Fetal Development Month 3

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Questions and Answers

What is the fetal component of the placenta derived from?

Trophoblast and extraembryonic mesoderm (correct)

Uterine endometrium and chorionic plate

Decidua basalis and junctional zone

Amnion and blood vessels

Which measurement is NOT typically determined using ultrasound in gestational assessments?

Chorionic plate thickness (correct)

Crown-rump length (CRL)

Head circumference

Biparietal diameter (BPD)

Which structure is formed from the maternal contribution to the placenta?

Chorionic plate

Umbilical cord

Decidua basalis (correct)

Chorion frondosum

What is the average weight range of a newborn considered healthy?

2,500-4,000g Signup and view all the answers

Which of the following structures connects the fetus to the placenta?

Umbilical cord Signup and view all the answers

At the beginning of the third month, what proportion of the crown-rump length (CRL) does the head constitute?

Approximately one half Signup and view all the answers

What happens to the size of the head by the fifth month of fetal development?

It grows to approximately one quarter of the crown-heel length (CHL) Signup and view all the answers

Which measurement is correlated with the age of the fetus in weeks?

Crown-rump length (CRL) Signup and view all the answers

What characterizes the fetal period from the 9th week to birth?

Maturation of tissues and organs with rapid body growth Signup and view all the answers

What is the maximum crown-rump length (CRL) for a full-term baby around 37-38 weeks?

Up to 36 cm Signup and view all the answers

During what stage of development does the majority of bodily growth accelerates while head growth slows down?

From the fifth month onward Signup and view all the answers

Which length measurement refers specifically to the sitting height from the vertex of the skull to the heel?

Crown-rump length (CRL) Signup and view all the answers

What structural component of pregnancy is responsible for nutrient and gas exchange between the mother and fetus?

Placenta Signup and view all the answers

What is the significance of the swelling at the base of the umbilical cord in an 11-week fetus?

It is caused by herniated intestinal loops. Signup and view all the answers

At what stage does the amnion and chorion fuse, resulting in the obliteration of the uterine cavity?

End of the third month Signup and view all the answers

How are infants identified as having Intrauterine Growth Restriction (IUGR)?

By their weight at birth being below average. Signup and view all the answers

What overall age of gestation is taken into account for measuring fetal development?

266 days or 38 weeks after fertilization Signup and view all the answers

What developmental feature is observed in the skull of an 11-week fetus?

It lacks the normal smooth contours. Signup and view all the answers

What characteristic is notable about the face of a 12-week fetus?

It has developed primitive ears. Signup and view all the answers

What happens to the chorionic villi at the abembryonic pole by the end of the second month?

They disappear and form chorion laeve. Signup and view all the answers

When do fetal movements typically begin during gestation?

At 12 weeks gestation Signup and view all the answers

At what stage of pregnancy can the testicles of a male fetus be seen within the scrotum via ultrasound?

By the third month Signup and view all the answers

What is the characteristic that allows determination of the fetus's sex by external examination during the third month?

Development of external genitalia Signup and view all the answers

What fetal development milestone occurs between the fourth and fifth month?

Movement of the fetus felt by the mother Signup and view all the answers

Which feature becomes pronounced by the end of the third month of fetal development?

Pronunciation of sexual characteristics Signup and view all the answers

What physical characteristic is notable about the skin of the fetus during the third month?

Translucent skin revealing blood vessels Signup and view all the answers

What factor can be used by a doctor to determine the month of pregnancy during a prenatal check-up?

Feeling of fetal movement Signup and view all the answers

What embryonic characteristic is evident as the fetus develops between the third and fourth months?

Development of eyelids and eyebrows Signup and view all the answers

What happens to the intestines by the sixth week of fetal development?

They cause umbilical herniation Signup and view all the answers

What is the average length of pregnancy in days considered from the last normal menstrual period?

280 days Signup and view all the answers

During which months does growth in length particularly accelerate for a fetus?

3rd, 4th, and 5th months Signup and view all the answers

What is the specific structure of the chorion that has many villi known as?

Chorion frondosum Signup and view all the answers

What is the primary change in weight during the stages of gestation?

Increase in weight is most noticeable during the last two months Signup and view all the answers

How long is age typically calculated from fertilization in days?

266 days Signup and view all the answers

What does the yolk sac and long vitelline duct indicate in a fetus?

They are remnants of early embryonic development Signup and view all the answers

What is the maximum crown-heel length (CHL) noted in the content for a fetus?

51 cm Signup and view all the answers

In terms of fetal development, what is a notable feature of the chorionic cavity during the gestational period?

It is characterized by the presence of the yolk sac and long vitelline duct Signup and view all the answers

Study Notes

Fetal Development Overview

Begins at 9 weeks and continues to birth, characterized by rapid growth and maturation of tissues and organs.
Fetal size is measured as Crown-Rump Length (CRL) and Crown-Heel Length (CHL).
CRL can reach approximately 36 cm by weeks 37-38.
CHL can reach up to 51 cm in full-term babies.
Growth speed fluctuates: significant length increase in the 3rd to 5th months, weight gain peaks in the last two months.

Armamentarium for Assessing Fetal Age

Age is typically calculated based on the last normal menstrual period (LNMP) or fertilization date.
Average pregnancy length is 280 days (40 weeks) from LNMP or 266 days (38 weeks) post-fertilization.
Ultrasound imaging is central to determining gestational age using CRL, biparietal diameter (BPD), and other size metrics.

Physical Development Milestones

By the end of the 3rd month, primary ossification centers emerge, and external genitalia can be identified through ultrasound.
Body proportions shift: head is large compared to body at 9 weeks; by the 5th month, head is about one-third of body size.
Skin remains thin and transparent, making underlying blood vessels visible.
Fetal movement begins around the 4th month and may be felt by the mother.

Placenta Overview

The placenta consists of fetal (derived from trophoblast and mesoderm) and maternal components (derived from uterine endometrium).
The fetal side has blood vessels covered with the chorionic plate, while the maternal side includes the decidua basalis and decidual plate.
Functions to provide nutrients, gas exchange, and waste elimination between mother and fetus.

Umbilical Cord and Amniotic Fluid

Connects the fetus to the placenta, essential for nutrient transport and waste removal.
Amniotic fluid serves as a protective cushion for the developing fetus and aids in growth and movement.

Parturition (Birth)

Birth occurs in three stages, with successful delivery of a healthy infant being the goal.
Intrauterine Growth Restriction (IUGR) refers to infants who do not achieve normal growth; these infants may be at risk for health complications.
Low Birth Weight (LBW) classification is essential for identifying babies at risk for adverse outcomes.

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Description

Explore the crucial developments of the fetus and placenta during the third month of pregnancy. This quiz covers major changes in size and proportion as the fetus grows. Test your knowledge on key milestones and anatomical features during this stage of gestation.