Factors affecting the decision regarding amniocentesis in women at genetic risk because of age 35 years or older.

OBJECTIVE: To evaluate the effects of anamnestic factors and sonographic findings on the patient's decision regarding amniocentesis in a cohort of women at genetic risk because of advanced age. METHODS: All women 35 years of age or older registered for prenatal care between January 1990 and December 1998 were asked about their attitude towards genetic amniocentesis during the course of individual genetic counseling and once again after ultrasound examination inclusive of markers of aneuploidies (nuchal fold thickness greater than 6 mm, renal pyelectasis, choroid plexus cysts, and hyperechogenic bowel). Their attitudes towards genetic amniocentesis before and after ultrasound examination were compared using chi-square, Fisher's exact test, Mann-Whitney U-test, and logistic regression analysis, with a two-tailed p < 0.05 or an odds ratio (OR) with 95% confidence interval (CI) not inclusive of the unity considered significant. RESULTS: Among the 1486 women in the cohort, 1368 (97%) expressed an opinion towards genetic testing at the time of counseling: 501 (37%) were in favor and 867 (63%) were against having the procedure. After ultrasonographic examination, 33% (446/1368) of women opted for amniocentesis, 36% (146/402) after abnormal findings and 31% (300/966) after normal ultrasound findings. Significantly more women with abnormal than normal ultrasound findings opted for diagnostic testing in both groups. Overall, only 8% (115/1368) of women changed their attitude towards diagnostic testing after ultrasonographic examination. Normal sonographic findings were three times more likely to change the attitude of women initially interested in amniocentesis than abnormal sonographic findings did in women a priori not interested in the procedure (20% versus 7%, p < 0.001, OR = 3.2, 95% CI 1.8; 5.8). CONCLUSIONS: In a cohort of women at genetic risk because of advanced age, the key determinant of the choice regarding genetic amniocentesis is the a priori opinion of the woman towards the procedure, which was expressed by 93% of women. Ultrasonography plays a secondary role in changing or confirming women's attitude towards invasive diagnostic testing. Normal sonographic findings affect women's decisions more powerfully than abnormal sonographic findings, suggesting that ultrasonography has an important reassuring function for the woman.