The identification of risk of spontaneous fetal loss through second-trimester maternal serum screening

Objective The purpose of this study was to investigate associations between risk of spontaneous fetal loss and risk estimates for Down syndrome, trisomy 18, and neural tube defects assigned by second-trimester maternal serum screening. Study design The study involved 264,653 women with available pregnancy outcomes who were screened between 15 and 20 weeks of gestation in the Ontario Maternal Serum Screening Program between October 1995 and September 2000. Pregnancies complicated by fetal chromosomal or structural abnormalities, insulin-dependent diabetes mellitus, and multiple pregnancies were excluded. Spontaneous fetal loss was defined as spontaneous miscarriage and intrauterine fetal demise as classified by the ICD-9 system, but including only those ≥15 weeks of gestation. Women were grouped according to risk estimates for Down syndrome, trisomy 18, and neural tube defects, respectively. Spontaneous fetal loss rates by each risk group were evaluated after adjusting for losses associated with maternal age and amniocentesis. Results Fetal loss rates increased in women with risk estimates of ≥1 in 1110 for trisomy 18 or neural tube defects, and ≥1 in 130 for Down syndrome. The excessive fetal loss rates for these 3 groups of women were 14.4%, 3.2%, and 1.5% respectively. Conclusion Fetal loss rate markedly increased in women with high-risk estimates for trisomy 18, neural tube defects, and Down syndrome. Risk estimates assigned by triple marker screening may provide an early means of stratifying pregnancies into risk for fetal loss.