Differences in the timing of the prenatal diagnosis of BDs associated with singleton and multiple births
Table 4 shows the timing of the prenatal diagnosis of BDs associated with singleton and multiple births. For BDs as a whole that were associated with multiple pregnancies, 70.08% of BDs were diagnosed before 28 weeks of gestation, which was significantly lower than the 74.82% diagnosis rate for BDs associated with singletons (χ2 = 5.51, P =0.019). The significantly lower rate of early diagnosis of BDs associated with multiple pregnancy was also found for cleft lip with cleft palate (χ2 = 7.75,P =0.005), trisomy 21 syndrome (χ2 = 5.46,P =0.020), and congenital malformation of the urinary system (χ2 = 10.07, P =0.002).