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Why We Should Not Abandon the 12 Week NT Ultrasound in Favor of Cell-free DNA Screening Only

David L. Berry, M.D.
Austin Perinatal Associates

Problem:
Since the advent of widespread non-invasive prenatal testing (NIPT) via maternal cell-free DNA evaluation, many obstetricians have abandoned the 12-week ultrasound previously used for nuchal translucency evaluation. While focusing upon the chromosomal make up of high and low-risk pregnant women, other more common fetal anomalies have been forgotten.

First Trimester Ultrasound:
Very early first trimester ultrasound is commonly used for confirmation of a live embryo, for accurate gestational dating, to identify a failed pregnancy, to evaluate for ectopic pregnancy and to identify multiple gestations. These ultrasound evaluations should be done between 6 and 10 weeks and have great value. Failed pregnancy, tubal pregnancy, chorionicity of multiples and dating +/- 5 days can easily be done by transabdominal or transvaginal ultrasound.

Late First Trimester Ultrasound/NT:
The following is a list of many severe fetal anomalies actually diagnosed at Austin Perinatal Associates that would have been missed if a 12-14 week ultrasound evaluation was not done:

  • Anencephaly
  • Exencephaly/Acrania
  • Encephalocele
  • Holoprosencephaly
  • Spina bifida
  • Major heart defects
  • Ectopia cordis
  • Lung masses (CCAM)
  • Gastroschisis/Omphalocele
  • Limb-body wall defect
  • Twins, Triplets, Quadruplets, Quintuplets
  • Monoamniotic twins
  • Conjoined twins
  • Amniotic band syndrome
  • Limb reduction defects
  • Oral and sacral teratomas
  • Bladder extrophy
  • Hydatidiform molar pregnancy
  • Unusual aneuploidies (Trisomy 9, Trisomy 13 with a normal NIPT, Cri-du Chat, Partial Trisomy 2)

Diagnostic Ultrasound at 12 Weeks?
Early diagnosis of severe, non-chromosomal fetal birth defects is vitally important into setting expectations of a pregnancy. In the case of a severe anomaly, the patient must first plan for any fetal diagnostic or surgical intervention, including consideration of a referral to a fetal surgical center. Most severe birth defects require planning a delivery in a tertiary medical center with a level III NICU. Early diagnosis of severe or fatal anomalies also allows the patient the opportunity to make timely, informed decisions regarding termination.

Austin Perinatal Associates Recommendations:
As ultrasound technology advances, the opportunities to accurately diagnose fetal anomalies at progressively younger gestational ages increase. A 12-week ultrasound should be considered an early anatomical survey of the fetus. Large and severe birth defects can be identified. Subtle and smaller defects will require the traditional 18 - 20 week full anatomic survey. Patients with a strong family history of heart defects or risk factors for heart defects should have a fetal echocardiography ultrasound at 22 - 24 weeks. Regardless of age, risk factors or NIPT results, APA recommends a viability ultrasound at 6 - 8 weeks, an early anatomy/NT exam at 12 - 14 weeks, an anatomic survey at 18 - 20 weeks and a fetal echo, serial growth exams, cervical length exams and biophysical profiles as dictated by the maternal or fetal conditions or exposures.

For any questions or concerns, please contact Dr. Berry at (512) 206-0101 at any time.

Dr. David L. Berry

A 4th generation physician and Austinite since 1978, Dr. Berry is board certified by the American Board of Obstetrics and Gynecology both in OB/GYN and maternal-fetal medicine.

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