Physiology of Normal Pregnancy PDF

PHYSIOLOGY OF NORMAL PREGNANCY Dr Hanan Elsayed Mohamed Elsayed Developmental stages during pregnancy There are three different stages of human development during pregnancy - Pre-embryonic stage. - Embryonic stage. - Fetal stage.  Pre-embryonic stage This stage begins at f...

PHYSIOLOGY OF NORMAL PREGNANCY Dr Hanan Elsayed Mohamed Elsayed Developmental stages during pregnancy There are three different stages of human development during pregnancy - Pre-embryonic stage. - Embryonic stage. - Fetal stage.  Pre-embryonic stage This stage begins at fertilization and to end of the second week after fertilization. During the pre- embryonic stage, cellular division and implantation occur.  Fertilization : Union of the sperm and the ovum  Conception: process that begins with the fertilization of an egg and ends with the implantation of the zygote into a woman’s uterus  Cellular reproduction The zygote begins the process of division or cleavage through mitotic division. As the cells divide, the zygote transforms from one cell into two cells ,four cells, eight cells and so on.  Morula formation Nearly, about 3rd day after fertilization, the total cell count has reached 32. The solid cell mass cluster is now referred to as a (morula).  Blastocyst At about the 5th day after fertilization, the dividing cell mass has developed a hollow, fluid-filled core and is now called a blastocyst.  Implantation - 7th day after fertilization, the trophoblast develops finger-like projections that help the blastocyst to burrow itself into the nutrient- rich endometrium. - By the 10th day, the blastocyst is completely buried in the uterine lining, and the endometrium is known as the decidua.  Embryonic stage - The embryonic stage lasts from the end of the second week until the end of the 8th week. (embryo). - By the end of the embryonic stage, all of the organ systems and major structures are present, and the embryo is fully recognizable as human in form  Embryonic stage - During the embryonic period, differentiation process occurs in which the cells and tissues of the embryo multiply to form organs. - In the 3rd week, three germ layers develop in the embryo, (ectoderm, mesoderm, and endoderm)  Fetal stage The fetal stage starts from the beginning of the 9 th week after fertilization and continues until birth.  Sex determination If the egg is fertilized by a sperm containing an X chromosome, the baby will be a girl (XX). If the sperm contains a Y chromosome, the baby will be a boy (XY). Supportive structures development  Fetal membranes: two fetal membranes, amnion and chorion.  Amniotic fluid - protect the fetus from injury. - A temperature control mechanism. - A medium that allows for free movement and unrestricted growth Supportive structures development Placenta - Transfers nutrients, such as oxygen and glucose, to the fetus while removing waste products - acts as a barrier to some harmful substances from passing to the fetus. - it secretes hormones as HCG, estrogen, and progesterone Supportive structures development Umbilical cord The umbilical cord extends from the umbilicus of the fetus to the fetal surface of the placenta. There are two arteries and one vein  Signs and symptoms of pregnancy Presumptive signs and symptoms  Absent menstrual periods (amenorrhea).  Nausea and/or vomiting (morning sickness).  Unexplained fatigue.  Frequent urination.  Breast tenderness and changes.  Excessive salivation (ptyalism).  Skin changes.  A sensation of movement in abdomen (quickening).  Probable signs and symptoms  Probable signs of pregnancy are changes observed by an examiner and may be false or caused by something other than pregnancy  Hegar sign.(Softening of the cervical isthmus)  Abdominal ballotment.  Positive pregnancy test.  Positive signs and symptoms Sure signs that attributed only to the presence of the fetus. - Hearing fetal heart sounds by a Doppler. - Visualization of the fetus by ultrasound. - Movement of the fetus felt by a doctor  Physiological changes during pregnancy Changes weight of the uterus  It increases its original weight from 50-70 grams to 1000 grams Changes in the Cervix  Increased vascularity and become softer (Goodell's sign). th  A plug of mucus( formation) is formed by the 8 week from the secretions of the cervical glands Changes in the Vagina Chadwick's sign  In the non-pregnant state, vagina is pink color. Early in pregnancy the vagina and cervix become blue, that is caused by venous dilatation due to the action of progesterone Changes in the breast - The breasts increase in size and weight( 500 g each). - Surface veins are visible at about 8 weeks. - The nipples become larger, more erect and darker in colour. - The areolae become darker and are surrounded by prominent glands (Montgomery's tubercles), which appear at about 12 weeks.  Changes in the urinary & digestive system Frequency of micturition caused by hormonal or mechanical causes Changes in the digestive system  Nausea and vomiting (If persists after the 14th week and severe (hyperemesis), it requires active treatment  Heartburn caused by mechanical pressure which the enlarged uterus displaces the stomach upwards  Constipation caused by reduced motility of the intestines and crowding of the intestines by pressure from the enlarged uterus.  Weight gain The average total weight gain during normal pregnancy ranging between 9 and 12 kilograms ❑ Fetus 3.5 kg ❑ Amniotic fluid 1.0 kg ❑ Placenta 0.5 kg ❑ Uterus 1.0 kg ❑ Breasts 0.5-1.0 kg ❑ Maternal storage of fats and protein 3.0 kg ❑ Maternal blood volume and interstitial fluid 2.0 kg Changes in the respiratory system  Dyspnea in the last trimester due to elevation of the diaphragm  Skin changes Pigmentation  Darker pigmentation occurs in the nipples and areolae, abdomen  Chloasma or pregnancy mask  Linea nigra  Stretch marks (Striae gravidarum) Changes in cardiovascular system Haemodilution - The blood volume increases during pregnancy by about 40-50% to meet the requirements of the placental circulation. - The plasma volume is increased more than the red cell volume therefore there is a state of haemodilution, which lead to physiological anemia of pregnancy Changes in cardiovascular system  Coagulability of blood is slightly increased during pregnancy. If it failed to increase, there would be danger of excessive bleeding at the time of delivery. Because coagulability does increase, the danger of venous thrombosis is present. Therefore careful observation and education about immobility is an important aspect of preventive care during pregnancy, labor and the postnatal period.  Minor discomfort during pregnancy Nausea and vomiting (morning sickness):About half of all pregnant women experience nausea and sometimes vomiting in the first trimester. Varicose veins: Swollen, purple veins which are common in the legs and around the vaginal opening during late pregnancy Heartburn: feeling burning sensation behind sternum.It can be reduced by eating smaller meals throughout the day and by avoiding lying down shortly after eating. Minor discomfort during pregnancy Bleeding gums : Gums may become spongier because blood flow increases during pregnancy, causing them easily bleed. A pregnant woman should continue to take care of her teeth and gums and go to the dentist for regular checkups. This symptom usually disappears after pregnancy. Minor discomfort during pregnancy Backache and lordosis Lordosis is excessive inward curvature, usually in the lower back. Proper posture and proper lifting techniques throughout the pregnancy can help reduce the strain on the back