Fetal development

Knowledge on fetal development will guide you to know the sequential development of fetus.

1. PREPARED BY: SRUJANI SWETASINA DASH NURSING TUTOR G.N.M.SCHOOL, A.N.M.M.C.H, GAYA FETAL DEVELOPMENT

2. OBJECTIVES To discuss the periods of development. To elaborate sequential development of fetus.

3. PERIODS OF FETAL DEVELOPMENT The fetal development is divided into 3 periods: Ovular Period- Begins from fertilization and lasts upto 2 weeks. Embryonic Period- Starts from 3 rd week following fertilization and lasts upto end of 7 th week. Fetal Period- Begins from 8 th week following fertilization until birth.

4. SEQUENTIAL DEVELOPMENT DURING OVULAR PERIOD (0-14 TH DAY) TIME IMPORTANT EVENTS 0-Hr Fertilization 30-Hrs 2- Cell Stage ( Blastomere ) 40-50 Hrs 4- Cell Stage 72 -Hrs (3 rd Day) 16 Cell Stage 96- Hrs (4 th Day) 16-64 Cell Stage ( Morula ), Morula enters uterine cavity 5 th Day Blastocyst 6 th -7 th Day Zona Pellucida disappears Interstitial Implantation occurs 8 th Day Differentiation of inner cell mass into bilaminar embryo: Ectoderm & Endoderm Differentiation of Trophoblast into 2 layers: Cytotrophoblast & Syncitiotrophoblast 10 th -11 th Day Interstitial Implantation completed 13 th Day Primary Villi

5. SEQUENTIAL DEVELOPMENT DURING EMBYONIC PERIOD (3 RD WEEK –END OF 7 TH WEEK) TIME IMPORTANT EVENTS 16 th Day Secondary Villi 21 st Day Tertiary Villi Fetal Heart is formed 3 rd Week Mesodermal Germ layer appears Neural Tube(rudiment of Brain & Spinal Cord ) is formed. Notochord (rudiment of vertebral column) is formed Primitive blood cells are formed 4 th Week Heart starts to beat Longitudinal & transverse folding of embryonic disc which converts embryo into curved & cylindrical form. Rudiments of ear ( otit pits), arms (arm buds), leg (leg buds), Facial and neck structures forms. 5 th Week Rapid brain development occurs resulting in extensive growth of head Growth starts from cephalic to caudal end Eyes are developed with retinal pigment, lens 6 th Week Nose, mouth, palate begins to start Neural tube closes Eyelids become visible Placenta development begins. 7 th Week Neck region is established Urogenital organs begins to develop. Arms & legs are fully developed with clearly well defined fingers & toes

6. SEQUENTIAL DEVELOPMENT DURING FETAL PERIOD (8 TH WEEK –UNTIL BIRTH) TIME IMPORTANT EVENTS 8 th Week All essential structures have developed Embryo has distinct human characteristics and hence marks the beginning of fetal period Fetus is 3 cm in length. 9 th Week- 12 th Week (3 rd Month) Intestine are fully developed External genitalia have male & female characteristics but not fully dev eloped. Anus is formed Fetus can swallow, urinate, move specific parts of limbs Open and shut mouth Eyelids are fused Fetal heart rate can be detected by doppler Placenta development is completed by 12 th weeks Fetal circulation is functioning Length-6 to 8 cm Weight- 15-30 gms 13 th Week- 16 th Week (4 th Month) Body growth accelerates Sex is clearly distinguishable by 14 th week Rapid skeletal development Lanugo hair appears on head Stronger fetal movement felt by mother at the end of 16 th week. (Quickening) Meconium in gut CRL-11.5 cm Weight- 99 to 113 gms contd ………..

7. SEQUENTIAL DEVELOPMENT DURING FETAL PERIOD (8 TH WEEK –UNTIL BIRTH) TIME IMPORTANT EVENTS 17 th Week- 20 th Week (5 th Month) Visible & frequent fetal movement Quickening may experienced by mother around 18 th week (if not felt earlier) Vernix caeseosa covers body Lanugo covers body especially on back FHS heard on auscultation Skin wrinkled due to less fat CRL- 13 to 14 cm FL- 19 cm Weight- 435 to 465 gms 21 st Week- 24 th Week (6 th Month) Hair growth is prominent & fetus is covered with lanugo Skin red and wrinkled with little subcutaneous fat Eyebrows & eyelids are formed Periods of sleep & activity Responds to sound (startle reflex) Most organs are capable of functioning CRL- 20 cm FL- 26 cm Weight- 780- 820 gms 25 th Week- 28 th Week (7 th Month) Eyelids reopen Respiratory movements seen Lungs are developed enough to provide sufficient gas exchange Suckling reflex is stronger Body becomes proportioned Survival is possible if born with life support system CRL-22.5 cm FL- 30 cm Weight- 1200 to 1250 gms contd ………..

8. SEQUENTIAL DEVELOPMENT DURING FETAL PERIOD (8 TH WEEK –UNTIL BIRTH) TIME IMPORTANT EVENTS 29 th Week- 32 nd Week (8 th Month) Respond to external stimuli Nails extend to finger tips Increase muscle & fat CRL- 27.5cm FL- 32 cm Weight- 1800 to 2100 gms 33 rd Week- 36 th Week (9 th Month) Lanugo hair disappears Skin is smooth Left testis descend into scrotum Increased fat makes body more rounded CRL- 31 cm FL- 35 cm Weight- > 2250 gms 37 th Week- 40 th Week (10 th Month) Vernix caeseosa mainly seen in skin folds and creases. Body organs mature. Lanugo fully dissappear except on shoulders. Both testes descended to scrotum. Full growth and development attained and fetus is ready to born CRL-35 cm FL- 50 cm Weight- > 3200 gms

9. SUMMARY Fetal development has 3 periods – Ovular, Embryonic and fetal. Blastocyst penetrates into the compact layer of endometrium called as implantation. This is the final stage which confirms conception. Blastocyst differentiates into inner cell mass and trophoblast . Fetus, amnion and umbilical cord develops from inner cell mass. Placenta and chorion develops from trophoblast . Placenta is an essential structure which provides nourishment to fetus and connects mother with fetus. Placental development begins at 6 th week and completed by 12 th week. During ovular and embryonic periods, the development of all essential organs of fetus occurs. It is a crucial period of pregnant woman. Embyro has human characteristics at 8 th week which marks the beginning of fetal period. During fetal period the growth and development occurs. Growth of fetus accelerates at 4 th month. At 10 th month fetus is ready to born.

10. REFERENCES Dutta D.C, Textbook of Obstetrics, Jaypee Brothers Publishers, 8 th Edition, Pg. No. 23- 31 Jacob Annama , A Comprehensive Textbook of Midwifery, Jaypee Brothers Publishers, 2 nd Edition, Pg. No. 71- 87

11. ASSIGNMENT Draw the schematic diagram of embryonic and fetal development in class notebook. Draw or download colored diagrams as per sequential development during embryonic and fetal development.

12. EVALUATION Answer following questions: When does fetal period starts? Which month the body growth accelerates? The fetal movements felt by mother for the first time is called as _________. Define lanugo and vernix caeseosa ? Placenta development begins at _________ week and completed at __________week. Survival is possible at ___________ month if born earlier. Lanugo disappears at _________ month. When does zona pellucida disappears? Name the rudiment of brain & spinal cord. Trophoblast differentiate into ______________ & ______________. Bilaminar gem disc are _______________ & ______________. Deeper penetration of blastocyst into compact layer of endometrium is called as ____________ The stage in which cells appears a cluster of ball resembling a mulberry is ______________ Name the rudiment of vertebral column. At what week the embryo has distinct human characteristics.

13. ANSWER KEY Answer following questions: When does fetal period starts? Ans : 8 th week until birth ii. Which month the body growth accelerates? Ans : 4 th month iii. The fetal movements felt by mother for the first time is called as Quickening iv. Define lanugo and vernix caeseosa ? Ans : Lanugo is the first hair in fetus & fine & soft which covers the body and limbs of fetus. Vernix caeseosa is a waxy, sticky substance coating on skin of fetus and newborn baby whci act as thermal insulator. v. Placenta development begins at 6 th week and completed at 12 th week. vi. Survival is possible at 7 th month if born earlier. vii. Lanugo disappears at 9 th month. viii. When does zona pellucida disappears? Ans : 6 th - 7 th Day ix. Name the rudiment of brain & spinal cord. Ans : Neural tube x. Trophoblast differentiate into cytotrophoblast & syncitiotrophoblast . xi. Bilaminar gem disc are ectoderm & endoderm . xii. Deeper penetration of blastocyst into compact layer of endometrium is called as interstitial implantation xiii. The stage in which cells appears a cluster of ball resembling a mulberry is morula . xiv. Name the rudiment of vertebral column. Ans : Notochord xv. At what week the embryo has distinct human characteristics. Ans : 8 th week