Fetus with osteogenesis imperfecta presenting as increased nuchal translucency thickness in the first trimester: a case report

Abstract

Background: Nuchal translucency (NT) has been used successfully in screening for chromosomal abnormalities at 11–14 weeks of gestation. Increased NT thickness is also associated with lots of fetal anomalies in chromosomally normal fetuses. We report a case of osteogenesis imperfecta (OI), type II, presenting with increased NT thickness. A 26‐year‐old Taiwanese woman, gravida 2, para 1, without medical or family history was scanned for confirmation of menstrual gestational age at 13 weeks of gestation. Crown‐rump length was compatible with menstrual age. Increased NT thickness was noted (3.6 mm). Follow up scan 2 weeks later revealed hypomineralization of skull, multiple fractures of long bones and ribs and severe micromelia. A presumptive diagnosis of OI type II was made based on sonographic findings. After counseling, the parents decided to terminate the pregnancy. A stillborn weighing 70 g was delivered after intravaginal misoprostol application. Postmortem radiograph and autopsy confirmed the diagnosis of OI.Discussion: NT screening for chromosomal and structural abnormalities at 11–14 weeks of gestation was proposed by Nicolaides in the 1990s. It has gained worldwide popularity due to early screening and high detection rate. Distorted and narrow thoracic cage due to rib fractures or altered composition of the extracelluar matrix has been thought to be the possible mechanisms of increased NT thickness in fetuses with OI. In our opinion, the characteristic of hypomineralization in OI enables clear visualization of intracranial structures which may resemble the sonographic features of increased NT thickness in some cases. This finding should prompt the sonographer to measure NT thickness and scan for possible anomalies.