused on those born in earlier ages, but the monitoring of GA distribution trends can contribute to assess its consequences in the short, medium and long term 1,7 .…”

Variation in and factors associated with timing of low risk, pre-labour repeat caesarean sections in NSW, 2008-2011

“…4 In April 2007, the New South Wales (NSW) Ministry of Health released a mandatory policy directive for all NSW public hospitals (PD2007_024), 'Maternity − timing of elective or pre-labour caesarean section', requiring that "where there are no compelling medical indications, elective or prelabour caesarean section does not occur prior to 39 completed weeks gestation". 5 Although a slight change in timing of prelabour caesarean sections has been observed since 2008 6 , current practice and compliance with the policy directive are unknown. Additionally, the relationship between hospital and patient factors and timing of low-risk caesarean sections has not been explored.…”