Physiological changes in pregnancy

• The anterior pituitary gland produces more ACTH, prolactin and melanocyte stimulating hormone
• Hormonal changes:

  • Raised ACTH causes a rise in cortisol and aldosterone. Susceptibility to diabetes and infection
  • Raised prolactin - suppress FSH and LH
  • Raised melanocyte stimulating hormone - increased pigmentation - linea nigra and melasma
  • TSH remains normal by T3 and T4 levels rise
  • HCG levels rise and plateau around 8-12 weeks
  • Progesterone rises throughout pregnancy - prevents contractions and suppress immune system to foetal antigens
• Uterus, cervix and vagina:

  • Size of uterus increases from 100g to 1.1kg
  • Hypertrophy of the myometrium and blood vessels
  • Increased oestrogen may cause cervical ectropion and increased cervical discharge
  • Oestrogen causes hypertrophy of the vaginal muscles and increased vaginal discharge
  • More prone to bacterial and candida infection
  • Before delivery prostaglandins break down collagen in the cervix - dilation and effacement
• Cardiovascular changes:

  • Increased blood volume
  • Increased plasma volume
  • Increased cardiac output, with increased stroke volume and heart rate
  • Decreased peripheral vascular resistance
  • Decreased blood pressure in early and middle pregnancy, returning to normal by term
  • Varicose veins can occur due to peripheral vasodilation and obstruction of the inferior vena cava by the uterus
  • Peripheral vasodilation also causes flushing and hot sweats
• Respiratory changes:

  • Increased tidal volume
  • Increased respiratory
  • to meet increased oxygen demands
• Renal changes:

  • Increased blood flow to the kidneys
  • Increased glomerular filtration rate (GFR)
  • Increased aldosterone leads to increased salt and water reabsorption and retention
  • Increased protein excretion from the kidneys (normal is up to 0.3g in 24 hours)
  • Dilatation of the ureters and collecting system, leading to a physiological hydronephrosis (more right-sided)
• Haematology:

  • increased red blood cell production - increased iron, folate and B12 requirements
  • Plasma volume increases more than red blood volume - reduced haemoglobin and haematocrit concentration - anaemia
  • Clotting factors such as fibrinogen, factors VII, VIII and X increase - hypercoagulable state - increased risk of VTE
  • Increased WBC
  • Decreased platelet count
  • Increased ESR and D-dimer
  • Increased ALP - secreted by the placenta
  • Reduced albumin due to renal loss
• Skin changes:

  • Increased skin pigmentation due to increased melanocyte stimulating hormone, with linea nigra and melasma
  • Striae gravidarum (stretch marks on the expanding abdomen)
  • General itchiness (pruritus) can be normal, but can indicate obstetric cholestasis
  • Spider naevi
  • Palmar erythema