When does the second trimester start? When does it end? Your second semester starts at week 13 and ends on the last day of week 27. What are some of the pregnancy symptoms in the second trimester?
The first trimester lasts for the first 12 weeks of the pregnancy and is crucial for the baby’s development. At conception, the egg and sperm combine to form a zygote, which will implant in the uterine wall. The zygote becomes an embryo as the cells divide and grow. All of the major organs and structures begin to form.
Pregnancy trimesters: A guide The typical pregnancy has three trimesters and lasts around 40 weeks from the first day of a woman’s last period. In each trimester, the fetus will meet specific developmental milestones. While 40 weeks is the usual time frame, a full-term baby can be born as early as 37 weeks and as late as 42 weeks.