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Trigonocephaly is a congenital condition due to premature fusion of the metopic suture (from Ancient Greek metopon 'forehead'), leading to a triangular forehead. The premature merging of the two frontal bones leads to transverse growth restriction and parallel growth expansion.
In obstetrics, a cephalic presentation or head presentation or head-first presentation is a situation at childbirth where the fetus is in a longitudinal lie and the head enters the pelvis first; the most common form of cephalic presentation is the vertex presentation, where the occiput is the leading part (the part that first enters the birth canal). [1]
The fold is more focal and at the level of the posterior fossa. This measurement has a higher threshold of normal, although the implications of increased thickness are similar to those of translucency. The nuchal fold thickness is considered normal if under 5mm between 16 and 18 weeks gestation and under 6mm between 18 and 24 weeks gestation.
The sex of the fetus may be discerned by ultrasound as early as 11 weeks' gestation. The accuracy is relatively imprecise when attempted early. [15] [16] [17] After 13 weeks' gestation, a high accuracy of between 99% and 100% is possible if the fetus does not display intersex external characteristics. [18]
Trisomy 16 is a chromosomal abnormality in which there are 3 copies of chromosome 16 rather than two. [1] It is the most common autosomal trisomy leading to miscarriage , and the second most common chromosomal cause (closely following X-chromosome monosomy ). [ 2 ]
Saethre–Chotzen syndrome (SCS), also known as acrocephalosyndactyly type III, is a rare congenital disorder associated with craniosynostosis (premature closure of one or more of the sutures between the bones of the skull). This affects the shape of the head and face, resulting in a cone-shaped head and an asymmetrical face.
An ultrasound showing an embryo measured to have a crown-rump length of 1.67 cm and estimated to have a gestational age of 8 weeks and 1 day. Crown-rump length (CRL) is the measurement of the length of human embryos and fetuses from the top of the head (crown) to the bottom of the buttocks (rump).
Cranial ultrasound is a technique for scanning the brain using high-frequency sound waves. It is used almost exclusively in babies because their fontanelle (the soft spot on the skull) provides an "acoustic window". A different form of ultrasound-based brain scanning, transcranial Doppler, can be used in any age group.