Growth & Development of a Fetus

There are many stages in the growth of a fetus. These stages range from cell division to formation of specialized organs and nerves to general weight and length increases. Each stage of development requires different things from the mother, both consciously and physically. Being aware of the growth stages of a baby can help an expectant mother make the right decisions to promote its healthy development.

Stage Division

There are three stages and four phases of pregnancy. The three stages mark the initial development of the pregnancy and the fetus in the first trimester, the finer development of the second trimester and the growth of the third trimester. Three of the four phases happen during the first trimester, leaving the fourth phase to continue into the second and third trimesters.

First Trimester

This stage of pregnancy begins before you are even pregnant. Doctors count the two weeks from the end of the last menstrual cycle to ovulation and fertilization as the first two weeks of pregnancy. By the third, fourth and beginning of the fifth week, when the egg has been fertilized to become a zygote, it makes its journey through the fallopian tubes to the uterus. When the fertilized egg takes up residence in the uterine wall, it is called an embryo. The embryo then divides into the placenta and the fetus during the sixth week. From this point on the growing life-form is referred to as a fetus. The final weeks of this trimester see the development of the heart, eyes, nervous system and liver begin.

Second Trimester

Not only are finer details such as hair and fingerprints developing, but the fetus's reproductive organs and bones are formed. The fetus will begin hiccuping and even hearing the mother's voice at this time in the pregnancy. Milestones such as the risk of miscarriage dramatically decreasing, beginning to feeling the baby moving move and the possibility of determining the gender of the fetus occur during this stage. Mothers must also be mindful of the signs of premature labor during the second trimester. The odds of survival increase with each passing week.

Third Trimester

By week 28, the start of the third trimester, the gestation or development stage is complete. Now begins the growth stage. A fetus will gain approximately 1/2 lb. per week during the last six weeks of pregnancy. Along with growth comes maturation of the lungs and muscle functions in preparation for birth. At 38 weeks the fetus is considered full-term, though official full-term is not reached until 40 weeks. Some pregnancies may even last up to 42 weeks, at which point, if labor is not in sight, an obstetrician will induce labor.

Determining Stages and Awareness

The stages of pregnancy are determined in various ways: time calculation, ultrasound imaging and measurement of the fetus. The mother needs to be aware of the changes taking place as risks of miscarriage, premature labor and birth defects change with each trimester. The obstetrician and sonogram technician will help keep the mother abreast of stage changes.

References

• Parenting Village
• Expectant Mother's Guide
• Epigee