Does Prone Position Alter Maternal Cardiorespiratory Status?
Does Prone Position Alter Maternal Cardiorespiratory Status?
During pregnancy women may need or choose to undergo physical therapies such as
 physiotherapy, massage or osteopathy. Recent findings from studies of mothers who had a
 stillbirth in late pregnancy found that the position in which women went to sleep in was
 linked to stillbirth, as was the frequency of day time naps. This link is thought to be due
 to changes in mother's blood flow from her heart when lying flat leading to changes in the
 amount of oxygen going to her baby. This raise concerns that spending extended periods laid
 flat could be detrimental to baby's health. However, it is not known whether lying flat for
 extended periods for physical therapies could also alter a baby's heart rate or levels of
 oxygen. One small study of 33 women from Brazil found that there were no differences in a
 mother's heart rate, blood pressure, oxygen saturation or baby's heart rate. But there were
 changes in mother's breathing rate and systolic blood pressure when a mother laid on her
 front. All the women reported feeling comfortable lying flat (on a bent surface). However, in
 this study women only spent 6 minutes in each position which is less than a woman would be
 expected to spend lying in a position for a session of physical therapy. The investigators
 plan a study to assess whether using a device to support a prone position (Anna cushion)
 would be associated with changes in mother's heart rate, blood pressure, breathing rate and
 blood oxygen levels and baby's heart rate. The investigators will also ask about mother's
 levels of comfort while she is laid in the prone position. The findings of this study will
 give an indication whether supporting a mother to lie in a prone position for physical
 therapies is safe and comfortable.
Women frequently experience lower-back or pelvic pain during pregnancy. This may lead to a
 need for physical therapies such as physiotherapy, osteopathy or massage in late pregnancy.
 Several case-control studies, and a recent individual patient data meta-analysis has
 demonstrated an association between going to sleep position and late stillbirth (a greater
 than 2-fold increased risk with going to sleep supine) and increased frequency of daytime
 naps. This is thought to be related to maternal haemodynamic changes when a mother lies
 supine in late pregnancy which decreases cardiac output and uterine blood flow. These changes
 are accompanied by alterations in fetal behaviour which are consistent with a reduction in
 oxygenation. This observation raises concerns that spending extended periods laid flat could
 be detrimental to baby's health. However, it is not known whether lying flat for extended
 periods for physical therapies could also alter a baby's heart rate or levels of oxygen. One
 small study of 33 women from Brazil which randomised the order of maternal positions found
 that there were no differences in a mother's heart rate, blood pressure, oxygen saturation or
 baby's heart rate between a supine, lateral and prone position (bent over a concave couch).
 However, there were observed changes in mother's breathing rate and systolic blood pressure
 when a mother laid on her front. Nevertheless, all the women reported feeling comfortable
 lying flat (on a bent surface). However, in this study women only spent 6 minutes in each
 position which is less than a woman would be expected to spend lying in a position for a
 session of physical therapy. Therefore, further work is required to determine whether
 spending extended periods laid prone is safe for mother and baby.

 The co-investigator (Karli Büchling) has developed a cushion to support mothers in a prone
 position (Anna cushion). This study will investigate whether adopting this position supported
 by the cushion is associated with changes in mother's heart rate, blood pressure, breathing
 rate and blood oxygen levels and fetal heart rate as assessed by the cardiotocograph. The
 investigators will also ask about mother's levels of comfort while she is laid flat. The
 findings of this study will give an indication whether supporting a mother to lie in a prone
 position for physical therapies is safe and comfortable.
Inclusion Criteria:

 -  Viable singleton pregnancy ≥28 weeks' gestation

 -  No fetal anomalies according to Fetal Anomaly Screening Programme definition

 -  Ability to give written informed consent

 -  Maternal Age >16 years

 Exclusion Criteria:

 -  Unable to read English (as the survey instruments are only available in English)

 -  Multiple pregnancy

 -  Pre-existing maternal cardiovascular or respiratory disease

 -  Fetal anomaly

 -  Contraindication to lying prone (severe pain etc.)

 -  Allergy to self-adhesive electrodes used for standard electrocardiography (ECG)

 -  Unable to give written informed consent