Fetal biometric parameters, twin type and birth weight difference - A longitudinal study

Objective: To examine the relationship between twin type, divided by zygosi ty, chorionicity, and birth weight difference [more or less than 15% intert win weight difference at delivery] on fetal biometric measurements, includi ng biparietal diameter, transverse abdominal diameter, hr:ld and abdominal circumferences (AC) and head and abdominal areas, femur length (FL), transv erse cerebellar diameter, cerebellar circumference and cerebellar area at 1 8, 23, 28 and 32 weeks of gestational age. Study design: A prospective and longitudinal study was dune on 75 twin pairs that did not present the twin- twin transfusion syndrome (150 fetuses) divided into birth weight differenc e group 1 (<15%) and group II (greater than or equal to 15%). The twin pair s were divided into three groups: dizygotic, monochorionic, and dichorionic -monozygotic. In each group the differences in various ultrasound indices w ere evaluated in reference to discordant growth or concordant growth. Resul ts: In our sample, there were no monozygotic twin pairs with dichorionic pl acentation with a birth weight difference of more than 15%. Significant ass ociations of group and gestational age were found in dizygotic and monochor ionic twins. Intrapair differences were significantly higher in group II (g reater than or equal to 15%) than in group I (<15%) for all Fetal parameter s studied except for AC, abdominal urea and all cerebellar parameters. The value of these discrepancies increased according to gestational age except for FL. Significant interactions between group and zygosity type indicated that intrapair FL differences were more associated with group in monochorio nic twins, whereas intrapair transverse cerebellar diameter differences wer e more associated with group in dizygotic twins. Conclusion: Our data show that most fetal biometric parameters are associated with birth weight disco rdancy. Abdominal area could be a relevant marker for twins with obstetric complications. Note that this is the first research that has studied a twin sample divided by both twin type and birth weight group. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.