Final answer:
Quickening is the first time the mother perceives fetal movements, usually occurring between weeks 16 to 20 of the pregnancy.
Step-by-step explanation:
Quickening refers to the first time the mother feels the baby move, which typically occurs during approximately weeks 16-20 of pregnancy. As the fetus grows and its limb movements become more pronounced, the space within the uterus becomes more confined, leading to noticeable movements. However, these movements are often limited due to spatial restrictions, causing the fetus to adopt the 'fetal position.'