Nuchal translucency thickness and crown rump length discordance for the prediction of outcome in monochorionic diamniotic pregnancies.
BACKGROUND
Ultrasonographic features of the underlying hemodynamic changes in twin-twin transfusion syndrome (TTTS) may be present at the first trimester scan.


OBJECTIVE
To investigate the value of intertwin discordance in nuchal translucency (NT) thickness and crown-rump length (CRL) to predict TTTS and other adverse outcomes.


METHODS
Cohort study.


METHODS
One hundred and thirty-five unselected consecutive monochorionic diamniotic twin pregnancies.


METHODS
NT and CRL discordance were assessed at 11 to 13(+6) weeks' gestation. Receiver-operating characteristics (ROC) curves were used to determine their predictive ability for the subsequent development of TTTS.


RESULTS
TTTS complicated 16/135 (12%) pregnancies. Four other pregnancies were complicated by selective intrauterine growth restriction (sIUGR) and 3 by miscarriage <24 weeks gestation. The median NT discordance was 15% (range 0-37%) in TTTS pregnancies, 13% (12-19%) in those with miscarriage <24 weeks' gestation, 47% (30-50%) in those with sIUGR, and 14% (0-86%) in those without complications. Prediction for subsequent development of TTTS provided by the discordance in CRL, expressed as the area under ROC curve, was 0.52 (95% confidence interval 0.38-0.67), while it was 0.50 for NT discordance (95% confidence interval 0.35-0.64). NT discordance was significantly higher in sIUGR compared to both uncomplicated and TTTS pregnancies (p=0.004 and p=0.003, respectively).


CONCLUSIONS
In an unselected population of monochorionic twin pregnancies, discordance in CRL and NT measured during first trimester scan is not a clinically useful predictor of the subsequent development of TTTS. Therefore, strict ultrasound follow up is recommended for the timely diagnosis of TTTS.
Fratelli
Nicola
N
Maternal Fetal Medicine Unit, Department of Obstetrics and Gynaecology, University of Brescia, Piazzale Spedali Civili 1, Brescia, Italy. nicolaf23@gmail.com
Prefumo
Federico
F
Fichera
Anna
A
Valcamonico
Adriana
A
Marella
Daria
D
Frusca
Tiziana
T
D015331:Cohort Studies; D018568:Crown-Rump Length; D005260:Female; D005330:Fetofetal Transfusion; D006801:Humans; D007621:Karyotyping; D053589:Nuchal Cord; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D014429:Twins, Dizygotic