Differences in the prenatal diagnosis rates of BDs between singleton and multiple pregnancies
The prenatal diagnosis rate of BDs associated with multiple pregnancies was 14.38%, which was significantly lower than that associated with singletons (32.00%; χ2 = 452.94,P <0.001). A significantly lower prenatal diagnosis rate was found not only for BDs in their entirety associated with multiple births (χ2 = 452.94, P <0.001), but also for 10 types of BD (all P <0.05) (Table 2). These were congenital heart defects (χ2 = 213.89,P <0.001), congenital hydrocephalus (χ2 = 22.05, P <0.001), cleft lip with cleft palate (χ2 = 50.23, P <0.001), congenital talipes equinovarus (χ2 = 5.37,P =0.020), cleft lip without cleft palate (χ2 = 18.84, P <0.001), limb reduction defects (χ2 = 7.74, P =0.005), congenital diaphragmatic hernia (χ2 = 12.73, P <0.001), trisomy 21 syndrome (χ2 = 28.40, P <0.001), congenital malformation of the urinary system (χ2 = 29.90, P <0.001), and other chromosomal malformation (χ2 = 4.91, P =0.027).