Characteristics of the Unborn Child
Growth and Development

In Oklahoma, the definition of Unborn Child (Title 63 O.S. §1-730) means the unborn offspring of human beings from the moment of conception, through pregnancy and until live birth including the human conceptus, zygote, morula, blastacyst, embryo and fetus.

Physicians often refer to the gestational age of an unborn child as measured from the first day of the last menstrual period (referred to as "LMP"). Another way the age of the unborn child is referred to is based upon the number of weeks since conception (fertilization). Therefore, two (2) weeks after conception corresponds approximately to four (4) weeks gestational age (LMP). Some women have irregular periods and other methods can be used to determine the age of the unborn child. For example, ultrasound can be used to measure the length of the unborn child, which then can help estimate the gestational age of the unborn child.

Conception begins when a woman’s egg is fertilized by the male sperm. The union of the male sperm and female egg form a one-celled entity called a zygote. The zygote has 46 chromosomes, 23 from the mother and 23 from the father. Chromosomes contain genetic material that are the blueprint for growth and development throughout life, determining physical characteristics such as gender, the shape of the nose and ears, and the color of the hair, eyes, and skin, facial features, and at least to some extent, intelligence and personality.

During the first 8 weeks following fertilization, the unborn child is known as an embryo. After that time, the unborn child is known as a fetus (Latin for offspring). During the first ten weeks of pregnancy, the unborn child is most likely to be affected by things like:

  • Alcohol.
  • Nicotine in cigarettes or other tobacco products.
  • Some prescription medicines or over-the-counter drugs (Consult with your doctor before taking drugs of any kind).
  • Illegal drugs (like heroin, cocaine, methamphetamine, marijuana, and others).
  • Viruses (such as rubella or cytomegalovirus).
  • X rays, radiation therapy, or accidental exposure to radiation.
  • Vitamin deficiencies (such as folic acid).

The development of an unborn child depends on many factors. This booklet will discuss only normal growth and development. The gestational stages photos and drawings are not meant to convey precise size and/or detail, but rather the general shape and progression of the unborn child as he or she develops.

Ages in this website are listed as both the estimated day when conception (fertilization) occurs and from the first day of the last normal menstrual period (LMP).



The content on this site is provided for educational and informational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Use of this website signifies your understanding of and your agreement to these terms.
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