The effect of maternal position on placental oxygen transfer in the growth restricted fetus: an MRI study

Late stillbirth is a tragedy that occurs all too frequently. About 160 normally formed babies die each year in New Zealand before they are born and whose cause of death is termed "unexplained". Our research group has shown that maternal supine position during sleep is a risk factor for stillbirth. This study explores mechanisms that may explain why maternal position affects the unborn baby, especially babies who are not growing as well as expected. We are using a new technique of magnetic resonance imaging (MRI) scanning and a novel analysis process to measure the oxygen transfer from mum to baby across the placenta (afterbirth) and oxygen levels in the baby. This lets us examine the effect of the pregnant woman moving from lying on her left side to being on her back. We are also able to compare the results from healthy normal pregnancy with those where the baby is growth restricted (too small). After the birth we will study the placenta in detail and relate our MRI findings to the structure of the fine blood vessels which are responsible for transporting oxygen and nutrients from mother to the baby. Our long term goal is to provide a better understanding of how vulnerable unborn babies respond to stress such as mum lying on her back so that they may be monitored in different ways from presently, to prevent stillbirth.