FISH as a new technology for o last three decades as become an important too for chromosome analysis

For   any foetal   problem be it anatomic / genetic such abnormalities are usually but not always it is reflected   on NT changes . Why it happens is unclear. As gestation changes   - NT    varies as per CRL.    .If the risk calculation (statistical risk probability) is above 1: 50 then only CVS procedure for confirmation.

Risk stratification:  We always  are concerned about  probability of chromosomal abnormality in any foetus ? If mother has one child with Down’s syndrome, than recurrent risk will be 2%. . The chromosome analysis can be done either by 1) cell culture ( traditional karyotyping)  or by more recently FISH method ( Fluorescent  In situ Hybridization).. In FISH method  Fluorescent probe is used on the nuclei of amniocytes one signal means that the said nucleus is having monosomy ( Fluorescent probe), two signals means euploid nucleus and if some nuclei reveals three florescent signals it applies trisomy..

FISH:- Usually there are five DNA probes(probes with Fluoro Chrome)  are used like 1) LS-1--21,    2) CEP-18,    3)  LS-1-13 4 & 5 ) CEP- two Sex chromatins    , The cells which shows two different signals after FISH procedure means normal cells i. e diploid chromosome with no alteration in number or decrease in number.&    5) Usually five chromosomes are  studied in nuclei of amniocytes .like 21, 13, 18 and two sex chromosomes. This tets of FISH may occasionally exhibit trisomy or monosomy.

Normally NT steadily increase    for the period foetal CRL from 44  mm  to 85 mm .What is normal NT(subcutaneous fluid collection behind the nape of the neck??  The fluid thickness is  for  a  CRL of 45 mm (  means 11 weeks ) will be  1.9 mm  in 85 percentile   and 50 percentile NT  will be   & NT  will  in 85 mm ( CRL at 13.6 ) but it will be 2.8 mm in 95 percentile

The nuchal translucency has to be differentiated from with cystic hygroma   which are two   dilated   Inguinal    lymphatic    sac or Tr   scar   it   the level of neck  which  is septate   for NT .

High resolution    scan is warranted. Search not only NT but also anatomic defect & cardiac defect. If NT is high along with then no   foetal  anatomical defect   ( cardiac   defect  then go for CVS

The NT is only reliable   from   45  - 84 mm  caliper     of  USG   should be  able   to read upto 0.1 mm.

 Sonoembryology:_---A) UPT will be +   13 day after  ovulation dose (trigger)   but B) in blood earlier   (RIA method  )  +   9 days after  ovulation .Therefore estimation  hCG   5 days after   test ovulation     done of hcg . Average  of 3  CRL measurements sac ( GDS)

Menstrual  week

4^th  M . Week = 2 mm sac

5thM. Week =  5mm  sac

6^th  M. week = 10 mm sac

7^th   M. week = 20 mm sac

8 th  M. week = 25mm sac

Vaginally USG:--  sac is visible  when   serum beta HCG  is  > 1500 to  1000 . But in abd USG(TAS) sac is visible when hCG is  > 3000. But usually at 5^th Weeks = SAC is visible almost always. By the end of 6th   weeks = Y. sac and cardiac    activity seen .At  8^th weeks  limb  buds are usually seen.

Biochemical pregancy??  :-  When  two  hcg values are greater than   10 IU/ lit   then  at this juncture if sac is not visible  - then it is called “Biochemical     Pregnancy”. 

Average 5 days + possible even in first trimester     usg

Clinical preg = Sac visible

hCG  at missed   dose ?

At the time of missed period (expected day of cycle, hcg in blood  will be   100miu/ ml

16-23 day=  10-30 IU

24-30 days  =  30-100 IU

31-38 days  = 10,000 to 16000 IU

Day 35- day 45   =  200-4000 IU

2-3 mm   =12000-200,000 IU

12weeks =  10,000 IU

Second  Tri  = 24000 – 55000 IU

3^rd Trimester   6000-48000 IU

Viability  Scan :-

1)                       Blighted ovum  - GSD > 8mm but there is   no Y sac in the USG  . 2) Anembryonic   pregnancy.  GSD > 16 mm , no foetal . p. signs  of failing IUP, )  bradycardia in   relation     to CRL   , MSD  ,  CRL is  < 5mm   I e  oligomaniotic sac , Poor  sac growth profile   , large Y. sac > 5.6 mm prior to 10 weeks  / abnormal Y. sac   , disappearance  of CL

Normally   rise of beta hCG   is > 1.24 times   , > 1.53, times  , >1.88 times  & > 2.33 times    in 24 h , 48 h   , 72 h    & 96 hours   but in ectopic   there will be only 20%  rise of B hCG   . If no intra uterine preg is visible preg then possibilities are a) EP b) missed abortion c)   failing IUP or d) self   resolution of EP

Always   perform USG if  B hCG is above 1500   . If at such  beta HCG(  above 1500)   sac  is demonstrated at USG then  in all fairness it is =normal pregancy,   no sac either   medical   treatment  MTX  or better  RPT  b hCG   after 48  hours  prog is less than   10   . In abdominal USG  sac should  be visible  when HCG  level  will be increases  6500 IU/ lit or

In normal pregancy the rise of b hCG will be  > 55%  by 48 hours   & at least   > 88 % by 72 hours