Introduction
Preterm Labor (PTL) is one of the most important problems of obstetricians and the most common cause of infant mortality. A premature labor is a labor whose pregnancy lasts less than 37 weeks (1). In different regions, the prevalence of PTL is about 5-10% of all pregnancy cases. Studies in different countries show that, despite a decrease in infant mortality over the past 20 years, PTL has a high prevalence, so that it is between 12-13% in the United States and 5-7% in Europe (2). The majority of preterm labors in the world occurs in South Asia and sub-Saharan Africa (3). In Iran, the prevalence of preterm labor is high, and it has been reported as about 4.39 to 6.5 in various studies (4).
PTL has different influencing risk factors (5). Preeclampsia and/or fetal growth restriction (FGR) are mainly medical reasons for one-third of PTLs, and spontaneous preterm labor is two-thirds of PTLs. Prevention of PTL is one of the most important purposes of birthing specialist care (6). Because there are many reasons for this problem, different types of scientific search and clinical strategies are needed to prevent it (7). For a desirable PTL prevention method, a combination of three items including maternal risk factors, obstetric history, and screening tools should be considered for stratification of risk (5).
Contractions of the uterine during pregnancy are monitored to evaluate PTL threat. External measurement of uterine electrical activity is known as a substitute way of monitoring and analyzing uterine contractions. Tocodynamometry (TOCO) is the most common tool (8). Besides the benefits, TOCO has some disadvantages that negatively affect correct identification of PTL (9). So, a more accurate method is needed. Another method is electrohysterogram (EHG), which was developed in the 1960s (10). It is a signal related to electrical waves emitted by smooth muscle cells of the uterus, which is also known as the uterine contraction signal (11). EHG provides better results in aspects of accuracy and reliability compared with tocodynamometry (12).
Because uterine activity related to PTL often cannot be identified by patients, home uterine activity monitoring can be suitable for early detection of uterine contractions without hospitalization. Various devices for this purpose were created and studies performed to evaluate their efficacy. Some studies show that using a home uterine activity monitoring device can increase the length of pregnancy in women with high PTL risk (13). This leads to a decrease in infant mortality, because gestational age has an inverse relationship with the risk of neonatal morbidity and mortality (14).
In Iran, the prevalence of PTL is high, and accessibility to health facilities in some regions is low. A home monitoring device could be a good option. Regarding this, we decided to develop a tool to monitor uterine activity at home for pregnant women. Also, the noises of EHG signals were removed by the composition of filters and amplifiers.