Fetal Discrepancy During First Trimester In Dichorionic Twins

Objective:To investigate the incidence and distribution of fetal discrepancy during the first trimester in dichorionic twins, and its influencing factor and clinical significance.Method:This was a prospective analysis of dichorionic twin pregnancies that underwent11+0～13+6week scan at a tertiary hospital from Sep2008to Oct2010. Differences in crown-rump length (CRL), nuchal translucency (NT), heart rate (HR), deepest vertical pockets of amniotic fluid (DVP) for every pair of twin fetuses were calculated and expressed as absolute value and percentage of discordance. The incidence and distribution of discrepancies were analyzed according to gestational age, mode of conception, and the gender in twin pairs. Then, the efficacy of first trimester discrepancy in the prediction of subsequent birthweight discordance was evaluated.Results:A total of66dichorionic twin pregnancies were included. The average CRL was significantly different between the larger fetus and the smaller one, which were65.28±8.54mm and62.34±8.49mm respectively (P<0.001). The average NT was significantly different between two fetuses, which were1.56±0.35mm and1.28±0.30mm respectively. HR and DVP were also statistically different between two fetuses (P<0.001). The discrepancy of those parameters in twins (⊿CR1,⊿CR1%,⊿NT,⊿NT%,⊿HR,⊿HR%,⊿DVP and⊿DVP%)did not change significantly with gestational age between11+0and13+6weeks(P>0.05). In8twins conceived spontaneously and58twins following assisted reproductive technologies, the discrepancy of CRL, NT, HR and DVP were not statistically different (P>0.05). In20male twins,14female twins and32twins with discordant gender, first trimester growth discrepancy were not significantly different. The birth weight discrepancy was11.99%±8.96%in all the66dichorionic twins, which was not correlated with CRL discrepancy such as⊿CR1(Spearman’s rho=0.056, P=0.656) and⊿CRL%(Spearman’s rho=0.056, P=0.657).Conclusions:1. The growth of two fetuses in normal dichorionic twins is not uniform during the first trimester.2. Discrepancy of CRL, NT, HR, and DVP from11+0to13+6weeks of gestation are not significantly correlated with gestational age, mode of conception and fetal gender.3. CRL with discordant measurements in first trimester is not related to subsequent birth weight discordance.