Physiological changes during pregnancy

Maternal physiological changes in pregnancy are the adaptations during pregnancy that a woman's body undergoes to accommodate the growing embryo or fetus. ... The pregnant woman and the placenta also produce many other hormones that have a broad range of effects during the pregnancy.

1. PHYSIOLOGICAL CHANGES DURING PREGNANCY

2. During pregnancy there is progressive anatomical physiological, biochemical change not only confined to genital organs but also to all other systems of the body. Reproductive system Cardiovascular system Respiratory system Urinary system Breasts Weight gain Endocrine system Nervous system Digestive system Musculoskeletal system Skin

3. INTRODUCTION The changes of pregnancy are the direct result of the interaction of 4 factors. Hormonally mediated changes in the collagen and involuntary muscle. Increased total blood volume with increased blood flow to the uterus and kidneys. Growth of fetus enlargement and displacement of uterus.

4. ENDOCRINE SYSTEM Changes of pregnancy are orchestrated by hormones and their action. Progesterone, oestrogens and relaxin are the important hormones.

5. Progesterone is produced first by corpus luteum , then by placenta. Output of corpus luteum reach maximum of 30 mg/24 hrs at about 10 weeks and then declines. Placenta begins increasing production from 10 weeks. The amount produced rises from 75mg/24 hrs at 20 weeks to 250-300mg/24 hrs at 40 weeks.

6. Oesterogen is produced first by corpus luteum , then by placenta. Output of about 5mg/24 hrs at 20 weeks and 50mg/24 hrs at 40 weeks. Relaxin is thought to be synthesized in the corpus luteum and later in the decidua . It is produced as early as 2 weeks of gestation, it is at highest level in the 1 st trimester and then drops by 20% to remain steady till delivery

7. Effect of progesterone Reduction in tone of smooth muscle: food may stay longer in stomach, nausea, peristaltic activity reduced, increased water absorption in colon, constipation, uterine tone reduced, bladder tone reduced. Increase in temperature Reduction in alveolar & arterial Pco2 tension, hyperventilation. Development of breasts, alveolar and glandular milk producing cells.

8. Effect of Oestrogens Increase in growth of uterus and breast ducts. Increasing level of prolactin to prepare breasts for lactation. Increased water retention, may cause sodium to be retained.

9. Effect of Relaxin Gradual replacement of collagen in target tissues with a remodelled modified form that has greater extensibility and pliability. Role in mammary growth May have a role in cervical ripening

10. REPRODUCTIVE SYSTEM Amenorrhoea is first sign of pregnancy. Within few days of conception the color of the cervix will change from pink to bluish shade. Cervix in the final weeks involves changes like- softening, greater distensibiity and dilatation of cervix. Growing uterus rises out of pelvis to become an abdominal organ at about 12 weeks of gestation displaces the intestines

11. In the final 2-3 weeks the fetal head comes in pelvic inlet. The uterus increases in size. The weight of the uterine tissue increases from 50-1000g at term. Increase in elasticity by hormonal influence. Isthmus develops to become the lower uterine segment. Muscle fibres of the uterus increase in activity and coordinated contraction of the uterus, detected by 20 weeks of gestation.

12. Bursts of irregular, short, usually painless contractions become evident and systematic. These are called Braxton Hicks contractions . At some stage regular and increasingly painful contractions establish and labour is said to begin. The fetal heart can be heard using sonic- aid from about 14 weeks and by stethoscope at about 24-26 weeks. Fetal movement felt by multigravida between 16-18 weeks and by primigravida between 18-20 weeks. Outline of fetus can be palpated from 24 weeks.

13. CARDIOVASCULAR SYSTEM Blood volume increases by 40% or more to cope up with increasing requirements of uterine wall, placenta. Increase in plasma than in red cells, hence hemoglobin level falls by 80%. Called physiological anemia , this causes tiredness and malaise from early pregnancy

14. Progestrone acts on smooth muscle of vessel wall to produce hypotonia and cause rise in temperature. Pregnant women have a good peripheral circulation hence they don’t feel cold. Heart increase in size increase in stroke volume & cardiac output by 30-50%. Small increase in heart rate. In 2 nd trimester, little fall in BP. Hence fainting can occur.

15. In 3 rd trimester, wt of fetus may compress aorta & inferior vena cava against lumbar spine in supine position. Dizziness and unconsciousness Pregnancy hypotensive syndrome Exercise in heat should be avoided as there are chances of teratogenic effect of raised core temp in early weeks.

16. Reasons for varicose veins and gravitational oedema are- Vascular hypotonia Downward pressure of the enlarging uterus Weight gain Raised intra-abdominal pressure Progestrone and relaxin mediated changes in collagen Varicosites of vulva and anus ( haemorrhoids,piles ) may occur.

17. Oestrogens are responsible for fluid retention in body tissue Shape of the eye changes. Increased peripheral circulation and hormonal stimulation, mucous membranes ( eg . Nasal, vaginal) become more active n lush snuffy nose and increase vaginal discharge.

18. RESPIRATORY SYSTEM Resting respiratory rate - from 15 to 18 bpm Tidal volume - upto 40% Alveolar ventilation – Expiratory reserve volume – In 3 rd trimester because of enlarging uterus the diaphragm descents, by the term it displaces the diaphragm upward by 4cm or more.

19. Upward pressure of fetus causes flaring of ribs Subcostal angle increased by 10-15 cm. Relaxin softens costochondral junction and makes them mobile

20. BREASTS By 3-4 weeks, enlargement begins. Stimulated by rising level of oestrogens , progesterone and relaxin . Increases in Breasts weight in pregnancy is around 500-800g. Sebum secreted assists the nipple to become more softer and pliable. By 12 th week pigmentation starts.

21. Pigmentation is d/t stimulation of melanin production by anterior pituitary. By 16 th week colostrum can be expressed. Human milk ‘comes in’ about 3 rd or 4 th postpartum day.

22. SKIN Pigmentation is seen in linea alba, vulva and face. Stretch marks developed over buttocks, abdomen and breast Increase in blood flow to the skin which increases the activity of sebaceous and sweat glands Females are expected to drink more to compensate Fat is laid on thighs, upper arms, abdomen & buttocks

23. URINARY SYSTEM Increased blood supply to kidney and urinary tract Increase in size of kidney by 1cm & Dilation of ureter , renal pelvis. In later pregnancy , uterus compresses the ureters at the pelvis brim , causing slowing of urine flow. Increases in urine output, small changes in tubular resorption . Increases frequency of micturition is noticed at 6-8 weeks of pregnancy, which subsides after 12weeks . Stress incontinence may occur due to urethral sphinter weakness.

24. DIGESTIVE SYSTEM Nausea, vomiting occur most commonly in early pregnancy. Muscle tone and motility of entire GI tract decrease due to high progesterone level. Decreased gastric secretions, increased gastric emptying time. Increased relaxation of smooth muscle and water absorption in colon leads to constipation.

25. NERVOUS SYSTEM Anxiety , increased mood lability , vivid nightmares, food fads and insomnia are common. More prone to compression of distal nerves because of increase in fluid. Eg . Carpal Tunnel Syndrome.

26. BODY WEIGHT GAIN Weight gain in first 20 weeks of pregnancy is small (0-2)kg. It then increases to 1.0 kg/month to 30 weeks , then increasing to 1.0kg/fortnight between 30 and 40 weeks.

27. The total weight gain during the course of pregnancy for woman averages 10-12 kg. Weight distribution : Breasts : 0.5 kg Foetus : 3.3 kg Blood volume : 1.2 kg Placenta : 0.6 kg Amniotic fluid : 0.8 kg Uterus : 0.9 kg Fat deposits : 4.0 kg Extracellular fluid : 1.2 kg

28. MUSCULOSKELETAL SYSTEM Generalized increase in joint laxity . The muscles of abdominal wall adapt to increasing foetal growth with stretching of muscle fibres. Maternal COG shifts posteriorly to accommodate the increase in abdominal size. this reduces stability & may results in ‘waddling gait’ . Women usually walks with wider base of support. Back pain is a common symptom in pregnancy.

29. Thoracic and lumbar curves increase. Upper back become rounded , with scapular protraction , tightness of pectoralis muscles and scapular muscle weakness Cervical lordosis increased which leads to forward head posture. Many women experience painful muscle cramps during pregnancy , mainly in lower limbs.

30. REFERENCES Physiotherapy in Obstetrics and Gynecology- Margaret Polden , Jill Mantle pg-26-40