pregnancy

Question 1

describe the trimesters

Answer 1

0-13 weeks: spontaneous loss of pregnany common here
14-26 weeks: end of this trimester marks limit of infant survival
27-39 weeks

Question 2

what is term?

Answer 2

39-40 weeks

around 280 days (40 weeks) since LMP

Question 3

what are the main maternal changes?

Answer 3

• abdo changes seen from 2nd trimester
• inc. weight
• inc. blood clotting
• inc. vaginal mucous
• altered appetite
• altered joints
• inc. hormone levels
• dec. BP
• morning sickness
• altered emotion, brain function

Question 4

when is the start of the pregnancy?

Answer 4

• from first day of last menstrual period

- embryologists and an obstetrician use different time scales

Question 5

describe the IVF pregnancy timing

Answer 5

• fertilisation occurs 2-3 days before

- difference in time of 2/2.5 weeks from GA and GA in IVF pregnancy

Question 6

what causes the inc. weight in mothers? how much?

Answer 6

• 10-15kg

- baby, placenta, amniotic fluid, inc. fluid retention, inc. stores

Question 7

what hormones are inc.in mothers?

Answer 7

• hCG: peaks 1st trimester, dec. thereafter

- progesterone, oestrogens, lactogen: slowly inc. as pregnancy progresses

Question 8

why is progesterone important?

Answer 8

• key to maintaining pregnancy

- progesterone antagonists = loss of pregnancy at all gestational stages

Question 9

what is the source of progesterone?

Answer 9

• fertilisation –> 8 weeks: corpus luteum source via hCG
  8+ weeks: placenta supplies progesterone
  change over = luteo-placental shift

Question 10

describe the oestrogen source

Answer 10

• fertilisation –> luteo-placental shift = corpus luteum

- 8+ weeks = complex interplay b/ foetal/maternal adrenals and placenta

Question 11

describe this complex interplay

Answer 11

• human placenta doesn’t express enzymes needed to convert pregnenolone to androgens
• this occurs in foetal adrenals
• weak androgen produced (DHEA) sulphated to give DHEA-S
• DHEA-S is inactive so female foetus not exposed to androgens
• DHEA-S goes to placenta to be converted to 17-beta oestradiol

Question 12

why are there low FSH and LH levels throughout?

Answer 12

high steroid levels suppress HPG-axis

Question 13

why is there an inc. blood clotting tendency?

Answer 13

• protective against losing blood at delivery

Question 14

when is blood pressure lowest?

Answer 14

• during 2nd trimester

- why pregnancy women should not stand for too long

Question 15

why is there an inc. basal body temp?

Answer 15

• possible by progesterone

- mediated by foetal size

Question 16

what causes the altered brain function?

Answer 16

high levels of steroid e.g. progesterone

Question 17

what causes the altered appetite?

Answer 17

• due to height of fundus
• stomach may be impinged
• mother may need smaller meals

Question 18

why is there altered flui balance and frequent urination?

Answer 18

• kidney functions change –> around 50% inc in plasma fluid volume by term
• inc, abdo size puts pressure on ballder

Question 19

why are there altered joints?

Answer 19

• changes in pelvis to make connections more flexible to permit childbirth

Question 20

why is there an altered immune system?

Answer 20

• production of factors: suppress maternal immune system from utero-placental interface
  results in reduction of Th1 responses and inc. Th2 responses

Question 21

describe placenta HLA

Answer 21

• placental HLA are almost invariant and very simple
• identify tissue as human but no other info
• HLA-G can suppress some leucocytes and down regulate maternal immune responses

Question 22

define conceptus and embryo

Answer 22

conceptus: everything resulting from fertilised egg
embryo: baby up to week 8 of development

Question 23

define foetus and infant

Answer 23

foetus: baby for rest of pregnancy
infant: after delivery

Question 24

what are the weights of the baby in trimesters?

Answer 24

1st: 50g
2nd: 1050g
3rd: 2100g

Question 25

give examples of the chromosomal abnormalities

Answer 25

• too few sex chromosomes = Turners
• too many sex chromosomes = Klienfelter’s
• too few autosomes = non-viability
• too many autosomes = trisomy 21

Question 26

what are the 4 organs that have late development? why?

Answer 26

• lungs
• digestive system
• immune system
• brain
• have limited use in utero so late development
• problems developing here become apparent at birth

Question 27

what are the functions of the placenta?

Answer 27

• exchange of nutrients and waste products
• connection/anchorage
• separation
• biosynthesis
• immunoregulation

Question 28

describe the anatomy of the placenta

Answer 28

• primary subunit = placental villus that has branches
• provides large SA for exchange b/ maternal and foetal vascular systems
• veins = oxy blood, arteries = deoxy
• placenta carries out parallel function to lungs in pregnancy

Question 29

what are cotyledons?

Answer 29

• maternal surface of placenta is sub-divided into cotyledons
• 30-60/ placenta
• each contains one or more villi

Question 30

describe the development of the placenta

Answer 30

• approx 9 days post fertilisation, conceptus completely in maternal endometrium
• placenta originates from cytotrophoblasts layer
• cytotrophoblasts proliferate into syncytium to form columnar structure
• this becomes villous structure
• overall structure then doesn’t change but is modified

Question 31

what are the levels of cytotrophoblasts at term?

Answer 31

fewer

so there can be a closer apposition b/ syncytium and placental capillaries

Question 32

describe the contact of the conceptus with endometrial cells

Answer 32

• Early: conceptus contact with endometrial cells
• as it grows, conceptus makes transient contact w/ maternal capillaries
• rapidly cytotrophoblasts cells form capsule around conceptus
• this isolates it arounf 4 weeks PF
• decidual glands hypertrophy during 1st trimester to provide nutrients for placenta and baby

Question 33

how long does the cytotrophoblast shell remain in place for?

Answer 33

until 8 weeks PF

blocks spinal artery formation

Question 34

describe the blood supply formation

Answer 34

• 10-12 weeks GA, cytotrophoblast plugs break down and spiral arteries form to supply foetus w/ blood normally

Question 35

what is the main risk time during pregnancy?

Answer 35

if placenta is not anchored properly, there is inc. pressure as it is exposed to maternal blood supply
can lead to detachment and a miscarriage

Question 36

describe the spiral artery remodelling

Answer 36

• cytotrophoblast (ctb) cells remodel sprial arteries during 1st trimester until 16/18 weeks GA
• remodelling converts narrow bore spiral vessels into wide-bore vessels to transport more volumes of blood
• ctb cells replace vascular endothelium and VSMCs
• vessels here cannot respond to vasoconstrictors

Question 37

what are the maternal risks of pregnancy?

Answer 37

• lie in labour and delivery
• remodelling of spiral artiers (vessels can lose a lot of blood after delivery)
• placenta checked to see if all been delivered, quite inflexible, any left in uterus may lead to ineffective uterine contractions

Question 38

how is the loss of blood in labour reduced?

Answer 38

contractions of uterus after placenta delivery

Question 39

what are the risks to the infant?

Answer 39

• defects to gametes
• loss of any autosome not compatible with life (miscarriage)
• changes in sex chromosomes is less severe

Question 40

what are the risks to the placenta?

Answer 40

• incomplete anchorage in 1st trimester
• once pregnancy passes viability, early delivery problem
• infants born before 32w GA are greatest risk due to incomplete development of 4 organs

Question 41

what is stillbirth?

Answer 41

death of infant within uterus, delivered without signs of life

Question 42

how do you detect stillbirth?

Answer 42

• via monitoring of foetal well being
• US: monitor foetal movements
• foetal blood flow assessment: doppler US