Bedside estimation of Down syndrome risk from second-trimester ultrasound prenasal thickness.
OBJECTIVE
To construct tables for 'bedside' estimation of Down syndrome risk based on maternal age and ultrasound prenasal thickness (PT) measurements.


METHODS
Likelihood ratios were calculated using a log Gaussian model of the PT distribution in multiples of the gestational age-specific median (MoM). The model parameters were derived from 80 Down syndrome and 850 unaffected pregnancies scanned at 14-27 weeks; these data had been published previously, in three series, except for 18 Down syndrome and 119 affected pregnancies. The means were estimated as the median, and the SDs as the 10(th)-90(th) range divided by 2.563.


RESULTS
A log Gaussian model fitted well the distribution of PT values in Down syndrome and unaffected pregnancies with medians of 1.31 MoM and 1.01 MoM, and log(10) SDs of 0.075 and 0.082, respectively.


CONCLUSIONS
The tables provide a simple 'bedside' estimation of Down syndrome risk without the need for computerized software or complicated calculations. More prospective data on PT in combination with other first- and second-trimester screening markers are needed.
Maymon
R
R
Department of Obstetrics and Gynecology, Assaf Harofe Medical Center, affiliated to the Sackler Faculty of Medicine, Tel Aviv University, Israel. intposgr@post.tau.ac.il
Moskovitch
M
M
Levinsohn-Tavor
O
O
Weinraub
Z
Z
Herman
A
A
Cuckle
H
H
D000293:Adolescent; D000328:Adult; D001699:Biometry; D004314:Down Syndrome / Q000000981:diagnostic imaging*; D005260:Female; D005865:Gestational Age; D006801:Humans; D008423:Maternal Age; D015233:Models, Statistical; D009295:Nasal Bone / Q000000981:diagnostic imaging* / Q000196:embryology; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012016:Reference Values; D018570:Risk Assessment; D016216:Ultrasonography, Prenatal; D055815:Young Adult