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NASHVILLE -- Pregnant patients taking heparin and/or aspirin at the time of their cell-free DNA screening seemed to have a significantly higher likelihood of "no-call," or uninterpretable test results, a researcher said here.

A multivariate analysis found that use of heparin and/or aspirin was associated with higher odds of no-call (adjusted OR 6.0, 95% CI 3.0-12.6), reported Daniel Lovell, of the Wake Forest School of Medicine in Winston-Salem, North Carolina.

Moreover, heparin or aspirin use comprised over half of the no-call results in the small study presented at the American College of Obstetricians and Gynecologists (ACOG) annual meeting.

Lovell explained that allows for screening of genetic disorders, but its performance is dependent on the fetal fraction -- or fraction of maternal DNA versus placental DNA -- available. The average is around 15%, with a lower limit of 4%, he said. About 1%-3% of pregnancies that require this type of testing end up being no-call, and factors known to affect cell-free DNA levels include gestational age, maternal weight, fetal karyotype, and .

Because cell-free DNA screening is recommended for high-risk women, Lovell said that these results should give pause to the clinician when working with a woman on heparin or aspirin.

"Clinicians should consider or diagnosis methods to prevent delay in counseling the patient if there were some kind of risk of abnormality," he said.

Courtney Olson-Chen, MD, of the University of Rochester Medical Center in New York added that no-call results are associated with a higher risk of there being a problem with the pregnancy.

"It's possible to repeat the test even after a no-call, it just adds more time to process finding out what's going on with the pregnancy, and patients would rather know as soon as possible," Olson-Chen, who was not involved in the study, told 木瓜直播. "It's been suggested that perhaps we should use other methods of screening, but we need more information before we make that decision."

Lovell and colleagues did a retrospective chart review of patient data from 2014-2018, and performed univariate and multivariate analyses including:

• Heparin/aspirin use
• Gestational age at collection
• Weight
• Chronic hypertension
• Pre-gestational diabetes
• Autoimmune disease

Lovell said that the last three conditions were included because they were "potentially relevant comorbidities that could confound results."

Overall, 1,396 charts had complete data, with 1,349 obtaining results and 47 no-calls (3.48%). Patients were a mean age of 33 to 36, with a gestational age of 15 to 17 weeks. The weight in the no-call group was substantially higher, but Lovell noted that was to be expected, as obese women tend to have a higher rate of no-call.

Of the 47 no-calls, 25 had heparin/aspirin use, 20 had chronic hypertension, and eight had pre-gestational diabetes. While all covariates were significantly associated with higher odds of no-call in the univariate analysis, only heparin/aspirin use remained significant after adjusting for confounders.

However, Lovell noted that their group was to his knowledge, the first to look at the effect of diabetes on no-call rates, which "could be a potentially novel finding."

An ACOG attendee asked why heparin, a blood thinner, and aspirin, which has been used to treat preeclampsia, were combined, and Lovell said it was to increase the number.

Olson-Chen said that in her practice, most patients don't start on aspirin until the end of the first trimester for preeclampsia, but that patients who come from infertility clinics will come to the practice on aspirin, and those patients could be affected by this.

Lovell recommended a larger multicenter analysis to try and understand the effects of different factors on the no-call rate.

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