Utilization of Amniocentesis by Women Screening Positive for Down Syndrome on the Second-Trimester Triple Test

Abstract

Objective: Second-trimester maternal serum screening for Down syndrome has become widely accepted in the United States. However, many women with screen-positive results forgo definitive diagnostic testing that involves chromosomal analysis of amniotic fluid cells. We have reviewed 2,879 cases of women with screen-positive results in an effort to identify determining factors for the utilization of amniocentesis. Methods and Results: The lowest rate of utilization of amniocentesis was seen among very young women, with peak utilization among women of age 33. Although all women in the study had screen-positive results, amniocentesis was most likely to be performed when the patient-specific risk for an affected pregnancy was high. Black or Hispanic women were less likely to receive amniocentesis than white or Asian women. Amniocentesis utilization was also negatively associated with gestational age, maternal weight and an ultrasound examination prior to screening. A sharp decline in the utilization of amniocentesis was noted between 1993 and 1998. A logistic regression model was estimated to assess the independent effect of the variables. The model predicted 67% of the observed amniocenteses and had 66.6% concordance in the evaluation of paired cases with different response values. Conclusions: Our observations indicate that there are multiple medical, social and demographic factors that influence the utilization of amniocentesis by women with screen-positive results. Early screening and a prompt response to screen-positive results, together with accessible and appropriate genetic counseling, should assist women in making an informed choice.