Effect of the presence of amniotic fluid for optical transabdominal fetal monitoring using Monte Carlo simulations

Abstract

About a third of babies are delivered by Cesarean section. There has been an increase in maternal deaths during labor due to complications with subsequent births after a C-section. Therefore, there is a clinical motivation to reduce the C-section rate. Current techniques are, however, inefficient at determining fetal distress leading to a high false positive rate for complications and ultimately a C-section. For the current study, Monte Carlo simulations were used to calculate the amount of signal received on a model of a pregnant mother, as well as, the percent of the signal that comes from the fetal layer. Models with and without a 1 mm amniotic fluid were compared and showed differing trends.

The effect of adipose tissue on transdermal monochromatic light presented to the human fetus using Monte Carlo simulations

“…We present a single option for consideration here: each image shows the beam's simulated relative fluence rate at the tissue-fluid interface for tissues with differing adipose thicknesses (in line with the source stimuli). This decision is due to the low absorption coefficient [11] and relatively low scattering coefficient [12] in amniotic fluid for the considered wavelength. Hence, we propose that light which reaches this interface is likely to continue propagating to the fetus with minimal attenuation -especially when noting that the typical separation between the fetal eye and the uterus is on the order of 1-2 cm.…”

“…Fourth, in transabdominal fetal monitoring (and similar fields), computational modelling has been employed to simulate light transport to the fetus for observation of fetal wellbeing. For example, various efforts have been made in fetal pulse oximetry to model light transport in maternal tissue; recently, MC simulations were used to determine the effect of amniotic fluid on recovering fetal signals through the maternal abdomen [12]. In this work, researchers utilise a three-layer maternal tissue model and vary the subdermal layer, though their focus (and that of others in these fields) is on aspects not directly related to our interests.…”

Review of optical methods for fetal monitoring in utero

“…• Computational models understand the fetal fraction of the signal. [12,20,24,26,29] Fetal signal hiding behind Mother harmonic in FFT.…”

“…Additionally, the fetus could also move in utero and cause artifacts. The movement could cause a change in fetal depth, which has been an important parameter in the amount of light that reaches the fetus and then is collected [24, 29].…”

“…MC simulations were also used to determine the effect of amniotic fluid on the output measurements of a transabdominal optical system (static light measurements) [24]. Since amniotic fluid is fairly translucent (low scattering), the diffusion approximation cannot be used to estimate how light propagates through the medium.…”