Maternal changes in the menstrual cycle Flashcards
What are the causes of the maternal changes in pregnancy?
How long does it take for systems to return to normal after delivery?
- High levels of steroids (E2 and P)
- Mechanical displacement (uterus enlarges a lot, displacing other structures)
- Foetal requirements
6 weeks but not everything returns to how it was before
What can the effect of pregnancy be on pre-existing, hidden or mild conditions?
Pregnancy exacerbates pre-existing conditions and uncovers hidden/ mild conditions e.g. someone with high BP has their BP get higher, an obese woman with borderline diabetes (i.e. some insulin resistance) can become diabetic
What sorts of changes occur during pregnancy?
- Uterus increases in size/ metabolic requirements
- Foetus has own structural/ metabolic requirements/ has to remove wastes
- Amniotic fluid provision
- Pelvis, uterus and breast tissue prepare for delivery
- Peurperium occurs (6 weeks after childbirth during which the mothers reproductive organs return to their original non-pregnant condition)
Which systems are effected in pregnancy?
- Respiratory
- CVS
- GI
- Urinary
- Endocrine
- Energy balance
What hormones are produced in pregnancy and from where?
Which hormones contribute to insulin resistance?
The placenta produces steroid and peptide hormones
Peptides - hCG, hPL (identical to GH), GH, prolactin
Steroids - Oestrogen forms (oestradiol, oestriol), progesterone (after the 7th week since the CL was responsible for that before + for oestrogen synthesis - kept alive by beta hCG)
Foetal pituitary produces GH, thyroid hormone, prolactin, CRH, oestradiol/ oestriol
CRH, GH, hPL and oestrogens all contribute to insulin resistance
Where are the effects of the placental steroids?
- Sex organs
- Breasts
- RAAS
- Respiratory centre
- GI tract
- Blood vessels
- Uterine myometrial contractility (P causes uterus to relax in pregnancy otherwise the big and thick organ would contract and cause early delivery/ miscarriage)
What is the total weight gain during pregnancy and how is this broken down?
12.5-13kg
- 4-5 kg of fat/ protein
- 5 kg of foetus + placenta
- 1.5 kg of body water (includes interstitial fluid, intracellular fluid and intravascular fluid)
- 1 kg of breast
- 0.5-1 kg of uterus
Why is there an increased need for energy during pregnancy?
Why is energy output and storage increased?
Where is the most gain in fat and protein stores?
When are the stores used?
More requirement of energy for yourself and child
CO and respiratory output both increase by 40-50%
Need fat and protein stores for baby growth/ to cope with labour demands/ cope with breastfeeding (as a lot of calories lost through that)/ puerperium
Most stored in anterior abdominal wall
Stores mainly used in 2nd and 3rd trimester and puerperium
By how much does the basal metabolic rate increase in mid and late gestation?
What uses the energy?
How many calories in 1g of fat?
Mid - 350 cal/day
Late - 250 cal/day
The foetus and uterus use 75% of the energy and 25% is used in respiration
9 cal
When does availability of glucose have to increase in pregnancy?
How can maternal glucose be used by the foetus?
Where does the foetus store some glucose?
What happens to glucose levels in the first trimester?
What happens to glucose levels in the second trimester? What can this cause?
2nd trimester - growth phase of foetus
FD across the placenta into foetus
Liver
1st trimester - hormones increase, antagonize insulins effects, body increased number of beta pancreatic cells to increase plasma insulin in response, fasting serum glucose decreases and glucose stored in e.g. muscle cells
2nd trimester - hormones keep increasing (hPL causes insulin resistance), less glucose taken up into stores so increases serum glucose levels to move across placenta - can cause gestational diabetes
How do you gain more water when you are pregnant? What are the other effects of this?
Where does the water go?
What happens if amniotic fluid escapes to other compartments?
E2 and P act on RAAS system to increase sodium retention, drawing water into blood plasma (increasing plasma volume). This decreases the thirst threshold, plasma oncotic pressure (albumin) and resets the osmostat.
Water goes to foetus, placenta, amniotic fluid (foetal urine since baby urinates into amniotic cavity), uterine muscle, mammary glands
It can cause oedema e.g. in the ankles causing swelling and in the lungs/ connective tissue/ ligaments
How does respiration change during pregnancy?
- Respiratory centre sensitivity increases to carbon dioxide + thoracic anatomy changes (ribcage displaces upwards as uterus pushes up to diaphragm + ribs flare out)
- Causes faster breaths and deeper breaths (minute volume increases by 40%)
- Arterial pO2 increases by 10% and pCO2 decreases by 15-20%
- When blood goes into the uterus and placental vessels, this aids transfer between maternal and paternal blood (of oxygen and carbon dioxide)
How does maternal blood change during pregnancy?
13
Features of foetal blood?
What happens over the first 2 years of life to Hb?
Why does a baby get harmed if their mother smokes during pregnancy?
Increased Hb content and a different type of Hb, HbF
HbF has increased oxygen binding capacity, with it’s dissociation curve shifted to the left
So increased oxygen binding, allowing for oxygen to diffuse from maternal to foetal blood
It converts from HbF to HbA
The carboxyHb reduces the amount of oxygen transferred to the foetus
Which type of Hb does smoking increase?
Smoking increases CO. CO binds stronger to Hb than O forming carboxyHb. This leads to decreased oxygen binding for the foetus, so foetal hypoxia occurs
What is the effect of an expanding uterus on the heart?
It pushes the heart around, changing it’s ECG and heart sounds
How do the heart and vessels change during pregnancy?
Heart
- HR and SV increases so CO increase by 40-50%; mainly SV so deeper breaths for longer and harder, since long term tachycardia is not energy efficient
- Maternal myocardium changes too
Blood vessels
- As BP = CO/TPR, an increase in CO means TPR has to decrease so vasodilation occurs (by progesterone) to reduce TPR
- Also increased flow to uterus, placenta, muscle, kidney and skin
- Neoangiogenesis occurs - including extra capillaries in skin (spider naevi) to help with heat loss
What is the time course for Cardiac Output change?
Begins as early as 3 weeks and increases by a maximum 40% at 28 weeks
What is preeclampsia?
Women with an increase in TPR and increase in BP –> increased blood pressure + protein in urine during pregnancy
What happens to the GI tract during pregnancy?
- Appetite and thirst increase
- Progesterone causes smooth muscle relaxation throughout the gut, so reduced tract motility which can cause constipation
- The lower oesophageal sphincter relaxes causing acid reflux (also due to large uterus)
To overcome this have small frequent meals
Why do we require more folic acid when we are pregnant?
Folic acid is required in DNA production, growth and blood cells. In pregnancy a lot of this is occurring in the uterus, placenta and foetus.
What is folic acid deficiency linked to?
Spina bifida - incomplete closing of the backbone and membranes around the spinal cord
This is why dietary supplementation is advised - 5mg/day up to week 12
Effect of pregnancy on urinary tract?
- Progesterone causes the smooth muscle of the bladder, uterus and kidneys to relax and dilate.
- Urinary tract relaxation causes urine to remain static, so risk of getting a UTI increases (why this is tested at every pregnancy check up)
- Kidney relaxation (+increased CO) means increased blood flow, increased filtration rate and increased clearance of creatinine, urea and uric acid and decreased levels in the blood
The reference ranges for these chemicals change in pregnancy. - Also get increased frequency of peeing (even from early pregnancy). This is because the uterus expands and puts pressure on the bladder; in the 2nd trimester it becomes less of an issue as the uterus grows up into the pelvis, but in the 3rd trimester the baby starts to head out so the frequency increases again.
How does uterine size change during pregnancy?
- It changes from 100ml to 14,000ml
- Muscle cells increase in size (hypertrophy) in response to oestrogen
- Increase in blood flow too
What orientation do the muscle cells of the uterus grow in and why?
In a spiral around the uterus so that at the time of delivery there are spiral contractions to push the baby out
Where are cuts made in abdomen in C sections?
Lower uterine segment formed by the elongation of the isthmus
This is at the top of the cervix/ bottom of the fundus which starts to thin by the end of the 3rd trimester
How do the uterus and cervix change in terms of contraction and relaxation in pregnancy?
When pregnant, you do not want the uterus to be contracting and you need the cervix to be firm and closed.
When delivering = opposite = uterus contracting and cervix dilated to allow baby through
What happens to the cervix during labour?
- Local inflammatory reaction
- Connective tissue broken
- Water influx in
- Myometrium contracts and cervix opens
- Thick ball of mucus falls out (mucus plug, known as bloody show, dislodges)
How does the cervix change during pregnancy?
- Increase in vascularity
- Connective tissue stacked with collagen for firmness
- Oestrogen causes proliferation of mucus glands/ production of thick sticky mucosal layer. These secrete mucus, forming a thick plug to keep bugs in the vagina out and keep the uterus sterile
What happens in afterbirth?
Placental expulsion (also called afterbirth) occurs when the placenta comes out of the birth canal after childbirth. The period from just after the baby is expelled until just after the placenta is expelled is called the third stage of labor
What happens after birth?
- Placental expulsion
- Rapid fall in steroids
- Endocrine driven changes rapidly return to normal
- Uterine muscle loses oedema and contracts slowly but never returns to pre-pregnancy size
- Removal of steroids releases feedback on breast tissue (hypertrophy’d due to oestrogen and progesterone) and allows for increased prolactin action on breast
- Insulin resistance gone in 24 hours
- Cardiac output back to normal in 2 weeks.
