RESUMO
Objective: To investigate the difference of intertwin estimated fetal weight (EFW) in normal dichorionic pregnancy and the impact factors. Methods: Prenatal ultrasonic parameters of 550 normal dichorionic twins (1 100 fetuses) were retrospectively analyzed. Fetal weight was estimated based on head circumference, abdominal circumference, biparietal diameter and femur length. The growth discordance ratio of EFW was calculated between the two fetuses. The correlation between the gestational weeks and the discordance ratios was assessed. In addition, whether the gender difference and different fertilization way could be impact factors of EFW discordance was evaluated. Results: No obvious correlation was observed between EFW discordance ratio and gestation age. EFW discordance ratio was skew distribution, with median of 6.65%, interquartile range of 8.92% and the 95th percentiles of 20.81%. There was no statistical significant difference of EFW discordance ratio between gender-identical group and gender-specific group, nor between two groups with different fertilization way (both P>0.05). Conclusion: Ultrasound is valuable to obtain EFW in dichorionic twins. EFW discordance ratio can be used as a relatively date-independent index in evaluation of the growth of dichorionic twins.
RESUMO
Blood chimerism in twins is known to occur through the transfer of hematopoietic stem cells between the fetuses via a common placenta. We present a case of blood chimerism in a dizygotic dichorionic twin pregnancy. The female twin was delivered at 34 weeks of gestation, and the male twin was stillborn. Pathologic examination confirmed dichorionic diamniotic placentas. The karyotype of the female child was obtained using peripheral blood sample, and it revealed a mixture of 46,XX and 46,XY cells (chi 46,XY[13]/46,XX[7]). FISH analysis performed on the buccal cells by using CEP X/Y probe (Abbott Molecular Inc., USA) revealed 100% XX signals (nuc ish Xcen(DXZ1x2)[500]). Gross examination of the external genitalia and abdominal ultrasonography revealed no definitive abnormal findings in relation to sex differentiation. When XX/XY chimerism is present in blood lymphocytes, careful examination of external genitalia and reproductive organs and further studies are required to detect chimerism in non-hematopoetic tissues. This is a rare case of blood chimerism in dichorionic placentas, in contrast to those in monochorionic placentas.