Is routine amniocentesis for advanced maternal age still indicated?

OBJECTIVE

To evaluate a policy of selective rather than routine use of amniocentesis for advanced maternal age.

METHOD: A consecutive series of 359 pregnant women aged 38-47 underwent nuchal translucency measurement (NTM) at 10-14 weeks, maternal serum screening (MSS) by alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG) at 15-17 weeks, and second trimester ultrasound at 21-23 weeks. Women with NTM <3 mm, MSS-derived risk <1/250, and a normal second trimester sonography were considered at low risk and were suggested not to have an amniocentesis.

RESULTS

Either the NTM or MSS test was positive in 130 women; 105 (81%) of them elected to have an amniocentesis, versus 122 (53%) of 229 in whom both tests were negative (p < 0.001). Nineteen (5%) of 359 patients had NTM > or =3 mm; all 7 cases of Down's syndrome were in this group; 122 (34%) of 359 patients had a MSS-derived risk > or =1/250; 6 of the 7 cases of Down's syndrome were in this group: Ten patients had an abnormal second trimester ultrasound, 1 of which had trisomy 18. Of the 219 patients with MSS-derived risk <1/250, a NTM <3 mm, and a normal second trimester ultrasound, none had a baby with a chromosomal abnormality (95% confidence interval: 0-1.4%).

CONCLUSION

Amniocentesis may be offered on a selective rather than routine basis in women over 38, based upon the results of noninvasive screening tests.