Physiologic Changes in Pregnancy

Physiologic Changes in Pregnancy

Dr. Huda Adnan Al-Rubaiy C.A.B.O.G.

General Principles

Most changes begin earlyEven before pregnancy recognizedMost are hormonally drivenProgesterone, estrogen, renin / aldosterone, cortisol, insulinSome ‘mechanically’ drivenDesigned to optimize conditions for fetus & prepare for delivery and for delivery of oxygen & nutrients

Hematologic Changes

Hematologic Blood volume increases 50-100% RBC increases 25-40% leading to relative anaemia Increased heart rate by 40%. Increase cardiac output with peak increase at 3rd stage of labor. Hyper coagulable state with increased S.fibrinogen ,clotting factors e.g. factor 2, 7, 8, 9, 10. Fall in factor 6, 11. Increased WBC.

Cardiovascular changes

Cardiac axis displaced cephalad and left leading toLeft axis deviation on ECG.Murmurs > 96% of women (systolic murmer)Ventricular distention – 25% increase.Decreased blood pressure especialy at 2nd trimester.ECG changes e.g. left axis deviation, prominent Q wave, flat or inverted T wave.

Signs & Symptoms of Normal Pregnancy that may Mimic Heart Disease

Signs Peripheral edema Symptoms Reduced exercise tolerance Dyspnea
Auscultation S3 gallop Systolic ejection murmur Chest x-ray Change in heart position & size Increased vascular markings ECG Nonspecific ST-T wave changes Lt. Axis deviation LVH

Respiratory Adaptations

Most respiratory changes occure due to progressive uterine distention and progesteron effect. No change in rate Increased minute ventilation Reduced FRC (functional residual capacity) and ERV (expiratory reserve volume). Increased Tidal Volume 30-40%



No changes in forced vital capacity , FVC forced expiratory volume in 1 second, peak expiratory flow.Increased respiratory resistance.Compensated respiratory alkalosispH 7.4+PaO2; PaCO2 (40 – 30)

Respiratory Changes

Genital changes
Increased uterine blood flow Uterne muscle hyperplasia and hyperatrophy due to effect of estrogen and progesteron, uterus increased inweight from 50 g to 1000g In third trimester the uterus will describe in upper and lower segments , lower segment

consist of lower part of uterus and cervix which is the thinner part and contain less

consist of lower part of uterus and cervix which is the thinner part and contain less Vessels and muscles and is the site of incision at caeserian section. cervical hyperatrophy. increased vaginal discharg.

Uterine Position over Time