Pregnancy

• Endocrine


  Relating to the endocrine system, which produces hormones
• Hypothalamic-Pituitary-Gonadal axis

  • GnRH - Gonadotropin Releasing Hormone
  • LH - Luteinizing Hormone
  • FSH - Follicle Stimulating Hormone
• Feedback

  May be negative or positive
• Hormonal changes during the menstrual cycle

  1. Follicular phase

  2. Ovulation

  3. Luteal phase

  
• Ovarian hormones

  • Estrogen
  • Progesterone
  • Inhibin
• Pituitary gonadotropins

  • LH
  • FSH
• Luteal phase of the menstrual cycle

  1. Corpus luteum is a progesterone factory with a limited life span

  2. Progesterone induces endometrial secretory phase

  3. If no fertilization, progesterone decreases and endometrium becomes ischaemic and lost
• What if fertilisation occurs?

  1. Zygote formed, begins dividing

  2. Implants into uterus around 6-7 days after fertilization

  3. Corpus luteum 'rescued' by human chorionic gonadotrophin (hCG)
• Human chorionic gonadotropin (hCG)

  • Glycoprotein synthesised by zygote, even before implantation
  • Placental (trophoblast) cells produce and release hCG into maternal circulation
  • Tells corpus luteum to continue making progesterone and estrogens

  
• Maternal hormones in pregnancy

  • Progesterone
  • Human chorionic gonadotrophin (hCG)
  • Total estrogen
  • Human placental lactogen (hPL)

  
• Progesterone effects


  1. Maintains endometrium

  2. Decreases contraction of myometrial cells

  3. Increases tidal volume

  4. Preparation for lactation

  5. Smooth muscle relaxation

  6. Increased erythropoiesis

  7. Natriuretic properties
• Endocrine System


  Physiological adaptations in pregnancy
• Estrogens effects

  1. Regulates secretion of progesterone by placenta

  2. Vital for development of foetus

  3. Stimulates hypertrophy of myometrial and placental cells

  4. Stimulates breast development

  
• Plasma and extracellular fluid

  • ~50% increase
  • Includes sequestering of sodium in placenta and amnion
  • Mediated by increased aldosterone and cortisol (opposed by progesterone and atrial natriuretic peptide)
  • Oedema clinically identifiable in 50% of pregnancies
  • Increased connective tissue fluid can increase laxity and pain of some joints
• Hypothalamic osmostat

  Reset, thirst increased at lower than usual osmolality, helps protect lower osmolality
• Other hormone changes

  • Human placental lactogen (hPL)
  • Relaxin
  • Insulin
  • Aldosterone and corticosteroids
  • Thyroid axis
  • Prolactin
  • Calcitriol (activated Vitamin D)
  • PTHrp (Parathyroid hormone-related peptide)
• Plasma and extracellular fluid

  • Increased water reabsorption
  • ¯ plasma oncotic pressure (due to dilution of plasma protein concentration)
  • ­ hydrostatic (venous) pressure
  • Contributes to oedema

  
• Haematological changes

  • Erythropoiesis (RBC production) increases, not as much as plasma volume decreased haematocrit and Hb concentration normal
  • ­ fibrinogen and clotting factors
  • ¯ endogenous anticoagulants
  • Helps to stop bleeding after delivery but increases risk of thrombosis and thromboembolism (further increased by venous stasis due to venodilation and compromised venous return)
• Calcium demand increased during pregnancy
• Mild haemodilution

  Normal in pregnancy
• Cardiac physiology

  • Cardiac output is increased by 30-50%
  • Heart rate increases by 15 beats/min
  • Stroke volume increases by 10%
  • Often heart murmurs can be heard due to ­blood flow through heart, altered heart configuration, mammary vessels

  
• Cardiac output

  • Stroke volume
  • Heart rate
• Blood pressure


  • Due to peripheral vasodilation
  • Mediated by progesterone, prostaglandin E2 & prostacyclin; increased NO production
  • Triggers volume expansion (via renin-angiotensin-aldosterone system)
  • ­ cardiac output ¯ vascular resistance
  • « systolic pressure; ¯ diastolic pressure during 1st half by ~15mmHg
• Renal physiology

  • Increased GFR (ñ50% by end of first trimester)
  • Increased renal plasma flow (decreased pre- and post-glomerular resistance)
  • Decreased plasma urea and creatinine (increased clearance)
  • Microalbuminuria (due to haemodynamic, permeability & tubular reabsorption changes)
  • Glucosuria (glucose in urine) (increased filtration rate of glucose, impaired reabsorption?, may increase chances of UTI)
• GFR (single nephron)

  • glomerular plasma flow
  • ultrafiltration pressure
  • mean arterial BP
  • Glomerular capillary ultrafiltration coefficient (Kf)
• Respiratory physiology


  • Progesterone increasing sensitivity of respiratory centre to CO2
  • ­ tidal volume x « respiratory rate =­minute ventilation (MV) – helps meet increased O2 demand
  • Keeping maternal pCO2 low encourages CO2 removal from fetus
  • Renal excretion of HCO3- maintains normal pH
  • Breathlessness (dyspnoea) not unusual
• Alveolar ventilation


  • Minute ventilation
  • Tidal volume
  • Respiratory rate
• Lung volume changes

  • Increased tidal volume
  • Expiratory reserve volume and Functional residual capacity (FRC) decrease
  • The enlarging uterus can elevate the diaphragm by as much as 4 cm the transverse chest diameter can be increased by 2 cm.
• Gastrointestinal system

  • Taste often altered
  • Reduced gastric secretion
  • Delayed gastric emptying
  • Reduced gut motility – constipation
  • Nausea and vomiting common (in ~50% of pregnancies)
• Hormones of pregnancy can also affect the brain
• Hormones affecting the brain

  • Oestrogen & progesterone - enlarge cell bodies of neurons of the medial preoptic area of the hypothalamus (maternal behaviour), increase surface area of neuronal branches in the hippocampus (memory & learning)
  • Oxytocin - stimulates the hippocampus
• Hormones of pregnancy can cause insomnia and darken the skin
• Physiological changes


  • Increased awareness of foetal movements at rest
  • Feeling too hot due to peripheral vasodilation
  • Nocturia
  • Hyperpigmentation occurs due to increased secretion of melanocyte stimulating hormone (MSH) (secreted from pars intermedia of pituitary gland), promotes linea nigra, darkening of areola, facial chloasma / melasma 'pregnancy mask'
• Pyogenic granuloma


  Rare, inflammatory, benign growths that develop on the gums as part of an exaggerated response to plaque. Pregnancy tumours usually subside shortly after childbirth.
• Pregnancy gingivitis


  Usually in 2nd trimester, hormonal excesses causes gums to react differently to bacteria. Periodontitis has been linked to preterm labour (­prostaglandins?)
• Fetal alcohol syndrome increases the incidence (x 3.4) of orofacial clefts. Can also lead to cranio-facial dymorphisms
• Enamel hypoplasia in young children linked to prolonged/difficult deliveries; viral infections, uncontrolled diabetes during pregnancy
• Low birth weight has been linked to increased risk of periodontal disease
• A positive attitude to oral health (of both prospective mothers and fathers) is likely to be carried over to the growing infant