Amniocentesis-related pregnancy loss in monochorionic and dichorionic twin pregnancies: preliminary data from a large, single-center, retrospective case series analysis

Objective. We aimed to investigate the amniocentesis-related pregnancy loss (ARL) rates in monochorionic and dichorionic twin pregnancies. Patients and Methods. We performed a single-center, retrospective case series analysis collecting data from the prenatal diagnosis database of the Altamedica Main Center (Rome, Italy) from October 2010 to December 2014. We selected women with twin pregnancy who underwent amniocentesis for prenatal diagnosis between 16 and 19 gestational weeks. We excluded patients with maternal pre-gestational metabolic, endocrine, immune, infectious, cardiovascular and oncological diseases, fetal chromosomal abnormalities and fetuses affected by any other malformations detectable by ultrasound. Before the amniocentesis, all patients underwent antibiotic therapy with 500 mg oral azithromycin at 24-h intervals for 3 days and ultrasound examination focused on early prenatal detection of fetal intrauterine anatomy. Amniocentesis was performed following the instructions and the recommendations based on clinical evidence as provided by the Italian College of Fetal Maternal Medicine’s guidelines. Two needle-insertion was done in dichorionic pregnancies (one for each sac) and one needle-insertion in monochorionic ones. We performed a further ultrasound scan and then discharged women 30 minutes after the amniocentesis. No bed-rest was suggested and we recommended to use 450 mg of oral magnesium/day for a week. For each enrolled patient, we recorded maternal age and gestational age at the amniocentesis, chorionicity and if ARL (defined as pregnancy loss detected within 20 days from amniocentesis) occurred. Statistical analysis was performed using T test to compare continuous variables and χ2 to compare categorical ones; p value < 00.5 was considered statistically significant. Results. As evidenced in Table 1, we enrolled 311 women with twin pregnancy, 36 (11,5%) monochorionic and 275 (88,5%) dichorionic. We found no significant differences (p= 0,522) between monochorionic group (17,6 ± 0,7 weeks) and dichorionic group (17,5 ± 0,9 weeks) for gestational age at the amniocentesis. Conversely, maternal age was significantly higher (p= 0,001) in dichorionic group (37,0 ± 5,2 years) respect to monochorionic group (26,5 ± 4,3 years), probably due to the higher rate of assisted reproductive technology in this kind of patients. Finally, we recorded only 1 ARL cases in the dichorionic group (0,32% considering the whole sample; 0,37% considering the subgroup) and no ARL cases in the monochorionic group: in any case, the difference between the two groups regarding ARL rate was not significant (p= 1,000). Conclusion. Basing on our data analysis, amniocentesis could be considered a safe procedure with low level of ARL, even in twin pregnancies. Furthermore, our preliminary data allow us to evidence that there is not a significant difference in ARL rate between monochorionic and dichorionic twin pregnancies.