L35 Pregnancy Flashcards
What is the role of NK cells in embryo implantation?
Local signalling occurs secondary to the blastocyst. This signalling is through trophoblast, which migrate through the endometrial tissue. The trophoblasts encounter NK cells that appear in the early implantation window. The trophoblast express pattern antigens. The embryo is not rejected due to the NK cells. The extra-villous trophoblasts bind to NK cells and are less attractive to cytotoxic T cells. NK cells have specific HLAs. The NK cells in the decidua (the thick mucus layer that lines the uterus during pregnancy and is shed after birth) have a characteristic phenotype - CD56bright. They have the capacity to facilitate or impede trophoblast invasion. Since trophoblast implantation is so important and the grip the trophoblasts must have on the uterus, NK cells are very important. The main source of decidual cytokines and so may determine the response to pregnancy.
Describe systemic signalling in an implanting embryo.
The blastocyst comes in and releases hCG which effects the corpus luteum in the production of progesterone. hCG is another glycoprotein and is very similar to LH and FSH. hCG comes from the chorion - the outer layer of the blastocyst. hCG also has a trophic effect on the gonad - it continues to stimulate the corpus luteum through progesterone which is requires for foetal survival.
How can imaging be used in clinical dating of an embryo.
- 5 weeks: gestation sac
- 6 weeks: fetal pole, secondary yolk sac
- 7 weeks: fetal heart activity
8 weeks: fetal limbs, movements
How are miscarriages managed?
25% of fertile women have at least one miscarriage. There is usually a good prognosis, even a after 3 miscarriage, there is a 70% chance of success. Management can be expectant, medical or surgical.
How are ectopic pregnancies managed?
Implantation outside the uterine cavity. There is a rising incidence with assisted conception, pelvic inflammatory disease (Chlamydia) and sterilisation reversal. Treatment can be expectant, medical or surgical. There is an increased risk of recurrence in future pregnancies.
What is the function of oestrogens?
Oestrogen
- Oestradiol (E2) produced by corpus luteum and placenta - Oestriol (E3) produced by foetus and placenta :- foeto-placental unit Function: • growth/strengthening of myometrium • Increase contractile proteins accommodation of growing foetus • Increase in blood flow through placenta to exchange of nutrients/waste products • Negative feedback on FSH/LH • Stimulation of hormone binding proteins that act as reservoir CBG, SHBG, TBG • Preparation of breasts for lactation Increase in sensitivity of uterus to smooth muscle uterotonics towards term (PGF2a, oxytocin)
What is the function of progesterone?
Progesterone
Functions: • Reduces uterine smooth muscle contractility to keep uterus quiescent during pregnancy • Inhibits production of PGF2a and oxytocin Blocks T-lymphocyte cell-mediated responses and cellular immune response
What is the function of human placental lactogen?
Human Placental Lactogen
- Is a polypeptide hormone - Lactogenic (PRL) and GH-like actions - Secreted in increasing concentrations during pregnancy as the placenta grows - Stimulates lipolysis in the mother, increases free fatty acids as energy substrate - Inhibits glucose uptake in the mother and favours glucose and protein transport to the foetus Promotes the growth and differentiation of the breasts in preparation for lactation
What cardiovascular changes occur in a pregnant woman?
- Increase in blood volume
- Increase in red blood cell mass but not the blood volume leading to physiologic anaemia. The Hb levels fall from around 14 (normal) to a normal of 12.
- There is sodium and water retention and oestrogen stimulates the renin-angiotensin-aldosterone system.
- Cardiac output increases to match the increase in blood volume, this is done through a raise in stroke volume and heart rate.
There is a greater fall in total peripheral resistance leads to an initial drop in blood pressure before it rises later on in pregnancy. Typically there is a slight fall in blood pressure and then it rises again.
What renal changes occur in a pregnant woman?
- Increase in renal blood flow
* Rise in plasma volume and CO
* Fall in renal vascular resistance/increase in renal vasodilatory prostaglandins (PGI2; PGE2)- Increase in GFR
- Urea and creatinine fall as no change in production
- Renal threshold to glucose diminished
- Renin-angiotensin-aldosterone system, increased in 1st trimester
- Pelvicalyceal and ureteric dilatation (smooth muscle) - due to progesterone
- Bladder capacity decreases as there is a baby pressing on it and women will tend to go to the bathroom more frequently
- Clinical consequences
- Increased frequency of micturition
- Tendency to UTIs due to stasis of urine within the system
- Increase in GFR
What coagulatory changes occur in a pregnant woman?
During pregnancy you have a hypercoagulable state, these have been attributed to sex steroids as women on the pill or on hormone replacement therapy are on a greater risk of coagulation:
• Increased clot formation
• factors I, V, VII, VIII, IX, X, XII
• Decreased clot lysis
• Increased plasminogen activator inhibitors (placenta)
• Activated protein C resistance
• Reduced protein S levels
This is again a leading killer in maternal death. Prevention is very important in venous thrombosis as after you are more likely to develop venous ulceration and venous insufficiency in later life.
What respiratory changes occur in a pregnant woman?
• Increase in oxygen consumption
• Demands of developing foetus
• Respiratory compensation in order to get rid of higher carbon dioxide
• Increase in tidal volume
• Increase in alveolar ventilation
• Vital capacity unchanged
• Change in central control of respiration
• Altered chemoreceptor PaCO2 sensitivity,
• Triggers increase respiration
• Clinical consequence
Disproportionate sense of dyspnoea on exertion
What gastrointestinal changes occur in a pregnant woman?
• Altered appetite (cravings)
• Lower oesophageal pressure and incompetence of cardia - leading to a greater likelihood of nausea due to reflux. There is also heart burn and a water rash in the upper pharynx.
• Decrease in motility due to progesterone.
• Prolongation of gastric emptying; prolongation of transit time, increase in water reabsorption
• Constipation: transition time extended, greater water reabsorption:
• Clinical consequences
• Nausea and vomiting, can lead to hyperemesis gravidarum
• Heartburn
Constipation
What is pre-eclampsia?
Pre-eclampsia is characterised by persistently high blood pressures throughout the pregnancy. There is also proteinuria and peripheral oedema. Occasionally there is an endothelial disorder. Eclampsiais the onset of seizures (convulsions) in a woman with pre-eclampsia. It is the leading cause of maternal death globally. Treatment is through delivery of the baby with the placenta and anti-hypertensives. There is a tendency to hypertension in later life in those women who develop pre-eclampsia.
