Spontaneous fetal loss rates in a non-selected population

The objective of this work was to determine the rate of spontaneous fetal l oss up to 28 weeks of gestation in uncomplicated pregnancies of a low-risk population after sonographically identified intact intrauterine pregnancy d uring the first trimester, Transvaginal ultrasounds were given to 2,534 wom en at between six and 12 weeks of gestation, Inclusion criteria were a posi tive fetal cardiac activity and no antecedent signs of vaginal bleeding. Ge stational age was confirmed by measurement of the crown-rump length and/or biparietal diameter (BIP), Patients were followed until delivery or up to a fetal loss. The mean fetal loss rate between 12 and 28 weeks was 3.86% (n = 99), Fetal loss increased with maternal age: fetal loss rate under 20 yr: 2.94% (OR 0.75; CI 0.23-2. 46), 20-24 yr: 3.20% (OR 0.77; CI 0.48-1.23), 2 5-29 yr: 3.39% (OR 0.77; CI 0.50-1.19), 30-34 yr: 3.89% (OR 1.01; CI 0.59-1 .71), 35-39 yr: 7.82% (OR 2.13; CI 1.04-4.32), 40-45 y: 50% (OR 13.84; CI 6 .67-28.72) and > 45 yr: 50% (OR 13.05; CI 1.96-86.71) respectively. The fre quency of spontaneous fetal loss before 28 weeks gestation was assessed sys tematically in a low-risk population. There was a very clear correlation wi th advancing maternal age. These data now can be used as background loss ra te information for evaluating the safety of invasive prenatal diagnosis, an d they will be more valid for this purpose than the available data taken fr om selected cohorts of women, such as those from hospital clinics or from i nfertility programs. (C) 2001 Wiley-Liss, Inc.