Table 1 Clinical characteristics of 642 patients undergoing routine prenatal screening in mid-trimester (18-24 weeks of gestation)

Pregnant women

n = 642

    Mean Maternal age (years)

30(±3)

    Cervical canal length (mm)

51(±12)

    History of cesarean section

12

    Previous open abdominal surgery

10

    Prior laparoscopic abdominal surgery

13

Fetal

n = 642

Gestational week

    18 weeks

5

    19 weeks

13

    20 weeks

39

    21 weeks

207

    22 weeks

265

    23 weeks

95

    24 weeks

18

Placental position

    Posterior

251

    Anterior

258

    Fundal or lateral

133

Amniotic fluid anteroposterior diameter (mm)

47 ± 5