PHYSIOLOGICAL CHANGES IN THE MATERNAL ORGANISM DURING PREGNANCY .
Obstetric terminology The attitude refers to the relationship of parts of the fetus to one another (fetal head is flexed on fetal chest, thighs are flexed on fetal abdomen). The lie of the fetus is the relationship of long axis of the fetus to the long axis of the uterus and is either longitudinal or transverse. Can be longitudinal, oblique, transverse
Obstetric terminology The presentation indicates that portion of the fetus that overlies the pelvic inlet. Can be cephalic or breech The position refers to the relationship of definite part of the fetus to the right or left side of maternal pelvis. With each presentation there may be two position, left or right (1 st and 2 nd ). The occiput, chin and sacrum are the determining points in vertex, face and breech presentation, respectively.
Obstetric terminology Variety (visus, face) - the relation of the given portion (occiput, back or chin of the fetus) of the presenting part to the anterior and or posterior portion of the mother's pelvis. Engagement exists when the bi parietal diameter of the fetal head have passed the plane of the pelvic inlet.
Abdominal palpation: Leopold's maneuvers The first maneuver: the examiner hands palpate the fundal area and distinguish which part of the fetus occupies the fundus. Importance: estimation of gestational age of the pregnancy and fetal lie. The second maneuver is accomplished when hands are placed on either side of the abdomen to determine on which side the fetal back lies. Importance: estimation of fetal lie, position, variety, amount of amniotic fluid, fetal movement.
Abdominal palpation: Leopold's maneuvers The third maneuver is done with a single examining hand placed just above the symphysis. Importance: determination presentation and presenting part. The presented part is grasped between the thumb and third finger. The fourth maneuver is done with the examiner facing the patient's feet and placing both hands on either side of the lower abdomen just above the inlet. Importance: determination of fetal head station (relation of presenting part to the pelvic inlet).
Vaginal examination In vaginal examination a doctor should examine vaginal walls; dilation, effacement, consistency and position of the cervix; presence of amniotic fluid; fetal presentation and position, pelvis also.
Auscultation In cephalic presentation, the point of maximal intensity of fetal heart sounds is usually midway between the maternal umbilicus and the anterior-superior spine of her ilium. The rhythm of the fetal heartbeat should be estimated thoroughly. In case of arrythmia/bradycardia/tachycardia/ the emergency measures may be needed
Ultrasound examination Ultrasonic dating of the pregnancy and an ultrasonic fetal survey to detect gross abnormalities have been recommended as a routine part of early prenatal care. Routine ultrasonography is most cost -effective in patients in whom the date of the last menstrual period is uncertain and in patients with a family history of congenital anomalies. If ultrasonography is performed, it is most informative between 9-11 and 18-20 weeks.
Ultrasound examination Structural defects that have been diagnosed with this technique include craniospinal abnormalities ( e.g., anencephaly, hydrocephaly, spina bifida, microcephaly), gastrointestinal anomalies ( e.g., omphalocele, gastroschisis), excretory system anomalies (e.g., renal agenesis, renal dysplasia, urinar obstruction), skeletal dysplasia and congenital heart defects.
Presumptive evidence of pregnancy Nausea with or without vomiting, disturbances in urination, fatigue, perception of fetal movement. The signs include cessation of menses, anatomic changes in the breasts, increased skin pigmentation and the development of abdominal striae, the patient's belief that she is pregnant.
Probable signs of pregnancy Include enlargement of the abdomen; changes in the shape, size and consistency of the uterus; anatomic changes n the cervix, the results of endocrine tests. On physical examination, softening and enlargement of pregnant uterus (Hegar’s sign) become apparent six or more weeks after the last normal menstrual period.
Probable signs of pregnancy Endocrine tests for regnancy is based on the presence of human chorionic gonadotropin (hCG). hCG) is important in the maternal recognition of pregnancy by its action on the ovary to prevent involution of the corpus luteum, the principal site of progesterone formation in the first 6-8 weeks of pregnancy. High levels of hCG can suppose chorionepithelioma
Positive signs of pregnancy Fetal heart action, established separately and distinctly from that of the mother Perception of fetal movements by the examiner Recognition of the embryo or the fetus using imaging techniques such as ultrasound
Calculation of the date of delivery By adding 7 days to the first day of the last menstrual period flow and counting back 3 months. From 16 to 18 weeks of gestational age until 31-32 weeks of gestation, the fundal height in centimeters is roughly equal to t number of weeks of gestational age in normal singleton pregnancy.
Calculation of the date of delivery Obstetric ultrasound examination is the most accurate measurement available in the determination of gestational age. In the first trimester, transvaginal an transabdominal techniques allow gestational age determination within ±1 weeks' accuracy by using measurement of the gestational sac and embryo.
Assessment of fetal well-being Cardiotocography – the registration of the fetal heartbeat in combination with uterine contractions Normal heart rhythm is 120-160 beats per min Accelerations – the increasing of frequency of heart beating by 15 beats/min for at least 15 sec. Normal is presence of 5 accelerations. Sign of normal condition of fetus
Cardiotocography The nonstress test (NST) measures the response of the fetal heart rate to fetal movement. Interpretation of the nonstress test depends on whether the fetal heart rate accelerates in response to fetal movement. A normal, or reactive, NST occurs when the fetal heart rate increases by at least I5bpm over a period of 15 seconds following a fetal movement. Two such accelerations in a 20-minute span is considered reactive, or normal.
Cardiotocography Contraction stress test (CST) measures the response of the fetal heart rate to the stress of a uterine contraction. With uterine contraction, placental blood flow is temporary reduced. A healthy fetus is able to compensate for this intermittent decreased blood flow, whereas a fetus who is compromised is unable to do so, demonstrating abnormalities such as fetal heart rate decelerations.
Amnioscopy It’s visualization of the low part of amniotic shells, amniotic fluid and presenting part of fetus via special tube – amnioscope Indications – over-termed pregnancy, immune conflict Contraindications – infection of the genital tract, released amniotic fluid , bleeding, placenta praevia
Biophysical profile of fetus Includes ultrasonic parameters: muscle tonus of fetus, breathing movements, spontaneous movements, quantity of the amniotic fluid, condition of placenta. Includes cardiotocography: non-stress test. Each parameter can be evaluated from 0 to 2 points. 7-10 points – normal, less then 4 points – urgent delivery might be needed
The following factors influence psychological disorders development during pregnancy: hormonal and physiological changes; personal qualities; socio-economic status; unsolved conflicts; genetic propensity (e.g. for depression); physical and mental diseases; alcohol and drug abuse.
RESPIRATORY CHANGES Physical changes in the respiratory system begin early in pregnancy and are responsible for the improvements in gaseous exchange. The respiratory rate is unchanged and the elevation of the diaphragm decreases the volume of the lungs at rest, but the tidal volume is increased by up to 40% leading to an increase in minute ventilation from 7.25 litres to 10.5 litres.
Fetal plasma carbon dioxide tension exceeds that of maternal plasma and therefore passes easily into maternal blood. Despite this, due to the pulmonary hyperventilation, the concentration of carbon dioxide in maternal plasma is reduced by around 8% compared with nonpregnant levels.
CARDIOVASCULAR PHYSIOLOGY Cardiac output increases dramatically in pregnancy. The average increase is from 4.5 I/minute to 6.0 I/minute. The greatest increase is seen within the first trimester although further rises lead to a peak at around twenty-four weeks. This increase results from an increase in both heart rate and stroke volume. Heart rate increases from 70 bpm in the non-pregnant state to 78 bpm at twenty weeks gestation with a peak of around 85 bpm in late pregnancy. Stroke volume increases from 64 ml to 70 ml in mid-pregnancy. Stroke volume actually reduces towards term and the increase in cardiac output is maintained by the increase in heart rate.
Reduced pulmonary vascular resistance results in a 40% increase in pulmonary blood flow. Renal blood flow increases by 35% and uterine blood flow by around 250%. Blood volume and organ perfusion increase.
BLOOD VOLUME CHANGES In the non-pregnant state 70% of body weight is water. Of this 5% is intravascular. Intracellular fluid makes up about 70% and the remainder is interstitial fluid. In pregnancy intracellular water is unchanged but both blood and interstitial fluid are increased. Plasma volume increases at a greater rate than red cell mass and protein levels resulting in a reduction in blood viscosity.
As extreme example of this occurs when the uterus compresses the vena cava and reduces cardiac output to the point where the mother feels faint and may become unconscious. A sensation of nausea also occurs and vomiting may result. This condition, SUPINE HYPOTENSION SYNDROME , should be borne in mind when examining women in late pregnancy.
HAEMATOLOGICAL CHANGES The change in blood values such as haemoglobin content is the result of demands of the growing pregnancy modified by the increase in plasma volume. This represents an increase in red cell mass of 18%.The plasma volume increases by 40-45%.Thus there is a reduction in the red cell count per millilitre from 4.5 million to around 3.8 million. Similarly the haematocrit falls during pregnancy with a slight rise at term.
The increasing plasma volume, however, produces an apparent reduction in haemoglobin. The haemoglobin concentration falls throughout pregnancy until the last four weeks when there might be a slight rise. The fall is apparent by the 12th week of pregnancy and the minimum value is reached at 32 weeks.
GASTRO-INTESTINAL TRACT Changes in the gastro-intestinal tract are chiefly the result of relaxation of smooth muscle.This effect is induced by the high progesterone levels of pregnancy.
RENAL SYSTEM Frequency of micturition is a common symptom of early pregnancy and again at term. This is due to changes in pelvic anatomy and is a feature of 'normal' pregnancy. Striking anatomical changes are seen in the kidneys and ureters. A degree of hydronephrosis and hydro-ureter exist. These result from loss of smooth muscle tone due to progesterone, aggravated by mechanical pressure from the uterus at the pelvic brim. Vesico-ureteric reflux is also increased. These changes predispose to urinary tract infection.
Glycosuria occurs commonly because the increased glomerular nitration rate presents the tubules with a sugar load which cannot be completely reabsorbed. Glycosuria of mild degree occurs in 35-50% of all pregnant women. Increased glomerular filtration leads to more sugar reaching the tubules than can be reabsorbed. Glycosuria occurs therefore with lower blood sugar levels than in the non-pregnant, the so-called lowered renal threshold.
REPRODUCTIVE SYSTEM Breasts Each breast is made up of 15-20 glandular lobules separated by fat. The glands lead into tubules and then into ducts which open onto the nipple. The breasts increase in size in pregnancy due to proliferation of the glands and ducts under the influence of oestrogen and progesterone.
Body of Uterus Under the influence of oestrogen the uterus grows by hyperplasia and hypertrophy of its muscle fibres. Its weight increases from the non-pregnant level of 50 g up to 1000 g. The lower segment is formed from the isthmus, the area between the uterine cavity and the endocervical epithelium.
Cervix The cervix softens due to increased vascularity, and changes in its connective tissue, due mainly it seems to oestrogen. There is increased secretion from its glands and the mucus becomes thickened thus forming a protective plug, the so-called operculum, in the cervical os.
Vagina and Pelvic Floor The changes of increased vascularity, muscular hypertrophy and softening of connective tissues are seen, allowing distension of the vagina at birth.
Pelvic Ligaments There is softening of the ligaments of the pelvic joints, presumably due to oestrogen. The effect is to make the pelvis more mobile and increase its capacity.
ENDOCRINE CHANGES IN PREGNANCY Progesterone is produced by the corpus luteum in the first few weeks of pregnancy. Thereafter it is derived from the placenta. Levels rise steadily during pregnancy with, it has been suggested, a fall towards term. Output reaches a maximum of at least 250 mg per day.
Possible actions: 1. Reduces smooth muscle tone — stomach motility diminishes — may induce nausea. Colonic activity reduced — delayed emptying — increased water reabsorption — constipation. Reduced uterine tone — diminished uterine activity — reduced bladder and ureteric tone — stasis of urine. 2. Reduces vascular tone — diastolic pressure reduced — venous dilatation. 3. Raises temperature. 4. Increases fat storage. 5. Induces over-breathing — alveolar and arterial carbon dioxide tension reduced. 6. Induces development of breasts.
Oestrogens. In early pregnancy the source is the ovary. Later oestrone and oestradiol are probably produced by the placenta and are increased a hundredfold. Oestriol, however, is a product of the interaction of the placenta and the fetal adrenals and is increased one thousandfold. The output of oestrogens reaches a maximum of at least 30 to 40 mg per day. Oestriol accounts for 85% of this total. Levels increase up to term.
Possible actions: 1. Induce growth of uterus and control its function. 2. Responsible, together with progesterone, for the development of the breasts. 3. Alter the chemical constitution of connective tissue, making it more pliable — stretching of cervix possible, joint capsules relax, pelvic joints mobile. 4. Cause water retention. 5. May reduce sodium excretion.
Cortisol. The maternal adrenals are the sole source in early pregnancy but later considerable quantities are thought to be produced by the placenta. Some 25 mg are produced each day. Much of this is protein bound and therefore may not be generally active. Possible actions: 1. Increases blood sugar. 2. Modifies antibody activity.