detection of neural tube defect in the first and second trimester of pregnancy by ultrasound in imam hospital, ahwaz between december 2008-2010

background: central nervous system malformations are the second most common congenital malformations after congenital heart diseases. these malformations are associated with many instances of morbidity and mortality which underline the importance of prevention and their early diagnosis. objective: the objective of this study is the diagnosis of neural tube defect (ntds) in the first trimester and its comparison to second trimester diagnoses in order to reduce the complications associated with late pregnancy terminations and its costs. materials and methods: this study was a trans-sectional study. a total number of 1074 patients who referred to imam khomeini hospital were enrolled in this study. during the 11th-13th (+6 days) gestational week the patients were screened sonographically; subsequently they were re-scanned for fetal anomalies during 18th-20th gestational week, and we followed the babies after birth. considering that intracranial translucency (it) was introduced in the newer researches, it was, too, measured in 125 of the cases. results: in a total number of 1074 patients we had one patient with an anencephalous fetus whom was diagnosed in the first trimester of pregnancy. in the second trimester, we detected one case of myelomenigocele; when we referred to this patient’s first trimester sonography, there was no visible it. in the 125 cases in whom the it length was measured, it was normal; the 2nd trimester sonographies in these patients were also normal. conclusion: it must be noted that the diagnosis of ntd is more accurate in the second trimester of pregnancy. consequently it is recommended that in high risk patients, the second trimester sonography be performed transvaginally, and in an earlier gestational age (14th-16th gestational weeks).