First Trimester Increased Nuchal Translucency Associated with Fetal Achondroplasia

ABSTRACT

A 30-year-old woman, gravida 2, para 1, was referred for nuchal translucency, free beta-human chorionic gonadotropin (β-hCG), and pregnancy-associated plasma protein A (PAPP-A) screening at 12 weeks gestation. The nuchal translucency was increased to 3.8 mm, resulting in a post-test result of 1:15 risk for Down syndrome by a combination of maternal age plus nuchal translucency, and 1:5 by a combination of maternal age plus nuchal translucency plus free β-hCG plus PAPP-A. The patient underwent uncomplicated chorionic villus sampling that demonstrated a normal 46,XY fetus. The patient was then followed-up weekly by ultrasound. At 18 weeks gestation, generalized features of rhizomelic micromelia together with macrocrania and narrow thorax were seen. All fetal long bones were less than 2 standard deviations from the mean value. At that time, DNA analysis was performed on stored villi and a G380R mutation in the locus gene encoding for the fibroblast growth factor receptor 3 on chromosome 4p16.3 was found, leading to a prenatal diagnosis of achondroplasia. The couple opted for termination of pregnancy after counseling. Postmortem X-ray was done and confirmed the ultrasound diagnosis of achondroplasia. This is the second known case of increased nuchal translucency in the first trimester associated with prenatal confirmed diagnosis of fetal osteochondrodysplasia.

KEYWORDS

Nuchal translucency - CVS - DNA analysis - achondroplasia

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