PRENATAL DEVELOPMENT
| From zygote to neonate, prenatal development is nothing short of a miracle.A life begins! Prenatal development is typically divided into three trimesters. Journey with us through these periods of development. |
Related topics include:
Teratogens
Infertility
Miscarriage and Abortion
Assisted Reproduction
The Periods of Prenatal Development
The intricate details of life begin with a single cell that develops into a full term fetus within approximately 38 weeks. The course of this prenatal development is divided into three main periods: germinal, embryonic, and fetal.
The Germinal Period takes place in the first two weeks after conception and includes the creation of the zygote (fertilized egg), cell division, and the attatchment of the zygote to the uterine wall.
The second period is known as the Embryonic Period and occurs 2-8 weeks after conception. During this period, the rate of cell division increases, support systems for the cells form, and organs appear. The mass of cells attatched to the uterine wall forms two layers and is now called the "embryo". The inner layer of cells of the embryo is the endoderm which develops into digestive and respritory systems. The ectoderm (outer layer of cells) will become the nervous system and sensory receptors (ears, nose, and eyes, and skin) and the mesoderm (middle layer) will develop into the circulatory system, bones, muscle, excretory system, and reproductive system. All this occurs in the first two months of development!
The final period is the Fetal Period. This period begins two months after conception and lasts for seven months. During this period, development is most dramatic.
| Three months after conception, the is fetus 3 inches long and weighs about an ounce. It is activly moving its arms and legs, opening and closing its mouth, and moving its head. |
Trimesters in Development - Below are several tables that illustrate the developmental accomplishments during each of the trimesters.
|
|
|
|
| Less than 1/10 inch long | Less than 1 inch | 3 inches 1 oz. |
| Begining development of spinal cord, nervous system, heart intestinal system, and lungs. | Face forming (eyes, ears, mouth, toothbuds). | Moving fingers and toes. |
| Amniotic sac | Arms and legs moving. | Finger prints |
| "Ovum" | Heartbeat detectable | Can smile, suck, frown, swallow, and urinate. |
| "Embryo | "Fetus" |
|
|
|
|
| 5 1/2 inches 4 oz. | 10-12 inches 1 lb. | 11-14 inches 1 1/2 lbs. |
| Strong heartbeat | Sucks thumb | Wrinkled skin |
| Thin skin | Hiccups | Opens eyes |
| Downy hair over body | Hair, eyelashes, and eyebrows. | Strong grip |
| Fingernails and toe nails developing | Rolls over in fluid |
|
|
|
|
| 14-17 inches 2 1/2-3 lbs. | 16 1/2-18 inches 4-5 lbs. | 19 inches 6 lbs. |
| Adding body fat | Sleep / Awake | Skin less wrinkled |
| Very active | Responds to sound | Gaining immunities from mother. |
