Department of Obstetrics & Gynecology Normal Pregnancy, Anatomical & Physiological changes Dr. Dina Nawfal Department of Obstetrics & Gynecology College of Medicine University of Mosul

Normal Pregnancy, Anatomical & Physiological changes During early pregnancy the developing fetus, corpus luteum and placenta produce and release increasing quantities of hormones, growth factors into the maternal circulation most pregnant women report symptoms of pregnancy by the end of the sixth week it is assumed that most of the physiological adaptation are completed during the first trimester.

Volume homeostasis Blood volume expands during pregnancy to allow adequate perfusion to the vital maternal organs , placenta and fetus The increase mainly involve the extracellular fluid volume specially plasma and begun at 6-8wk, plateau at 32-34wks. The total body water increase from 6.5 to 8.5L by the end of pregnancy changes in osmoregulation of renin-angiotensin system result in active sodium reabsorption in renal tubules and water retension the plasma osmolality decrease by about 10mOsmol/kg

thirst threshold decreased Plasma oncotic presure is mainly determined by albumin concentration this decrease by about 20% leads to peripheral edema Consequences of fluid retention: decrease hemoglobin concentration reduce hematocrite reduce albumin concentration increase stroke volume increase ranal blood flow

Hematology hemoglobin level: Hemoglobin concentration fall from 13.3 to 10.9 g/dl the transfer of iron stores to the fetus contribute to the development of physiological anemia iron level: iron requirements is increased and hence its absorption from the gut is increased as a result pregnancy without iron supplementation lead to depletion of iron stores and iron deficiency anemia.

folic acid: renal clearance of folic acid increased plasma folate concentration fall but red cell folate do not decrease Platelet count platelet count usually remain stable throughout pregnancy Although it may be lower than pre pregnancy state due to increased aggregtion

WBC count mainly the polymorph nuclear cells will increase during pregnancy from 3rd weeks of gestation and more pronounced postpartum. Haemostasis and coagulation Pregnancy is a hypercoagulable state and return to normal after 4 weeks postpartum At term the placental bed blood flow is 500ml/min

Almost all clotting factors including factors Vll,Vlll lX,X, Xll and fibrinogen are increased. antithrombin lll remain unchanged protein S activity decreases activated protein C resistance increase

Respiratory system Anatomical changes The neck , oropharyngeal tissues , breasts and chest wall are affected by weight gain during pregnancy and may lead to difficult intubation during general anasthesia nasal congestion As pregnancy progresses the diaphragm is elevated 4cm by the enlarging uterus Increase pulmonary blood flow

Physiological changes the tidal volume increase by 40% Increase minute ventilation by 40% ( amount of air move in and out of lungs in 1minute ) forced expiratory volume in one second (FEV1) is not affected Blood gas changes   Decrease pco2 . Increase po2. Increase production 2,3 DPG within the maternal RBCs to facilitated oxygen delivery to the fetus .

Cardiovascular system palpitation are common (sinus tachycardia) COP increase by 30-50% heart rate increase by about 10-15 beats higher than the pre pregnancy state stroke volume also increase due to changes in plasma volume during early pregnancy blood pressure will decrease by 10-15 mmHg diastolic & 5-10mmHg systolic, later on the diastolic blood pressure will increase to a level at least equivalent to pre pregnancy state.

Gastrointestinal tract: Loud first heart sound and sometimes split while third heart sound is audible at 20 weeks of gestation an ejection systolic murmur is common 96% of pregnant women peripheral vascular resistance decrease by 35% Gastrointestinal tract: increase the chance of reflux esophagitis. progesterone delay stomach and bowel motility leading to constipation , hemorrhoid , and increase the risk of aspiration of the gastric content during general anesthesia

Liver Increase hepatic blood flow . liver function unchanged. Increase protein production specially albumin. Serum ALT and AST are slightly reduced. Serum alkaline phosphatase increase due to placental production.

The kidney and urinary tract Anatomical changes Kidney increase in size with 1-2cm . there is dilatation of pelvic calyces systems under the influence of progesterone and return to normal by 6 weeks postpartum. Increase Renal blood flow by 80% in the 2nd trimester

Physiological changes Increase glomerular filteration rate by 50% after conception. creatinine clearance increased by 25% . plasma renin and angeotensin 2 activity are increased. plasma urea , creatinine , uric acid are decreased due to increase renal excretion . Sodium and potassium metabolism remain unchanged. Renal excretion of calcium ,proteins and folic acid increase. Glycosuria are common

Reproductive organs Uterus hyperplasia and hypertrophy of the myometrial cells increasing the weight of the uterus from 70 gm prior to pregnancy to 1000gm by term Normally the uterus is anteverted but become more axial and vertical when enlarged and rotate in its long axis, usually to the right the intercellular gap junctions develop with increasing gestation.

Cervix Early in pregnancy the cervix become soft and its color change to purple due to increase vascularity The cervix become soft in consistency (Hegar sign ) Cervical mucosal cells produce large amounts of thick mucus that obstructs the cervical canal soon after conception it has abundance of leucocytes and acts as antibacterial and mechanical barrier  

Vagina Increased vascularity of the vagina resulting in the violet color characteristic of pregnancy . Estrogen cause thickening of the vaginal epithelium with increase rate of desquamation , glycogen storage and lactic acid production , transudation of the fluid resulting in increase in the acidic vaginal discharge .

Breast Tenseness and pain in the breast are the symptoms of pregnancy The breast progressively increase in size The primary areola become larger and darkly pigmented Secondary pigmented areola develops around the primary areola Montgomery's tubercles appears Estrogen causing increase glandular ducts formation while Progesterone and human placental lactogen increase glandular alveoli proliferation

Skin Changes Cloasma or the mask of pregnancy is hyper pigmentation with irregular areas on the cheeks and nose , it may be due to melanocyte stimulating hormone produced by the placenta and estrogen and progesterone which may also have a melanocyte stimulating effect. Striae gravidarum : Reddish to purple depressed lines develop in the skin of the abdomen , breasts and thighs , after pregnancy becomes silvery white due to stretching of the skin and breaking of the underlying tissue.

Linea nigra: The midline of the abdominal skin that extending from the umbilicus to the symphysis pubis becomes pigmented , brownish-black color Sebaceous glands activity increase . Pruritis and hirsuitism are common .

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