Perinatal Center of Iowa offers the entire array of genetic and prenatal diagnosis options for patients, including first trimester screening (FTS), chorionic villus sampling (CVS), conventional second trimester screening, genetic amniocentesis, fetal blood sampling, high resolution genetic sonography, fetal echocardiogram and in-house genetic counseling.

To make a referral for any of the services offered below, please call (515) 643-6888 or toll-free (877) 415-7447.

First-trimester screening

Great efforts have been made in refining screening tools for chromosomal aneuploidies during the last three decades. First trimester screening is intended to be made available to all pregnant women, similar to multiple marker serum screening, and not just for women at increased risk for chromosome abnormaility, such as the advanced maternal age (AMA) patient.

This test, performed between 10-13 weeks gestation, is currently the most reliable screening test for Down syndrome—the most common chromosomal abnormality among babies born today. It also screens for other chromosome abnormalities and birth defects, and can accurately determine gestational age and diagnose a multiple pregnancy.

The first-trimester screening combines an ultrasound measurement of the skin thickness on the back of the baby’s neck (nuchal transulcency or NT) with a finger-stick blood test performed on the mother. These results are then analyzed and assigned a risk estimate.

For example, the risk of Down syndrome before first-trimester screening could be 1/200 (based solely on the mother’s age). After the test, the lab may reduce the risk for Down syndrome to 1/5000— which is quite reassuring. Although this is a screening test and has limitations, the results of this first-trimester screening can provide significant reassurance your patient’s baby is developing normally.

The American College of Obstetricians and Gynecologists now recommends that all women, regardless of age or family history, be offered first-trimester screening. Ultimately, it is the woman’s choice as to whether she wishes to have this test, but all pregnant women should be offered the test.

The doctors and staff at PCI are specially trained in providing this first-trimester screening to expecting women. The ultrasound measurement of the skin thickness at the base of the baby’s neck is a very precise measurement and requires additional training and certification to perform properly. Competent laboratories will not perform the test unless the sonographer in the physician’s office is certified to perform the NT. All PCI sonographers are certified in first-trimester screening. PCI doctors continue to attend educational conferences to be on the leading edge in this ever-changing field of prenatal diagnosis and screening to provide patients the highest level of knowledge and care.

Abnormal first-trimester screening results

If patients receive abnormal first-trimester screening results, a follow-up appointment with PCI for further testing will be scheduled. PCI offers both chorionic villus sampling (CVS) and genetic amniocentesis to patients who opt for these tests. Our goal is to schedule follow-up appointments within 48 to 72 hours for patients with abnormal first-trimester screening results to minimize undue anxiety.

PCI offers patients the only certified genetics counselor in central Iowa to assist in this assessment and help patients fully understand results and options for further testing. 

Chorionic Villus Sampling (CVS)

Chorionic villus sampling (CVS) is a procedure in which a small amount of tissue (chorionic villi) is obtained from the developing placenta between weeks 10 and 12 of gestation. The tissue is then sent to a lab for chromosomal analysis and, if indicated, specific genetic diseases. One advantage of CVS is that this test can be performed much earlier along in pregnancy than amniocentesis.

A disadvantage is that CVS does not detect neural tube defects, such as spina bifida. However, an alpha-fetoprotein (AFP) test and a high-resolution ultrasound examination can be performed later in your patient’s pregnancy to screen for these defects.

In addition, approximately one percent of CVS test results are considered unclear or indeterminate. Most of the fetuses in these pregnancies are normal, but additional testing — including amniocentesis — may be indicated.

CVS is offered for:

• Women who will be 35 years of age or older at the time of delivery
• Couples with a previous child or other family member with a chromosomal abnormality
• Couples in which one partner has a chromosomal rearrangement (for example, a translocation or an inversion)
• Couples at increased risk of having a child with a genetic disease for which testing is available

Amniocentesis

Amniocentesis is a procedure performed during pregnancy to examine a baby's chromosomes. Most often, an amniocentesis is done between weeks 16 and 20 of gestation.

During this procedure, amniotic fluid, which contains cells that the baby has naturally shed, is removed for testing. Cells and proteins within the amniotic fluid are then examined in the lab to test for specific fetal disorders. Alpha-fetoprotein (AFP) is also found in the amniotic fluid and can be measured in the laboratory.

Amniocentesis is generally offered for:

• Women who will be 35 years of age or older at the time of delivery
• Couples with a child or other family member with a chromosomal abnormality
• Women with a positive screening test result (for example, an expanded AFP test)
• Couples in which one partner has a chromosomal rearrangement (for example, a translocation or an inversion)
• Couples with an increased risk of having a child with a genetic disease for which testing is available
• Couples with a previous pregnancy or child with a neural tube defect (for example, spina bifida or anencephaly)