Fetal growth and Nutrition

Question 1

What are the issues of a small baby?

Answer 1

<2.5 kg
Lower IQ
6 fold increase in perinatal morbidity and mortality
Inattention, hyperactivity, behavioural problems
20% of adult short stature
Lower income
Increased adult non-communicble disease (hypertension, diabetes, metabolic syndrome).
30-50% of still births have suboptimal growth

Question 2

What are the problems with large babies?

Answer 2

Determined by percentiles for each gestational age.

Birth trauma
Increased neonatal admissions - jaundice, hyperglycaemia
Increased adult non-communicable diseases (childhood obesity, metabolic syndrome)

Question 3

What fetal age is the mortality and morbidity the lowest?

Answer 3

39-40 weeks - lower respiratory distress, cerebral palsy, and childhood mortality

Question 4

How much weight does a fetus gain?

Answer 4

16-17 g/kg/d

Hyperplasia > hypertrophy

Question 5

What is the difference between fetal growth restriction and small for gestational age?

Answer 5

You can be growth restricted but stay within the normal gestational range

Question 6

What determines how a fetus grows?

Answer 6

Nutrition, hormones and genetics.

In the embrionuc period the placenta gets nutrition is from the uterine glands, mostly carbohydrates and lipids. This supports the period where all the organs are being layed down.

Maternal placental circulation is established at the end of the first trimester. Increase in the oxygen and chorionic villous regression and formation of he discoid placenta. Around 10-12 weeks once all the organs are formed you get haemotropic nutrition.

Question 7

What is the fetal suppl line or nutrients after 10-12 weeks?

Answer 7

Mothers diet -> [metabolic and endocrine status of mother determine what’s in the circulation] -> uterine blood flow -> placenta (transport and metabolism) -> umbilical blood flow -> fetus [metabolic and endocrine status] -> fetal growth.

Under nutrition is largely caused by the placenta.

Question 8

What is the fetal diet?

Answer 8

Glucose: crosses by facilitated diffusion - provides energy to fetus and placenta, provides a carbon source.

Amino acids - active transport. Some are synthesized by the placenta. Feto-placenta shuffle. Role in the metabolic balance between oxidation vs. growth.

Lactate - produced by the placenta - energy for fetus.

Fatty acids - Readily cross placenta by diffusion. Energy store and for cell membranes.

Question 9

What is the role of hormones in fetal growth?

Answer 9

Mainly in orchestration of growth with the supply of nutrition.

Insulin-like growth factor and insulin are the most common.

Question 10

What are the main growth factors or the fetus and what do they do?

Answer 10

Insulin like growth factor 2 - embryonic and palcental growth , main circulating IGF, tissue differentiation in late gestation

Insulin-like growth factor 1 - matches fetal growth to nutrient supply. IGF-1 correlates with birthweight

Insulin levels correlate with fetal growth. Insulin promotes glucose uptake into cells and promotes protein and fat deposition. Main role is tissue accretion and fuel storage. Promotes IGF-I.

Question 11

What is the role of growth hormone in fetus growth?

Answer 11

High level in the fetus. Does not regulate IGF-1. Deficiency has minimal effect on fetal weight, but affects length. Deficient infants are measurably short.

Question 12

What is the role of glucocorticoids and fetal growth?

Answer 12

Important at the end of pregnancy.
Turn off hypeplastic growth and causing tissues to mature.

Maternal cortisol can’t cross the placenta except in disease. In pathology, it can prepare fetus for preterm delivery (maturation) but at a cost of reduced growth.

Question 13

What is the role of genetics on fetal growth?

Answer 13

Less than 20% variance in birth weight caused by genetics.

Genetic factors have an influence on lean mass.

Growth is usually limited by constraint, such as oxygen supply, which depends on placenta size.

Question 14

What constrains fetal growth?

Answer 14

The size of the mother (uterus). The fetus always wants to grow bigger.
Maternal age also constrains the growth.
Short pregnancy interval
Multiple pregnancy - twins
Macronutrient imbalance.

It is constrained to promote survival.

Question 15

What are he differences between fetal and postnatal growth?

Answer 15

Fetal is normally constrained by the maternal environment and if endocrine status is adequate then growth is normally regulated by substrate supply.

Postnatal: normally genetic potential. If nutritional status is adequate then growth is regulated by endocine.

Question 16

What causes fetal growth restriction

Answer 16

1) Fetal undernutrition caused by placental insufficiency - either vascular disease [inadequate remodeling of the spiral arteries causing maldevelopment of the terminal villi resulting in reduced surface area/diffusing capacity, placental inflammation, hypoxic stress, antiangiogenic state, thrombo occlusion]

or idiopathic

2 fetal pathology – congenital malformation, congenital infection, toxins, chromsomal disorders, specific genetic disorders

Genetic disorder: genes regulating growth are commonly imprinted - maternal expressed genes suppress growth and paternal induce growth. If the maternal allele is not working you get over expression of the paternal gene = Beckwith Wiedemann Syndrome

Question 17

What is Beckwith Wiedemann syndrome?

Answer 17

Overexpression of IgF2 - usually due to paternal uniparental disomy (two copies of paternal copy).

Macrosomia (large baby), macroglossia (large tongue), omphalocele,

Question 18

What is Russell Silver Syndrome?

Answer 18

Over expression of the maternal IGF2 allele (reduced IGF2)

Small baby

Question 19

What are the effects of poor fetal growth?

Answer 19

Thrifty phenotype: low nephron mass, low lean mass, endothelial dysfunction, insulin resistance, dyslipidaemia, exaggerated stress response.

Health risks: hyperension, ischaemic heart disease, stroke, diabetes, metabolic syndrome, osteoporosis

Question 20

What is the issue with having poor fetal growth followed by infant growth?

Answer 20

The fetal growth constains the metabolic capacity and then the rapid infant growth overloads the metabolic capaity leading to disease.

Question 21

What is a maternal metabolic disease causing fetal over growth?

Answer 21

Gestational diabetes.
10% in Auckland.
Glucose intolerance developing in pregnancy.

Excess fetal glucose and FFA -> excess fetal insulin -> stimulating fatty growth. Causes fat babies.

Fetal outcomes:
Macrosomia
Respiratory distress, hypoglycaemia.
diabetes
obesity

Matenal: increased risk of type II diabetes, birth trauma, preeclampsia

Question 22

What is the weight for low birthweight, very low birthweight, extremely low birthweight and macrosomia?

Answer 22

Low birthweight: <2.5 kg
Very low birthweight: <1.5 kg
Extremely low birthweight: <1.0 kg
Macrosomia: >4.5 kg