Physiological Changes in Pregnancy Dr AUGUSTINE CYIMANA BScHB, MBChB, MMed (MMOG)-[UNZA],FCOG[ECSA] Last updated: 12-07-18 Ecclesiastes 1:18; ‘For in much wisdom is much grief: and he that increaseth knowledge increaseth sorrow’ Definition • Changes that are a positive adaptation of the mother to accommodate and support the fetus as it grows and develops through out the pregnancy • Are temporal and produce no permanent deleterious effect on the mother Introduction • The anatomical, physiological and biochemical adaptation to pregnancy are profound • Most occur in response to physiological stimuli provided by the fetus • It is important to know what ‘normal’ parameters of the changes are in order to diagnose and manage common medical problems in pregnancy Organ Systems • Skin • Breast • Genital tract • Cardiovascular system • Respiratory • Urinary • Gastrointestinal tract • Endocrine Skin Changes • Chloasma or Melasma gravidarum • Striae • Linea nigra • Angiomas (vascular spiders) • Palmar Erythma • Increased pigmentation of breast nipples Skin Changes (Cont’d) Chloasma or melasma gravidarum • Also called mask of pregnancy • Irregular brownish patches of varying sizes that appear on the face and neck • Fades a few months after deliver • Repeated pregnancy can intensify them Skin Changes (Cont’d) Striae Gravidarum • Stretch marks • Seen on the skin of the abdomen, breasts and sometimes the thighs • Results from rapid and excessive stretching of the skin accompanied by breaking of underlying connective tissue Skin Changes (Cont’d) Linea Nigra • Caused by hyperpigmentation • Aetiology same for melasma • Possibly increased malanocyte stimulating effect • Oestrogen and progesterone also implicated Skin Changes (Cont’d) Angiomas (Vascular spiders) • Mostly a consequence of hyperestrogenemia • Are of no clinical significance and disappear shortly after delivery • 2/3 of whites and 10% of black women • Common on neck, face, upper chest and arms Skin Changes (Cont’d) Palmar Erythma • 2/3 white & 1/3 black pregnant women are prone to experiencing primary palmar erythema • Increased estrogens may act as the trigger • May be linked to the changes in the functions of the vasculature and skin Breast Changes (Cont’d) Breast Changes (Cont’d) Genital Changes Vulva • Oedematous and hyperemic with viscosities Vagina • ↑ vascularity → violet color (Chadwick’s sign) • Vagina with supporting structures becomes progressively distensible • Ruggae disappear • pH is 3.5-6 (Action of Doderlen’s Bacilli) Genital Changes (Cont’d) Chadwick’s sign Genital Changes (Cont’d) Cervix • As early as 1 month after conception the cervix begins to undergo pronounced softening (Goodwell’s sign) • Results from ↑ vasularity and oedema together with hypertrophy and hyperplasia of cervical glands • Endocervical glands produce copious amounts of mucus that obstruct cervical canal • Expelled as blood show at onset of labour Genital Changes (Cont’d) Uterus • Non pregnant uterus weighs 50g and measures 7.5X5X2.5 with capacity of 4mls • At term weighs 1000g and measures 28 X24 X 21cm with capacity of 5L • Enlargement due to hypertrophy stimulated by oestrogen and probably progesterone • Uterine musculature arranged in 3 strata; inner circular, intermediate cris-crossed and outer longitudinal Genital Changes Uterus (Cont’d) Genital Changes Uterus (Cont’d) Genital Changes (Cont’d) ovaries • Ovulation ceases and maturation of new follicles suspended • Only single corpus luteum of pregnancy can be identified • A decidual reaction beneath the surface of the ovaries occurs • Diameter of ovarian pedicle increases from 0.9cm to 2.6cm Cardiovascular changes • Changes first seen at 8 weeks of pregnancy • Cardiac output increased by 40 % with peak at 30 to 32 wks • Peripheral resistance decreased • Resting pulse rate increased by about 10 bpm • Apex beat moves to the 4th intercoastal space • First heart sound is amplified • But 2nd heart sound remains unchanged Cardiovascular changes(cont’d) • Systolic murmur in 90 % Haematological changes • These occur by the 8th week • Blood volume increases by about 40-45% with maximum at 30 -32wks • Benefits of increased volume are: a) Meets the demands of the enlarged uterus b) Protects mother from effects of impaired venous return c) Safe guards against effects of blood loss d) ↓viscosity ensure optimal gaseous exchange Haematological changes (cont’d) • Plasma volume increases by 40% • Red cell volume increase by 18-20% • White cell count varies from 7000 to 15000/uL • In pueperium the WBC may rise up to 25000 • Platelets fall from an average of 250000 to 213000 • Blood coagulation factors all go up except factor XI and XIII (Greatest increase in Fibrinogen Heamatological changes (cont’d) • Fibrinolytic activity is depressed until 15 minutes after delivery • Protein C levels remain unchanged • Resistance to activated protein C increases Respiratory changes • The diaphragm rises to about 4cm • Subcoastal angle widens • Breathing becomes diaphragmatic • The physiological dead space decreases • Respiratory rate is slightly changed • Functional residual capacity decreases Urinary system • Kidney size increases slightly by about 1cm • GFR and renal plasma flow increase early in pregnancy • 24 hrs urine creatinine clearance increases by 40 to 50% • Glycosuria is not necessarily abnormal Gastrointestinal changes • Decreased motility due to progesterone • Increases appetite and thirst from growth of conceptus • Late in pregnancy, pressure of a large uterus reduces capacity for large meals GIT changes (cont’d) • Gastric emptying time is unchanged except in labour • Heartburn is common • Appendix displaced upwards Metabolic changes • Average weight gain of about 12.5kg from ➢Uterus and its contents ➢Breast increase with fat deposition ➢Blood volume and extravascular volume increase • Woman gains about 6.5L of water ➢3.5 in featus,placenta and amniotic fluid ➢3.0 in the mother Metabolic changes (cont’d) Protein metabolism • is that of positive nitrogen balance • Peak values are reached at 28wks • 500g retained by term • At term featus and placenta weigh 4kg,500g of which is protein Metabolic changes (cont’d) Carbohydrate metabolism • Characterised by mild fasting hypoglycaemia and post prandial hyperglycaemia • Increased basal level of plasma insulin associated with state of peripheral resistance • Ensure sustained post prandial supply to fetus • Insulin action is 50-70 % 0f normal health • Probably due to placental lactogen Metabolic changes (cont’d) Fat metabolism • Shows increases in the concentrations of lipids, liproteins, apoproteins in plasma • Fat is mainly stored in abdominal wall, back, thighs and retroperitoneally Endocrine Changes Pituitary gland • Enlarges by approximately 135 % • Changes in vision from compression of optic chiasma are minimal • Growth hormone secreted predominantly from maternal pituitary gland during 1st trimester (placenta starts secreting at 8 weeks • Prolactin levels increase (10 fold by term) Endocrine Changes Thyroid gland • 3 modifications in regulation of thyroid ➢Marked increase in circulating levels of major thyroxine transport proteins ➢Several thyroid stimulating factors of placental origin are produced ➢Decreased availability of iodine for maternal thyroid Endocrine Changes (Cont’d) Thyroid gland (Cont’d) • Thyroxine binding globulin increases early in pregnancy, peaks at 20wks and stabilises after • Total T4 ↑btn 6-9wks, plateaus at 18wks • Rise in T3 pronounced at 18 weeks then plateaus • TRH are not increased Endocrine Changes (Cont’d) Adrenal glands • Undergoes little or no morphologic change • Serum cortisol increased but much is bound to cortisol binding globulin • Increase is due to lower cortisol clearance • Aldosterone secretion increased from 16 wks • This protects against natriurect effects of progesterone and natrieretic peptide