Monitoring of Foetal Movements

By Santiago Campo

Women are recommended to monitor their baby’s kicks during their last trimester of pregnancy. Indeed, a baby’s quickening’s can give doctors substantial information concerning its health and development (Nowlan, 2015). The research group of Dr Nowlan at Imperial College London were able to find several correlations between foetal biomechanics and pre/post-natal conditions of the baby. Among the various research methods used by Dr Nowlan’s group is MRI scanning.  It can provide researchers with accurate representation of a baby’s activity in utero. However, it is a process that is rarely used clinically due to expense and lack of evidence of risks.

MRI is a technique that allows the formation of a picture of anatomy and physiological processes at any point in time and hence can be used to monitor movement. It is based on the detection of the energy released by protons after a magnetic field is introduced to them. Indeed, this field makes protons align with it. After this alignment, the MRI technician sends a radiofrequency pulse that twists the protons into a 90- or 180-degree realignment with the static magnetic field. Because the protons are now pushed against their own nature, they will realign with the magnetic field as soon as the pulse is turned off, generating the release of energy. The MRI sensors are able to detect it and differentiate various tissues based on how quickly they are able to release this energy after the pulse is turned off (Murphy et al., 2020). Dr Nowlan specifically uses Cine MRI, which is a classic MRI with the addition of either a wristband or ECG leads on the patient’s chest to measure the heart rate (Pelc et al., 1991). In this setup, the MRI machine will also show the inward and outward flow of cerebrospinal fluid in response to the flow of blood entering and exiting the brain (Chaptinel et al., 2017).

Dramatic changes in foetal movement patterns detected by the MRI are an important sign of foetal health. It can give indication to pregnancy complications or future risks. Biomechanical influences are essential for normal musculoskeletal development, close assessment can enable early treatment in some cases, or preparation for inevitable implications. It can help detect the future diseases and complications of the pregnancy that could risk the life of both the mother and the foetus or complications in the future. Another of its big impacts in society is the ability to give more accurate diagnostics and correcting wrong ones, which can help reduce the stress of the mother during pregnancy. 

A possible abnormality which could be detected is developmental dysplasia of the hip, leading to the need for hip replacement in adulthood. This can be a result of a restricted mechanical environment, inadequate amniotic fluid or the foetal breech position. Early diagnosis of this condition can allow early treatment with a fabric splint, or Pavlik harness. Without diagnosis, this may lead to the person living more cautiously, while stiffness and joint pain cause discomfort (NHS, 2018). Other pre-natal recognition of life-threatening or life-limiting complications, such as foetal akinesia, or arthrogryposis (both caused by abnormal biomechanical movements of the foetus) could lead the mother to abort the foetus. This promotes a society moving to look for perfection in children instead of accepting slight imperfections. An early diagnosis could generate anxiety in the patient and make her take early and premature decisions that would not be taken in a non-stressful situation. Foetal skeletal issues seem like insurmountable challenges. However, they can be aided by physical activity with a healthy lifestyle, and in some cases physiotherapy. 

MRI technology comes at great cost and is widely inaccessible. Ultrasound remains the common method of choice of foetus imaging due to its availability, safety, and low cost. Foetal MRI produces no known harmful effects, but long-term safety of radiofrequency fields and the loud acoustic environment are not yet fully understood. MRI can be challenging for claustrophobic patients and can cause increased anxiety; however, the process is very fast, eliminating the need for maternal or foetal sedation (Deborah Levine, 2006). 

MRI is a great resource for ectopic pregnancy. It is helpful in defining the level of peritoneal involvement for preoperative planning. I can also show the extent of uterine invasion, and the location of the vasculature supplying the pregnancy. It has also proven to be useful in evaluation of the foetal CNS, typically poorly visualized with ultrasound (Deborah Levine, 2006). 

Health issues are hardest to detect in the first trimester, the small foetal size is difficult to evaluate with MRI. Use during the first trimester of pregnancy has not been shown to increase risk to the foetus, however dividing cells are typically susceptible to injury, so use is minimised. MRI tends to be limited to late pregnancy or cases of oligohydramnios since foetal motion is lessened. 

MRI’s diagnostic accuracy can be improved with gadolinium, an intravenous contrast medium (Levine, 2006). Unfortunately, it could cross the placenta, to be excreted by the foetal kidneys into the amniotic fluid and recirculated by the foetus. Persistence of gadolinium could lead to nephrogenic systemic fibrosis in the child. Hence it is rarely used but is valuable to assess the placenta/myometrial interface in cases of placenta accreta. When performed just before delivery the issue of the long half‐life within amniotic fluid is greatly reduced. However, with possible risks including stillbirth or neonatal death, use of gadolinium is minimised (Ray et al., 2016). 

Currently Cine MRI scans are used for research purposes but are expensive and not widely adopted medically. A reliable, objective method of monitoring foetal movement patterns (FM) and biomechanical stimuli outside of clinical environments is not currently available. A system that is both wearable and non-transmitting, capable of sensing such biomechanical stimuli and FM would be undoubtedly invaluable, not only for monitoring individual foetal health and providing treatment necessary to avoid consequential problems at birth (as previously mentioned), but also for establishing the median/optimum levels of FM within the population i.e. as a means of medical research (Lai et al., 2018). Accelerometer-based, wearable monitors have been previously proposed as a method for tracking FM. However, a clear disadvantage of these systems would be the difficulty in distinguishing between maternal and foetal activity/stimuli. As a result, such systems have not yet matured to the level of clinical use (Lai et al., 2018).  

A feasible way to improve these somewhat redundant systems is to combine alternate sensing methods so that the different types of stimuli can be differentiated between. Some solutions to address the current issues with MRI are further research into the definite risks involved so that these can be evaluated against their use, further investment into this technology’s development would increase accessibility by reducing its cost. Subsequently, the use of multimodal sensing is promising for the development of low-cost, non-transmitting wearable monitors for FM. Introducing a novel combination of advanced signal processing architecture together with bespoke acoustic sensors and accelerometers are able to discriminate and identify between different types of FM.  

References:

Niamh Nowlan (2015). Biomechanics of Foetal Movements. AO Reasearch Institute (1-21)

Levine, D., 2006. Obstetric MRI. Journal of Magnetic Resonance Imaging: An Official Journal of the International Society for Magnetic Resonance in Medicine24(1), pp.1-15.

Ray, J.G., Vermeulen, M.J., Bharatha, A., Montanera, W.J. and Park, A.L., 2016. Association between MRI exposure during pregnancy and fetal and childhood outcomes. Jama316(9), pp.952-961.

Alorainy, I.A., Albadr, F.B. and Abujamea, A.H., 2006. Attitude towards MRI safety during pregnancy. Annals of Saudi medicine26(4), pp.306-309.

Bulas, D. and Egloff, A., 2013, October. Benefits and risks of MRI in pregnancy. In Seminars in perinatology (Vol. 37, No. 5, pp. 301-304). WB Saunders.

NHS website (2018). Developmental dysplasia of the hip.

Murphy, A., Ekpo, E., Steffens, T. and Neep, M.J., 2019. Radiographic image interpretation by Australian radiographers: a systematic review. Journal of medical radiation sciences66(4), pp.269-283.

Pelc, N.J., Herfkens, R.J., Shimakawa, A. and Enzmann, D.R., 1991. Phase contrast cine magnetic resonance imaging. Magnetic resonance quarterly7(4), pp.229-254.

Chaptinel, J., Yerly, J., Mivelaz, Y., Prsa, M., Alamo, L., Vial, Y., Berchier, G., Rohner, C., Gudinchet, F. and Stuber, M., 2017. Fetal cardiac cine magnetic resonance imaging in utero. Scientific reports7(1), pp.1-10.

Lai, J., Woodward, R., Alexandrov, Y., ain Munnee, Q., Lees, C.C., Vaidyanathan, R. and Nowlan, N.C., 2018. Performance of a wearable acoustic system for fetal movement discrimination. PloS one13(5), p.e0195728.

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