Physiology- pregnancy Flashcards
General
o Mechanical o Metabolism o Fatigue – particularly early pregnancy o Heartburn/reflux o Oedema o General state of immunosuppression Women with asthma on steroid inhalers might need IV hydrocortisone cover during labour o Weight gain
Breast change
♣ Increased size and vascularity – warm tense and tender
♣ Increased pigmentation of the areola and nipple
♣ Secondary areola appears
♣ Montgomery tubercules appear on the areola
Colostrum like fluid can be expressed from the end of the 3rd month
cardiac related
output increases by 30-50%
• Palpitations are a common complaint
♣ At term, blood flow to the uterus must exceed 1L/min
Blood pressure drops in second trimester
♣ Expansion of the uteroplacental circulation
♣ A fall in systemic vascular resistance – maximal at 20-32 wks
♣ A reduction in blood viscosity
♣ A reduction in sensitivity to angiotensin
♣ In supine position – 25%reduction in cardiac output
BP usually returns to normal in the third trimester
intrapartum cardio changes
pain-increasing catecholamines
CO increases
Post partum
♣ Most return to normal by 3 mths
♣ Blood volume decreases by 10% 3 days post delivery
♣ BP initially falls then increases again days 3-7 (pre preg levels by 6 wks)
♣ SVR increase over first 2 wks to 30% above delivery levels
♣ HR returns to pre preg over 2 weeks
♣ CO increases by up to 80% 1st hr post-delivery then continues to fall over the next 24 weeks
urinary system
dramatic dilatation
increase urine output
♣ Renal plasma flow increases by 60-80% by end of 2nd trimester
♣ Glomerular Filtration Rate (GFR) increases by 50%
-serum urea and creatinine decrease (increased plasma volume dilution)
- protein excretion
-glycosuria common
urate increases with gestation
increased incidence of UTI
♣ Hydronephrosis is physiological in the third trimester pyelonephritis more common
♣ Can be associated with preterm labour so important to treat
Bladder capacity is reduced in the third trimester because of pressure
♣ increases the incidence of preterm labour (PTL) therefore low threshold for MSSU and antibiotics if +ve
Haematology
o Anaemia
♣ Plasma volume increases by about 50% and RBC mass by about 25%
♣ This results in a drop in haemoglobin by dilution from 133-121g/L
• ↓ hcrit, rcc
• No change MCV nor MCHC
Iron requirements are increased by 1g during pregnancy (2-3 fold)
WBC increase slightly to 9000
o Platelet count falls by dilution
♣ Most of increased iron requirement is for the feto-placental unit. Iron supplements should be given if Hb at booking is <110 or less than 100 on routine testing at 28 weeks.
o 10-20 fold increase in folate requirements
o Hypercoagulable state
♣ If high risk factors, woman will be on LMWH
respiratory
o Progesterone acts centrally to reduce CO2 ♣ Tidal volume, Respiratory rate ♣ 40-50% increase in minute ventilation ♣ Decreased functional residual capacity ♣ PEFR and FEV1 unchanged ♣ Plasma pH o O2 consumption by 20% ♣ Hyperaemia of respiratory mucous membranes
GI
• GI
o Oesophageal peristalsis is reduced
o Gastric emptying slows
o Cardiac sphincter (stomach) relaxes
o GI motility is reduced due to progesterone and motilin
If Bile acids , consider cholestasis of pregnancy. Usually 3rd trimester, associated with an itch.
Due to increased levels of hormones which causes flow of bile to slow
Problems in pregnancy
morning sickness\o Worse in conditions where b-HCG is higher e.g. twin, molar pregnancy
o Can progress to hyperemesis gravidarum
♣ Dehydration, ketosis, weight loss, hypotension
♣ Anti-emetics, vitamin B6, B12, steroids, admission
♣ Increased risk of getting HG in subsequent pregnancies
pre pregnancy couselling
♣ Obesity – associated with a higher rate of poor outcomes including miscarriage and stillbirth. It also affects the function of the uterus in labour.
• Routine measurements of fundal height may be impossible on abdominal palpation.
• Venous thromboembolic events are more common in obese patients.
o Reduce alcohol consumption
♣ Fetal abnormalities
♣ Fetal alcohol syndrome produces a typical facial appearance and affects learning, the routine advice given to pregnant women is to avoid alcohol although there is no evidence of harm from minimal alcohol consumption during pregnancy
parity
o Parity ♣ Pre-eclampsia is predominantly a condition of nulliparity (never given birth), occurring in the first pregnancy. Grand multiparity (4 or more deliveries) predisposes women to postpartum haemorrhage
substance misuse
♣ Heroin, methadone and benziodiazapines are addictive to the fetus and cause a withdrawal syndrome in the baby when it is cut off from its supply at birth.
♣ Cocaine and crack are associated with abruption resulting in fetal death.
multidisciplinary clinic involving obstetricians, midwives, members of the substance misuse team (psychiatrists & CPNs), social workers and health visitors.
women with known medical problems
o Phenylketonuria: An inborn error of protein metabolism which causes an inability to metabolism essential amino acid phenylalanine.
o Thyroid disease most commonly encountered during pregnancy is hypothyroidism.
♣ high blood glucose levels are associated with congenital anomalies.
♣ Women with type 2 diabetes who are on oral hypoglycaemics need to be switched to insulin.
♣ Diabetic patients are more at risk of pregnancy complications such as pre-eclampsia, stillbirth and macrosomic infants. They should be cared for in a joint diabetic obstetric antenatal clinic.
Renal patients are more likely to develop pre-eclampsia
♣ Sodium valproate is associated with a higher rate of spina bifida
Previous pregnancy complication
maternal: caesarean section • after 2 previous caesareans it is customary to deliver by elective caesarean again. ♣ DVT – thromboprophylaxis Pre-eclampsia
o Fetus: ♣ Pre-term delivery • Treatment of infection ♣ Intrauterine growth restriction ♣ Fetal abnormality • High dose folic acid
antenatal examination
feeling fetal movments (after 20 wks) blood pressure & urinalysis Abdominal palpation -assess symphyseal fundal height estimate size of baby liquor volume -determine fetal presentation • breech presentation after 36 weeks it is normal to offer external cephalic version (ECV) o Listen to fetal heart
antenatal screening
Hep B
syphilis-• Congenital syphilis causes intrauterine growth restriction, hepato-splenomegaly, anaemia, thrombocytopenia, skin rashes.
Easily treated with Penicillin
♣ Rubella
• No longer screened for in UK
• Congenital rubella syndrome occurs if a woman is infected with Rubella up to about 16 weeks of pregnancy. It can result in mental handicap, blindness, deafness and heart defects. Women who are not immune to rubella are offered immunisation on postnatal discharge.
HIV
♣ HIV
• Maternal treatment and careful planning reduces vertical transmission
Use of anti-retroviral drugs to reduce viral load, usually delivery by caesarean section and avoidance of breastfeeding in order to reduce vertical spread.
Rhesus disease
anti D igG is offered to all Rh negative women
hydatidiform mole
• – is a rare mass or growth that forms inside the womb (uterus) at the beginning of a pregnancy. It is a type of gestational trophoblastic disease (GTD).
Results from abnormal fertilisation of oocyte abnormal fetus
down syndrome screening
1 in 30 at age 45 yrs
1 in 1667 at age 20 yrs
first trimester screening
serum BHCG
pregnancy associated plasma protein
fetal nuchal translucency
CVS-chorionic villus sampling 10-14 wks
Amniocentensis 15 wks onwards
screening for NTDs
not routinely offered
o Personal or family history of NTD are at increased risk
♣ Should be advised to take 5mg folic acid to reduce risk
o First trimester ultrasound to detect anencephaly and sometimes spina bifida (variants of NTD)
o Second trimester biochemical screening
♣ Carried out if not able to get NT measurement
♣ Maternal serum is tested for alpha fetoprotein
♣ >2.0 MoM is high risk and warrants investigation
o Second trimester (20wk) ultrasound will detect >90% of NTD
♣ Ultrasound markers: Lemon sign (indentation of frontal bone), banana sign (cerebellum)
second trimester USS
good screening test for major structural abnormalities but a poor test for chromosomal abnormalities
Contraception
o Pearl index:
♣ Failure rate = no. of accidental pregnancies x 1200
no. of months of exposure
♣ The number of failures expected if 100 women used the method for one year
♣ The failure rate per 100 women years
♣ Over 99% effective = Pearl index 0.3 - 4.0 per HWY
combined oral contraceptive pill
Ethinyl oestradiol (EE) and Synthetic progesterone (progestogen)
o Second generation: levonorgestrel (LNG) and norethisterone (NET)
o Third generation: gestodene (GSD) and desogestrel (DSG)
Usual dose 20 – 35 microgram
MOA
♣ prevents ovulation by altering FSH and LH cycle No surge
♣ It prevents implantation by providing an inadequate endometrium
♣ It inhibits sperm penetration of the cervical mucus, altering quality & character of mucus
taking COCP
start day 1 up to day 5 without barrier contraception
♣ Takes 7 days to “switch off” ovaries
• Start anytime if not pregnant but use condoms for 7 days
♣ 21 days and stop for 7 days
♣ Contraceptive protection remains
♣ Can use 3 months continuously then pill free week
