Maternal and perinatal factors associated with adverse perinatal outcomes at term and the development of a predictive model for identification of at–risk pregnancies.

Abstract

The perinatal period is defined as being between 20 weeks gestation and up to 28 days after birth.Despite advancements in antenatal care, diagnostic tools, interventions and treatments, adverse perinatal outcomes such as stillbirth, fetal growth restriction, preterm birth, hypoxic ischaemic encephalopathy, serious neonatal morbidity and neonatal death still occur. Placental dysfunction is one of the major contributors to these adverse outcomes regardless of gestation. While the majority of fetuses are able to cope with the increase in metabolic requirements in the last few weeks of pregnancy, those with impaired placental function are more susceptible to hypoxic events leading to increased mortality, serious short-term morbidity and long-term neurodevelopmental delays including neonatal encephalopathy and cerebral palsy.Doppler assessment of fetal blood flow and fetal growth are effective methods to evaluate fetal wellbeing. The umbilical artery pulsatility index can identify growth restriction from suboptimal placentation. The middle cerebral artery pulsatility index can identify the "brain sparing" effect caused by increased perfusion of the fetal brain. The ratio of these two measures (middle cerebral artery pulsatility index/umbilical artery pulsatility index) known as the cerebroplacental ratio has been suggested to be a better predictor than the individual components. This thesis will investigate the associations between maternal and perinatal factors and adverse perinatal outcomes. It will assess Doppler indices for the identification of fetal growth restrictedsmall for gestational age fetuses and those at risk of emergency caesarean for non-reassuring fetal status. The creation of accurate reference centiles using the generalised additive model for location, scale and shape approach, will allow for meaningful interpretation of those Doppler measurements. This information will be used to create predictive tools that will enable the clinician to identify pregnancies at risk of adverse perinatal outcomes and emergency caesarean for non-reassuring fetal status.iii