Maternal Physiological Adaptations in Pregnancy

1. DR. Areefa Albahri Chapter 7Change & adaptation in pregnancy By DR. Areefa Albahri Assistant Prof. of MCH Islamic University of Gaza

2. The major maternal physiological adaptation to pregnancy Reproductive organs cardio vascular system Respiratory changes. Changes in Central nervous system Changes in urinary system Changes in GI system -Blood volume homeostasis Change in metabolism Change in endocrine changes.

3. The anatomical and physiological adaptations occurring throughout pregnancy affect virtually every body system. • The midwife's appreciation of the normal adaptations to pregnancy and recognition of abnormal findings are fundamental in the management of normal as well as high risk pregnancies, enabling her to provide appropriate midwifery care to all women including those affected by pre-existing illness. • A common feature of these changes are influenced by physical, mechanical, genetic and hormonal factors. Many aspects of the physiology of pregnancy remain poorly understood and controversies continue to be researched.

4. Reproductive organs the uterus: • The uterus plays an essential role in pregnancy by expanding & stretching to accommodate the growing fetus. it is able to contract regularly and forcibly to expel the fetus due to its unique properties of contractility and elasticity. The uterine wall consists of three layers: an external serous epithelial layer or perimetrium, the middle muscle layer or myometrium, and the internal layer of endometrium (decidua)

5. The perimetrium • The perimetrium is a thin layer of peritoneum that protects the uterus. • It provides a relatively inelastic base upon which the myometrium develops tension to increase intrauterine pressure. The increasing tension exerted on the broad ligaments causes them to become longer and wider, therefore it accommodate the greatly enlarged uterine and ovarian arteries and veins.

6. Myometrium • The myometrium is muscular wall of the uterus that undergoes dramatic remodeling during pregnancy and provide support to growing fetus. • It is the layer of the uterine wall which is involved in contraction during labour. • Its function different from upper & lower uterine segment have contractile phenotype in the upper and relax phenotype in the lower segment. • Myometrium developed by hypertrophy and hyperplasia mechanism • By 12 week some irregular electrical cell contraction will occur known as Braxton Hicks contractions painless some women will not feel these cont.

7. Endometrium (Decidua) • Decidualization prepares the uterine lining for the invading trophoblasts . • The decidua in the cervix and the isthmus are less well developed than in the corpus, which prevents implantation in this region. • This happen by rising levels of progesterone. • The glands within the decidua may provide an important source of nutrients, growth factors and cytokines for the fetoplacental unit placental developed. • The decidua also produces large amounts of prostaglandins, which either enhances or initiates labour.

8. Changes in the uterine shape & size • At 5 weeks' gestation, the uterus feels like a small, unripe pear. • By 8 weeks it feels like a large orange and by 12 weeks it is about the size of a grapefruit. • The traditional method of assessing gestational age is to relate the progressive increase in the height of the fundus at different gestations to abdominal landmarks throughout pregnancy.

9. 12th week of pregnancy • As pregnancy advances, however, the corpus and fundus assume a more globular form becoming almost spherical by 12 weeks and too large to remain totally within the pelvis.

10. 16th week of pregnancy • Between 12 and 16 weeks' gestation, the fundus becomes dome-shaped. • The uterus now increases more rapidly in length than in width. From about 16 weeks, the internal os gradually relaxes and the lower uterine segment develops from the greatly expanded and thinned out muscular isthmus. • 20th week of pregnancy • As the uterus rises in the abdomen, it assumes an ovoid shape, the round ligaments appear to insert at the junction of the middle and upper thirds of the organ and the uterine tubes elongate.

11. 30th week of pregnancy • As the uterus continues to enlarge it contacts the anterior abdominal wall, displacing intestines laterally and superiorly and continues to rise, ultimately reaching almost to the liver. • In the supine position the uterus falls back to rest on the vertebral column and the adjacent great vessels, in particular the inferior vena cava and aorta.

12. 36th week of pregnancy • By the end of the 36th week of pregnancy, the enlarged uterus almost fills the abdominal cavity. The fundus is at the tip of the xiphoid, which is pushed forward. • The diaphragm is pressed upward, reducing the vertical diameter of the chest cavity by as much as 4cm.

13. 38th week of pregnancy • By 38 weeks' gestation, Descent of the fetal head into the pelvic brim (engagement) leads to slight lowering of the fundus, known as lightening which causes a change in shape of the abdomen. Women describe this as ‘the baby dropped’. Descent of the fetal head into the pelvic brim (engagement) leads to slight lowering of the fundus, known as lightening which causes a change in shape of the abdomen. Women describe this as ‘the baby dropped’. When this occurs breathing becomes easier and heartburn occurs less frequently but the increased pressure on the bladder may lead to urinary frequency. As pressure increases in the pelvis constipation may occur and as the pelvic ligaments are stretched more, low backpain may be experienced.

14. The cervix • Within 1 month of conception, the cervix becomes softer and cyanosed due to oedema and increased vascularity . • The glands of the cervix undergo such marked hypertrophy and hyperplasia. The endocervical mucosal cells produce copious amounts of a tenacious mucus resulting in the development of an antibacterial plug in the cervix. In the last 6 weeks of pregnancy, the cervix undergoes many changes (‘ripening’) in preparation for expelling the fetus. Cervical thinning, softening and effacement can be readily detected on vaginal examination. This process causes the expulsion of the mucus plug as a bloody show at the onset of labour. There are controversies around when cervical shortening occurs

15. The vagina • During pregnancy, increased vascularity and hyperaemia develop in the skin and muscles of the perineum and vulva with softening of the underlying connective tissue. Increased vascularity affects the vagina and results in the violet colour characteristic of Chadwick's sign. • The increased volume of vaginal secretions due to high levels of oestrogen results in a thick, white discharge known as leucorrhoea . • In pregnancy, larger amounts of glycogen are deposited in the vaginal epithelium due to high oestrogen availability. • Glycogen is metabolized to lactic acid by the Lactobacillus acidophilus, (‘Döderlein's bacillus’), a normal commensal of the vagina. This leads to increased vaginal acidity (pH varying from 3.5–6).

16. Changes in the cardiovascular system • These complex changes are necessary to: • meet evolving maternal changes in physiological function • to promote the growth and development of the uteroplacental-fetal unit • to compensate for blood loss at the end of labour. • The key physiological changes that occur are

17. A summary of the key components and functions of the cardiovascular system including changes in pregnancy

18. The key physiological changes that occur cardiac system

19. Blood changes: The marked increase in plasma volume associated with normal pregnancy causes dilution of many circulating factors. Hematological changes Increase in : • Oxygen 20-30% • Plasma volume 45-50% • Red cell mass 20-30% • Total blood volume30- 50% • Heart rate 10- 20% • fibrogen concentration (cloating factor)

20. Increase total blood volume needed to • meet the demands of the enlarged uterus • provide extra blood flow for placental perfusion • supply the extra metabolic needs of the fetus • provide extra perfusion of kidneys and other organs • counterbalance the effects of increased arterial and venous capacity • safeguard the mother against adverse effects of excessive blood loss at birth.

21. normal changes in heart sounds during pregnancy: • increase loudness of both S1 & S2. • >95% develop systolic murmur which disappears after delivery. • 20% have a transient diastolic murmur. • Relative tachycardia

22. Pregnancy problem due these changes • Physiological edema • Renin and aldosterone activity are increased by oestrogens, progesterone and prostaglandins, leading to increased fluid and electrolyte retention. • Physiological anemia • The total plasma volume is increase in higher percentage in comparison to RBC which result in hemodilution

23. Decrease blood pressure • Increase cardiac output is this lead to decrease arterial blood pressure by 10%, therefore resistance to flow must be decreased. In addition this can be result in decrease in systemic vascular resistance, particularly in the peripheral vessels. The decrease begins at 5 weeks' gestation, reaches a nadir in the second trimester (a 21% reduction) and then gradually rises as term approaches

24. supine hypotensive syndrome • The enlarging uterus compresses both the inferior vena cava and the lower aorta when the woman lies in supine position. This reduces venous return to the heart this condition happen in 10% of pregnant women. • Sign of supine hypotension • hypotension, bradycardia, dizziness, light-headedness. Supine hypotension occurs in around 10% of pregnant womens

25. Varicosities • Varicosities develop in approximately 40% of women, and are usually seen in the veins of the legs, but may also occur in the vulva and as haemorrhoids in the anal area. The effects of progesterone and relaxin on the smooth muscles of the vein walls, and the increased weight of the growing uterus all contribute to the increased risk of valvular incompetence. A family tendency is also a factor Some suggestions for alleviating them include: spraying the legs with hot and cold water, resting with the legs elevated and wearing supportive stockings.

26. Respiratory changes • Pregnancy is associated with marked changes in respiratory physiology mediated by biochemical and mechanical factors. These accommodate the progressive increase in oxygen consumption of the enlarging uterus. Normal oxygen consumption is 250mL/min at rest and increases by 20% in pregnancy in order to meet the 15% increase in the maternal metabolic rate

27. Changes in pregnancy result in an overcompensation to this respiratory demand. The resulting hyperventilation causes the arterial oxygen tension to increase and arterial carbon dioxide tension to fall, accompanied by a compensatory fall in serum bicarbonate. A mild respiratory alkalosis is therefore normal in pregnancy.

28. Hyperventilation can be extremely uncomfortable and may lead to dyspnoea and dizziness. Although it is not usually associated with pathological processes, care must be taken not to dismiss it lightly and miss a warning sign of cardiac or pulmonary disease (Steinfeld & Wax 2001).

29. The shape of the chest changes as diameters increase, by about 2cm, resulting in a 5–7cm expansion of the chest circumference.’ • The flaring of the lower ribs, causes the diaphragm to rise by up to 4cm, its contribution to the respiratory effort increasing with no evidence of being impeded by the uterus. • These changes are thought to be mediated by the effect of progesterone, which together with relaxin, increases ribcage elasticity by relaxing ligaments. Progesterone also mediates

31. Respiratory changes • increaseO2 demand by 18 %. • ↑tidal volume with normal respiratory rate 40 % . • ↑po2 and ↓pco2 withcompensatory ↓HCO3(mild compensated respiratory alkalosis). • Breathlessness due to hyperventilation and elevation of diaphragm. • tissue and oxygen availability to placenta improves.

32. ventilatory changes: • thoracic anatomy changes. • tidal volume increases. • vital capacity (maximum amount of air that can be forcibly expired after maximum inspiration) No change. • functional residual capacity decrease.

33. Breathlessness • Breathlessness during pregnancy occurs in approximately 75% of women with exertion and under 20% at rest. • This physiological dyspnoea often occurs early in pregnancy and does not interfere with daily activities and usually diminishes as term approaches.

34. Distinguishing this physiological dyspnoea from breathlessness caused by disorders complicating pregnancy or diseases that might coexist with pregnancy is essential. It can be alleviated by maintaining an upright posture and holding hands above the head while taking deep breaths. Avoiding excessive exertion is advisable.

35. Central nervous system • The pituitary gland increases in size by 30–50% in pregnancy accounting for much of the increased pituitary activity. • Oestrogen and progesterone readily enter the brain acting on a multitude of nerve cells changing the balance between inhibition and stimulation.

36. Central nervous system • Oxytocin neurons are inhibited from releasing the stored oxytocin prematurely through several hormonal mechanisms involving progesterone, oestrogen and opioid peptides. At term, progesterone secretion falls and the inhibitory mechanism modified to allow gradual release of oxytocin in labour followed by a surge at the time of birth.

37. Sleep disturbances are a common complaint of pregnancy. Various hormonal and mechanical influences promote insomnia leading to disturbed sleep during pregnancy in most women. With up to 90% of women report frequent night awakenings. Sleep disturbance may increase the labor length and chance of CS delivery.This worsens toward the end of pregnancy and continues to some extent for 3 months postpartum (Hedman et al 2002).

38. Interventions include establishing sleep – wake habits, avoiding caffeine, relaxation techniques, massage, heat and support for lower back pain, modifying sleep environment, limiting fluids in the evening and avoiding passive smoking. Sleep medications should be avoided. Some studies have shown that sleep loss in the last few weeks of pregnancy are associated with increased labour length and LSCS rates.

39. Pregnant women's sleep patterns are affected by both mechanical and hormonal influences. These include nocturia, dyspnoea, nasal congestion, stress and anxiety as well as muscular aches and pains, leg cramps and fetal activity.

40. The urinary tract and renal function • blood flow increase (60-70%). • glomerular filtration increased (50%). • clearance of most substances is enhanced. • plasma creatinine ,urea,urate are reduced. • glycoseuria is normal.

42. UTI in pregnancy • Progesterone may be involved in the relaxation of bladder smooth muscle, and in extreme cases, lead to retention of urine . the above factor can lead to urinary stasis and an increased risk of urinary tract infection in pregnancy. Glycosuria provides substrates for bacterial growth and is therefore another cause of asymptomatic bacteriuria

43. Urinary frequency • Urinary frequency (>7 daytime voidings), urgency, incontinence and nocturia may be experienced. It is primarily due to the effects of hormonal changes, hypervolaemia, increased renal blood flow and glomerular filtration rate although the increased fluid intake during pregnancy may also play a part. Later in pregnancy it is likely to be caused by the enlarged uterus, or descent of the presenting part.

44. Urinary incontinence • Urinary incontinence can begin early in pregnancy and the incidence increases as pregnancy progresses. Stress incontinence appears to be more common than urge incontinence although mixed symptoms are frequent. Women's descriptions of their incontinence range from mild to ‘terrible’. There is some evidence that pelvic floor strengthening can prevent incontinence during pregnancy and in the postpartum period. Normal function usually returns for most women soon after the birth of the baby

45. Changes in the gastrointestinal system • Anatomical and physiological changes take place in each organ of the gastrointestinal system. Influenced by oestrogen the gums become highly vascularized and oedematous. Associated with this is dental plaque, calculus and debris deposits which increase during pregnancy. Advanced gingivitis can lead to a specific angiogranuloma known as epulis.

46. Nausea and vomiting is experienced by more than half of all pregnant women. In spite of this, an increase in appetite is common in pregnancy and may be due to the effects of progesterone, which acts as an appetite stimulant • Taste often changes early in pregnancy. Even before the first missed period, there may be a loss of taste for something usually enjoyed.The development of cravings or aversions to food is also often reported. • Pica, the persistent craving and compulsive consumption of non-food substances is poorly understood.

47. Abdominal distension and a ‘bloated’ feeling occur when nutrients and fluids remain in the intestinal tract for longer, particularly in the third trimester due to the prolonged transit time. Increased flatulence may also occur due to decreased motility and pressure of the uterus on the bowel

48. Constipation • Constipation occurs because progesterone enhances absorption of sodium and water in the colon resulting in smaller stools with lower water content. Iron supplements may also aggravate constipation. Pregnant women are advised to consider changing the type of iron supplement (if used), to increase their intake of bran or wheat fiber and fluids and to take gentle exercise to alleviate this problem. Dietary bulking agents may also be helpful

49. Haemorrhoids are also fairly common in pregnancy due to both constipation and pressure in veins below the level of the enlarging uterus. Poor support for haemorrhoidal veins in the anorectal area and lack of valves in these vessels can lead to reversal in the direction of blood flow and stasis of blood. Women should be offered dietary advice and if symptoms remain troublesome should consider standard haemorrhoid creams.

50. Heartburn or acid reflux into the lower oesophagus during pregnancy occurs up to 85% of women, particularly during the third trimester. • Frequent or more severe heartburn can interfere with sleep and deter the woman from eating adequately. Lifestyle modifications may be necessary, for example elevating the head of the bed 6 inches, stopping smoking, sleeping on the left side, avoiding reclining for 2–3 hrs after a meal. • Dietary modifications which may be helpful include eating less fat and more protein, avoiding chocolate and certain drinks such as coffee, citrus juices, tomato products, and alcoholic drinks