The Fetal Period

When does the fetal period begin and end?

From week 9 to birth.

What are the key focuses of the fetal period?

Growth, differentiation, and physiological function.

What are the two main functions of the placenta?

Exchange and endocrine.

Why is fetal development clinically important?

It informs obstetrics, pediatrics, and neonatology.

What characterizes early fetal growth?

Accelerated cephalic growth (head grows faster).

What happens in the intermediate phase?

Increase in length and weight.

What are key features of the final phase?

Fat and glycogen storage, system maturation.

Fetal size at weeks 9–12?

5–8 cm, ~14 g.

What is the liver's role during this period?

t is the main hematopoietic organ.

Can genitalia be identified via ultrasound at this stage? ( weeks 9-12)

No, not yet identifiable.

Fetal size at weeks 13–16?

12–14 cm, ~100 g.

When are genitalia identifiable by ultrasound?

Around week 14–16.

Which glands increase activity in this period?

Thyroid and adrenal glands.

What is "quickening" and when is it felt?

First fetal movements felt by mother, around weeks 17–20.

What skin features appear?

Lanugo and vernix caseosa.

Where is hematopoiesis occurring now? (weeks 17-20)

Bone marrow.

When does surfactant production begin?

Around weeks 21–24, but it’s insufficient for respiration.

What physical changes occur to the eyes and skin?

Eyelids open, skin is thin and reddish.

Which axis matures to regulate metabolism?

HPA axis (hypothalamic-pituitary-adrenal).

How does surfactant production change?

Increases, improving viability.

What hormone promotes lung and liver maturation?

Cortisol.

What is the main site of hematopoiesis now? ( Week 25- 28)

Bone marrow (definitive hematopoiesis).

What allows thermoregulation at this stage? Weeks 29–32

Fat deposition.

Which CNS reflexes are now controlled?

Breathing and swallowing.

What endocrine organ becomes more active?

Pancreas (produces insulin).

What immune components are present now?

Fetal IgM and maternal IgG.

What respiratory behavior becomes rhythmic?

Breathing movements.

How does the skin appear? Weeks 33–36

Smoother and pinker.

What is the typical weight and length of a full-term fetus?

50 cm, 3,000–3,400 g.

What hormone peaks before birth and why?

Cortisol – for lung, liver maturation, and labor onset.

What energy stores are important at this stage?

Liver glycogen and brown fat.

What closes to adapt the fetal circulation?

Fetal shunts: foramen ovale, ductus arteriosus, ductus venosus.

What helps with heat production in newborns?

Brown fat metabolism.

What provides initial immune protection?

Maternal IgG.

What change occurs in the renal system?

Kidneys take over excretion.

What is the fetal period mainly about?

Consolidation of systems, not organ formation.

What organ regulates fetal growth and development?

The placenta.

Why are weekly fetal milestones important clinically?

They guide viability assessment and perinatal care.