Obstetric emergency Dr. Miada Mahmoud Rady Lecture 1 Physiology of conception and physiological changes during pregnancy

Lecture outlines 1.Physiology of conception : ovulation, fertilization and implantation. 2.Function of the placenta. 3.Umbilical cord 4.Gestational period

Physiology of conception  It starts with ovulation.  Ovulation : expulsion of the ova into peritoneal cavity.  Expelled ovum is picked up by the fimbria of the fallopian tube.  Then the ovum gets fertilized by male sperm in the Outer Third Of The Fallopian Tube.

Fertilization to Implantation

 Fertilization : is fusion of genetic material from sperm and ovum into a single nucleus to form zygote.  Cell continuously divides as it moves down the fallopian tube to the uterus where it become Implanted. Physiology of conception

 Implantation : adherence of the Blastocytes stage into the endometrium, it takes place around 6 day post conception.  Implantation of ovum triggers the formation of the placenta.  placenta is fully formed by the 4 th week of gestation, before that corpus luteum supports the pregnancy. Physiology of conception

Function of the placenta 1.Serves to maintain fetus by supplying oxygen and nutrients and removing carbon dioxide and wastes 2.Serves as a protective barrier against most microorganisms 3.Serves to maintain pregnancy via secretion of hormones.

Umbilical cord It is vascular connection between fetus and mother: It contains : 1.One umbilical vein : carries blood rich in nutrients and oxygen to the fetus from the placenta. 2.Two umbilical arteries : carry carbon dioxide and wastes away from the fetus to the placenta.

Amniotic sac  It is fluid filled sac that surrounds the growing embryo.  Function of amniotic sac and fluid: 1.Serves as shock absorber for fetus; 2.Helps regulate fetal temperature; 3.Prevents adhesions between skin of fetus and other tissues. 4.Fetal cells slough off into this fluid and may be removed during a procedure called an amniocentesis.

Gestational period  Normally 38 weeks in average from date of conception.  but in practice it is calculated from the first day of the pregnant woman’s last menstrual period and it is estimated to be about 40 weeks ( as ovulation is about 2 weeks before the menstruation).

Summary 1.During the menstrual cycle one follicle releases an ovum which, if it becomes fertilized, develops into an embryo, and then a fetus. 2.The fallopian tubes transport the ovum from the ovary to the uterus. Once an egg is fertilized, it implants in the endometrium. 3.The fetus is enclosed in the amniotic sac. 4.The gestational period normally lasts 38 weeks.

Maternal Physiological changes during pregnancy

Lecture topics 1.Causes. 2.Changes in the uterus. 3.Fundal level. 4.Respiratory System Changes. 5.Cardiovascular System Changes. 6.Gastrointestinal system changes. 7.Urinary System Changes. 8.Skin changes.

Causes 1. Altered hormone levels. 2. Mechanical effects of enlarging uterus. 3. Increased uterine blood supply. 4. Increasing metabolic demands on the maternal system.

Changes in the uterus During pregnancy the uterus becomes bigger : 1.Before pregnancy, the uterus : Weighs about 2 g and Has a fluid capacity of about 10 mL. 2.At the end of the pregnancy, the uterus: Weighs as much as (1 kg) and Has the capacity to hold about 5,000 mL.

Fundal level Fundal level : it gives a rough estimate about the gestational age. Measured in centimeters vertically from the top of the pubic bone to the top of the fundus. If the measurement is different than expected, it could indicate: 1.Uterine growth problems or breech position (shorter). 2.Possibility of twins (longer).

Respiratory System Changes 1.Increase in oxygen demand so tidal volume and oxygen consumption. 2.Slight increase in respiratory rate. 3.Diaphragm pushed upward by growing uterus.

Cardiovascular System Changes 1.Maternal blood volume increases by 50% :  To meet fetus demand.  To adequately perfuse maternal organs.  To compensate for expected blood loss during labor. 2.Cardiac output and heart rate increases.

Cardiovascular System Changes  The heart workload increases significantly during both gestation and labor, So if the woman has heart disease or other cardiac compromise, this can result in: i.Ventricular failure ii.Pulmonary edema iii.Congestive heart failure iv.Pain and pressure of labor can result in cardiac arrest.

Gastrointestinal system changes 1.Nausea & vomiting are common in 1 st trimester. 2. Bloating and constipation common. 3.Delayed gastric emptying (due to slowed peristalsis).

Body Weight Changes  There is an average weight gain of about 12.3 kg due to : 1. Increased blood volume, intracellular and extracellular fluid 2. Increased breast tissue. 3. Increased proteins and fat deposits. 4.Uterine, placental and fetal growth.

Distribution Of Weight Gain Distribution Of Weight Gain

Urinary System Changes 1.Kidneys increase in size and volume. 2.Ureters increase in diameter.  Both leads to : I.Increased urinary frequency II.Increased chance of urinary tract infection if bladder is not emptied frequently.

Skin changes 1.Increased hair and nail growth along with changes in texture. 2.“Pregnancy mask”: brown and yellowish color changes to the face 3.Darkened skin around the areola, axilla, and genitalia 4.Linea nigra: a dark line of pigment down the abdominal midline

Summary 1.Physiologic changes during pregnancy can alter a woman’s response to trauma and create or exacerbate medical conditions. 2.Physiological changes of pregnancy affect various body organs and system.

Review questions  Regarding cardiovascular changes during pregnancy state what is true and what is false and correct false: a.Cardiac out put decreases during pregnancy. b.Labour can lead to heart failure in women with preexisting heart disease. c.Maternal blood volume increases by 50%. d.The heart workload decreases significantly during both gestation and labor

Review questions  Enumerate the possible complication of pregnancy and labour in women with pre- existing heart disease?