Final answer:
The first trimester of pregnancy involves organ and structural development, and the formation of the placenta. The second trimester continues organ development and is marked by mother's experience of fetal movements and significant weight gain. The third trimester culminates with the greatest growth of the fetus and preparations for labor, delivery, and breastfeeding.
Step-by-step explanation:
Main Tasks for Each Trimester of Pregnancy
First trimester: The initial stage of pregnancy, laying down the basic structures of the body. Limb buds, heart, eyes, and liver start to develop. During the early weeks, nutrition and waste are mediated by the endometrial lining, later giving way to the placenta, which then takes over nutrient and waste requirements. Key hormones such as thyrotropin and prolactin increase, which adjusts the maternal metabolic rate and prepares for milk production.
Second trimester: Continues the development of all organs and systems. This is also when the mother may feel the fetus’s movements for the first time. Notable weight gain occurs due to the grown fetus, enlarged uterus, increased blood volume and tissue. Vital nutrients like calcium, iron, and omega-3 fatty acids are critical during this phase.
Third trimester: Marks the greatest growth spurt of the fetus leading up to labor and delivery. The pregnant woman's body prepares for the birth process, which includes contractions, delivery of the fetus, and expulsion of the placenta. This period also involves preparing for breastfeeding, mobilizing calcium for the fetus, and ensuring an adequate fat reserve is established.