Your Logo EXTERNAL APPEARANCE DURING SECOND MONTH

CROWN RUMP LENGTH CORRELATED TO AGE IN WEEKS CRL (mm)AGE (WEEKS)

 During 2 nd month size of head increases and the limbs, face, ears, nose and eyes form.  By the beginning of the 5th week, forelimbs and hind limbs appear as paddle shaped buds.  The forelimb buds are located dorsal to the pericardial swelling at the level of the C4 – T1 somites  Hind limb buds appear at the level of the lumbar and upper sacral somites CRL= 9.8mm; 5 th week Forelimbs Paddle shaped

 Terminal portions of buds flatten and 1st circular constriction separates them from proximal more cylindrical segments  Soon 4 radial grooves separates 5 slightly thicker areas appearing on the distal portion of buds  These grooves are called rays which appear in hand region first and shortly afterwards in foot  Upper limb is slightly more advanced in development than lower limb  While fingers and toes are formed 2 nd constriction divides the proximal portion of buds into two segments and 3 characteristic features of adult extremity are recognizable CRL=13mm; 6 th week

CRL=21mm; 7 th week chorionic sac open, embryo in amniotic cavity Compare the size of head with the rest of body

CRL= 25mm; 7 th to 8 th week embryo. Chorion and amnion have been opened Size of head, the eye, auricle and well formed face. Physiological umbilical herniation

BIRTH DEFECTS  Most major organs and organ systems are formed during the 3rd to 8th week. This period is called the period of organogenesis. Stem cell populations are establishing each of the organ primordia, any insult from genetic and environmental influences can result in birth defects. The 3rd and 4th weeks are particularly vulnerable.

Your Logo HUMAN FETAL PERIOD BY DR SAMINA ANJUM

PERIOD OF FETUS The period from the beginning of the 9th week to birth is known as Fetal period. Tissue and organs mature; become competent to assume their specialized functions. Rapid growth of body

 Transformation of embryo to fetus is gradual.  CRL or CHL  Growth in length is particularly striking during the 3rd, 4th and 5th months  While increase in weight is most striking during the last 2 months of gestation.

LENGTH OF PREGNANCY  280 days or 40 weeks from LNMP  266 days or 38 weeks after fertilization

MONTHLY CHANGES  The growth of the head during fetal period is slow compared to the rest of body.  At the beginning of 3rd month, the head constitutes approximately ½ of crown – rump length (CRL).

 By the beginning of 5th month, the size of the head is about 1/3rd of crown – heel length (CHL)

 At birth the size of the head is approximately 1/4th of CHL.

THIRD MONTH (9-12 wks) FACE: More human looking broad HEAD: Disproportionately large Makes up nearly half of the fetus' size EYES: Directed ventrally Eyelids fused EARS: Rise to their definitive position on the side of head

LIMBS: Reach their relative length PRIMARY OSSIFICATION CENTERS: A re present in the long bones and skull by the 12th week.

PREUMBLICAL HERNIATION: During the 6th week, intestinal loops cause a large swelling (physiological herniation) in the umbilical cord. By the 12th week, loops withdraw into the abdominal cavity.

11 th week fetus: Intestines are no longer in the umbilical cord

ERYTHROPOIESIS, : At 9 th week liver is the major site, after 12 th week activity is reduced and begins in spleen EXTERNAL GENITALIA: Appear well differentiated MUSCULAR ACTIVITY: Evoked in aborted fetuses SWALLOWING REFLEX: 10 WEEKS

4 TH AND 5 TH MONTHS  During the 4th and 5th months, the fetus lengthens rapidly and at the end of first half of intrauterine life, its CRL is approximately 15cm, about ½ the total length of newborn.  Weight is less than 500 gm Fine hair (LANUGO) Head and eye brow hair are visible Fetal movements felt by mother (QUICKENING)

6 TH AND 7 TH MONTHS  During the 2nd half of IUL, weight increases considerably and particularly during last 2.5 months, when 50% of the full term weight (approx. 3200gms) is added.  During the 6th month, the skin of the fetus is reddish and has wrinkled appearance because of the lack of underlying connective tissue.

 The respiratory and the central nervous system have not differentiated sufficiently, and coordination between the two systems is not yet well developed.  By 6.5 to 7 months, fetus has length of about 25 cm and weighs approximately 1100gms.  If born at this time, the infant has a 90% chance of surviving.  Sucking movements  Some sounds can be heard  Eyes are sensitive to light

NINTH MONTH (33-36 wks) SKIN: Dull redness of the skin fades Wrinkles smooth out Lanugo begins to disappear BODY AND LIMBS: Become rounded Deposition of subcutaneous fat

VERNIX CASEOSA: By the end of IUL, the skin is covered by a whitish fatty substance

 At the end of 9th month, the skull has the largest circumference of all parts of the body.  At the time of birth, the weight of a normal fetus is 3000 to 3400gms, its CRL is about 36cms, and its CHL is about 50cms.  Testes should be in the scrotum (end of 9 th month)

GROWTH IN LENGTH & WEIGHT DURING FETAL PERIOD Age (weeks)CRL (cm)Weight (g)

DEVELOPMENTAL HORIZONS DURING FETAL LIFE EVENTSAGE (weeks) Taste buds appear7 Swallowing10 Respiratory movements14 – 16 Sucking movements24 Some sounds can be heard24 – 26 Eyes sensitive to light28

MEASUREMENTS AND CHARACTERISTICS OF FETUSES  Various measurements and external characteristics are useful for estimating fetal age.  Until the end of first trimester, CRL is the method of choice.  In the second and third trimesters, several structures can be identified and measured ultrasonographically  Gestational sac appear on transabdominal sonography at 5 th week and approx a week earlier by TVS.

ULTRASONOGRAPHY MEASUREMENTS  BPD  Head circumference  Abdominal circumference  Femur length  Foot length  Fetal weight

CROWN RUMP LENGTH

BI-PARIETAL DIAMETER

CIRCUMFERENE

FEMUR LENGTH

FOOT LENGTH

FACTORS INFLUENCING FETAL GROWTH Following factors stimulate fetal growth:  Glucose  Aminoacids  Insulin (secreted by fetal pancreas)  Insulin like growth factors  Human growth hormone