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Length of Fetus
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04.05.06 (2 years ago)
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Length of fetus is measured during pregnancy as:-i.e., the progress of growth of the fetus in length in IU life. It should not be confused with the length of fundal ht.
Crown-rump length:- is measured in first
half of pregnancy i.e., upto 20 wks measure from Vx to Coccyx
fetal length is more helpful in - prematurity than in post maturity
Crown-heel length:- from the end of square the no. of lunar month at the time of --- - exam and multiply *5 in cm. e.g., 8th month * - 5 =40 cm
20 wks in the 2nd half of pregnancy
CHL in 1st half of pregnancy=squaring the no. of lunar months*4 e.g.., 4*4=16 cm
Normally at the end of:-
12w=7cm 32w=39-41cm
16w=18-27cm 36w=42-44cm
24w=28-34cm 40w=50-53cm
28w=35-38cm
After 20wk the fetal length in inches is equal to half of no. of gestational age in weeks.e.g., at 28wk =14 inches.
Estimation of fetal wt in grams
1) Johnson’s Formula :-it is applicable only in Vx presentation e.g., F Ht(cms)—above the pubic symphysis minus 12 if Vx above I S or minus 11 if below I Spines. Then multiply by 155=fetal wt in gms e.g., 32-12*155(155 is constant)=20*155=3100gms
2) (Fetal ht in cms-n)/3=lbs.
3) Calculation of Intrauterine fetal wt by pelvimeter
It is 90% accurate(see new Dawn 112 page)
Age of the fetus by clinical methods
i.e., calculation of gestational age clinically
A) Haase’s rule: 1st 5 lunar months::the fetal length in cms=16=4*4—it’s square is the no. of lunar month
2nd 5 lunar months::the fetal length in cms divided by 5=e.g., 40cm/5=8th lunar month
B) Gravidography: (Gravidogram):serial tape measurements of the distance from pubic symphysis to fundus in cms (after emptying the bladder) throughout pregnancy are taken. These are charted graphically against gestational maturity in completed weeks. On repetition these values get increased with advancing gestation. The continued increase in fundal ht and abdominal girth indicate continued fetal growth. Height of the topmost level of the uterine fundus=5 cms(2inches) above the pubic symphysis=16 w
=2.5 cm( 1 inch) below umbilicus=20 w
=lower border of umbilicus =22 w
=upper border of umbilicus =24 w
MacDonald’s rule:- after 24-26 wk of pregnancy, onwards upto term
The ht of the growing fundus (in cms) divided by 3.5=gestational age in lunar months.e.g., if it is 32 cms=then it is 8 ˝ months (34wks)
But this is a poor measurement since=
1) the volume of am fluid (hydramnios)
2) multiple pregnancies
3) variations in abd wall thickness
4) full engagement of fetal head near term
may alter the measurement.
Before 20-24wks=height of the fundus from pubic symphysis to umbilicus *2/7=duration of pregnancy in lunar months or *8/7=duration of pregnancy in weeks.
-At 28 weeks, the fundal ht lies at the lower 1/3rd of the distance between the xiphisternum and umbilicus.
-At 30wks it lies midway between them.
-At 36wks, it reaches upto the level of xiphisternum.
-From 36-40wks, it lies at the level of 32-34wks again due to
a) engagement of fetal head / breech into pelvis
b) or simple dropping down of fetal head or breech into pelvis
c) due to liquor amnii absorption
this is known as Lightening-a sensation felt by mother at the level of her stomach after 38 wk --she feels a sense of emptiness at the epigastric region.
=the mean fundal ht at 20w=about 20 cms
at 40w=about 36cms( fundal ht from superior border of symphysis pubis to xiphisternum) standard charts are available for this( P K Din p23)
-at the end of 16wks, the fundus may be felt nearly midway between the umbilicus and symphysis pubis
-at the end of 20wks, the fundus occupies the 2/3rd of the distance between umbilicus and the sym pubis
-after the 12th week, the fundus rises about ˝ per week or 1 inch/2 weeks( 2.5 cm/ 2weeks)
-after 20th week average upward growth of the fundus is 3.75-5cms( 1 ˝ -2 inches) per month ( non TLT)
-at about 24wks, the fundal ht lies at the upper border of the umbilicus (Eastman)
Fundal ht is clinically assured on repeated obstetric exam by the same obstetrician by relating the top level of the uterine fundus, above the pubic symphysis to certain abd landmarks
Serial Measurement of Abdominal Girth at the Level of Umbilicus after 1st half of Pregnancy
(Not before that)
At 30 wks = normal in 30 inches; 1 inch increase per week occurs till near term. The progressive increase is more important than a single measurement. So serial measurement of increase in abd girth with advancing are taken. This is not accurate.
Changes in Weight Gain
Normally there is a steady increase in weight of a pregnant women until the last 2-3 weeks of pregnancy. It stops increasing at about term. It may remain stationary----may begin to fall which means that pregnancy is at least mature.
In normal pregnancy –the wt gain should not exceed 2 ˝ kilograms in any one month or 0.9 kg in a week.
The max permissible wt gain throughout the whole period of pregnancy is about 10 or 11 kg( about 24 lbs) although 12 ˝ kgs is allowed—1/3rd of this wt—increases in 1st 20 wks. Another 1/3rd =next 10 wks. Remaining 1/3rd =between 30 wk to term.
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