Pregnancy Flashcards
What is the process from fertilisation to foetal life?
Fertilisation
6-7 days - implantation
8-14days - Blastocyst formation (blastogenesis)
Embryonic development - Organogenesis, cell differentiation (6 weeks)
Foetal life (7 months)
What supplies nutrients to the blastocyst?
Placenta not yet formed so nourished by uterine secretions
What is the critical period
Between 2 and 8 weeks where organs are being developed. Any problems in this area could effect development.
What is present after 1 month in utero?
Organs - Heart, liver, eye, brain - not mature or functional
Branchial arch - embryonic pharynx
Somites - Neural tube and spinal cord
Arm, tail and leg bud
What can cause neural tube defects?
Lack of folic acid
Doesn’t close properly between day 17 and 30
What is present in the second trimester?
Ear, eyelids
Rapid growth, linear
Crown-rump length measured- at 6months, 70% of length but 20% of birth weight
What occurs in the third trimester?
Laying down of adipose tissue
Lanugo - downy hair
Organ system maturation
Surfactant produced in lungs in prep for 1st breath
Gut maturation
Sexual organ development
Less uterus space
Meconium production, lines the bowels for 1st bowel movement, dark sticky material
Full functional kidneys
What nutrients does the placenta supply?
Non-esterified fatty acids + cholesterol via diffusion, foetus then synthesises own TAG
Glucose via facilitated diffusion
- 75% of foetal energy
- Higher post prandial glucose peaks to increase glucose transfer
- Weeks 24-28 increase in insulin resistance to drive glucose
- Those with IR pre pregnancy or with obesity need to be monitored for gestational diabetes
Amino acids via active transport
- Concentration higher in foetus that mother
Water soluble vitamins e.g. calcium and iron via active transport
Maternal and foetal blood doesn’t mix - nutrients cross through blood vessels.
What are some maternal changes that occur in pregnancy?
Growth of adipose, breast and uterine tissues
- Breasts increase by 50%
- Uterus grows from 46g to 1000g
Increase blood volume, red cell and plasma volume increase
- More plasma than RBC - Later stages, dilution of red cells in plasma, decreased haemoglobin from 14g/dl to 10g/dl.
Slower GI motility
- Constipation, heart burn, nausea
Heart rate increases by 20%
Curvature of spine increases
Pushing up of diaphragm can cause reflux
Why are the maternal nutrient requirements increased during pregnancy?
Cell replication
- DNA synthesis - zinc, folate, iron and B12
- Protein synthesis - protein, B12
Foetal skeletal development
- Mineral formation - ca, p
- Calcium formation - Vit D, Mg
- Matrix formation- Fe, Cu, Vit C, A, protein
Energy metabolism
- Electron transport - Fe, Cu
- ATP synthesis - Mg, Vit B1, 2, 3
Oxygen transport
- Haemoglobin synthesis - Fe, Cu B6
- Erythropoiesis - Folate, Bq2, iron, cell rep nutrients
How are energy needs in pregnancy calculated?
Estimation of nutrient components of weight gain and efficiencies of dietary nutrient utilisation
Average total weight gain = 12.5kg
Products of conception + Maternal tissues and stores
Increased blood volume, breast and uterus size, foetus, amniotic fluid, extracellular fluid, maternal fat stores.
Theoretically from 12.5kg weight gain, 320kcal extra is required. However in reality on 200kcal extra required in last trimester
BMI increase occurs later but can differ between developed and underdeveloped countries.
What are the energy requirements for pregnancy?
No increase in DRV until 3rd trimester ~ 191kcal/d
Non preg ~ 2079kcal/d
If overweight/ obese may not require energy increase
Depends on body size and activity
No weight gain recommendations in UK.
Wouldn’t want weight loss, even if overweight/ obese. Risk of insufficient nutrition to the baby.
What is the protein increment?
RNI - 45g/d
Increment ~ 6g/d = ~ 51g/d
increased throughout pregnancy - Growth and development of foetus, uterus and placenta.
Most women meet this target
- May need to look closer and vegans, teenagers (have increase reqs for their own growth)
What vitamin and mineral increments are needed in pregnancy?
Vitamin A - +100ug/d (600ug –> 700ug)
Thiamine - +0.1 (0.8g/d –> 0.9g/d)
Riboflavin - +0.3 (1.1mg/d –> 1.4mg/d)
Vitamin C - + 10 (40mg/d –> 50mg/d)
No iron increment due to no menstrual cycle and extra iron used for maternal and foetal tissues.
Why is folate needed in pregnancy?
What are the increments?
Adult ~ 200ug/d
In pregnancy 300ug/d
Preconception and first trimester 400ug/d
- Neural tube closes around the 6th weeks so helps to support that.
Folate helps with DNA synthesis which is required for all dividing cells.
UK government agreed to add folate to non-wholemeal flour.
NTD is not a straight forward results of folate deficiency - Megaloblastic anaemia.
