Duration and Stages of Pregnancy

Pregnancy in humans is an amazing physiological process that lasts an average of 266 days, or around 38 weeks or 9 months. This gestational time is carefully divided into three separate periods, or trimesters, that last around three months each. These trimesters mark particular developmental turning points and physiological shifts for the developing fetus as well as the mother.

1. First trimester (0-12 weeks): The duration of this period is first three months. Pre-embryonic and embryonic development stress, nutritional deficiencies are the common problems during this period. Foods such as raw cabbage, potatoes, coffee should be avoided during this time as these have harmful effects on embryo. During this time, “morning sickness,” a condition marked by nausea and vomiting, is common. It is thought that this state serves as a defense mechanism, maybe guarding against ingesting chemicals that could harm the developing fetus.
2. Second trimester (13-24 weeks): The duration of this period is from fourth to sixth months. This period is characterized by development of fetus in which most of the organs are developed. In this stage, most organs go through their formation and maturation. The fetus starts to show physical characteristics and its physiological systems begin to work. This stage is marked by the fetus’s apparent growth and development and is frequently linked to a decrease in the mother’s pregnancy-related discomforts.
3. Third trimester (25 weeks-birth): It includes seventh to nine months. The baby continues to grow and develop during the last trimester. The developing fetus starts to move more and more, kicking and straining. Important developmental milestones are reached by the thirtieth week: the sense organs are fully formed, fingernails appear, bones ossify, and the bone marrow begins to produce red blood cells. In addition, the foetus loses its covering of lanugo, a tissue that resembles hair and acts as protection.In this stage growth of baby occurs. Various body movements including kicking, stretching starts in baby. The development of red blood cells (RBC) in bone marrow, fingernails, sense organs take place.

Also Read:

• Human Pregnancy
• Spermatogenesis
• Oogenesis
• Human Reproduction
• Diploblastic And Triploblastic Organization
• Anatomy – Overview, Types and Application

Embryology is the study of the origin and prenatal development of an organism which comprises the germinal, embryonic, and fetal periods. The germinal period consists of the first two weeks from conception, the embryonic period includes the third to eighth week from conception, and the fetal period consists of the ninth week from conception to birth. Gestation in embryology refers to the period from conception to birth. The gestation period is different from gestational age which is measured in weeks starting from the first day of the mother’s last menstrual period.