Physiology of Pregnancy

1. Physiology of Pregnancy Weirong Gu Obsterics & Gynecology Hospital of Fudan university

2. 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

3. Contents • Fertilization, development, transport and implantation of fertilized ovum • Formation and function of fetal attachment • Maternal changes during pregnancy

4. Concepts Sperm capacitation Fertilization Acrosome reaction Zona reaction

5. 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

6. Acrosome reaction Acrosome ruptures, acrosomal enzymes release and lysis the radiate corona and zone pellucida The spermatozoon can penetrate and fuse with oocyte

7. 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

8. Fertilization The course of combination of the oocyte and sperm Time : 12h after ovulation Place : usually in ampulla of the oviduct (fallopian tube)

9. Development and transport of the zygote the volume doesn’t enlarge the morula (early blast) is fomulated early blastomere fomulated enter uterine cavity form blastomere by cleavage zona disappear blastocyst enlarge begin to move towards cavity after 30 hours late blastocyst implants in endometrium

10. Implantation • Late blastosphere implanted in endometrium • Apposition : at upper part of paries posterior uterus • Adhesion: with innner cell mass • Penetration: syncytiotrophoblast secrete proteinresolvase to lysis endometrium cells, stroma,and vessels

11. The necessary condition of implantation Disapearing of the zona pellucid Formation of syncytiotrophoblast Synchronizing development of blastocyst and endometrium Adequate progesterone

12. Changes of endomertium after implantation Basal decidua Ture decidua capsular decidua • 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

13. Embryo and fetal development Embryo the first 8 weeks from pregancy organs differentiated Fetus after 9 weeks from pregnancy organs matured

14. 4 gestational weeks8 gestational weeks balstoderm and body stalk recognized human shape formed，early cardiac tube pulse visible on ultrasound

15. 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. 16 Gestational Weeks • Fetal crown-rump length: 12 cm • Weight : 110 g • Gender can be determined by 14 weeks

17. 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.

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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)

24. Anatomy characters • Foramen ovale between interatrial septum • between aorta and pulmonary artery • between superior and inferior vena cava • Mixed arterial and venous blood • Ductus arteriosus • Foramen ovale • Ductus venosus

25. Hematology • Erythropoiesis • From yolk sac: 3 weeks • From liver: 10 weeks • From bone marrow and spleen: term (90%) • EPO production: engender quantity at 32nd week, so fetal red cell numbers increase • Fetal blood volume:125ml/kg of the fetus at term

26. Fetal hemoglobin • Fetal hemoglobin: early pregnancy • Adult hemoglobin: 32nd week • Term : fetal type Hb 25% • White cells • Leukocytes: emerge at 8 week in fetal circulation • Lymphocytes (antibody production): 12 week thymus and spleen

27. 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 Ⅱcells of the lung alveoli; active component is a specific lecithin or phosphatidyl glycerol

28. Gastrointestinal tract • Swallowing begins at 10-12 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

29. 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), 11-12 weeks(female)

30. Attachment of fetus Placenta Fetal membranes Umbilical cord Amniotic fluid

31. Placenta • An exchange organ between mater and fetus • Organization • Amniotic membrane • Chorion frondosum • Basal decidua

32. Chorion frondosum • 13-21 days after ovulation, villi fomulating gradually • Primary viilus • Syncytiotrophoblast trabecula arrange radially • Cytotrophoblast enter trabecula • Secondary villus • extra-mesodermenter trabecula • Third class villus Fetal capillary enter the stroma

33. Structure of placenta Round Weight: 450-650g Diameter: 16-20cm Thickness: 1-3cm thick in center and thin in margin

34. 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

35. 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

36. The way of substance exchange Simple diffusion Facilitated diffusion Active transportion Phagocytosis

37. 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)

38. Placental hormone level in pregnancy

39. 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

40. 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

41. 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) mother fetus adrenal glands (DHEA-S) placenta Liver (16OHDHEA-S)

42. 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 Fetal membrane • Chorion • Amnion • A double-layered translucent membrane • Become distended with fluid

43. 羊膜 绒毛膜 脐带 Umbilical cord Extends from the fetal umbilicus to the fetal surface of the placenta Length: 30-70cm, average : 50cm Diameter: 0.8-2.0cm Consist of 2 artery and 1 vein, Wharton jelly

44. 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

45. Feature of amniotic fluid pH: 7.20 Density: 1.007-1.025 Contained: water(98-99%) inorganic substance organic substance(1-2%) Early transparent Late slighty turbid (Suspended matter like vernix caseosa , dropped fetal epithelial cell)

46. 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

47. 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

48. Changes of reproductive system • Uterus • Capacity : 5ml - 5000ml • Weight: 50g – 1000g • Hypertrophy of muscle cells • Fundus > inferior portion > cervix (contractility at delivery) • Endometrium –decidua

49. Blood supply • Increases 4-6times (500-700ml/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

50. 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)