Comparison of spontaneous fetal loss rates between women with singleton and twin pregnancies after mid‐trimester amniocentesis ‐ A historical cohort study

Abstract Objective To assess and compare fetal loss rates before 28 weeks of singleton and twin pregnancies after mid‐trimester amniocentesis. Method This historic cohort study included 13 773 women with singletons and 426 women with twins undergoing mid‐trimester amniocentesis from 1/2015 to 3/2017. Pregnancies resulting in termination or selective reduction before 28 weeks were excluded, as well as twin gestations undergoing single‐puncture amniocentesis. Fetal loss rates were compared between singleton and twins taking into account maternal characteristics, amniocentesis procedure, and fetal chromosomal abnormalities. Results The rates of fetal chromosomal abnormalities were similar in singleton and twin gestations (1.13% vs 0.70%, P = .253). No difference was found in maternal or fetal characteristics, or amniocentesis procedure between the two groups. The fetal loss rate was significantly higher in twin compared with singleton pregnancies (1.91% vs 0.24%, P < .001, RR = 8.25 [95% CI: 4.51 to 15.09]). The fetal loss rate between monochorionic twins and dichorionic twins was similar (1.80% vs 1.78%, P = 1.000). Conclusions Twin pregnancies have higher risk of fetal loss after mid‐trimester amniocentesis, which cannot be explained by differences in rates of fetal chromosomal abnormalities, maternal characteristic, or amniocentesis technique.