Down Syndrome Screening: My Fetus Passes the First Test


My husband and I got some good news today about our fetus: His or her nuchal fold measures 1.4 millimeters.

I never imagined that I'd know so much about the folds on fetuses' necks, but now that it has become the most accurate noninvasive method by which to determine the odds of chromosomal abnormalities—such as trisomies 13 (Patau syndrome), 18 (Edwards syndrome), and 21 (Down syndrome)—it's all the rage among women who fall into the "advanced maternal age" category.

The nuchal fold is the translucent space in the tissue at the back of the fetus's neck, and more fluid there means a higher risk of problems with the pregnancy. I found an excellent explanation of the scan on the blog of a New Hampshire midwife.

"What's the danger zone?" I asked the perinatologist as he played Slip 'N Slide with the ultrasound wand on my gelled-up belly.

"Three millimeters. And this kid is well below that."

I thrust my fists into the air, inspiring my fetus to perform a victory flip of its own. "Yes!" I hissed quietly, just in case the women in the rooms around me weren't feeling as victorious.

See, as we've worked to add to our family, I've watched my odds of chromosomal disorders start to rise. (The full book from the American Society for Reproductive Medicine regarding the risks that mothers face as they age is here.)

And it's made me think long and hard about whether we would be willing to raise a child with a chromosomal disorder. Our inclination is that we would not terminate such a pregnancy, but we've decided to cross that bridge when and if we come to it. With the 1.4-mm reading, I feel more certain that we will not have to.

Next Page: Is that a nose bone? [ pagebreak ]I was delighted also to see a nasal bone on the monitor. It not only further eliminates the possibility of Down syndrome, but it looks precisely like my husband's. I'm still baffled and amazed that we went from a misdiagnosed chemical pregnancy to a somersaulting 12-week-old fetus who looks like his Daddy and seems to have every intention of sticking around.

Not that we are totally out of the woods yet—and not that I will ever believe that we are totally out of the woods until I am wearing a backless gown with a small child in my arms. The next hurdle is the full genetic analysis.

After the scan, our perinatology center took my blood to measure the level of free beta-hCG in my body, as well as a protein called pregnancy-associated plasma protein A (PAPP-A). If these two protein levels are abnormal, it could raise our odds of a Down syndrome baby, in which case I'd most likely opt for a chorionic villus sampling (CVS) just to be able to relax for the rest of the pregnancy.

(A South Carolina doctor has some great details regarding what these blood test results mean on his blog, Fruit of the Womb.)

It won't be until next week that I will get The Call from a genetics counselor. She will dump my age, the nuchal fold scan, and the blood test results into some sort of fancy calculator and give us the odds that our baby will be born with a chromosomal abnormality.

With our second daughter, our odds came back 1 in 300 for Down syndrome and 1 in 4,000 for spina bifida. For me, those were numbers I could live with, because they were smaller than the odds based on my age alone.

But for now, I'm celebrating the 1.4-mm measurement. And the perinatologist was pretty merry about it too. Both of us feeling relieved, he walked me to the desk to schedule my 20-week ultrasound in mid-January.

"See you then!" he said.

I hope so.