Fetal Period Development Quiz

Embryo to Fetus Transformation

• The transformation of embryo to fetus occurs at the end of the eighth week.

Fetal Development Milestones

• At the beginning of the third month, the head is approximately half of the crown-rump length (CRL).
• The size of the head becomes approximately one-fourth of crown-heel length (CHL) by the end of the third month.
• External genitalia show differences during the fetal period by the end of the third month.
• The legs become short and the thighs small during the third month.
• The primary ossification center appears by the end of the eighth week.
• The spleen becomes an important site of hematopoiesis during the ninth week.
• The fetus lengthens rapidly and gains fine hair known as lanugo by the fourth month.
• The intestines withdraw into the abdominal cavity, ceasing the umbilical cord swelling, by the tenth week.
• The respiratory and central nervous system do not differentiate sufficiently, although type II pneumocytes secrete surfactant, by the end of the eleventh week.
• The skin becomes covered and protected by vernix caseosa by the end of the twelfth week.
• The fetus gains substantial weight and its skin becomes wrinkled and translucent, pink to red, by the fourteenth week.
• The testes begin to descend in male fetuses by the fourteenth week.
• The fetus is able to breathe air by functioning lungs and have fully formed CNS control over rhythmic breathing and body temperature by the twenty-fourth week.
• The spleen shifts from being an important site of hematopoiesis to bone marrow taking over this function by the twenty-eighth week.
• The fetus exhibits substantial weight gain, wrinkled skin with visible toenails, and responds to noise with blink-startle responses by the twenty-eighth week.