Comparison of First and Second Trimester Screening for Fetal Anomalies

Abstract

Four thousand fifty unselected pregnant women bearing a total of 4,078 fetuses were examined by transvaginal sonography (TVS) at 14 weeks of gestational age and rescreened via transabdominal sonography (TAS) at 21 weeks. Fifty-four of 88 anomalies were correctly identified at first scan whereas 34 were not; of these, 24 were discovered at second trimester rescreening, and the remaining 10 were observed later in pregnancy or after birth. The sensitivity of TVS screening with respect to final outcome was 61.4% (54 of 88 malformations in total) and 69.2% in comparison to TAS screening results (54 malformations detected among 78 recognized within 21 weeks). The association between fetal malformation and chromosomal aberrations was also investigated: in our study population there were 21 aneuploidies, 14 of which were recognized because of abnormal findings at the 14 weeks' TVS, 5 at the TAS rescreening, and 2 after birth in neonates free of structural abnormalities.

CNS Abnormalities at 11-14 Weeks

“…Due to the early stages of calvarium ossification, fetal brain structures are easily seen and a certain number of CNS anomalies can be detected during this period [11][12][13]. Anomalies like anencephaly and holoprosencephaly can be confidently diagnosed at the end of the first trimester (Table 1), because the respective defective structures, as calvaria and falx cerebri are already well seen.…”

“…Indeed, most of the CNS MA are indeed undetectable, but the most important CNS congenital anomalies concerning prevalence and severity are usually detectable in the first trimester: holoprosencephaly and neural tube defects (Table 1) [11][12][13][14][15][16][17][18][19][20][21][22].…”

First Trimester Anomaly Scan—The Last Redoubt Won: Open Spina Bifida

“…In a series of 18 published screening studies [4][5][6][7][8][9][10][11][12][13][14][15][16][17]34,[74][75][76] reporting on the effectiveness of the first-trimester scan in the diagnosis of fetal major abnormalities, all using a standard screening protocol, we numbered 118110 cases and we collected 5 cases diagnosed, and 34 cases missed. This underlines the difficulties encountered in OSB diagnosis in the FT. On the contrary, it is likely that adding at least a marker for OSB, we will be ending up by diagnosing the majority of cases, since introducing just a simple and reproducible parameter as BPD resulted in detecting half of the cases.…”

Transvaginal sonographic evaluation of fetal anatomy at 14 to 16 weeks. Why it is not feasible in the United States.

“…It is important, however, to know that to achieve the maximum benefit of the sonographic technique for reassuring the patient of normal anatomy or for detecting malformations, 2 scans have to be done: 1 at 14 to 16 weeks and a complementary transabdominal scan at 20 to 24 weeks. This was more than adequately borne out by 2 studies performed by Yagel et al 1 in Israel and D'Ottavio et al [2][3][4] in Italy. In Hungary, Hernadi and Töröcsik 7 scanned 3991 patients at 12 weeks and found 51% of malformed fetuses and stated that a second scan is needed later in pregnancy.…”

“…Given the facts that 60% to 80% (and in certain centers ≈90%) of clinically significant anomalies are detected, and that, in experienced hands, transvaginal and transabdominal sonography used in combination detects 90% or more of those anomalies, [1][2][3][4] it is very difficult to understand why transvaginal sonography (TVS) as a means of early structural evaluation of every fetus is so underused in the United States.…”