The purpose of this study was to investigate age- specific spontaneous fetal loss rates of pregnancies without known chromosomal or structural abnormalities from mid- second trimester onward. The study consisted of 264,653 women screened between October 1995 and September 2000 with available pregnancy outcomes. Pregnancies associated with fetal chromosomal or structural abnormalities, insulin dependent diabetes mellitus, and multiple pregnancies were excluded. Spontaneous fetal losses at or after 15 weeks of gestation were identified. Women were grouped according to maternal age at expected date of delivery. Spontaneous fetal loss rates in each group were evaluated after adjusting fetal losses associated with amniocentesis and identifiable ethnic groups. Fetal loss rates increased in both younger and older women. The lowest rate was seen in women at mid- 20s. Compared with Caucasian and Asian women, black women had higher fetal loss rate at nearly every age group. The results of the study provided a baseline agespecific spontaneous fetal loss rate of pregnancies at a specified gestational window. The purpose of this study was to investigate age- specific spontaneous fetal loss rates of pregnancies without known chromosomal or structural abnormalities from mid- second trimester onward. The study consisted of 264,653 women screened between October 1995 and September 2000 with available pregnancy outcomes. Pregnancies associated with fetal chromosomal or structural abnormalities, insulin dependent diabetes mellitus, and multiple pregnancies were excluded. Spontaneous fetal losses rates in or after 15 weeks of gestation were identified. Women were grouped according to maternal age at expected date of delivery. group were evaluated after adjusting fetal losses associated with amniocentesis and identifiable ethnic groups. Fetal loss rates increased in younger and older women. The lowest rate was seen in women at mid- 20s. Compared with Caucasian and Asian women, black women had higher fetal loss rate at nearly every age group. The results of the st udy provided a baseline maypecific spontaneous fetal loss rate of pregnancies at a specified gestational window.