Ultrasound imaging is a key prenatal tool during the first and second trimester for revealing structural anomalies that may point to genetic conditions. Above are examples of anomalies that should not be missed when performing ultrasound during the first and second trimesters of pregnancy.More information on ultrasound diagnoses can be found in, 'Using ultrasound to recognize fetal anomalies.' This is Part 1 of a 2-part collection. The second part of the collection will be available soon.
Late in the first trimester, the brain can be imaged in the transverse plane, identifying both hemispheres and midline structures. Anencephaly (absent skull and brain) is a major anomaly that can be identified.
First trimester holoprosencephaly
First trimester cephalocele
A profile view can identify a small mandible, or in this case a micrognathia, during the first trimester.
One of the most common abnormalities identified during the first trimester is the ventral wall defect, omphalocele.
First trimester gastroschisis
An enlarged urinary bladder (megacystis) in the first trimester can represent early evidence of bladder outlet obstruction.
First trimester polydactyly
Holoprosencephaly should not be missed in the first trimester and definitely not in the second semester.
Second trimester cephalocele
Second trimester anencephaly
Enlarged ventricles (ventriculomegaly hydrocephalus) in the second trimester can indicate several conditions.
Ventriculomegaly is present in the Dandy-Walker malformation, a malformation characterized by the absence of the middle portion of the cerebellum. It should not be missed during the second trimester.
Arnold-Chiari Type II malformation includes herniation of the hindbrain into the spinal canal, which causes the cerebellum to elongate and become distorted into a "banana" shape. It should not be missed during the second trimester.
Arnold-Chiari Type II malformation can also cause the frontal bones of the calvarium to collapse, causing a "lemon" shaped skull.
Another diagnosis that can be suspected based on second-trimester ultrasound is agenesis of the corpus callosum, a condition in which the large midline bundle of white matter connecting neurons in the two hemispheres is absent.
A profile view in the first and second trimester can identify a small mandible, or micrognathia.
Second trimester cleft lip and palate
Median or bilateral cleft lip can be suspected based on profile views.
