Physiology of Pregnancy

Daniel Hodyc Department of Physiology

Pregnancy

1. Fertilization 2. Placenta development, nutrition 3. Hormonal changes during pregnancy 4. Other physiological changes 5. Metabolism

Fertilization

Fertilization in the ampulle of the FT.

• Prostaglandins • Oxytocin

Ectopic (extrauterine) gravidity Fertilization

Fertilization

Transport into the uterus - 3-5 days • Contraction of the FT isthmus • Relaxation progesteron

Fertilization

Implantation 5-7 days after fertilization • Proteolytic enzymes of the trophoblast cells

Placenta

Placenta development

• Early nutrition of the embryo - invasion of trophoblastic cells into the decidua • Progesteron produced by CL - stimulates decidual cells to concentrate glycogen, proteins and lipids

Placenta works as a physiological A-V shunt

Placenta - oxygen transport

•Similarities betwen placenta and lungs •Oxygen transport - simple difusion Lungs • pO

2

• pO

2

• dO

2 in alveoli…………………………..100mmHg

in the venous blood……………40mmHg in (pressure gradient)…………60mmHg

Placenta: • pO • pO 2 • dO 2 2 in placental sinuses…………50mmHg in fetal umbilical vein………30mmHg in (pressure gradient)………20mmHg

How is a sufficient oxygenation of the fetus possible?

Placenta - oxygen transport 1. Fetal hemoglobin

2. Higher Hb concentration in the fetal blood (50% more than in adults)

3. Double Bohr effect

- Hb can carry more oxygen in

low pCO 2 than in high pCO 2

Placenta - CO 2 , nutritients, waste products transport

• CO

2

gradient - 2-3 mmHg, but extreme solubility (diffuses 20times faster than oxygen) • facilitated diffusion for glucose (high glucose need in 3dr trimester) • free diffusion of fatty acids • diffusion of waste products based on concentration gradient • drugs crossing placental barier - teratogens: • Talidomide, Carbamazepine, Coumarins, Tetracycline… • Alcohol, nicotine, heroin, cocaine, caffeine • drugs (excluding alcohol) - 3% of all congenital malformations

Hormonal Changes During Pregnancy

HCS Hormonal changes HCG Human Chorionic Gonadotropin

• prevent involution of CL (pregesterone, estrogen) •effect on the testes of male fetus - development of sex organs

Human Chorionic Somatomammotropin

• effect on latation (HPL) ?

•growth hormone effects •decreases insulin sensitivity more glucose for the fetus • low levels - placental insuf.

Hormonal changes Progesterone

• development of decidual cells • decreases uterus contractility • preparation for the lactation

Estrogens

• enlargement of uterus • breasts development • relaxation of ligments • estriol level - indicator of vitality of the fetus

Progesterone and Cortisol metabolism Placenta

Placenta

CRH HCG HC thyrotropin

Hormonal changes Mother

ACTH aldosterone cortisol

hyperthyroidism hypertension edema insulin resistance gestational diabetes

Calcium demands

Hyperparathyroidism

Other Physiological Changes

Cardiovascular changes Cardiac output (CO)

• 30 -50% above normal • placental circulation • increased metabolism • skin - thermoregulation • renal circulation • ECG changes • functional murmurs • heart sounds • decreases in last 8 weeks (uterus compresses vena cava) • incr. 30% more during labor • •

Heart rate

(HR) increases up to 90/min

Blood pressure

(BP) drops, periferal resistance decreases • with twins CO increases more, BP drops more

Hematologic changes

• plasma volume increases (50%) • erythropoesis (RBC) increases (25%) • decreased Hb, hematocrite • Iron requirements increases significantly • Iron suplements needed

Respiratory changes

• oxygen consumption increases • 20% above normal • Progesterone increases sensitivity for CO 2 in respiratory centre • Growing uterus • Frequency increases • Minute ventilation increases (50%) • pCO 2 decreases slightly

Urinary system

• Glomerulat filtration rate and renal plasma flow increases (up to 30 - 50 %) • Increased reabsorption of ions and water - placental steroids - aldosterone • Slight increase of urine formation • Postural changes affect renal functions - upright position - supine position - lateral position during sleep

Preeclampsia, Eclampsia

• Preeclampsia - pregnancy induced hypertension + proteinuria • Incresing BP since 20th week - hypertension • Salt and water retention - edema formation • RBF and GFR decreases • extensive secretion of placental hormones ?

• insufficient blood supply to placenta - ischemia - increased resistance - TNF alfa, cytokines ?

•Eclampsia - vascular spasms, chronic seizures, coma

Nutrition and Metabolism

Maternal weight gain Fetus 5 kg Mother 6 kg

Maternal-Fetal Metabolism

• 250 - 300 extra kcal/day should be ingested - 85% fetal metabolism, 15% stored in maternal fat • Extra protein intake - 30g/day • End of pregnancy - fetal glucose need 5mg/kg/min (mother 2,5mg/kg/min) • 2 phases of pregnancy:

1st - 20th week mother´s anabolic phase:

- anabolic metabolism of the mother - quite small nutrition demands of the conceptus

21 - 40 week (esp. last trimester):

- high metabolic demands of the fetus

- accelerated starvation

of the mother

Maternal-Fetal Metabolism Mother´s anabolic phase:

- normal or increased sensitivity to insulin - lower plasmatic glucose level - lipogeneses, glycogen stores increases - growth of breasts, uterus,weight gain

Catabolic phase (accelerated starvation):

- maternal insuln resistance - increased transport of nutritients trough placental membrane - lipolysis • Insulin resistance caused by HCS, cortisol and growth hormone

Special nutrition need in pregnancy

• High protein diet, higher energy uptake • Iron supplements - 300mg ferrous sulfate • B - vitamins - erythropoesis • Folic acid (folate) - reduces risk of neural tube defects • Vitamin D3 + Ca supplements • Before parturition - K vitamin (prevention of intracranial bleeding during the labor)

Thank you for attention