Flashcards in Fetal growth and Nutrition Deck (22):
What are the issues of a small baby?
6 fold increase in perinatal morbidity and mortality
Inattention, hyperactivity, behavioural problems
20% of adult short stature
Increased adult non-communicble disease (hypertension, diabetes, metabolic syndrome).
30-50% of still births have suboptimal growth
What are the problems with large babies?
Determined by percentiles for each gestational age.
Increased neonatal admissions - jaundice, hyperglycaemia
Increased adult non-communicable diseases (childhood obesity, metabolic syndrome)
What fetal age is the mortality and morbidity the lowest?
39-40 weeks - lower respiratory distress, cerebral palsy, and childhood mortality
How much weight does a fetus gain?
Hyperplasia > hypertrophy
What is the difference between fetal growth restriction and small for gestational age?
You can be growth restricted but stay within the normal gestational range
What determines how a fetus grows?
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.
What is the fetal suppl line or nutrients after 10-12 weeks?
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.
What is the fetal diet?
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.
What is the role of hormones in fetal growth?
Mainly in orchestration of growth with the supply of nutrition.
Insulin-like growth factor and insulin are the most common.
What are the main growth factors or the fetus and what do they do?
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.
What is the role of growth hormone in fetus growth?
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.
What is the role of glucocorticoids and fetal growth?
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.
What is the role of genetics on fetal growth?
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.
What constrains fetal growth?
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
It is constrained to promote survival.
What are he differences between fetal and postnatal growth?
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.
What causes fetal growth restriction
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]
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
What is Beckwith Wiedemann syndrome?
Overexpression of IgF2 - usually due to paternal uniparental disomy (two copies of paternal copy).
Macrosomia (large baby), macroglossia (large tongue), omphalocele,
What is Russell Silver Syndrome?
Over expression of the maternal IGF2 allele (reduced IGF2)
What are the effects of poor fetal growth?
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
What is the issue with having poor fetal growth followed by infant growth?
The fetal growth constains the metabolic capacity and then the rapid infant growth overloads the metabolic capaity leading to disease.
What is a maternal metabolic disease causing fetal over growth?
10% in Auckland.
Glucose intolerance developing in pregnancy.
Excess fetal glucose and FFA -> excess fetal insulin -> stimulating fatty growth. Causes fat babies.
Respiratory distress, hypoglycaemia.
Matenal: increased risk of type II diabetes, birth trauma, preeclampsia