Issues in pregnancy dating revisiting the evidence
FHR can be measured with affordable apparatus and little need for prior skill, and hence is a feasible approach in low income countries (Tezuka et al., 1998; Stroux et al., 2014). Google Scholar Marzbanrad, F., Kimura, Y., Funamoto, K., Sugibayashi, R., Endo, M., Ito, T., et al. Automated estimation of fetal cardiac timing events from Doppler ultrasound signal using hybrid models.
Early studies found a comparable accuracy of FHR-based method with CRL, in early pregnancy (38–64 days) (Tezuka et al., 1998), and the methods were further improved recently being more focused on neurological development (Hoyer et al., 2013; Tetschke et al., 2016).
Pathological conditions may also introduce a high levels of inaccuracy or significant bias in many estimation methods. “Application of automated fetal valve motion identification to investigate fetal heart anomalies,” in Healthcare Innovation Conference (HIC) (Seattle, WA: IEEE), 243–246. Quantifying the interactions between maternal and fetal heart rates by transfer entropy. doi: 10.1371/0145672 Pub Med Abstract | Cross Ref Full Text | Google Scholar Mc Clure, E. O., Saleem, S., Esamai, F., Garces, A., Chomba, E., et al. First look: a cluster-randomized trial of ultrasound to improve pregnancy outcomes in low income country settings. doi: 10.1186/1471-2393-14-73 Pub Med Abstract | Cross Ref Full Text | Google Scholar Mc Kenna, D., Ventolini, G., Neiger, R., and Downing, C. Gender-related differences in fetal heart rate during first trimester.
Although in high income countries routine skilled ultrasound screening is performed, many factors limit its use in low income countries, including high cost of the equipment, lack of trained sonographers or physicians, as well as the skill required to perform a GA estimation test (Wang et al., 2011; Mc Clure et al., 2014). doi: 10.1109/JBHI.2013.2286155 Pub Med Abstract | Cross Ref Full Text | Google Scholar Marzbanrad, F., Kimura, Y., Palaniswami, M., and Khandoker, A. doi: 10.1109/HIC.2014.7038920 Cross Ref Full Text | Google Scholar Marzbanrad, F., Kimura, Y., Palaniswami, M., and Khandoker, A.
As reported in the literature, the clinically estimated GA as collected on certificates of live birth based on prenatal and neonatal clinical assessments, exceeds the LMP-based GA by 2 weeks or more for more than 40% of the cases (Alexander et al., 1995).
One promising alternative GA estimator is Fetal Heart Rate (FHR) (Cha et al., 2001; Hoyer et al., 2013; Tetschke et al., 2016). doi: 10.1109/JBHI.2014.2363452 Pub Med Abstract | Cross Ref Full Text | Google Scholar Marzbanrad, F., Kimura, Y., Funamoto, K., Sugibayashi, R., Endo, M., Ito, T., et al. “Development of fetal cardiac intervals throughout 16 to 41 weeks of gestation,” in Computing in Cardiology Conference (Cin C) (Zaragoza: IEEE), 1155–1158. While ultrasound-based techniques are generally based on the physical development and influenced by genetic variations, FHR provides a marker for neuro-physiological development of the fetus, since it reflects the Autonomic Nervous System (ANS) control of the cardiovascular system, which matures through the progress in pregnancy. doi: 10.1109/cic.2015.7408662 Cross Ref Full Text | Google Scholar Marzbanrad, F., Kimura, Y., Funamoto, K., Oshio, S., Endo, M., Sato, N., et al. Model-based estimation of aortic and mitral valves opening and closing timings in developing human fetuses. Various linear, nonlinear and complexity-based FHR variability (FHRV) parameters have been found to be closely related to the fetal development (Van Leeuwen et al., 2003; Hoyer et al., 2009; Wallwitz et al., 2012; Hoyer et al., 2013; Tetschke et al., 2016). Fetal cardiac valve intervals are alternative measures which could be obtained from non-invasive, low cost and easy-to-operate devices, and used as reliable markers for fetal development and well-being (Shakespeare et al., 2001; Khandoker et al., 2009; Marzbanrad et al., 2013b). These intervals are based on the opening and closing time of the fetal cardiac valves, namely the atrioventricular and semilunar valves.