Ultrasound screening for fetal chromosomal abnormalities, 11-14 weeks, multiple pregnancy (photos included)

Ultrasound screening for chromosomal abnormalities between 11 and 14 weeks of a multiple pregnancy is a specialized, non-invasive and safe ultrasound examination designed to assess the development of each fetus and identify ultrasound markers associated with an increased risk of chromosomal abnormalities, including Down syndrome, Edwards syndrome and Patau syndrome.

In multiple pregnancies, the examination allows each fetus to be assessed individually, as well as the placenta or placentas, umbilical cord and amniotic fluid. Ultrasound findings may be correlated with biochemical screening to calculate the individual risk. Ultrasound photographs are included.

Structures assessed

• Each fetus — crown-rump length (CRL), fetal development and anatomy, position and activity.
• Nuchal translucency (NT) — an important ultrasound marker for assessing the risk of chromosomal abnormalities.
• Nasal bone — presence and appearance.
• Fetal blood flow — assessment of the ductus venosus and, when indicated, tricuspid blood flow.
• Early morphological examination — skull, brain, spine, heart, stomach, urinary bladder and limbs.
• Fetal heart — heart rate, position and activity.
• Umbilical cord — number of vessels and insertion site for each fetus.
• Placenta/placentas — location, structure and characteristics.
• Amniotic fluid — assessed for each amniotic sac, depending on the type of multiple pregnancy.

Purpose of the examination

• Estimation of the individual risk of chromosomal abnormalities for each fetus.
• Early detection of fetal structural abnormalities.
• Confirmation of gestational age and viability of each fetus.
• Assessment of fetal development and possible differences between fetuses.
• Determination of placentation type and the number of amniotic sacs.
• Assessment of risks specific to multiple pregnancies.
• Correlation of ultrasound findings with biochemical screening, when performed.
• Establishment of an individualized prenatal monitoring plan.

Indications

The examination may be recommended in cases of:

• any multiple pregnancy between 11 weeks and 13 weeks + 6 days;
• twin, triplet or higher-order pregnancies;
• suspected differences in development between fetuses;
• a history of complicated pregnancies or fetal abnormalities;
• a family history of genetic disorders or congenital malformations;
• an unfavorable result of previous prenatal screening;
• maternal factors that may increase the risk of complications;
• the need for detailed prenatal assessment at the physician’s recommendation.

Procedure / Duration

The examination is generally performed transabdominally. The physician applies gel to the abdomen and examines each fetus separately, taking the necessary measurements and assessing ultrasound markers specific to chromosomal screening. The placenta or placentas, umbilical cord and amniotic fluid are also assessed.

Depending on fetal position and image quality, the patient may be asked to change position or, in certain situations, the examination may be supplemented with a transvaginal assessment.

The examination usually takes approximately 30–45 minutes, depending on the number of fetuses, their position and the complexity of the assessment. Ultrasound photographs are included.

Limitations

Ultrasound screening allows risk assessment, but it does not provide a definitive diagnosis of a chromosomal abnormality. Results may be influenced by gestational age, fetal position, image quality and the specific characteristics of the multiple pregnancy.

If risk markers or suspicious findings are identified, the physician may recommend additional investigations, including biochemical screening, genetic testing or specialist consultation.

Contraindications

There are no absolute contraindications to ultrasound examination during pregnancy. The examination is non-invasive, painless and does not use ionizing radiation.

Advantages

• non-invasive and safe for the mother and fetuses;
• allows individual assessment of each fetus;
• contributes to early assessment of the risk of chromosomal abnormalities;
• allows identification of important ultrasound markers;
• provides an early assessment of fetal anatomy and development;
• allows assessment of placentation type and amniotic sacs;
• helps identify differences in development between fetuses;
• allows an individualized prenatal monitoring plan to be established for a multiple pregnancy;
• ultrasound photographs are included.
   

Medical sources:

https://www.ncbi.nlm.nih.gov/books/NBK573070/
https://fetalmedicine.org/fmf-certification-2/nuchal-translucency-scan
https://fetalmedicine.org/fmf-certification-2/nasal-bone
https://fetalmedicine.org/fmf-certification-2/ductus-venosus-flow
https://www.glowm.com/pdf/ultrasound_in_obstetrics_and_gynecology-chapter4.pdf
https://pmc.ncbi.nlm.nih.gov/articles/PMC6243450/
https://radiopaedia.org/articles/twin-pregnancy-1