The prevalence of non-viable pregnancy at 10-13 weeks of gestation.

In an ultrasound screening study at 10-13 weeks of gestation involving 17,870 women, the prevalence of early pregnancy failure was 2.8% (501 cases), including 313 (62.5%) missed abortions and 188 (37.5%) anembryonic pregnancies. Lower gestation and higher maternal age were associated with a higher prevalence (chi 2 = 143.5; p < 0.001 and chi 2 = 53.3; p < 0.0001, respectively). The prevalence was higher in women with a history of vaginal bleeding (chi 2 = 141.5; p < 0.0001), but there was no significant association with previous pregnancy losses (chi 2 = 2.8), parity (chi 2 = 0.6) or cigarette smoking (chi 2 = 0.0). Recent evidence suggests that the most effective method of screening for chromosomal abnormalities is measurement of fetal nuchal translucency thickness at 10-13 weeks, and therefore ultrasound examination at this gestation is likely to become universally available. As shown in this study, an additional advantage of such a scan is the diagnosis of early pregnancy failure, which will be found in about 3% of patients examined. Elective evacuation of retained products of conception is likely to be more cost effective and potentially safer than emergency surgery in a patient presenting during miscarriage.