Hs201fetalperiod Trans

2 February 2011

HD 201

FETAL PERIOD Dr. Imelda Luna IV. Monthly Changes

Lecture Outline: I: Introduction II: Growth Curve III: Fetal Growth IV: Monthly Changes

V: Time of Birth VI: Summary VII: Clinical Correlates

I. Introduction I.

INTRODUCTION 1. Blastocyst (1-2 wks) o Period of cell proliferation o Teratogens can lead to abortion 2. Main embryonic period (3-8 wks) o Formation of all organ systems; most vulnerable to birth defects o 5-6 wk : alien looking 3. Fetal period (9 wks-birth)  period of: o maturation of organ systems o rapid growth of the body II. Growth Curve A.

B.

Prenatal/fetal: measured in weeks  IGF – 1 (insulin-like growth factor) – major  In the lecture, IGF was defined as insulin-like growth factor -IGF-2 is said to have a pre-implantation effect, as opposed to IGF-1 which functions prenatally. Also, IGF promotes cell proliferation and prevents cell death (anabolic)  growth hormone – important in last 2 wks only Postnatal/after birth: measured in years  GH (growth hormone), steroids (during puberty) III. Fetal Growth

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dramatic fetal growth: most rapid phase striking at 3-5 mos: at the end of 5 mos, fetus has grown to half of fetal length (CRL=15 cm), and weighs 500 g no IGF o IUGR (intra-uterine growth retardation) + MR (mental retardation): continues after birth o MR is possibly due to need for high concentrations in brain o Evidence for mitogenic and anabolic effect of IGF 1 relative slowdown of growth of head (one of the most striking changes of fetal life) compared w/ rest of the body (see table below) Length of fetus indicated by o Crown-Rump Length (CRL) – sitting height; easier to see in ultrasound, measurement from vertex to buttocks. o Crown-Heel Length (CHL) – standing height; measurement from the vertex of the skull to the heel Time Head Length 9 weeks

½ CRL

16 weeks

1/3 CRL

Birth

¼ CHL

The head of the fetus becomes smaller RELATIVE to the body because of the slowdown in growth of the head compared to the rest of the body.

A. 3rd month (at end of 12 weeks)  Face becomes more human-looking with eyes moving ventrally, and ears near their definitive positions  Limbs reach their relative length compared to the rest of the body (LowerEx less developed/smaller than UpperEx)  Primary ossification centers present in long bones and skull (starts at 7th week)  External genitalia developed to a degree enough to determine fetal sex via ultrasound  Intestinal loops withdraw into the abdominal cavity (large swelling or herniation in umbilical cord in 6th week)  Reflex activity can be evoked in aborted fetuses indicating muscular activity B. 4th month (13-16 weeks)  Limb movement becomes coordinated and clearly visible via ultrasound (may be felt by sensitive mothers, especially those who’ve been pregnant before) and ossification of skeleton activated  Head is still big compared to the body  Slow eye movements occur  Sex of external genitalia can be recognized  Eyes face anteriorly, ears near definite position  “Thumbs-up” sign can be seen

C. 5th month (17-20 weeks)  Lanugo (fine hair) helps to hold the vernix caseosa (whitish, slippery film) on the skin  Eyebrows and head hair visible  Brown fat formed is the site for heat production (around 5% of baby fat); also seen in hibernating animals which, like fetuses, cannot shiver. (In adults, fat is found in the lower neck region and higher in lean individuals)  Testes/ovaries begin descent to scrotal sac or pelvis  Quickening (first movements) o subjective measure; felt by the mother o good sign that baby is alive o if 1st time – wk20 (latest) o if multiparous – felt as early as wk16 NOTE: Suspect that there is something wrong if there is no quickening by this time. D. 6th month (21-24 weeks)  Skin reddish and wrinkled: due to lack of underlying connective tissue; skin is shiny, without brown fat  24 wks: surfactant secreted  Dr. Luna: baby has good grasp even at wk21  The picture of the smiling fetus was placed under this category. Also, remember the story of the fetus whose hand protruded out of the uterus while in the OR. Grasp was demonstrated to be good at this stage. Surgical operations can already be done to the fetus during this period. E. 7th month (25-28 weeks)  Rapid brain development with some control of bodily functions o Neurological development is continuous – no clear-cut period of time, unlike other organ systems  Eyelids open and close  respiratory system develop to a point where gas exchange is possible (birth at this time = 90% chance of survival if born at 6.5 to 7mos.)

F. 8th month (29-32 weeks)

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 Increased CNS control over body functions  Rhythmic breathing movements  Partial control of body temperature  Rapid increase in body fat (causing weight spurt)  In cases of multiple fetuses there is weight constraint since they share space in the uterus  Bone fully developed but still soft and pliable G. Last 2 months Assumes “fetal position” already  well-rounded contour: due to deposition of subcutaneous fat  increase in weight greatest during last 4 weeks: up to 200300 g/wk  weight gain esp at last 4 weeks accounts for ½ of baby’s body weight at birth  Uterus becomes cramped leading to fetal position H. End of Intra-uterine life  vernix caseosa, a whitish substance from subcutaneous glands, covers skin  lanugo gone, except on upper arm and shoulders

V. Time of Birth A. End of 9th month  skull (not the chest) has largest circumference o important in its passage through birth canal o CRL (crown-to-rump length) = 36 cm o CHL (crown-to-heel length) = 50 cm o BW (body weight) = 3000-3400 g (for Filipinos, normal is as low as 2500g)  Just a guide, passage is determined by both the baby’s and the pelvic dimensions.  Sexual characteristics pronounced (testes should be in scrotal sacs) Additional info: If there is an overlapping sagittal suture of the fetus, it would lead to cephalic hematoma. Caesarian type of delivery is needed. Crowning- most painful part of delivery without anesthesia Abdominal push- anesthesiologist – sabayan ang contraction You need pain para sa pagpupush B. Estimated using the following 1. Fertilization  226 days/38 wk after fertilization (most accurate estimate)  oocyte usually fertilized within 2 hrs of ovulation (12hr sa Langman’s na source ng lec)  is not or cannot be elicited unless through IVF 2.    

LNMP (last normal menstrual period) 280 days or 40 wks from first day of last menses fairly accurate if menses are regular most used method Langman: bleeding may occur during implantation w/c would complicate computation

Reference point

Days

Weeks

Calendar Months

Lunar Months

Fertilization

266

38

8¾

9½

LNMP

280

40

9¼

10

3.

Ultrasound  For determining fetal age; more accurate than LNMP  Early stage: sac without baby (monitor: if after 2wk there is still no baby, mass is probably a blighted ovum)  Used if menses are irregular  CRL (7-14 wks): accuracy is +/- 1-2 days.  Look for a fetal pole.

April, Jillian and Mars

 Between 16-38 wks: to determine fetal estimate, average the following:  BPD (biparietal diameter): relate to size of pelvis (widest diameter)  Head/abdominal circumference  FL (femoral length)  Age obtained may be different for each method so the average of the three ages is used  CRL is not used because other factors (such as genetics) start to affect it

VI. Summary  Period of growth of all major structures already present  Birth defects that are not as severe or obvious o Small size o IUGR (Intrauterine Growth Retardation) o Mental retardation o Defects in eyes, ears, teeth, external genitalia Preemie growth chart FETAL PERIOD FETAL PERIOD EARLY FETAL MIDDLE FETAL - viable at 22 weeks LATE FETAL -plump at 32 weeks

WEEKS 9- 16 weeks 17- 30 weeks

CRL (cm) 5- 14 15- 28

31- 38 weeks

28- 36

VII. Clinical Correlates Intrauterine growth retardation (IUGR)  At or below the 10th percentile for their expected body weight at a given gestational age (small at gestational age [SGA] ~ 1 in 10 babies)  Increased risk of neurological deficiencies like: o Congenital malformation o Meconium (greenish first stool) aspiration o Hypoglycemia or calcemia o RDS (respiratory distress syndrome) if premature  Causative factors 1. Chromosomal abnormalities (10%) 2. Teratogens 3. Congenital infections like: a. Rubella (most dreaded – results to abnormalities especially to the heart) b. Cytomegalovirus c. Toxoplasmosis d. Syphilis (STD) 4. Poor maternal health like hypertension and renal or cardiac disease – placental circulation is compromised (usually in older mothers) 5. Poor nutrition – low socio-economic level 6. Cigarette, alcohol or drug use 7. Placental insufficiency 8. Multiple births (competition of fetus) For developing countries: poor maternal health, nutrition and smoking (at least for the Phils) are more common risk factors  In IUGR: o BW < 500g – seldom survive o BW < 1000g – may live w/ expert care; ~50% survive but w/ severe neurological deficits  Prenatal growth depends on IGF-1 which has mitogenic and anabolic effects  Mutations in IGF-1 gene causes IUGR and retardation continues after birth Postnatal growth caused by growth hormone ---------END OF TRANSCRIPTION-------April, Jillian and Mars greet everyone hello and give their love to everyone. 

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