Fill in the Blanks First 5 weeks of PregnancyOnline version Ovulation up to week 5 by Heather Shirley 1 first conception embryologic Gestational Conceptual age aka age considers is first day of pregnancy . age aka menstrual age considers day of last menstrual period is beginning of gestation . 2 first Gestational age aka menstrual age considers day of last menstrual period is beginning of gestation . 3 Zygote Fetus Embryo is the conceptus 12 days after conception , during implantation process is the conceptus from time of implantation until end of 10th week menstrual age is the conceptus after first 10 week s 4 14 progesterone cleavage pellucida corpus zona Fertilization luteum morula zygote ovulation Ampulla During 28 - day menstrual cycle , a mature ovum typically released on day this is called . The follicle that released it forms the and begins secreting . occurs within the distal fallopian tube ( ) 1 to 2 days after ovulation . Fertilized conceptus is now called a which includes an egg nucleus , sperm nucleus , and a membrane surrounding it called the . The zygote undergoes rapid cellular division to form 16 - cell this dividing is called . 5 12 embryo hCG 32 coelom placenta Secondary differentiated primary wall proliferation trophoblastic decidua blastocyst enzymes 23 Further cell proliferation brings morula to stage and it typically enters uterus 4 to 5 days after fertilization containing + cells The cells are not just copies of the originals , they have now into new cells that will form into new human parts . The " inner cell mass " forms the while the outer cells along the perimeter will become the and secrete hCG causes uterine endometrium to convert to , a glycogen rich mucosa that nourishes early pregnancy . Implantation into uterine decidua completed within days after fertilization During implantation , produced by trophoblasts " eat into " decidual tissue . This creates spaces for trophoblastic cell . At end of implantation process , zygote has buried itself within one of uterus . Implantation bleeding - when this process results in light vaginal bleeding about same time as expected menstrual period . Within the implanted conceptus , the inner cell mass matures into the embryonic disc ( future embryo ) and primary yolk sac . At approximately days menstrual age , yolk sac is pinched off by extra embryonic , forming the secondary yolk sac . yolk sac is the yolk sac seen sonographically throughout first trimester . 6 Embryonic flat heartbeat 10th C 35 human Cardiovascular Phase is between weeks 4 and 10 system undergoes rapid development , with initial occurring between 5½ and 6 weeks . Embryo appearance changes from , disk - like configuration to - shaped structure and develops a recognizable appearance During this period , crown - rump length ( CRL ) develops rapidly , measuring mm by end of week . 7 larger organs Fetal half Weeks 11 and 12 constitute the beginning of this period when there is continued growth of and structures formed during embryonic period . The fetal head is disproportionately than rest of fetus ( the same size as the body ) , constituting one of CRL . 8 3000 1 myometrial fundal capsularis basalis eccentrically trophoblastic Multiple capsularis echogenic basalis >3 Ectopic 5 chorionic embryo later Incorrect decidual Incorrect slowly Qualitative trophoblastic chorionic Smooth Embryonic hCG : urine results are positive or negative Quantitative hCG : provides specific levels of hCG in blood . Provide a specific number value . Normal gestational sac is expected to be seen when hCG level is mIU / ml or greater . With Down ? s Syndrome hCG levels plateau and fall more Greater than expected hCG levels seen with dates ( further along than expected ) , Gestational disease & gestations Lower than expected levels of hCG associated with dates ( not as far along as expected ) , pregnancy , demise / abnormal IUP / impending miscarriage . Gestational Sac aka sac is the first visual evidence of IUP during week . It appears as 1 - to 2 - mm sac with ring having sonolucent center which represents the cavity . Circumferential echogenic rim seen surrounding gestational sac represents tissue and associated reaction Echogenic ring around gestational sac divided into o Decidua - Portion on or burrowing side of conceptus . o Decidua - Villi covering developing . The double decidual sac sign is the interface between decidua and decidua . Normal gestational sac features o placed in relation to endometrial cavity , secondary to its implantation o location noted o Round or slightly oval in shape o contours o Decidual wall thickness mm ? Gestational sac grows at predictable rate of mm / day in early pregnanc y 9 Hematopoiesis stalk >12 15 Yolk 5½ amniotic endoderm >90% nutrients 8 5 6 10 chorionic 12 12 Sac should be seen when mean sac diameter is mm . Routinely visualized between and weeks of gestation o Provide to developing embryo o : Formation of blood o Development of embryonic At approximately weeks gestation , with amniotic cavity expansion , the yolk sac , which lies between and membranes , detaches from yolk . ? Visualization of yolk sac predicts viable pregnancy in of cases . ? Failure to visualize yolk sac , with minimum of - mm MSD , using transvaginal sonography , is suspicious for abnormal pregnancy . o Transabdominal studies have shown that yolk sac should be seen within mean sac diameters of to mm and should always be visualized with mean sac diameter of 20 mm . ? Normal diameter should not exceed mm measured from inner edge to inner edge ? Typically , yolk sac resorbs and is no longer seen sonographically by weeks .
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