Weirong Gu Obsterics & Gynecology Hospital of Fudan university Physiology of Pregnancy
Pregnancy The condition of being with baby, is the process of embryo and fetus growing and developing in the uterus From the fertilization to the expelling of the fetus with placenta and membranes last 40 weeks from the first day of the last menstrual period
Contents Fertilization, development, transport and implantation of fertilized ovum Formation and function of fetal attachment Maternal changes during pregnancy
Concepts Sperm capacitation Fertilization Acrosome reaction Zona reaction
Sperm capacitation Spermatozoons contact with endometrium The α-/β- amylase remove the decapacitation factor on spermatozoons’ acrosomal enzyme The spermatozoons with the ability of fertilization(capacitation)in uterus and fallopian tubes
Acrosome reaction Acrosome ruptures, acrosomal enzymes release and lysis the radiate corona and zone pellucida The spermatozoon can penetrate and fuse with oocyte
Zona reaction The cortical particle of cytoplasm release lysosomal enzyme Zona structure changed and sperm receptor degenerated to prevent other sperm into the zona ——single oocyte fertilization
Fertilization The course of combination of the oocyte and sperm Time : 12h after ovulation Place : usually in ampulla of the oviduct (fallopian tube)
Development and transport of the zygote begin to move towards cavity after 30 hours form blastomere by cleavage the volume doesn’t enlarge the morula (early blast) is fomulated early blastomere fomulated enter uterine cavity zona disappear blastocyst enlarge late blastocyst implants in endometrium
Implantation Late blastosphere implanted in endometrium Apposition : at upper part of paries posterior uterus Adhesion: with innner cell mass Penetration: syncytiotrophoblast secrete protein resolvase to lysis endometrium cells, stroma,and vessels
The necessary condition of implantation Disapearing of the zona pellucid Formation of syncytiotrophoblast Synchronizing development of blastocyst and endometrium Adequate progesterone
Changes of endomertium after implantation The endometrium changes into dicedua Basal decidua: contact with blastomere Capsular decidua: cover the blastomere Ture decidua: covers cavity, fuse with capsular decidua at 14-16w Ture decidua Basal decidua capsular decidua
Embryo and fetal development Embryo the first 8 weeks from pregancy organs differentiated Fetus after 9 weeks from pregnancy organs matured
4 gestational weeks 8 gestational weeks balstoderm and body stalk recognized human shape formed , early cardiac tube pulse visible on ultrasound
12 Gestational Weeks Uterus palpable above the symphysis pubis Fetal crown-rump length : 6 to 7 cm Fingers and toes differentiated Skin and nails developed The external genitalia beginning to show definitive signs of male or female gender Begin to make spontaneous movements
16 Gestational Weeks Fetal crown-rump length: 12 cm Weight : 110 g Gender can be determined by 14 weeks
20 Gestational Weeks Weight: more than 300 g, and increase in a linear manner Movement: about every minute and is active 10 to 30 percent of the time Skin : less transparent, a downy lanugo covers entire body, some scalp hair has developed.
24 Gestational Weeks Weight: about 630 g The skin is characteristically wrinkled, and fat deposition begins The head is still comparatively large, and eyebrows and eyelashes are usually recognizable The canalicular period of lung development, during which the bronchi and bronchioles enlarge and alveolar ducts develop, is nearly completed A fetus born at this time will attempt to breathe, but many will die because the terminal sacs, required for gas exchange, have not yet formed
28 Gestational Weeks The crown-rump length is approximately 25 cm, and the fetus weighs about 1100 g The thin skin is red and covered with vernix caseosa The pupillary membrane has just disappeared from the eyes The otherwise normal neonate born at this age has a 90-percent chance of survival without physical or neurological impairment
32 Gestational Weeks The fetus has attained a crown-rump length of about 28 cm and a weight of approximately 1800 g The skin surface is still red and wrinkled
36 Gestational Weeks The average crown-rump length of the fetus is about 32 cm, and the weight is approximately 2500 g Because of the deposition of subcutaneous fat, the body has become more rotund, and the previous wrinkled appearance of the face has been lost
40 Gestational Weeks This is considered term from the onset of the last menstrual period The fetus is now fully developed The average crown-rump length is about 36 cm, and the weight is approximately 3400 g
Physiology of fetus Circulation Fetus connects with mother by placenta and umbilical cord umbilical cord 1 umbilical vein (full of oxygen) 2 umbilical arteries (lack of oxygen)
Anatomy characters between aorta and pulmonary artery Foramen ovale between interatrial septum between superior and inferior vena cava Mixed arterial and venous blood Ductus arteriosus Foramen ovale Ductus venosus
Hematology Erythropoiesis From yolk sac: 3 weeks From liver: 10 weeks From bone marrow and spleen: term (90%) EPO production: engender quantity at 32 nd week, so fetal red cell numbers increase Fetal blood volume:125ml/kg of the fetus at term
Fetal hemoglobin Fetal hemoglobin: early pregnancy Adult hemoglobin: 32 nd week Term : fetal type Hb 25% White cells Leukocytes: emerge at 8 week in fetal circulation Lymphocytes (antibody production): 12 week thymus and spleen
Fetal respiratory system The timetable of lung maturation and identification of biochemical indices of functional fetal lung maturity are important to the obstetrician A sufficient amount of surface-active materials in the amniotic fluid is evidence of fetal lung maturity Surfactant: produced by type Ⅱ cells of the lung alveoli; active component is a specific lecithin or phosphatidyl glycerol
Gastrointestinal tract Swallowing begins at weeks Gastrointestinal function is established at 16weeks Liver Hepatic enzyme is lack during fetal period, a very limite capacity for converting free bilirubin to conjugating bilirubin
Urinary system The fetal kidneys start producing urine at 12 weeks’ gestation 7-14ml/d by 18 weeks 27ml/hr or 650ml/d at term Genital system Genital organ is developed from 9 weeks of pregnancy(male), weeks(female)
Attachment of fetus Placenta Fetal membranes Umbilical cord Amniotic fluid
Placenta An exchange organ between mater and fetus Organization Amniotic membrane Chorion frondosum Basal decidua
Chorion frondosum days after ovulation, villi fomulating gradually Primary viilus Syncytiotrophoblast trabecula arrange radially Cytotrophoblast enter trabecula Secondary villus extra-mesoderm enter trabecula Third class villus Fetal capillary enter the stroma
Structure of placenta Round Weight: g Diameter: 16-20cm Thickness: 1-3cm thick in center and thin in margin
Functions of placenta One important function of placenta is substance exchange between mater and fetus Gas exchange: oxygen, carbon dioxide Supply of nutrition Depletion of fetal product of metabolism
VSM (vasculosyncytial membrane) ——the position of exchange VSM is comprised of Syntrophoblastocyte Basal membrane of syntrophoblastocyte Stroma of villi Basal membrane of capillary Endothelium of capillary
The way of substance exchange Simple diffusion Facilitated diffusion Active transportion Phagocytosis
Other functions of placenta Defence function: limited Hormone synthesis Human chorionic gonadotropin (HCG) Human placental lactogen (HPL) Pregnancy specific ß-glycoprotein (PS ß1G) Human chorionic thyrotropin(HCT) Estrogen, Progestin, Oxytocinase, heat stable alkaline phosphatase(HSAP)
Placental hormone level in pregnancy
Human chorionic gonadotropin (HCG) Detection of hCG in maternal blood and urine provides the basis for endocrine tests of pregnancy This hormone is a glycoprotein with a high carbohydrate content The molecule is a heterodimer composed of two dissimilar subunits, designated α and ß, which are noncovalently linked The ß -subunit is identical to those of luteinizing hormone (LH), follicle- stimulating hormone (FSH), and thyroid-stimulating hormone (TSH). HCG prevents involution of the corpus luteum, the principal site of progesterone formation during the first 6 weeks
Human placental lactogen (HPL) Promote maternal lipolysis with increased levels of circulating free fatty acids. This provides a source of energy for maternal metabolism and fetal nutrition An anti-insulin or "diabetogenic" action that leads to increased maternal insulin levels. This favors protein synthesis and provides a readily available source of amino acids to the fetus A potent angiogenic hormone that may play an important role in the formation of fetal vasculature
Estrogen Estrogen Biosynthesis The pathways of estrogen synthesis in the placenta differ from those in the ovary of nonpregnant women Dehydroepiandrosterone sulfate (DHEA-S), secreted in prodigious amounts by the fetal adrenal glands DHEA-S is converted to 16- hydroxydehydroepiandrosterone sulfate (16OHDHEA-S) in the fetal liver DHEA-S and 16OHDHEA-S are converted in the placenta to estrogens that is, 17-estradiol (E2) and estriol (E3) motherfetus adrenal glands (DHEA-S) Liver (16OHDHEA-S) placenta
Fetal membrane Chorion Amnion A double-layered translucent membrane Become distended with fluid 胎膜外层为逐渐退化 的平滑绒毛膜 胎膜内层为羊膜, 为无血管膜
Umbilical cord Extends from the fetal umbilicus to the fetal surface of the placenta Length: 30-70cm, average : 50cm Diameter: cm Consist of 2 artery and 1 vein, Wharton jelly 羊膜 绒毛膜 脐带
Amniotic fluid Source: early from serum dialysis Mid-pregnancy from fetal urine Late from fetal lung Absorse: fetal membrane Umbilical cord Fetal skin Fetal swallowing (500ml/day) Amniotic exchange: between mater and fetus 400ml/h Volume: 50ml at 12 weeks, 400ml at midpregancy, 1000ml at term
Feature of amniotic fluid pH: 7.20 Density: Contained: water(98-99%) inorganic substance organic substance(1-2%) Early transparent Late slighty turbid (Suspended matter like vernix caseosa, dropped fetal epithelial cell)
The functions of amniotic fluid Protect fetus Move freely, allow musculoskeletal development, promote the normal growth and development of the lungs and gastrointestinal tract Cushion the fetus, protect it from trauma Warm, maintains temperature Protect mother Prevent infection from genital tract
Maternal changes during pregancy Produce a series of changes Influenced by placenta hormone and neuro-endocrine Adapted to the needing of fetal growth and development
Changes of reproductive system Uterus Capacity : 5ml ml Weight: 50g – 1000g Hypertrophy of muscle cells Fundus > inferior portion > cervix (contractility at delivery) Endometrium –decidua
Blood supply Increases 4-6times ( ml/min) Most transported to the placenta(80-85%) Uterine contraction Braxton hicks contraction——contraction without pain from 12-14w Rare, irregular,and asymmetric Intrauterine pressure: 5-25mmHg, duration <30s
Isthmus Softer and longer (1 7-10cm) Fomulate lower segment after 12w Cervix Increased vascularity colored Edema of the entire cervix soft Hyperplasia of cervical glands cerical mucus plugs (avoiding the uterus cavity suffer from infection)
51 corpus Isthmus cervix lower segment Hypertrophy of muscle cells Fundus > inferior portion > cervix
Changes of ovary Enlarged Ovulation and new follicle is stopped Luteum produces E and P from 7 weeks of pregnancy Start to atrophy after 10 weeks of pregnancy The function is replaced by placenta
Fallopian tubes: is prolonged but not hypertrophy Vagina: dilated and soft violet coloration desquamation of epithelium with more glycogen acidity pH (anti- bacteria) Vulva: pigmentation Ligaments: relaxed
Breasts Increasing in size and a nodular sensation due to the hypertrophy of the mammary alveoli The nipples larger, more deeply pigmented and more erectile Montgomery tubercles Scattered around the areola roundish nodules result from the hypertrophy of the sebaceous glands
Changes of the circulation The growing uterus pushes the diaphragm upward, with the result that the heart is displaced to the left, upward and somewhat in the direction of the anterior chest wall Heart border: become enlargement, move upward, hypertrophy of cardiac muscle Heart rate: increased beat per min at the late pregnancy Heart volume: increased 10% at the late pregancy
Cardiac output Very important for fetal growth and development Increase by 30%, from 10 weeks and up to the peak at 32 weeks 80ml/bp and keeps the level to the term pregnancy
Blood pressure No obvious change in systolic pressure Mild decrease in diastolic pressure Vein pressure No significantly changes in upper limb vein pressure Lower limb vein pressure increased demonstrable in later months of pregnancy because of the disturbance of vein reflux Supine hypotension syndrom: supine position for a long time--- inferior vene cava compressed---back volume ---output ---Bp ---hypotension
Changes of blood system Volume Increased (30-45%) from 6-8 weeks Peak at 32-34weeks, about 1500ml (including plasma 1000ml and erythrocytes 500ml--- hemodilution) ——physiologic anemia
Changes of blood component Red cell Hb decreased 110g/L Hct : 38%--31% WBC: Slightly increase Neutrophilic granulocyte increased Coagulating power of blood: Albumin: 35g/L
Urinary system Kidney Renal plasma flow (RFP): 35% Glomerular filtration rate (GFR): 50% Ureter: dilated ( P ) Bladder Frequent micturation
Respiratory system R rate : slightly Vital capacity: no change Tidal volume: 40% Functional residual capacity: O 2 consumption: 20%
Gastrointestinal system Gastric emptying time is prolonged nausea The motility of large bowel is diminished constipation Liver function: unchanged
Skin The pigmentation of the areola, linea alba, vulva, occasionally irregularly shaped Brownish patches of varying size appear on the face and neck, the cloasma or the mask of pregnancy, which fortunately usually disappears after delivery
During late months of pregnancy, reddish, slightly depressed streaks often develop in the skin of abdomen Sometimes also in the skin covering the breasts and the thighs These striae gravidarum occur in about ½ of all pregnancies
Endocrine changes Pituitary ( hypertrophy) Luteinizing/Follicle stimulating hormone Prolactin Thyroid stimulating hormone and Adrenocorticotropic hormone Thyroid Enlarged (TSH and HCG ) Thyroxine and TBG free T3 T4 unchanged no hyperthyroidism occurs
Metabolic changes BMR: mildly rising Weight: from 13w increases by 350g per week, about 12.5kg during the entire pregnancy Metabolism of carbohydrate Fasting-sugar lower due to higher insulin-secretion Insulin-resistant factors Fat metabolism: deposit of fat increasing chareterized by a hyperlipemia and a tendency to ketosis
Protein metabolism: positive nitrogen balance Water metabolism: water-retention of about 7L Mineral metabolism: in the late months of gestation Calcium and iron supplying---to avoid deficiency of calcium and iron
Bone, joint, and ligament Bone: no changes normally Joint and ligament: relaxin---loosening of joint and ligaments---the birth canal widened
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