Fetus - Developmental Stages and Growth Abnormalities

What Is a Fetus?

Prenatal development is as important as postnatal development for the baby. It not only plays a major role in physical development but also in psychiatric development.

Month by month, women’s bodies go through hormonal changes during menstruation cycle. Until women conceive, the cycle goes on every month. Few eggs are released from the ovary, and this phase is called ovulation. When a single egg is fertilized with sperm, it further grows and moves to the fallopian tube to get attached to the endometrium, which confirms the pregnancy as a fertilized egg gets implanted into the uterus wall. On the other hand, when the egg is not fertilized, the thin lining sheds off. Hence the beginning of another menstruation cycle occurs.

When the embryo is formed, the first few weeks are very important for pregnant women. However, once the embryonic period is over, it is now considered a growing fetus. Thus, the first day of the last menstruation cycle is counted as the start of the pregnancy, and it plays an important role in determining the due date for the baby. Every woman has a genetic combination of XX chromosomes, and every man is born with XY chromosomes. Thus, the genes of women (XX) give a single X to an egg, and men give either X or Y to an egg. If the fertilized egg has the XX combination, it is a girl; if it has the XY combination, it is a boy.

What Are the Fetal Developmental Stages?

There are the following fetal developmental stages seen:

Week 3:

• From three weeks of implantation into the endometrium, nerve formation begins in the embryo.
• The body releases the hCG (human chorionic gonadotropin) hormone (pregnancy hormone), which stops the formation of eggs.

Week 4:

• The embryo develops the structures that are responsible for face and neck formation. At this phase, the embryo develops into a fetus.
• The heart and circulatory systems have started developing.
• Pregnant women may feel symptoms like dizziness, nausea, swollen breast, and discomfort.

Week 5:

• It is also known as the “embryonic period,” where the fetus develops blood cells, kidney cells, and external features.
• The development of the brain and spinal cord starts during this week, and there is a higher risk of babies born with birth defects if there is any injury, drug abuse, or adverse effect of any medicine taken by the mother.

Week 6 to 7:

• The fetus grows into a bud that further develops extremities like arms and legs.
• The brain and nervous system are formed along with the electrical activity.
• The fetus begins to straighten up slightly.
• Other features like lip and nose are formed. Ears also start forming with a small indented mark on each side of the head.

Week 8:

• The head of the fetus is equal to half the size of the body.
• Arms, legs, ears, and neck are more identifiable now.
• A small movement of the baby starts in the womb. Although the mother does not feel it yet.
• The fetus also starts developing breathing pathways from its throat to the lungs.

Week 11 to 14:

• The fetus has a well-defined face now. Nails start appearing on fingers and toes, and the baby can make a fist.
• The embryonic tail disappears.
• The fetus can now kick, stretch, and hiccup; however, the mother still cannot feel the movement.

Week 15 to 20:

• The fetus develops fine hair.
• The hearing ability of the fetus is developed.
• Kidneys are developed now.
• Ears are now close to their final position.
• In the later stage of this period, the fetus develops senses like smell, vision, touch, taste, and hearing.

Week 22:

• Eyelashes and eyebrows appear.
• Increased muscle development leads to the movements of the baby.
• Heartbeat is significantly heard with a stethoscope.

Week 23 to 30:

• The baby’s skin is still translucent, and the body is still lean and grows in size with the passing of each week.
• Somewhere around the 24th week, the mother can feel fetal movements like rolling, swishing, and kicking.
• Their bone marrow formation, fat storage, hand, foot, and fingerprint formation occur.
• In the womb, the baby starts responding to loud noises. Also, it starts recognizing the voice by picking up the sound.
• The fetus can now inhale and exhale amniotic fluid because the lungs are developed.
• Later in this stage, the sleep cycle of the baby is right on schedule, which shows active brain functioning.

Week 31 to 40:

• Rhythmic breathing, an increase in body weight, and complete development of muscles and bones occur.
• The sutures of the skull have not fused yet, as they continue to grow until their adulthood.
• At week 37, it is considered to be full term, and by any day, the mother can experience labor signs and symptoms.

Week 41:

• With the passing of each day after the 40th week, it is considered to be late-term.
• With the passing of time, only health-related complications and risks are increased for the baby and the mother.
• Risks associated with post-term pregnancy include the following:
  1. Stillbirth: It is described as a loss of pregnancy or fetus before the delivery.
  2. Macrosomia: It is the terminology used for describing a fetus larger than normal size.
  3. Postmaturity Syndrome: It is a disorder caused by issue with placental blood supply to the fetus.
  4. Meconium in the Lungs of the Fetus: It can cause serious breathing problems after birth.
  5. Decreased Amniotic Fluid: It can cause the umbilical cord to pinch and restrict the flow of oxygen to the fetus.

What Are the Growth Abnormalities Seen in Fetus?

There are the following growth-related abnormalities seen in a fetus:

• Duodenal atresia.

• Dandy-Walker malformation.

• Limb defects.

• Down syndrome.

• Chromosomal abnormalities.

• Learning disabilities.

• Developmental delay.

How to Manage Fetal Growth?

Following are the options for the management of fetal growth:

• The mother should go for regular checkups.

• A balanced diet and active lifestyle are important.

• Regular yoga and exercise, especially suggested for pregnant women, have proved to be of great help during labor.

• If required, mothers should take supplements for their health not only during pre-pregnancy or pregnancy but also after pregnancy.

Conclusion:

Throughout pregnancy, the health of the mother is as important as the health of the fetus. And with extra care and nourishment, a healthy baby weighing around 7 pounds is born. Moreover, due to immature immunity, it is highly essential to take care of fetuses.