Fetal Development: Amniotic Fluid and Circulation

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Questions and Answers

What is the term for the condition characterized by too little amniotic fluid?

Amniotic disruption

Hydramnios

Polyhydramnios

Oligohydramnios (correct)

Which of the following is a function of amniotic fluid?

It acts as a shock absorber for the fetus. (correct)

It prevents all forms of infection.

It stabilizes fetal heart rate.

It is a primary source of nutrients for the fetus.

Which condition is associated with a volume of more than 2 liters of amniotic fluid?

Renal abnormalities (correct)

Gastrointestinal malformations

Neural tube defects

Pulmonary issues

Which complication is most commonly associated with decreased amniotic fluid?

Decreased fetal movement Signup and view all the answers

What is the typical volume of amniotic fluid present at birth?

700-1000 mL Signup and view all the answers

What is the function of the foramen ovale in fetal circulation?

It shunts blood from the right atrium to the left. Signup and view all the answers

Why do fetal lungs not participate in gas exchange?

Fetal lungs are filled with amniotic fluid. Signup and view all the answers

What role does the ductus arteriosus play in fetal circulation?

It connects the pulmonary artery with the aorta. Signup and view all the answers

What adaptation helps increase the oxygen-carrying capacity in a fetus?

Fetal hemoglobin carrying more oxygen. Signup and view all the answers

What condition makes a newborn more susceptible to jaundice?

Inability to conjugate bilirubin due to enzyme lack. Signup and view all the answers

At what gestational week does the gastrointestinal system begin to mature?

36 weeks Signup and view all the answers

Which statement is true regarding the liver's role in fetal iron storage?

Fetal liver stores enough iron to last up to 6 months post-birth. Signup and view all the answers

What is a consequence of a sterile gut in the fetus regarding vitamin K?

It cannot synthesize vitamin K. Signup and view all the answers

What is the threshold of viability for a fetus?

22-25 weeks Signup and view all the answers

Which structure connects the umbilical vein to the inferior vena cava in fetal circulation?

Ductus Venosus Signup and view all the answers

What condition is likely to occur due to a lack of adequate fetal renal function?

Oligohydramnios Signup and view all the answers

What is the primary function of the placenta related to nutrient supply?

Transport of glucose and vitamins Signup and view all the answers

Dizygotic twins originate from how many fertilized ova?

Two fertilized ova Signup and view all the answers

What role does amniotic fluid play in fetal development?

Aids in lung development Signup and view all the answers

Which type of twins can potentially develop into conjoined twins?

Monochorionic monoamniotic twins Signup and view all the answers

What describes the relationship between carbon dioxide and fetal blood in the placenta?

Carbon dioxide is produced by fetal blood and passes into maternal blood Signup and view all the answers

What condition is primarily caused by uncontrolled diabetes in pregnancy?

Fetal macrosomia Signup and view all the answers

At what point during pregnancy does the fetal pancreas begin to secrete insulin?

Week 6 Signup and view all the answers

What is a consequence of fetal hyperinsulinemia due to maternal diabetes?

Increased risk of hypoglycemia after birth Signup and view all the answers

Which system shows cephalocaudal development during pregnancy?

Neurologic system Signup and view all the answers

What is the function of thyroxine secreted by the thyroid during pregnancy?

To support fetal brain development Signup and view all the answers

What characteristic of urine is noted in the fetus during the first trimester?

Urine is secreted into amniotic fluid Signup and view all the answers

At birth, how does the size of the brain compare to that of an adult's brain?

One-quarter the size of an adult's brain Signup and view all the answers

What role does the adrenal cortex play during pregnancy?

Develops by week 20 Signup and view all the answers

What is the primary difference between dizygotic and monozygotic twins?

Dizygotic twins originate from two separate zygotes. Signup and view all the answers

Which of the following statements is true regarding monozygotic twins?

They can develop from one zygote into more than one type of twin pregnancy. Signup and view all the answers

Which type of monozygotic twin pregnancy can result in conjoined twins?

Monochorionic monoamniotic twins. Signup and view all the answers

What term describes twins that developed from two separate fertilized eggs?

Fraternal twins. Signup and view all the answers

How is the placenta involved in fetal development?

It facilitates the exchange of nutrients and waste between mother and fetus. Signup and view all the answers

How many liters of amniotic fluid indicate oligohydramnios?

Less than 1 liter. Signup and view all the answers

At what point is a fetus considered viable?

After 24 weeks of gestation. Signup and view all the answers

When does the fetal pancreas begin to secrete insulin?

By week 20. Signup and view all the answers

Study Notes

Amniotic Fluid

Amniotic fluid acts as a cushion, maintains constant body temperature, prevents entanglement in membranes, provides freedom of movement for musculoskeletal development, serves as a source of fluid and a repository for waste, and enhances lung development.
Approximately 700-1000ml of amniotic fluid is typically present at birth.
Oligohydramnios is a condition where there is less than 300ml of amniotic fluid, which is often associated with fetal renal abnormalities.
Polyhydramnios is a condition where there is more than 2L of amniotic fluid, which is associated with gastrointestinal and other fetal malformations.

Fetal Circulatory System

The fetal circulatory system is unique because the lungs don't function for gas exchange, and there are three unique vascular shunts: the ductus venosus, foramen ovale, and ductus arteriosus.
The ductus venosus connects the umbilical vein to the inferior vena cava, allowing oxygenated blood to bypass the liver.
The foramen ovale is a shunt that allows blood to bypass the lungs, diverting it from the right atrium to the left atrium. It is a “hole in the heart” that closes shortly after birth.
The ductus arteriosus connects the pulmonary artery to the aorta, allowing blood to bypass the lungs.

Fetal Oxygenation Adaptations

The fetus maintains oxygenation through increased oxygen-carrying capacity, increased carbon monoxide levels, fetal hemoglobin carrying 20-30% more oxygen, and a fetal heart rate between 110-160 beats per minute.

Gastrointestinal System

The fetus swallows amniotic fluid to promote GI system maturation, which is typically complete by 36 weeks.
Waste products accumulate in the digestive tract near term, leading to the creation of meconium.

Hepatic System

Fetal livers store glycogen, two times that of an adult at term.
Iron is stored in the liver and is enough to last 6 months.
Fetal livers lack enzymes to conjugate bilirubin, which can lead to jaundice, and cannot make key coagulation factors.
Sterile gut cannot synthesize vitamin K, and vitamin K is administered intramuscularly after birth.

Renal System

Fetal kidneys function in the first trimester and fully develop by birth.
The Glomerular Filtration Rate (GFR) is low in fetuses, and they lack the ability to concentrate urine.
Urine is secreted into the amniotic fluid.

Neurologic System

The neural tube closes by week four.
Cephalocaudal development occurs, where head to rump growth dominates.
The forebrain, midbrain, and hindbrain develop by week five.
At birth, the brain is approximately one-quarter the size of an adult brain.
Lower body parts must grow more to reach adult size.

Endocrine System

The thyroid gland secretes thyroxine by week eight.
The adrenal cortex forms during the sixth week.
The pancreas secretes insulin by week 20.
Hormones are secreted by weeks eight and nine.

Uncontrolled Diabetes in Pregnancy

Maternal hyperglycemia leads to increased glucose to the fetus, potentially resulting in fetal hyperinsulinemia, macrosomia, and hypoglycemia after birth due to the removal of the maternal glucose supply.

Multiple Births and Conjoined Twins

Dizygotic (fraternal) twins originate from two zygotes.
Monozygotic (identical) twins originate from a single zygote.
Monochorionic diamniotic twins have two amnions.
Monochorionic monoamniotic twins have one amnion and are at risk for conjoined twins.

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Description

Explore the crucial roles of amniotic fluid and the fetal circulatory system. Learn about conditions like oligohydramnios and polyhydramnios and their implications. Understand how fetal vascular shunts function to ensure proper development before birth.