Physiology of pregnancy Flashcards
(38 cards)
Premature delivery is birth prior to X weeks
37
Characteristics of first pregnancy trimester?
- Growth and development of the placenta
- Growth/development/establishment of the placenta
Key events (for the foetus) during trimester 1
- Fertilisation
- Implantation
- Initial development
- Placentation
Side effects of trimester 1 on the mother
- Weight gain
2. Nausea
Characteristics of trimester 2
- Continued growth and development
- Development of the placenta continues
Key events (for the foetus) during trimester 2
- Nervous system develops
- Hair
- Spine straightens
- Pain
- Proportions change
Side effects of trimester 2 on the mother
- Placental growth
- Uterus rises (characteristic bump)
- HYPOvolemia
- Cardiac remodelling
- Breast remodelling
Characteristics of trimester 3
- Development of the lung system
- Rapid growth of the foetus to the final birth weight
Key events (to the foetus) during trimester 3
- Growth
- Fat deposition
- Brain growth
- Blood cells
- Lung development
Side effects of trimester 3 on the mother
- Braxton-Hicks
- Tiredness
- Restricted breathing
- Lactation
What is decidualisation?
The change in structure of the endometrial lining, particularly the stroma which support the epithelium. Decidualised stroma supports/encourages/tolerates the invasion of trophoblast cells from the embryo
- The endometrium is changed in preparation for/during pregnancy
What can happen when decidualisation does not occur properly?
Recurrent implantation/ implantation failure
- This is where women are able to conceive but the embryo does not implant, so pregnancy is lost
After implantation, what happens to the trophectoderm trophoblast cells? (within the uterine lining, after decidualisation has occurred and the epithelium has grown back over the conceptus)
They begin to differentiate into 2 types of trophoblast cells:
- Outer-side are called SYNCITIAL TROPHOBLAST CELLS
- CYTOTROPHOBLAST CELLS: immediately next to the conceptus, they form important parts of the placenta
Explain the idea of histotrophic support and when it happens?
- How do syncitiotrophoblast cells play a role in this?
- Prior to implantation, the embryo was free-living in the uterus, but now it has become implanted.
- So when the conceptus invades the uterine wall, it can now be supported by the fluid produced into the uterine glands which we call histotrophic nutrition.
- The embryo is also supported by the destruction of underlying stroma by invading trophoblast (syncitiotrophoblast) cells which liberate nutrients and components to support the developing embryo’s growth!
When can pregnancy be recognised by a pregnancy test?
7-9 days AFTER implantation which is around wk 3-4 of pregnancy
- This is when HCG is produced by the uterine wall
Following implantation, HCG is produced by the uterine wall which does what?
Acts on the LH receptors within the ovary (corpus luteum) to maintain 17-beta oestradiol and progesterone necessary for assistance and maintenance of pregnancy
As HCG and progesterone levels rise, there is an impact on maternal physiology/signs of pregnancy, what are these?
- Suppressed menstrual cycle, to prevent shedding of the endometrial lining and loss of pregnancy = LATE PERIOD
- HCG and progesterone can lead to TENDER and ENLARGED breasts
- Fatigue
- Urinary frequency
- Nausea/vomiting = BIG SYMPTOM
- Constipation
Give the causes of urinary frequency during pregnancy
- HCG hormone
- Increases blood flow to the pelvic area and kidneys
- Kidneys work more efficiently as you are excreting waste for two (baby included) - Growing foetus puts pressure on the bladder
During implantation, we have histotrophic support to begin with, but what happens to this?
Cessation of histotrophic support and this is taken over by haemotrophic support from the maternal blood supply = placenta development
What are lacunae, how are they formed and what is their role?
As the syncitiotrophoblast cells digest the stroma of the uterus, pools of blood form within the syncitiotrophoblast cells that are called lacunae
- They allow the accumulation of nutrients to support growth of the foetus
Explain how spiral artery modelling is initiated
As the syncitiotrophoblast (multi-nucleated) cells expand, they come into contact with maternal blood vessels that line and feed the wall of the embryo
- These blood vessels are spiralled and the syncitiotrophoblast initiates spiral remodelling where the maternal vasculature is remodelled to support embryonic growth
What is meant by spiral artery remodelling?
The spiral arteries that feed the non-pregnant endometrium become more and more constricted, and to a very small overall volume
- So we end up with a high pressure system that supplies the epithelial cells that line the uterus
- The blood supply is released into the lacunae where they can nourish the developing conceptus’ cells in a low pressure environment
The growth of syncitiotrophoblasts are called…
Primary villi
Villi of chorionic syncitiotrophoblast penetrate the uterus at wk .. and terminate in the …
penetrate the uterus at wk 5 and terminate in the lacunae
- This is the initial vasculature of the placenta and foetal blood vessels
