IN THE NAME OF GOD

Fetal Growth and

Development

E.Naghshineh MD

-product of conception prior to implantation: zygot -Embryonic period: 3-8wks after fertilization

-Fetus:>8wks after fertilization

Pre-fertilization

Fertilized Ovum

2 individual cells

4th week

In 5 wks: -sac:10 mm

In 6 wks: -sac:20-30 mm

-Emberyo: 5 mm -Partitioning of primitive heart -Arm and Leg buds

6th Week

In 8 wks: -Emberyo:22-24 mm

-Heart completely formed

-Fingers and toes present

-Upper lip is complete

-External ears

8th Week

In 10 wks: -Emberyo:4 cm

-Major body structures are formed In 12 wks:

-CRL:6-7 cm -centers of ossification -skin; nails; hair -External genitalia -spontaneous movement

12th Week

14th Week

In 16 wks: -CRL:12 cm

-BW:110 gr

18th Week

In 20 wks: -BW>300 gr

-downy lanugo

20th Week

In 24 wks: -BW:630 gr

-skin wrinkled, fat deposition

-eyebrows , eyelashes

- canalicular period of lung development

24th Week

In 28 wks: -CRL:25 cm

-BW:1100 gr

-vernix caseosa

-moves limbs energetically

-cries weakly

-survival chance:90%

In 32 wks: -CRL:28 cm

-BW:1800 gr

32nd Week

In 36wks: -CRL:32 cm -BW:2500 gr -excellent survival

In 40 wks:-term pregnancy -CRL:36 cm -BW:3400 gr

Length of fetus: CRL, Standing height , More accurate than weight

Weight of newborn: 3000-3600 gr, race, parental economic status, size of parents, parity of the mother, altitude, diet, smoking, substance abuse

Fetal head: -labor: adaptation between fetal head and maternal bony pelvis

Sutures:

-Frontal: between two frontal bones

-Sagittal: between two parietal bones

-Coronal: between frontal and parietal bones

-Lambdoid: between parietal and occipital bones

Fontanel:-Greater or anterior: lozengeshaped, sagittal

and coronal sutures-Lesser or posterior: triangular, sagittal and

lambdoid sutures-Temporal or casserian: lambdoid and

temporal sutures ,no diagnostic significance

Diameters:

1-Occipitofrontal (11.5cm)

2-Biparietal (9.5 cm)

3-Bitemporal (8 cm)

4-Occipitomental (12.5 cm)

5-Suboccipitobregmatic (9.5 cm)

Amniotic Fluid (AF)

Early pregnancy: maternal plasma Second trimester: extracellular plasma,

fetal plasma

Fetal urine (more urea; cr; uric acid) Pulmonary fluid Fluid filtering trough the placenta

AF

12 wks:50 ml 20 wks:400 ml Term:1000 ml Roles:-Allowing musculoskeletal development -Protect from trauma -Maintains temperatures -Minimal nutritive facturs

Fetal Circulation

Differ from adult O2 & nutrient materials: placenta-single

umbilical vein Well-oxygenated blood: LV: heart & brain Less oxygenated blood: RV: rest of the body After birth: umbilical vessels; ductus

arteriosus ; foramen ovale; ductus venosus normally constricted and collapse

Fetal Blood

Hemopoiesis: 1- yolk sac

2-liver

3- BM Regulated by fetal EP; increase with GA EP: fetal liver, renal Fetal blood volume: 78 ml/kg

Fetal Hb

Yolk sac: Gower1,2- Portland Liver: Hb-F BM: Hb-A In term: Hb-F(75%)- decrease 6-12 months

Coagulation Factors

Not cross the placenta Vit-K dependent factores decrease after

birth, hemorrhage in newborn Prophylactic vit-K treatment Continues ooze from umbilical stump:

severe deficiency of factors 8,9,11,13

Immunocompetence of fetus

Almost totally: IgG, maternal compartment ,transferred across the placenta

IgG ;during last 4 weeks of pregnancy IgM ;not transport from mother, fetus

produced ,congenital infection (rubella, CMV ,toxoplasmosis)

IgA ; ingested from AF, mucosal protection against enteric infections

Nervous System

Spinal cord: -24wks:S1

-Term:L3

-Adult:L1

GI tract

Swallowing: 10-12 wks Meconium: undigested debris ,various

product of secretion; GPL from lung, desquamated fetal cells, lanugo, scalp hair, vernix.

Pigments; biliverdin

Meconium passage

1-normal bowel peristalsis in mature fetus 2-vagal stimulation due to cord

compression 3-hypoxia;AVP release

Urinary system:

1-Pronephros 2-Mesonephros

3-Metanephrose;9-12 wks•Urine production :12 wks

•In term :27 ml/hr -650 ml/day

Anatomic maturation :

1)Pseudo glandular stage (5-17 wks) 2)Canalicular stage (16-25 wks)3)Terminal sac stage

Pulmonary system

Surfactant

Type 2 pneumocytes line the alveoli Coposition:-lipid:90% (PC-DPPC)

-proteins:10% Corticosteroids: accelerated fetal lung

maturation Surfactant therapy

Endocrine Glands

Pituitary gland:

-Ant: PRL,GH, ACTH, TSH, LH, FSH. (17 WKS)

-Post: oxytocin, AVP

-Intermediate: alpha-MSH, beta-endorphin

Thyroid gland:-thyroid hormones –role in normal

development all fetal tissue; especially the brain

-congenital hypothyroidism: neurological abnormalities, respiratory difficulties, dysmorphic facies, lethargy ,hypotonia ,myxedema of the larynx and epiglottis

Fetal Gender:

1)Chromosomal

2)Gonadal

3)Phenotype

Genital Ambiguity of the newborn

1)Female pseudohermaphroditism

2)Male pseudohermaphroditism

3)Dysgenetic

4)True Hermaphroditism