The Houston Chronicle on Wednesday examined the growing popularity among OB/GYNs and pregnant women of an ultrasound test called nuchal translucency screening that helps to determine a woman's risk of giving birth to an infant with Down syndrome. The test, which is conducted when a woman is 11 weeks to 13 weeks pregnant, involves the measurement of the translucent space in the tissue in the back of a developing fetus's neck, which typically is larger in fetuses with Down syndrome because of excess fluid accumulation. The measurement then is put into a formula with the pregnant woman's age and the gestational age of the fetus to determine the likelihood that the fetus has Down syndrome. The test was developed in the United Kingdom and was introduced in the U.S. about 10 years ago, but it continues to be used more frequently in the United Kingdom, according to the Chronicle. However, Mildred Ramirez, an assistant professor of obstetrics and gynecology at the University of Texas-Houston Medical School, said the test is gaining popularity in the U.S., adding, "I think you will see it used far more often." About 4,000 infants are born with Down syndrome each year in the U.S. (Kurp, Houston Chronicle, 8/4).