Fetal Growth and Genetics Quiz

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Questions and Answers

What percentage of variability in fetal growth is attributed to genetics?

75-90%

50-80%

30-70% (correct)

15-25%

Which factor is implicated in the increased risk of intrauterine growth restriction (IUGR) in women?

High maternal age

Obesity during pregnancy

Nutrient deficiency

History of being small for gestational age (SGA) (correct)

What is the effect of knocking out the GH gene on fetal growth?

No effect on any stage of growth

Impaired fetal growth and low birth weight

Increased birth weight and growth after birth

Normal fetal growth but impaired growth after birth (correct)

What does the knockout of the IGF-I gene indicate about its role in fetal development?

It is crucial for growth both pre and postnatally Signup and view all the answers

What can be inferred about IGF-II based on the knockout findings?

It is crucial for fetal growth but its role after birth is unclear Signup and view all the answers

What is a significant predictor of neonatal and infant survival?

Birth weight Signup and view all the answers

What condition is characterized by a fetus that is proportionally small with early diagnosis?

Symmetric IUGR Signup and view all the answers

What can increase the risk for adult-onset type 2 diabetes and hypertension?

IUGR with rapid catch-up growth Signup and view all the answers

Which type of IUGR is associated with nutritional issues in the late second and third trimesters?

Asymmetric IUGR Signup and view all the answers

What condition can lead to cognitive dysfunction in infants?

Intrauterine growth retardation (IUGR) Signup and view all the answers

Large for gestational age (LGA) infants are more prone to developing which of the following?

Childhood weight gain Signup and view all the answers

What is a characteristic finding in a fetus with symmetric IUGR?

Proportional reduction in size Signup and view all the answers

What is a consequence of placental insufficiency during late pregnancy?

Decreased growth of abdominal circumference Signup and view all the answers

What is the role of thyroid hormones in fetal development?

Promote normal fetal growth and development Signup and view all the answers

How does cortisol affect IGF-1 levels in relation to stress?

Reduces IGF-1 levels Signup and view all the answers

What factor is correlated with birth weight in the context of hormone levels?

IGF-I levels in fetuses Signup and view all the answers

Which hormone is known to have anabolic effects on fetal metabolism?

Insulin Signup and view all the answers

What is the impact of glucocorticoids on IGFBP-1 levels during intrauterine growth restriction (IUGR)?

Increase IGFBP-1 levels Signup and view all the answers

What is the effect of low insulin levels associated with SGA/IUGR on birth weight?

Large decrease in birth weight Signup and view all the answers

How does the IGFBP-1 relate to birth weight in cases of severe IUGR?

It is increased, leading to lower birth weight Signup and view all the answers

What genetic mutation is associated with severe IUGR in Russell–Silver syndrome?

Loss of paternal expression of IGF-2 Signup and view all the answers

What hypothesis is suggested by low fat-free mass in SGA/IUGR in relation to growth factors?

Low fat-free mass is associated with low levels of IGF-1 Signup and view all the answers

Which condition is characterized by an overexpression of IGF-2, leading to fetal overgrowth?

Beckwith–Wiedemann syndrome Signup and view all the answers

What is the primary role of IGF-II during early gestation?

Promoting fetal growth Signup and view all the answers

What does a weak correlation with birth length indicate in relation to IGF-2 in SGA/IUGR?

IGF-2 has a variably correlated effect on birth length Signup and view all the answers

Which of the following is characterized by low birth weight and high levels of IGFBP-1?

Small for Gestational Age (SGA) Signup and view all the answers

Study Notes

Fetal Growth Factors

Birth weight is a crucial factor for neonatal survival and infant health
Energy reserves are significantly influenced by birth weight, with a correlation between weight and non-protein kcal and total kcal intake.
Birth weight is a critical determinant of neonatal morbidity and mortality.
Intrauterine growth retardation (IUGR)/small for gestational age (SGA) fetuses develop many complications. They're predisposed to hypoglycemia, hypocalcemia, hypothermia, asphyxia, and cognitive dysfunction
Intrauterine growth retardation (IUGR) with rapid catch-up weight gain in early childhood may correlate with increased risks of adult-onset type 2 diabetes, hypertension, preeclampsia, dyslipidemia, and ischemic heart disease
Large for gestational age (LGA) infants are also at risk. They're predisposed to childhood weight gain, type 2 diabetes mellitus (DM), and metabolic syndrome.
Fetal growth is characterized by distinct stages of hyperplasia, hyperplasia/hypertrophy, and hypertrophy based on weeks of gestation

Fetal Growth & Development

The femur's growth velocity and length correlate with gestational weeks, with peak velocity occurring around weeks 16-32.
Growth hormone (GH) affects fetal growth post-birth, not pre-birth. Fetal growth is normal if GH is knocked out. IGF-1 and IGF-2 are not regulated by GH during fetal development.
IGF-I plays a role in fetal development and impacts birth weight, and also affects growth after birth.
Knockout of the IGF-I gene leads to slow fetal development and low birth weights that exhibit continued growth impairment after birth.
IGF-II plays a key role in fetal growth, impacting development and showing a normal growth rate post-birth after knockout of this gene.

Types of IUGR

Symmetrical IUGR: affects all body parts equally (head circumference, abdominal circumference, femur length), one-third of cases, associated with early insult affecting cell number (e.g., intrauterine infection, karyotype anomaly, or genetic syndrome).
Asymmetrical IUGR (often referred to as "nutritional"): Body parts are not equally affected with the abdominal circumference growth impaired in relation to head circumference growth. This is associated with placental insufficiency late in the 2nd or 3rd trimesters, with lower abdominal circumference vs head circumference and femur length. Glycogen utilization by the liver, liver shrinkage, and decreased abdominal circumference may be observed in this type of IUGR.

Factors Affecting Fetal Growth

Genetics: Account for 30-70% variability. A two-fold increased risk of IUGR is associated with women who were small for gestational age (SGA) themselves
Physical Environment:
Placental Capacity: Essential for proper nutrient transfer to the fetus
Nutrient Availability: Maternal nutritional status impacts fetal development
Interaction Between Genetics and Environment: Altered fetal gene expression by the maternal uterine environment
Adverse Conditions: Preeclampsia, maternal/fetal malnutrition, smoking, alcohol use, high/low salt intake, certain drugs, and hypo/hyper-vitaminosis are factors negatively affecting fetal growth. Adverse conditions lead to epigenetic modifications impacting DNA and affect fetal development, including birth weight (and potential low nephron number). Also correlated to renal disease, cardiovascular disease, or metabolic disease.

Hormonal Regulation & Effects

Insulin: Weak correlation with birth length, strong correlation with birth weight, low levels observed in SGA/IUGR fetuses.
IGF-1: Strong correlation with both birth length and weight, Low levels observed in SGA/IUGR fetuses.
IGF-2: Weak correlation with birth length, variable correlation with birth weight, low levels of IGF-2 observed in SGA/IUGR fetuses.
IGFBP-1: Decreased levels related to negatively impacting birth weight and linear growth
IGFBP-3: Increased levels observed in IUGR fetuses.
Cortisol (Stress, Prescribed): Negatively correlates with birth length. Increased glucocorticoids can lead to increased IGFBP-1 levels and inhibit linear growth.
Sex Steroids: Slightly greater birth length and weight in boys compared to girls.
Thyroid Hormones: Crucial for normal fetal growth and development. They influence overall fetal size and contribute to discrete developmental events in the brain and somatic tissues. Thyroid hormones directly and indirectly affect fetal metabolism and impact the bioavailability of other hormones affecting fetal development.

Hormone Levels in Fetuses

Hormone levels (IGF-1, IGFBP-3, IGFBP-1, insulin) differ between control fetuses and IUGR fetuses. Data available from 1994 study.

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Description

This quiz explores the intricate relationship between genetics and fetal growth, focusing on factors that affect intrauterine growth restriction (IUGR). It delves into the roles of specific genes like GH and IGF-I in development, as well as the implications of nutritional issues and other conditions on neonatal health. Test your knowledge on the predictors of survival, growth patterns, and potential risks associated with fetal growth abnormalities.