Continuous objective recording of fetal heart rate and fetal movements could reliably identify fetal compromise, which could reduce stillbirth rates by facilitating timely management

Abstract

Stillbirth currently affects approximately 1 in every 200 pregnancies in the United Kingdom. Fetuses may exhibit signs of compromise as part of a stress response before stillbirth, including reduced fetal movements (RFM) and fetal heart rate (FHR) alterations. At present, and despite widespread use, current fetal monitoring is not associated with a reduction in perinatal mortality rate (PMR) as signs of fetal compromise are not adequately detected. This may be attributed to inaccuracies resulting from manual interpretation of results or subjective assessment of fetal activity. In addition, signs of compromise often occur only hours or days before fetal death, so may be missed by current monitoring methods, which are performed intermittently. A significant consideration is that correct identification of these signs and consequent intervention can result in the delivery of a healthy baby, thus preventing stillbirth. A hypothesis is presented, proposing prompt detection of fetal compromise with the use of 24-hour continuous objective fetal monitoring. With focus placed on obtaining long-term FHR and fetal movement data, prior interest has been found in developing devices for this purpose. However, introduction into clinical practice has not been achieved. Investigation of the hypothesis will begin with the design of a device to record the mentioned parameters, followed by an appropriate validation process. Should development and testing be successful, an eventual comparison in PMR with the use of continuous fetal monitoring vs current monitoring would address the hypothesis. It is suggested that a timely yet reliable indication of fetal wellbeing obtained via long-term monitoring would allow prompt and appropriate obstetric intervention and consequently reduce PMR.

Introduction

The impact of perinatal mortality – the death of a fetus after 24 weeks’ gestation or a new-born within the first seven days of life [1] – remains significant, even in high-resource countries. In the United Kingdom at present, approximately 11 stillbirths and six early neonatal deaths occur each day, figures that have not significantly declined in recent decades [1]. Stillbirths can sometimes be attributed to identifiable causes such as congenital abnormalities, maternal disorders or antepartum haemorrhage [1], and are classified using various systems. Notably, fetal growth restriction (FGR) in association with placental insufficiency is known to complicate up to 43% of stillbirths [2]. Importantly, signs of fetal compromise may occur before a stillbirth due to placental insufficiency. These include an initial reduced rate of fetal growth, followed by reduced fetal movements (RFM) in an effort to conserve energy, adaptations in the fetal circulation to perfuse vital organs and alternations in fetal heart rate (FHR) patterns (Fig. 1) [3].

In addition to those with known causative factors, a large proportion of stillbirths remain unexplained, reported to be between 14% and 60% depending on the classification system used [1], [4], [5]. The recent Centre for Maternal and Child Enquires (CMACE) report recorded that 29% of stillbirths in 2009 occurred in the absence of complicating factors [1]. In the same period, 34% of stillbirths were after 37 weeks’ gestation [1]; therefore a notable percentage of stillbirths occur late in pregnancies without apparent complications. These fetuses may also exhibit some signs and symptoms of compromise.

Various forms of fetal monitoring are currently used intermittently to examine for evidence of fetal distress (Fig. 1). These include ultrasound scanning to assess biometric measurements of fetal growth, fetal movement counting to examine fetal activity levels, Doppler ultrasound to analyse blood flow through various vessels and cardiotocography (CTG) to trace FHR patterns [3]. Many indicators of fetal demise occur only hours or days before fetal death (Fig. 1) [3], [6], [7], [8], [9]. If these are detected promptly, unexplained stillbirths or those due to FGR could be prevented; timely obstetric intervention in these cases could deliver a healthy baby.

It could be considered that the short-term and intermittent nature of current antenatal fetal monitoring means that signs of compromise are undetected when they arise. In addition, some monitoring modalities rely on subjective assessment, for example maternal perception of fetal movements, which may not be a reliable measure of fetal compromise. For these reasons, a hypothesis is introduced, proposing the use of 24-hour continuous fetal monitoring to provide a rapid objective assessment of fetal wellbeing in order to target the current static perinatal mortality rate (PMR) in high-resource regions.