13.0 Maternal Adaptations to Pregnancy Flashcards Preview

MedST IB: Human Reproduction (HR) > 13.0 Maternal Adaptations to Pregnancy > Flashcards

Flashcards in 13.0 Maternal Adaptations to Pregnancy Deck (32)
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1

In humans, what changes occur to the sex hormones in late gestation?

Oestrogen to progesterone ratio ↑
Oestrogen ↑
Progesterone stays stable (different to animals where progesterone decreases)

2

What does the change in oestrogen:progesterone ratio in late gestation induce?

Lactation and parturition

3

What hormones (other than sex hormones) increase during pregnancy?

1) Prolactin
2) Placental lactogen/placental variant GH
3) PTH
4) Cortisol and aldosterone (adrenal cortex)
- These do not actually increase. Just more are recorded in blood because of an increase in globulins (stimulated by oestrogen)

4

What happens to prolactin levels during pregnancy?

Increases (pituitary gland enlarges 30-50%)

5

What does increase in prolactin cause?

Mammary gland changes

6

What are the complications that can occur with enlargement of pituitary during pregnancy?

1) Blindness can occur if there is pre-existing acromegaly

2) Post-partum haemorrhage can cause Sheehan syndrome (Simmond disease)

7

What is Sheehan syndrome (Simmond disease)?

Ischaemia of the anterior pituitary due to compromised blood supply from the venous plexus.

Sufferers do not lactate and do not resume menstrual cycle

8

What is the average weight gain in pregnancy?

12.5kg (Due to foetus + placenta + fat)

9

What are the CVS changes in pregnancy?

1) ↑ Blood volume
2) Changes in blood composition
- ↑ RBC (but greater ↑ in plasma → overall haemodilution)
- ↑ clotting
3) ↑ CO
4) No change to BP

10

Features of pre-eclampsia:

1) HTN ( >140/90mmHg)
2) Non-dependent oedema (usually hands and face)
3) Proteinurea

11

What are the renal changes in pregnancy?

1) ↑ GFR
2) ↑ Na⁺ reabsorption
3) ↑ erythropoietin

12

What are the respiratory changes in pregnancy?

1) ↓ compliance and FRC
2) ↑ tidal volume

13

What are the metabolic changes in pregnancy?

1) Maternal insulin resistance
2) ↓ gastric emptying and ↑ GIT transit time
3) ↑ liver metabolism

14

What are the behavioural changes in pregnancy?

EARLY
↑ food acquisition (cravings etc but also nausea/vomiting)

LATE
Fatigue
Restlessness
Nesting

15

What is the definition of a small infant?

<2.5kg

16

What are the maternal factors that influence foetal size?

"
"

17

How does placental size correlate to foetal size?

↑ placental size → ↑ foetal size

18

What are the foetal factors that influence foetal size?

"
"

19

What is the mechanism that explains why foetal Hb has a higher affinity for oxygen than adult Hb?

Human foetal Hb has a ↓ affinity for 2,3 DPG therefore has an ↑ affinity for O₂ binding

20

What are the differences between foetal circulation and adult circulation?

• Differs from adult circulation in the following ways:
1. Supplies the placenta
- 55% of combined cardiac output goes to the placenta
- Placenta has low resistance
- Total peripheral resistance and blood pressure are lower in fetuses

2. Bypasses the lungs
- Only 7-13% of cardiac output goes to lungs
- Pulmonary vascular resistance is high in utero

3. Has two shunts
i. Foramen ovale (FO)
ii. Ductus arteriosus (DA)
- Achieves pulmonary bypass
- R + L heart beat in parallel in fetus

4. Total CO (both ventricles) =4x higher than in adults

21

What hormone is responsible for maturation of foetal tissue before birth?

↑ glucocorticoids (cortisol)

22

What induces parturition?

↓ progesterone:oestrogen ratio → ↑ prostaglandin synthesis

(in humans progesterone stays the same but oestrogen increases)

23

What fetal hormones are released to begin parturition induction?

1) Cortisol → fetal tissue maturation
2) DHAS → rapid ↑ in maternal oestrogen

24

What maternal hormones are released to begin parturition?

1) Oestrogen → cervical ripening and uterine contractions
2) CRH → ↑ fetal adrenal DHAS secretion, ↑ PG availability in uterus + ↓ myometrial contractions (↑cAMP)

25

Mechanism of myometrial contractions:

1) ↑ oestrogen (↓P:O) → ↑ actin + myosin expression and CAP proteins
2) ATP + myosin light chain kinase (MLCK) needed
3) Ca²⁺ → + CAM → + MLCK
4) ↑Ca²⁺ influx → contractions

26

Define uterotonins

Substances that stimulate uterine contractions

27

How are uterine contractions coordinated?

Via gap junctions

28

What contractions precede labour?

Braxton-Hicks contractions

29

What are the three stages of labour?

Stage 1 = uterine activity + cervical dilation
- 10-12hrs (primagravida) / 6-8hrs (multigravida)
- Blood + mucus
- Cervix → 10cm
- +ve feedback contractions

Stage 2 = expulsion of fetus
- 45-120mins (primagravida) / 15-45mins (multigravida)
- Voluntary effort needed
- Most dangerous stage for baby
- Mother's BP ↑ (30/25mmHg)

Stage 1 = placental expulsion
- 10mins
- Uterus continues to contract until placenta is removed
- Retained placenta = risk of haemorrhage

30

Factors influencing timing of delivery?

1) Light/dark cycle
2) Food supply
3) Infection
4) Climate (temp/rainfall)
5) Other animals who are parturient
6) Danger/disturbance