Physiological changes during pregnancy

Metabolic changes
Systemic changes

1. PHYSIOLOGICAL CHANGES DURING PREGNANCY

2. METABOLIC CHANGES General Metabolic Changes Total metabolism is increased due to the needs of the growing fetus and the uterus Basal metabolic rate is increased to the extent of 30% higher than that of the average for the non-pregnant women.

3. PROTEIN METABOLISM Positive nitrogenous balance throughout pregnancy i.e in ANABOLIC STATE . At term, the fetus and the placenta contain about 500 gm. of protein and the maternal gain is also about 500 gm. As breakdown of amino acid to urea is suppressed, the blood urea level falls to 15-20 mg%.

4. CARBOHYDRATE METABOLISM Insulin secretion is increased in response to glucose and amino acids. Hyperplasia and hypertrophy of beta cells of pancreas. Plasma insulin level is increased due to a number of anti insulin factors. These are estrogen , progesterone, human placental, lactogen ( hPL ), cortisol , prolactin , FFA, leptin , and TNF-alpha. Increased tissue resitance to insulin. Increased insulin level favours lipogenesis (fat storage).This mechanism ensures continuously supply of glucose to the fetus.

5. Overall effects is maternal fasting hypoglycemia (due to fetal consumption) and postprandial hyperglycemia and hyperinsulinemia (due to anti insulin factors).

6. FAT METABOLISM 3-4 kg of fat is stored during pregnancy in abdominal wall, breast, hips and thighs. LIPID METABOLISM HDL level increases by 15%. LDL is utilized for placental steroid synthesis. Activity of lipoprotein lipase is increased. LEPTIN - a peptide hormone secreted by adipose tissue and placenta regulates the body fat metabolism.

7. IRON METABOLISM Iron is absorbed in ferrous form from duodenum and jejunum and is released into the circulation as transferrin . 10% of ingested iron is absorbed. Total iron requirement during pregnancy is estimated approximately 1000mg.This is distributed in fetus and placenta as 300mg, expanded red cell mass as 400mg and obligatory loss of 200mg through normal routes. The iron in the fetus and placenta is permanently lost during delivery(45mg/day) and rest is returned to the store.

8. There is a saving of 300 mg of iron due to amenorrhea for 10 months. In the second half of pregnancy, the daily requirement increases about 6-7mg/day . The amount of iron absorbed from the diet and that mobilized from the store are inadequate to meet the demand. Serum ferritin level actually reflect the body iron stores. In the absence of iron supplementation, there is drop in haemoglobin, serum iron and serum ferritin concentration at term pregnancy. Thus pregnancy is an inevitable iron deficiency state .

9. Total body iron content average in normal adult females is 2gm Iron requirement for normal pregnancy is 1 gm 200 mg is excreted 300 mg is transferred to fetus 4 00 mg is need for mom Total volume of RBC inc is 350 ml 1 ml of RBCs contains 1.1 mg of iron 3 50 ml X 1.1 mg/ml = 400 mg Daily average is 6-7 mg/day Small intervals between pregnancies are most concerning.

10. SYSTEMIC CHANGES RESPIRATORY CHANGES Shape of the chest and the circumference increases in pregnancy by 5-7 cm. Progressive increase in oxygen consumption, which is caused by the increased metabolic needs of the mother and fetus . The mucosa of the nasopharynx becomes hyperaemic and oedematous and causes nasal stuffiness and rarely epistaxis . A state of hyperventilation occurs during pregnancy leading to increase tidal volume. The woman feels shortness of breath.

11. ACID BASE BALANCE: Hyperventilation causes changes in acid base balance. Pregnancy is in a state of respiratory alkalosis.

12. URINAY SYSTEM KIDNEY Dilatation of the ureter, renal pelvis and calyces. The kidneys enlarge in length by 1 cm. Renal plasma flow is increased by 50-75%, maximum by the 16 weeks and is maintained until 34 weeks. Thereafter it falls by 25%. Glomerular filtration rate (GFR) is increased by 50% all throughout the pregnancy URETER ureters become atonic due to high progesterone level. Dilatation of the ureter above the pelvic brim with stasis is marked on the right side specially in primigravidae .

13. BLADDER There is marked congestion with hypertrophy of the muscles and elastic tissues of the wall. Increased frequency of micturition is noticed at 6-8 weeks of pregnancy which subside after 12 weeks and In late pregnancy, frequency of micturition once more reappears due to pressure on the bladder as the presenting part descends down the pelvis. Stress incontinence may observe in late pregnancy due to urethral sphincter weakness

14. ALIMENTARY SYSTEM Gums become congested and spongy and may bleed to touch. Muscle tone and motility of entire GIT are diminished. Risk of peptic ulcer disease is reduced. Atonicity of the gut leads to constipation LIVER AND GALL BLADDER Liver functions are depressed Marked atonicity of gall bladder (progesterone effect). High blood cholesterol level during pregnancy, favour stone formation.

15. Difference in GIT in Pregnancy and Non pregnant state

16. NERVOUS SYSTEM Temperamental changes are found during pregnancy and in the puerperium Nausea, vomiting, mental irritability and sleeplessness are probably due to some psychological background Postpartum blues, depression or psychosis may develop in a susceptible individual Carpel tunnel syndrome may appear in the late months of pregnancy due to the compression of the median nerve underneath the flexor retinaculum .

17. CALCIUM METABOLISM AND SKELETAL CHANGES Increased demand of Ca by the growing fetus to the extent of 28 g. Daily requirement of calcium is about 1-1.5 g Ca absorption from intestine and kidneys are doubled due to rise in level 1,25 dihydroxy cholecalciferol . Relaxation of pelvic ligaments and muscles occurs because of the influence of estrogen and relaxtin reaches maximum during last weeks of the pregnancy Increased lumber lordosis during later months of the pregnancy due to enlarged uterus produces backache and wadding gait

18. ENDOCRINE SYSTEM Placental Hormones Protein hormones Human chorionic gonadotrophin (HCG) Human placenta lactogen (HPL) Human chorionic thyrotrophin (HCT) Human chorionic corticotrophin (HCC) Pregnancy specific b-1 glycoprotein (PS b G) Steroidal hormones Ostrogens – oestriol , oestradiol and oestrone Progesterone

19. Human chorionic gonadotrophin (HCG) Secretion of progesterone by the corpus luteum of pregnancy. HCG stimulates Leydig cells of the male fetus to produce testosterone in conjunction with fetal pituitary gonadotropins . It is thus indirectly involved in the development of male external genitalia. Human Placental Lactogen ( hPL ) Partial development of animal’s breast & lactation Acts like GH; ↓insulin sensitivity & ↓glucose utilization, & release free fats in mother to provide more glucose to fetus. Potent angiogenic hormone.

20. Steroidal hormones Oestrogen Progesterone Together maintenance of pregnancy. Oestrogen causes hypertrophy and hyperplasia of the uterine myometrium , thereby increasing the accommodation capacity, vascularity and blood flow of the uterus. Progesterone in conjunction with oestrogen stimulates growth of the uterus Development and hypertrophy of the breasts. Hypertrophy and proliferation of the ducts are due to oestrogen Both the steroids are required for the adaptation of the maternal organ to the constantly increasing demands of the growing fetus The steroids are involved in the complex pathway in initiation of normal labour

21. Pituitary Hormones The secretion of prolactin , adrenocorticotrophic hormone, thyrotrophic hormone and melanocyte -stimulating hormone increases Follicle stimulating hormone and luteinzing hormone secretion is greatly inhibited by placental progesterone and estrogen . The effects of prolactin secretion are suppressed during pregnancy Posterior pituitary gland releases oxytocin in low-frequency pulses throughout pregnancy. At term the frequency of pulses increases which stimulates uterine contractions

22. Thyroid Function Gland increases in size by about 13 percent due to hyperplasia of glandular tissue and increased vascularity Increased uptake of iodine during pregnancy Pregnancy can give the impression of hyperthyroidism, thyroid function is basically normal The basal metabolic rate is increased mainly because of increased oxygen consumption by the fetus and the work of the maternal heart and lungs