Fetus

A fetus is the developing stage of an organism after the embryonic stage and before birth. It is observed in viviparous animals, including humans, and begins from the end of the 11th week to the 12th week of gestation.

Characteristics

A developing fetus exhibits several distinct characteristics:

  • Size and Weight: The size of a fetus can vary throughout different stages of development, but by the end of the second trimester, it is typically around 13-15 inches long and weighs approximately 1.5-2.5 pounds.
  • Organ Development: During the fetal stage, organs continue to mature and develop, with most major organs being fully formed by the end of the second trimester.
  • Movement: Fetal movements, known as quickening, can usually be felt by the pregnant person during the second trimester. These movements gradually increase in intensity as the fetus grows.
  • Sexual Differentiation: By the end of the first trimester, the fetus’ biological sex can generally be determined.
  • Growth: The fetus undergoes rapid growth during the third trimester, with the body becoming plumper and the skin smoothing out as fat accumulates beneath it.

Developmental Stages

The development of a fetus can be divided into three main stages:

  1. First Trimester: This stage spans from conception to the end of the 12th week. Major organs and body systems begin to form, and the fetus grows rapidly.
  2. Second Trimester: Starting from the 13th week and ending at the 27th week, this stage is characterized by further organ development, the maturation of limbs, and the onset of fetal movements.
  3. Third Trimester: From the 28th week until birth, the fetus experiences a period of significant growth and refinement of organ systems. It gains weight and prepares for the transition to independent life.

Importance of Fetal Development

Understanding fetal development is crucial for prenatal care and ensuring the well-being of both the pregnant person and the fetus. Monitoring the growth and health of the fetus allows medical professionals to identify any abnormalities or potential complications.