N T Scan USG at 11-13 weeks.

Nuchal translucency  evaluation a component of first trimester aneuploidy  screening has had a major impact on the number  of pregnancies receiving  late first trimester ultrasound  examination . It  represents the maximum thickness of the subcutaneous  translucent area between the skin  and soft tissue overlying the fetal spone at the back of the neck . It is  measured in the Sagittal plane between 11 and 14  weeks using   precise criteria  When the nuchal  translucency is increased the r4isk for fetal aneuploidy and various structural  anomalies – including heart  defects-  is significantly  elevated. Aneuploidy   screening using nuchal translucency   measurement   in conjunctions with assessment   of maternal serum human chorionic   gonadotropin and pregnancy  associated plasma  protein

First Trimester  fetal anomaly detection

Assessment  for selected fetal abnormalities  in an at risk pregnancy7 is another indicatin for first trimester  sonography  . Research in this area has focused  on antomy visible at 11 to 14  weeks to coincide with sonography performed a s part of aneuploidy screening / With current  technology it is not realistic to expect that all major abnormalities   detectable in the second trimester may be visualized inj the first trimester . A study  of systematic  anatomy   evaluation between 11 and  14 weeks in more than 40,000   pregnancies  yielded a detectin rate of  approximately 40  percent for nonchromosomal abnormalities   . this  detection rate is nearly  identical to that  from a review of more than 60,000   pregancies  from 15   studies  and is also comparable  with other reports . Identification varies considerably  according to  the specific  abnormality .

For  example reported  detection rates  are extremely high  for anencephaly alobar holoprosencephaly  and ventral wall defects .  However   only one third  of major  cardiac  anomalies have been identified  with no detected  cases of  microcephaly agenesis  of the corpus   callosum cerebellar  abnormalities   congenital    pulmonary airway malformation or bowel  obstruction. Thus  as first trimester   sonography  is unreliable  for detection  of many  major  abnormalities. It   should not  replace   second  trimester  anatomical evaluation .

Second  and Third Trimester Sonography 

The many  indications for second and third  trimester  sonography  are listed .There  are three types of examinations Standard. Specialized and limited

1 Standard sonographic examination is the most commonly performed Components ar listed . The fetal anatomical structusres that should be evaluated during he examination which are listed . may be adequately assessed  after approximately  18 weeks   when examining  twins or other multiples documentation also includes  the number  of chorions and amnions comparison of fetal sizes  estimation of amnionic   fluid   volume   within each sac and fetal sex determination   .

There  are several types of specialized  examination . The  targeted examination is a detailed  anatomical survey  performed when an abnormality is suspected on the basis of history   screening test result or abnormal findings from s standard examination . A targeted examination  is performed and  interpreted by an experienced operator  . It includes the anatomical structures  listed.  Along with   additional views of   the brainadn cranium. Neck profile lungs and diaphragm  cardiac  anatomy   live shape  and curvature of the spine hands and feet and any placental abnormalities  . the physician performing the examination  further determines whether other examination components   will be  needed  on a case by case basis  . Other  specialized  examinations include  fetal echocardiography ad Doppler   evaluation   biophysical profile and  additional   biometric measurements.

3 A limited  examination  is performed  to address a specific clinical question Examples include amniotic fluid volume assessment   placental location  or evaluation of fetal  presentation or viability . In most  cases a limited  examination is appropriate   only when a prior   standard or targeted examination has previously   been performed  .

Nuchal translucency  evaluation a component of first trimester aneuploidy  screening has had a major impact on the number  of pregnancies receiving  late first trimester ultrasound  examination . It  represents the maximum thickness of the subcutaneous  translucent area between the skin  and soft tissue overlying the fetal spone at the back of the neck . It is  measured in the Sagittal plane between 11 and 14  weeks using   precise criteria  When the nuchal  translucency is increased the r4isk for fetal aneuploidy and various structural  anomalies – including heart  defects-  is significantly  elevated. Aneuploidy   screening using nuchal translucency   measurement   in conjunctions with assessment   of maternal serum human chorionic   gonadotropin and pregnancy  associated plasma  protein

First Trimester  fetal anomaly detection

Assessment  for selected fetal abnormalities  in an at risk pregnancy7 is another indicatin for first trimester  sonography  . Research in this area has focused  on antomy visible at 11 to 14  weeks to coincide with sonography performed a s part of aneuploidy screening / With current  technology it is not realistic to expect that all major abnormalities   detectable in the second trimester may be visualized inj the first trimester . A study  of systematic  anatomy   evaluation between 11 and  14 weeks in more than 40,000   pregnancies  yielded a detectin rate of  approximately 40  percent for nonchromosomal abnormalities   . this  detection rate is nearly  identical to that  from a review of more than 60,000   pregancies  from 15   studies  and is also comparable  with other reports . Identification varies considerably  according to  the specific  abnormality .

For  example reported  detection rates  are extremely high  for anencephaly alobar holoprosencephaly  and ventral wall defects .  However   only one third  of major  cardiac  anomalies have been identified  with no detected  cases of  microcephaly agenesis  of the corpus   callosum cerebellar  abnormalities   congenital    pulmonary airway malformation or bowel  obstruction. Thus  as first trimester   sonography  is unreliable  for detection  of many  major  abnormalities. It   should not  replace   second  trimester  anatomical evaluation .

Second  and Third Trimester Sonography 

The many  indications for second and third  trimester  sonography  are listed .There  are three types of examinations Standard. Specialized and limited

1 Standard sonographic examination is the most commonly performed Components ar listed . The fetal anatomical structusres that should be evaluated during he examination which are listed . may be adequately assessed  after approximately  18 weeks   when examining  twins or other multiples documentation also includes  the number  of chorions and amnions comparison of fetal sizes  estimation of amnionic   fluid   volume   within each sac and fetal sex determination   .

There  are several types of specialized  examination . The  targeted examination is a detailed  anatomical survey  performed when an abnormality is suspected on the basis of history   screening test result or abnormal findings from s standard examination . A targeted examination  is performed and  interpreted by an experienced operator  . It includes the anatomical structures  listed.  Along with   additional views of   the brainadn cranium. Neck profile lungs and diaphragm  cardiac  anatomy   live shape  and curvature of the spine hands and feet and any placental abnormalities  . the physician performing the examination  further determines whether other examination components   will be  needed  on a case by case basis  . Other  specialized  examinations include  fetal echocardiography ad Doppler   evaluation   biophysical profile and  additional   biometric measurements.

3 A limited  examination  is performed  to address a specific clinical question Examples include amniotic fluid volume assessment   placental location  or evaluation of fetal  presentation or viability . In most  cases a limited  examination is appropriate   only when a prior   standard or targeted examination has previously   been performed  .