The middle trimester is between 14 weeks of pregnancy and the end of 27 weeks of pregnancy. The gestation period is calculated from the first day of the last menstrual period and is approximately 280 days, totaling 40 weeks. It is clinically divided into three phases, early, midterm and late. Early pregnancy is defined as pregnancy before 14 weeks; midterm pregnancy is defined as between 14-27 weeks of gestation; and late pregnancy is defined as after ≥28 weeks. Mid- and late-term pregnancies are important periods for fetal growth and organ development. This period is mainly observed for fetal growth and development, intrauterine conditions and detection of fetal malformations to avoid the occurrence of birth defects.