chapter 18 - development of a human foetus Flashcards
what are changes in the mother that occur
- mood swings: hormones or fear of what pregnancy brings
- bigger abdomen: due to uterus enlargements, other organs being forced up / out
- breast enlargement: due to hormone secretion
- heart / blood volume: increases (to cater for extra blood to placenta)
- urine production: increases due to increased flow to kidneys
- bladder: first 3 months uterus presses on bladder -> urination, then uterus moves up -> less urination, end of pregnancy foetus applies pressure -> increased urination
what is the foetal period
- week 9 (start of month 3)-birth
- characterised by increase in size and maturation of organs
- foetus grows from 3->50cm, weight increases from 4->3000g, proportions change
what is a healthy pregnancy
- achieving the goal that ones baby is born healthy, the mother needs to look after their own baby
- increased nutrients, balanced diet, weight gain, avoiding chemicals, exercise and progesterone
how does increased nutrients ensure a healthy pregnancy
- causes increased blood flow through the placenta, increased blood flow (increased by 40% by end of pregnancy)
- functions slow down -> nutrients stay in blood longer -> increases diffusion across placenta, may lead to constipation
how does a balanced diet, weight gain and avoiding chemicals ensure a healthy pregnancy
- BD: increased energy intake (~850kJ / day), increased protein intake (~65g / day), increased calcium, iron, folic acid (folate), fluoride if not in water already
- WG: ~0.5kg / week (2nd half), foetus (3.4kg), placenta (0.7kg), amniotic fluid (1kg), increased blood volume (1.6kg), tissue fluid (1.6kg), uterus (1kg), fat (3.2kg) breasts (0.9kg) = 13.4kg
- AC: mother should not smoke, or consume alcohol or drugs
how doses exercise ensure a healthy pregnancy
- maintaining normal work out, walking regularly, vigorous exercise -> woman carry to full term
- allows mother to maintain stamina during labour and will get back into shape more quickly after birth
how does progesterone ensure a healthy pregnancy
- placenta is the major source of progesterone, maintains pregnancy
- increased progesterone prevents premature shedding of uterine lining -> can lead to premature delivery or a miscarriage
what are congenital disorders
- defects or diseases that are present at birth, can be due to inheritance of defective genes, mutations of genes and environmental factors
- teratogenic agent: one that causes physical defects in the developing embryo
how do infections disrupt normal foetal development
- some viruses can cause birth defects, while others cause congenital disorders
- rubella: viral infection, frequently contracted by school aged children, however if contracted by a pregnant woman disastrous consequences (deaf, blind, heart , malformations)
how does maternal diet disrupt normal foetal development
- important factor in normal foetal development
- folic acid: required for normal cell division, lack of folic acid before or during pregnancy can result in Spina bifida
- eating whole grains, green vegetables, cereals, take folic acid one before and three months during pregnancy
- calcium / vit. A: normal bone / cell growth, balanced diet, take vit A in last 10 weeks
- listeria infection: can cause miscarriages or still births, avoid eating pre-packed salads, soft cheese, pate, raw / smoked seafood, eat freshly prepared food
how does alcohol disrupt normal foetal development
- suspected teratogen, relationship has been found between alcohol intake and malformations
- foetal alcohol syndrome: describes effects of foetal exposure to alcohol (birth weight is lower, slower growth, small head, defects of heart, malformed limbs, mental retardation)
how does smoking and chemicals disrupt normal foetal development
- S: results in lower birth weight, addictions can be passed on to offspring, risk of abortion, gastrointestinal problems, respiratory probers, links to sudden infant death syndrome (SIDS)
- C: besides alcohol and smoking there are other teratogenic agents
- thalidomide: originally developed as a sleeping pill effective in preventing morning sickness, causes limb malformation, acts on limbs between the 28th-42nd day (limbs start developing at 10 days), it is now used to treat leprosy and some blood cancer
what is an ultrasound
- a probe that is placed on the abdomen and sound waves are reflected by the foetal tissue to obtain a visual ‘echo’
- fed into computer to produce an image
- malformations of brain, head and limbs can be detected
what is a fetoscopy
- involves looking directly at the foetus through the fetoscope (small telescope like instrument)
- detects cleft lip, palate, abnormal ears, deformed / absent limbs, Spina bifida
what is foetal monitoring
- regular recording of the babies heart rate, tales place during labour / birth using ultrasound or electrocardiography (records electrical changes)
what is biochemical analysis
- assessment of maker proteins (phenylketonuria)
- occurs with all new borns in Australia
what are dna probes
- enables detection of a range of genetic disorders
- DNA segments are ‘labelled’ and then attach to identical set antes of DNA to determine whether there is a ‘gap’ in the DNA being tested
what happens during month 3 (end of first trimester)
- posture more upright, hair, nails, limbs well developed, eyes closed, sex apparent
- 4g and 3cm
what happens during the second trimester (weeks 13-27 or months 4-6)
- foetus moves / stretches limbs, kicking and turning, skeleton completed, hair covered body, gripping reflexes, digestive glands begin to function
- 100-680g and 18-35cm
what happens during the third trimester (weeks 28-birth around 40-42 or months 7-9)
- all systems functioning except respiratory, accumulation of fat beneath skin, eyes open, body hair sheds, antibodies diffuse from mother
- 1000-3300g and 25-50cm
what are two ways to analyse chromosomes
amniocentesis: performed on women at higher risk, involves removal of amniotic fluid
- detects Spina bifida, Down syndrome, cystic fibrosis, Tay-sach
chorionic villus sampling (CVS): specimen of foetal cells are removed from chorion
- allows early termination, detects genetic / biochemical abnormalities (not Spina bifida)
foetal blood sampling: detects biochemical disorders, occurs early in the pregnancy
