Events during sleep may have an important impact on placental health and pregnancy outcome.
Events during sleep may have an important impact on placental health and pregnancy outcome. This is due to combined effects of low oxygen levels, poor blood vessel health and high blood pressure that accompanies obstructive sleep apnoea, the condition where upper airways collapse during sleep. Obstructive Sleep Apnoea results in frequent breathing pauses (or ‘apnoeas’) overnight.
We have previously established that sleep apnoea has an adverse effect on fetal growth. We have also shown that fetal heart rate changes may occur in response to low oxygen levels overnight among very small babies. This suggests that events at night may contribute to poor pregnancy outcome, particularly when the placenta is already known to be functioning poorly. Breathing and blood pressure events at night may plausibly contribute to stillbirth in these cases.
To investigate this, we are undertaking the Sleep and Oxygenation (SOX) study, where measures of sleep health and fetal heart rate monitoring overnight are combined in pregnancies complicated by severe preterm fetal growth restriction.
Why does sleep health matter in small babies?
The Sleep and Oxygenation (SOX) study is investigating whether sleep events may contribute to fetal distress (abnormal fetal heart rate responses) among women known to have a very small baby. In this study, we are performing sleep studies on 50 women whose babies are very small at less than 32 weeks, along with 50 well matched control patients (where the baby is known to be well grown).
Women found to have a very small baby, which has been confirmed on ultrasound will have a ‘sleep study’, where measures of breathing, oxygen levels and blood pressure are continuously recorded during sleep. Fetal heart rate monitoring will be recorded and stored all night for analysis on completion of the study. We are collecting outcome data on the rest of the pregnancy, and cord blood to assess critical growth regulators at birth.
We are hoping to determine whether abnormal fetal heart patterns occur more frequently overnight in women known to have a small baby. If this is confirmed, it could open up new possibilities for preventing or treating fetal growth restriction, and pave the way for an interventional clinical trial of Continuous Positive Airway Pressure in pregnancy.
How are we going?
The SOX study has already recruited over half of the required number of patients. When these women birth, their information is collated. Overnight fetal heart rate monitoring will then be compared between pregnancies affected with growth restricted versus control pregnancies.
Professor Sue Walker Dr Alison Fung Gabrielle Pell
Institute of Breathing and Sleep, Austin Health
Dr Maree Barnes Dr Mark Howard Lucy Sommers
NHMRC Project Grant 1065854 Norman Beischer Medical Research Foundation Austin Health Medical Research Foundation Mercy Health