Final answer:
The advised side-lying position for a pregnant client with increased blood pressure in the 38th week of gestation is mainly to increase blood flow to the fetus by minimizing compression of the inferior vena cava, which can enhance fetal nourishment and oxygenation.
Step-by-step explanation:
If a client in the 38th week of gestation develops a slight increase in blood pressure, and is advised to remain in bed at home in a side-lying position, it is primarily to increase blood flow to the fetus. This position helps in minimizing the compression of the inferior vena cava by the gravid uterus, which can impair venous return and thereby reduce the cardiac output and subsequent uteroplacental perfusion. A side-lying position, therefore, can optimize blood flow to the fetus by minimizing this compression.
This position also potentially decreases intra-abdominal pressure, which can further contribute to better blood circulation. While mean arterial pressure is not directly elevated from this position, and prevention of thromboses is more related to movement rather than position, the primary concern here is optimizing fetal blood supply which is of utmost importance for fetal health and development.