Detection of malformations in chromosomally normal fetuses by routine ultrasound at 12 or 18 weeks of gestation-a randomised controlled trial in 39,572 pregnancies.
OBJECTIVE
To compare the antenatal detection rate of malformations in chromosomally normal fetuses between a strategy of offering one routine ultrasound examination at 12 gestational weeks (gws) and a strategy of offering one routine examination at 18 gws.


METHODS
Randomised controlled trial.


METHODS
Multicentre trial including eight hospitals.


METHODS
A total of 39,572 unselected pregnant women.


METHODS
Women were randomised either to one routine ultrasound scan at 12 (12-14) gws including nuchal translucency (NT) measurement or to one routine scan at 18 (15-22) gws. Anomaly screening was performed in both groups following a check-list. A repeat scan was offered in the 12-week scan group if the fetal anatomy could not be adequately seen at 12-14 gws or if NT was >or=3.5 mm in a fetus with normal or unknown chromosomes.


METHODS
Antenatal detection rate of malformed fetuses.


RESULTS
The antenatal detection rate of fetuses with a major malformation was 38% (66/176) in the 12-week scan group and 47% (72/152) in the 18-week scan group (P= 0.06). The corresponding figures for detection at <22 gws were 30% (53/176) and 40% (61/152) (P= 0.07). In the 12-week scan group, 69% of fetuses with a lethal anomaly were detected at a scan at 12-14 gws.


CONCLUSIONS
None of the two strategies for prenatal diagnosis is clearly superior to the other. The 12-week strategy has the advantage that most lethal malformations will be detected at <15 gws, enabling earlier pregnancy termination. The 18-week strategy seems to be associated with a slightly higher detection rate of major malformations, although the difference was not statistically significant.
Saltvedt
S
S
Department of Obstetrics and Gynaecology, South Stockholm General Hospital, Stockholm, Sweden. sissel.saltvedt@kids.ki.se
Almström
H
H
Kublickas
M
M
Valentin
L
L
Grunewald
C
C
D000013:Congenital Abnormalities / Q000000981:diagnostic imaging*; D005260:Female; D005333:Fetus; D005865:Gestational Age; D006801:Humans; D048208:Nuchal Translucency Measurement; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D016216:Ultrasonography, Prenatal / Q000379:methods*