Abstract

Normal birth is defined as when a child is born between 37 and 42 completed weeks of pregnancy. If the child is born before 37 weeks of pregnancy, the birth is considered preterm. The causes of preterm births are still not understood properly and research is being carried out to identify the causes and to prevent preterm birth. Preterm birth has serious effects on preterm children. The child born preterm is prone to defective physical growth and also subject to poor psychological growth. Preterm birth is associated with deterioration in the cervical resistance. Cervical fatigue may be caused by static loads during extended periods of standing, dynamic loads while working which involve a lot of moving around and walking, or impulse loads caused by sudden jerky movements.
The present study is concerned with developing biomechanical models of the pregnant woman in order to study the biomechanical behavior of the pregnant woman under different types of loads. Previously developed 3-Degree of Freedom and 5-Degree of Freedom models are used to obtain the response of the pregnant woman to vertical vibration, and also to predict the cervical loads in the seated position. A 9-Degree of Freedom model is developed in this study in order to obtain the response of the woman’s body to walking generated excitation, and to predict the cervical loads.
Results from the 3 developed models are obtained at two different conditions, preterm “exactly at 37 weeks of pregnancy” and term “exactly at 42 weeks of pregnancy” conditions. The results from the 2 seated models are compared to the results obtained from the 9-Degree of Freedom walking model, in terms of cervical loads. The comparison shows that the cervical loads are higher in the walking position. Therefore, it is decided to identify the parameters of the walking model. The model consists of 7-Degree of Freedom for the woman’s body and 2-Degree of Freedom for the fetus and the uterus combination. As identifying all the 9 parameters of a 9-DOF pregnant woman through measurements is extremely difficult, it is decided that the identification process will take place on the 7-Degree of Freedom model. To identify such a model, experimental measurements are carried out on a walking individual. The error between the computed and experimental results is minimized using genetic algorithm. Parameters of the 7-Degree of Freedom model are identified through the optimization process. After identifying the 7-Degree of Freedom model parameters, the other 2-Degree of Freedom are added.
The optimized biomechanical model is used to obtain the response of the pregnant mother to dynamic environmental loads that the pregnant woman is normally subjected to during her daily activities. The results are presented and discussed, in order to get a better understanding of the loads bearing on the cervix. The results show that there is not much difference between the experimented model and the nominal model.