Possible sonlogical landmarks --Diagnosis of possible foetal anomalies

Soft markers of aneuploidy are nonspecific, often transient, and can be readily detected during the second and third trimester ultrasound. The most commonly studied soft markers of aneuploidy include a 1) thickened nuchal fold,2)  mild fetal pyelectasis,3)  echogenic bowel, 4) echogenic intracardiac focus and 5) choroid plexus cyst.6) Short long bone 7) ingle umbilical artery 8) Enlarged cisterna magnum 9) Mild cerebral ventriculomegaly

Nuchal fold thickness is not  to be confused with NT ( Nuchal  translucency at 11-13.6 weeks) The nuchal fold is the skin thickness in the posterior aspect of the fetal neck. A nuchal fold measurement is obtained in a transverse section of the fetal head at the level of the cavum septum pellucidum and thalami directed posteriorly to the cerebellum .The measurement is taken from the outer edge of the occiput to the outer skin in the midline. The definition of a thickened nuchal fold is that a measurement 6 mm or more between 15 and 23 weeks. However, a thickened nuchal fold should be distinguished from cystic hygroma, in which the skin in this area has fluid-filled Cysts. A thickened nuchal fold differs from nuchal translucency, which is a specific measurement of fluid in the posterior aspect of the neck at 11–14 weeks’ gestation Ultrasound screening at 16–20 weeks is one of the most common genetic screening tests used during pregnancy. The practical concern for ultrasound screening is false-positive and false-negative results. The use and understanding of ultrasound soft markers and their screening relative risks are an important option in the care of pregnant women.

Introduction

What do we mean by soft markers in foetal USG??? Ans;-“Soft markers” used in fetal genetic screening Soft markers of aneuploidy are nonspecific, often transient, and can be readily detected during the second and third trimester ultrasound. The most commonly studied soft markers of aneuploidy include a 1) thickened nuchal fold,2)  mild fetal pyelectasis,3)  echogenic bowel, 4) echogenic intracardiac focus and 5) choroid plexus cyst.6) Short long bone 7) ingle umbilical artery 8) Enlarged cisterna magnum 9) Mild cerebral ventriculomegaly

Chromosomal abnormalities occur in 0.1–0.2% of live births, and the most common clinically significant aneuploidy among live-born infants is Down’s syndrome (trisomy 21). Soft markers of aneuploidy are nonspecific, often transient, and can be readily detected during the second and third trimester ultrasound. The most commonly studied soft markers of aneuploidy include a thickened nuchal fold, mild fetal pyelectasis, echogenic bowel, echogenic intracardiac focus and choroid plexus cyst. There is a great deal of interest in the ultrasound detection of aneuploidy, as evidenced by the large number of publications in the literature on this topic.

Chromosomal abnormalities occur in 0.1–0.2% of live births . Trisomy 21 (Down’s syndrome) is the most common chromosomal abnormality in live-born infants (1 per 800 live births) (3). Sonographic findings in fetuses with Down’s syndrome include both structural and nonstructural markers. However, other aneuploidies like trisomy 13, trisomy 18, monosomy X, and triploidy can also be detected by ultrasound.

Many methods have been used to identify women at risk of carrying a fetus with aneuploidy, including maternal age biochemical markers , prenatal ultrasound and amniocentesis , However, there is a 0.5–1.0% fetal mortality associated with this invasive procedure .

A second-trimester ultrasound scan is usually done at 16–20 weeks. Two types of sonographic markers suggestive of aneuploidy can be observed in the second trimester. Major fetal structural abnormalities and soft markers of aneuploidy are less-defined, less significant and often transient  ,Although these markers are not pathognomonic because they may be seen in the normal fetus but they have been used to screen for Down’s syndrome and other aneuploidies . Thus, prenatal ultrasonography during the second trimester provides a “genetic sonogram” that is used to identify structural features of fetal Down’s syndrome 

Major and soft markers of aneuploidy.

System	Major	Soft markers
CNS	Ventriculomegaly, Holoprosencephaly, Microcephaly, Abnormal posterior fossa-dandy walker complex	Choroid plexus cyst
Musculoskeletal	Hand and feet anomalies – syndactyly, clinodactyly, clenched hand, radial ray aplasia, Clubfoot, a sandal gap, rocker-bottom foot	Short long bones
Face	Cleft palate and lips micrognathia, macroglossia, hypo- and hypertelorism, low set ears, small ear	–
Neck	Cystic hygroma	Nuchal fold thickening
Cardiac	Endocardial cushion defect, ventricular septal defect, hypoplastic left heart syndrome, tetralogy of Fallot, and other complex cardiac anomalies Echogenic focus	Echogenic focus
Gastrointestinal tract	Esophageal and duodenal atresia, small bowel obstruction, diaphragmatic hernia and Omphalocele	Echogenic bowel
Genitourinary tract	Moderate to severe hydronephrosis, dysplastic renal disease, and renal agenesis	Mild pyelectasis
Other	Symmetrical IUGR	Single umbilical artery

The comprehensive list of commonly observed soft markers:--The most commonly studied soft markers of aneuploidy include a thickened nuchal fold, limb shortening, mild fetal pyelectasis, echogenic bowel, echogenic intracardiac focus (EIF), choroid plexus cyst (CPC) and single umbilical artery. We review the most common ultrasonographic soft markers used to screen aneuploidy and discuss ultrasonographic technique and measurement criteria for the detection of soft markers. We also review the clinical assessment of soft markers for aneuploidy risk.

2. Sonographic soft markers of aneuploidy

Nuchal fold thickness is not  to be confused with NT ( Nuchal  translucency at 11-13.6 weeks) The nuchal fold is the skin thickness in the posterior aspect of the fetal neck. A nuchal fold measurement is obtained in a transverse section of the fetal head at the level of the cavum septum pellucidum and thalami directed posteriorly to the cerebellum .The measurement is taken from the outer edge of the occiput to the outer skin in the midline. The definition of a thickened nuchal fold is that a measurement 6 mm or more between 15 and 23 weeks. However, a thickened nuchal fold should be distinguished from cystic hygroma, in which the skin in this area has fluid-filled Cysts. A thickened nuchal fold differs from nuchal translucency, which is a specific measurement of fluid in the posterior aspect of the neck at 11–14 weeks’ gestation   An ultrasound can detect fluid at the back of a fetus's neck, which sometimes indicates Down syndrome. The ultrasound test is called measurement of nuchal translucency. During the first trimester, this combined method results in more effective or comparable detection rates than methods used during the second trimester.