Physiological Changes in Pregnancy Flashcards
What hormonal changes occur in pregnancy?
Progesterone synthesised by the corpus lute until 35 days post-conception and by placenta thereafter
Decreases smooth muscle excitability and raises body temperature
Oestrogen increase breast and nipple growth, water retention and protein synthesis
Maternal thyroid often enlarges due to increased colloid production
Pituitary secretion of prolactin rises
What are genital changes in pregnancy?
Muscle hypertrophy of uterus up to 20 weeks with stretching after that
Cervix may develop ectropion
Cervical collagen reduces late in pregnancy
Vaginal discharge increases due to cervical ectopy, cell desquamation and increased mucus production from vasocongested vagina
What changes in the blood occur in pregnancy?
From 10 weeks, plasma volume rises until 32 weeks when it is 3.8L
Red cell volume rises - more so if iron supplements are taken - hence Hb falls due to dilution (physiological anaemia)
WCC, platelets, ESR, cholesterol and fibrinogen are raised
Albumin, urea and creatinine fall
What CVS changes pregnancy?
Cardiac output rises to 6.5/7L/min in first 10 weeks by increaseing SV and HR (by 15bpm)
Peripheral resistance falls due to hormonal changes
BP, particularly diastolic falls during the 2nd trimester by 10-20mmHg then rises to non-pregnant levels by term
With increased venous dispensability, and raised venous pressure, varicose veins may form.
Vasodilatation and hypotension stimulate RAAS
What is aorto-caval compression? How do you deal with this?
From 20 weeks, gravid uterus compresses IVC and (lesser) the aorta in supine women reducing venous return
This reduces cardiac output by 30-40% (supine hypotension)
Placing woman in left lateral position or wedging her tilting 15 degrees to the left relieves the pressure and restores CO to more normal levels.
How does the respiratory system change in pregnancy?
Ventilation increases by 40% - rise in tidal volume
This is progesterone effect
O2 consumption increases 20%
Breathlessness is common as maternal pCO2 is set lower to allow fetus to off-load CO2
How does GI change in pregnancy?
Gut motility is reduced resulting in constipation, delayed gastric emptying and with a lax lower oesophageal sphincter, heartburn.
How does the renal system change in pregnancy?
Renal size increases by 1cm length
Increased frequency of micturition - GFR up by 60%
Later from bladder pressure by fetal head
Bladder muscle is lax but residual urine after micturition is not present
What skin changes are seen in pregnancy?
Linea nigra Nipples Chloasma - brown patches seen on face Palmar erythema Spider naevi Striae Hair shedding is reduced in pregnancy but increased in puerperium
What do pregnancy tests detect? When are they sensitive?
Beta-subunit of human chorionic gonadotrophin in early morning urine
From 9 days post conception
