Failure of getting intracranial translucency image in posterior fossa in the examination of singleton pregnancies at 11–13 weeks of gestation: reasons and outcomes

Objective: To investigate the reasons and outcomes of being unable to see intracranial translucency (IT), and to determine the sensitivity, specificity, positive and negative predictive values and our diagnostic accuracy rate for the poor outcomes that may follow IT negativity. Methods: This study was designed as the retrospective assessment of the data of 2670 singleton pregnancies. The evaluation of cerebral structures and posterior fossa was conducted on classical nuchal translucency evaluation plane and the cases, IT of whose could not be seen or measured, were included in the study. The distribution of chromosomal anomalies, malformations and fetal losses which may affect gestational prognosis as well as maternal characteristics of these cases was evaluated and they were compared with the group considered normal. Results: The rate of the cases whose IT could not be measured in posterior fossa was 4.05%. Compared to the group whose IT could be measured, poor prognosis of gestation, fetal loss or termination of pregnancy, chromosomopathy markers of early period and the presence of chromosomal anomaly, and the rate of central nervous system and other system malformations were higher in a statistically significant manner in the group whose IT could not be measured. Of the IT non-measurability, the sensitivity was 26.9%, the specificity was 95.9%, the positive predictive value was 21.9%, the negative predictive value was 96.9%, the accuracy rate was 93% and the odds ratio was 8.7 to predict the poor gestational prognosis mentioned above. Conclusion: The findings of our study make us think that intracranial translucency can be used as a parameter helping classical methods for the early diagnosis of the malformations of central nervous system and other systems, and some chromosomal anomalies, and that it can be useful to use it in routine perinatal assessment.