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

pregnancy The condition of being with child or gravid, 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

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 Semen enters vagina

acrosome reaction Acrosome rupture, acrosomal enzyme released and lysis the radiate corona and zone pellucida The spermatozoons 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

fertilization The course of combination of the oocyte and sperm Time : 12h after ovulation Place : usually in ampulla of the oviduct (fallopian tube) It onset 12h after ovulation usually in ampulla of the oviduct (fallopian tube)

development and transport of the zygote 3days after ovulation, the morula (early blast) is fomulated 4days after ovulation, the late blast is fomulated 6-7days after ovulation, the egg imbeds in the uterus Cleavage , blastomere 72h morula 4d, early blastocyst, Enter uterine cavity 5-6d, zona disappear 11-12d, late blastocyst,implantation

implantation Late blastosphere implanted in endometrium Apposition Adhesion penetration

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 Capsular decidua Ture decidua

Embryo and fetal development Embryo: the first 8 weeks from pregancy Fetus: after 9 weeks from pregnancy ,human shape

12 Gestational Weeks The uterus usually is just palpable above the symphysis pubis, and the fetal crown-rump length is 6 to 7 cm. Centers of ossification have appeared in most of the fetal bones, and the fingers and toes have become differentiated. Skin and nails have developed and scattered rudiments of hair appear. The external genitalia are beginning to show definitive signs of male or female gender. The fetus begins to make spontaneous movements.

16 Gestational Weeks fetal crown-rump length: 12 cm weight : 110 g Gender can be determined by 14 weeks Gender can be determined by experienced observers by inspection of the external genitalia 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. This is the midpoint of pregnancy as estimated from the beginning of the last menses. The fetus now weighs somewhat more than 300 g, and weight begins to increase in a linear manner. From this point onward, the fetus moves about every minute and is active 10 to 30 percent of the time (DiPietro, 2005). The fetal skin has become less transparent, a downy lanugo covers its entire body, and some scalp hair has developed.

24 Gestational Weeks The fetus now weighs 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---placenta---mother 1 umbilical vein (full of oxygen) 2 umbilical arteries (lack of oxygen) Mixed blood ( vein and artery) Ductus arteriosus Foramen ovale Ductus venosus

hematology erythropoiesis EPO production: 32nd week From yolk sac: 3 weeks From liver: 10 weeks From bone marrow and spleen: term (90%) EPO production: 32nd week Fetal blood volume:125ml/kg of the fetus at term

Fetal hemoglobin White cells Fetal hemoglobin: early pregnancy Adult hemoglobin: 32nd week Term : fetal type Hb 25% White cells Leukocytes: 8 week 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 Ⅱcells of the lung alveoli; active component is a specific lecithin or dipalmitoylphosphatidylcholine

Gastrointestinal tract Swallowing begins at 10-12 weeks, 16weeks, gastrointestinal function is established Liver Hepatic enzyme is lack during fetal period, a very limite capacity for converting free bilirubin to conjugating bilirubin

Urinary system Genital 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)

Attachment of the fetal Placenta Fetal membranes Umbilical cord Amniotic fluid

placenta An exchange organ between maternal and fetal Organization Amniotic membrane Chorion frondosum Basal decidua

Chorion frondosum 13-21 days after ovulation, villi fomulating gradually Primary viilus Syncytiotrophoblast cytotrophoblast Secondary villus Third class villus Fetal capillary enter the stroma

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

Function of placenta One important function of placenta is substance exchange between maternal and fetal Transfer oxygen and nutrients from the mother to the fetus and conversely the transfer of carbon dioxide and other metabolic wastes from fetus to mother

The position exchange is VSM(vasculosyncytial membrane) 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

The function of placenta Gas exchange Suply of nutrition Depletion of fetal product of metabolism Defence function Hormone synthesis Human chorionic gonadotropin (HCG) Human placental lactogen (HPL) Pregnancy specific ß-glycoprotein (PS ß1G) Human chorionic thyrotropin(HCT) Estrogen, P, Oxytocinase, heat stable alkaline phosphatase(HSAP)

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

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 amnion, yolk sac

Amniotic fluid Source: Absorse: early from serum dialysis Mid-pregnancy from fetal urine Late from fetal lung Absorse: fetal membrane Umbilical cord Fetal skin Fetal fetal swallowing (500ml/day) Amniotic exchange: between maternal and fetal 400ml/h Volume: 50ml at 12 weeks, 400ml at midpregancy, 1000ml at term

Volume of amniotic fluid 8 weeks: 5-10ml 10 weeks: 30ml 20 weeks: 400ml 38 weeks: 1000ml

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

The function of amniotic fluid Protect maternal and fetus Move freely Warm Protect mother Prevent infection Serve to cushion the fetus, allowing musculoskeletal development and protecting it from trauma Maintains temperature and has a minimal nutritive function Promote the normal growth and development of the lungs and gastrointestinal tract

Maternal changes during pregancy The maternal system may produce a series of changes in order to adapt to the needing of fetal growth and development influenced by placenta hormone and neuro-endorine

Changes of reproductive system Uterus Capacity : 5ml - 5000ml Weight: 50g – 1000g Hypertrophy of muscle cells fundus-inferior portion-cervix Endometrium –decidua corpus: Size: become enlargement and soft from 7*5*3cm pre-pregnancy to 35*25*22cm at term Capacity : become enlargement from 5ml pre-pregnancy to 5000ml at term Weight: be increased from 50g pre-pregnancy to 1000g at term thickness: become thickness and the thickest at mid-period from 1cm pre-pregnancy to 2-2.5cm at term The rate of the hypertrophy of different parts varies (fundus-inferior portion-cervix) so that the contractility decreases from fundus to cervix, the fetus is delivered

Blood supply Uterine contraction increases 4-6times (500-700ml/min) Most transported to the placenta(80-85%) Uterine contraction Braxton hicks contraction-contraction without pain Rare, irregular,and asymmetric Intrauterine pressure: 5-25mmHg, duration <30s blood flow increased significantly upto 500-700ml/min, increases 4-6times and most of blood flow is transported to the placenta(80-85%)

Isthmus Cervix softer and longer (1,7-10cm) lower segment Colored Cerical mucus plugs Isthmus: softer and longer (1,7-10cm) lower segment Cervix: increased vascularity, edema of the entire cervix, hyperplasia of cervical glands. be soft and coloration or stain secrete amount of mucus avoiding the uterus cavity suffer from infection

Maternal Physiology

Changes of ovary Enlarged Ovulation and new follicle is stopped. Luteum produces E and P from 7 weeks of pregnancy, but start to atrophy after 10 weeks of pregnancy, the fuction 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 An increase in size and a nodular sensation due to the hypertrophy of the mammary alveoli, the nipples soon become larger, more deeply pigmented and more erectile. Scattered around the areola are some roundish nodules called Montgomery tubercles which result from the hypertrophy of the sebaceous glands

Changes of the circulation Heart border: become enlargement, move upward, hypertrophy of cardiac muscle Heart rate: increased 10-15 beat per min at the late pregnancy Heart volume: increased 10% at the late pregancy 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. A certain degree of rotation is believed to take place. The capacity increases by 10%, the heart rate increases by 10-15bpm

Cardiac output Very important for fetal growth and development Increase by 30%, from 10weeks and up to the peak at 32 weeks 80ml/bp and keeps the level to the term pregnancy

Blood pressure changes due to pregancy No obvious change in systolic pressure Mild decreased 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 ---cm. of hypotension

Changes of blood system Volume: increased (30-45%) from 6-8 weeks , peak at 32-34weeks, about 1500ml (including plasma 1000ml and 500ml erythrocytes---hemodilution)

Changes of blood component Red cell Hb decreasd 110g/L Hct : 38%--31% WBC: Slightly increase neutrophilic granulocyte increased Coagulating power of blood: Albumin: 35g/L

Urinary system Kidney Ureter: dilated ( P ) Bladder Renal plasma flow (RFP): 35% Glomerular filtration rate (GFR): Ureter: dilated ( P ) Bladder Frequent micturation Both RPF, and GFR increase by about 35% and 50% respectively, the metabolites of the gravida/fetus can be excreted. Under the influence of progesterone, a condition of atonia in relaxation or loss of irritability not only of uterus, but also of the ureters, large bowel and bile ducts---dilatation of ureters and renal pelvis associated with stasis of urine---acute nephropyelitis especially in the right side

Respiratory system R rate : slightly Vital capacity: no change Tidal volume: 40% Functional residual capacity: O2 consumption: 20%

Gastrointestinal system Gastric emptying time is prolonged nausea The motility of large bowel is diminished constipation Liver function: unchanged Digestive sys: estrogen---gingiva---hyperplasia progesterone---atonia of stomach and bowel---heart burn, vomit, constipation

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, and 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) Thyroid LH/FSH PRL TSH and ACTH Thyroid Enlarged (TSH and HCG ) Thyroxine and TBG free T3 T4 unchanged Pituitary gland: the anterior lobe hypertrophy High level of E and P---inhibites Gn releasing PRL: increases from 7w, peak ante-delivery Adrenalin cortex: the level cortisol and aldosterone increases by 3 and 4 times respectively Thyroid gland: the enlargement usually concomitant with normal pregnancy due to hypertrophy of adenomatous tissue, to an increase blood supply and to the formation of new follicles. But most thyoxin is connected with thyroxin binging globulin, so 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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