Prenatal Development in the First Trimester of Pregnancy

The stages of pregnancy fall into three segments of about three months each. These segments, known as trimesters, contain important milestones for prenatal development. While every moment of a pregnancy matters, the first trimester may be the most important time. Learning how a baby develops during these early weeks can help parents-to-be understand the miracle developing inside the mother.

Significance

A fetus grows tremendously fast in the first trimester of pregnancy. In this early stage of prenatal development, all major internal parts are formed. Every body organ will begin developing. The fetus is also most vulnerable to injury or other health problems. Mothers-to-be also notice changes in their body.

Time Frame

In the first days of pregnancy, the fertilized egg will travel to the uterus and attach to its lining.The next eight weeks of pregnancy are called the embryo stage. During this time, early organ development begins. After eight weeks, the embryo is known as a fetus.
Most miscarriages take place during the first trimester. Miscarriages happen in about one-fifth of all pregnancies. A reason for the miscarriage cannot be determined in most cases.

Size

At the end of the embryo stage, the body is about 1-inch long. By the end of the trimester, the average fetus is three to four inches in length.

Development

By the end of the first month, arms and legs begin to form. The brain and spinal cord take shape. The fetus’s heart begins to beat.
After the second month, bones begin to develop. The ears and eyelids grow, and the genitals appear. All major organs and body parts are in place, but not fully developed.
By the end of the first trimester, prenatal development includes teeth buds, toe and fingernails, skin and continued organ growth.

Warnings

The University of Virginia Health System warns that a mother’s health and behavior can have a significant impact during the first trimester. During this period, the fetus is especially vulnerable to disease, alcohol, smoking, drugs and medications. Be sure to share any information on health and lifestyle habits with your health care providers.

Maternal Effects

According to the American College of Obstetricians and Gynecologists, a mother-to-be also goes through changes during the first trimester. Periods stop, of course, and breasts may become tender. Many women feel tired or nauseous. Cravings can occur, along with heartburn. Constipation and weight fluctuation can also take place.

Recommendations

Be sure to see a health care provider as soon as you learn you are pregnant. Your provider has valuable information on healthy diets, nutritional supplements, exercise and can set up a regular schedule of medical exams. Blood tests and screenings can identify potential problems and provide treatment at the earliest possible stage.
Studies show that mothers who have regular medical attention during pregnancy tend to have healthier infants and lower risks for complications.