First-trimester growth restriction and fetal aneuploidy: the effect of type of aneuploidy and gestational age.
OBJECTIVE
Our purpose was to determine the effect of type of aneuploidy and gestational age on first-trimester fetal growth.


METHODS
Crown-rump length measurement was obtained in pregnancies undergoing chorionic villus sampling in three large prenatal diagnosis centers. One hundred forty-four aneuploid fetuses, from 9 to 13 weeks' gestation, were compared with 440 matched control fetuses for evidence of crown-rump length shortening. Shortening was defined by the observed/expected crown-rump length. Expected values of crown-rump length based on last menstrual period were obtained from regression equations generated from a separate normal group. Threshold values for aneuploidy screening were determined on the basis of receiver-operator characteristic curves.


RESULTS
There was significant crown-rump length shortening in trisomy 18 compared with normal fetuses, with observed/expected values < or = 0.80 (odds ratio 13.78, 95% confidence interval 5.64 to 33.88, p < 0.000001); for trisomy 13 the observed/expected crown-rump length was < or = 0.90 (odds ratio 3.64, 95% confidence interval 1.08 to 12.96, p < 0.03). There was no significant shortening of crown-rump length in Down syndrome, with observed/expected values < or = 0.92 (odds ratio 0.86, 95% confidence interval 0.50 to 1.47, p = 0.6). With shortened crown-rump length (observed/expected value < 0.86) the risk of any aneuploidy is increased (odds ratio 2.52, 95% confidence interval 1.6 to 3.96, p < 0.0001). When the first-trimester crown-rump length was shortened by > or = 14 mm, the aneuploidy risk was high (odds ratio 9.04, 95% confidence interval 3.26 to 28.67, p < 0.00001).


CONCLUSIONS
In the first trimester fetuses with trisomy 18 and 13 appear to be growth restricted, in contrast to fetuses with trisomy 21. In at-risk pregnancies crown-length that is shorter than expected significantly increase the odds that aneuploidy is present.
Bahado-Singh
R O
RO
Department of Obstetrics and Gynecology, Yale University School of Medicine, New Haven, CT 06520-8063, USA.
Lynch
L
L
Deren
O
O
Morroti
R
R
Copel
J A
JA
Mahoney
M J
MJ
Williams
J
J
D000782:Aneuploidy; D015193:Chorionic Villi Sampling; D002887:Chromosomes, Human, Pair 18; D018568:Crown-Rump Length; D004314:Down Syndrome; D005260:Female; D005317:Fetal Growth Retardation / Q000235:genetics*; D005865:Gestational Age; D006801:Humans; D016015:Logistic Models; D011247:Pregnancy; D014314:Trisomy