Final answer:
The pulse rate of a fetus between 14 and 20 weeks gestation continues to develop along with other physiological functions. Week 20 marks the beginning of fetal breathing movements, and developmental weeks 21-30 are significant for rapid weight gain.
Step-by-step explanation:
During 14 and 20 weeks gestation, the pulse rate, or heart rate (HR), undergoes significant changes as the fetus develops. Fetal HRs can be quite elevated when compared to adults. For instance, newborn resting HRs may be around 120 beats per minute (bpm) and will gradually decrease until young adulthood. This developmental period is marked by substantial growth; organs continue to mature, and bodily functions become more refined. Specifically, developmental weeks 21-30 are characterized by rapid weight gain, important for the maintenance of body temperature post-birth, and the start of myelination in the nervous system, which is essential for efficient functioning. During this time, the fetus begins to exhibit the body proportions of a full-term newborn but is much leaner.
Furthermore, fetal development includes numerous physiological milestones. Fetal movements become noticeable by the mother, and the placenta has taken over the functions necessary for the fetus's continued growth. It's also around week 20 that fetal breathing movements begin, signaling further advancement in developmental stages.