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Ultrasound Obstet Gynecol. 2013 Jan;41(1):26-32. doi: 10.1002/uog.12331. Epub 2012 Dec 4.

Fetal fraction in maternal plasma cell-free DNA at 11-13 weeks' gestation: relation to maternal and fetal characteristics.

Author information

1
Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London, UK.

Abstract

OBJECTIVE:

To examine the possible effects of maternal and fetal characteristics on the fetal fraction in maternal plasma cell-free (cf) DNA at 11-13 weeks' gestation and estimate the proportion of pregnancies at high risk of non-invasive prenatal testing (NIPT) failure because the fetal fraction is less than 4%.

METHODS:

In 1949 singleton pregnancies at 11-13 weeks' gestation cf-DNA was extracted from maternal plasma. Chromosome-selective sequencing of non-polymorphic and polymorphic loci, where fetal alleles differ from maternal alleles, was used to determine the proportion of cf-DNA that was of fetal origin. Multivariable regression analysis was used to determine significant predictors of the fetal fraction among maternal and fetal characteristics.

RESULTS:

The fetal fraction decreased with increased maternal weight, it was lower in women of Afro-Caribbean origin than in Caucasians and increased with fetal crown-rump length, serum pregnancy-associated plasma protein-A, serum free β-human chorionic gonadotropin, smoking and trisomy 21 karyotype. The median fetal fraction was 10.0% (interquartile range, 7.8-13.0%) and this decreased with maternal weight from 11.7% at 60 kg to 3.9% at 160 kg. The estimated proportion with fetal fraction below 4% increased with maternal weight from 0.7% at 60 kg to 7.1% at 100 kg and 51.1% at 160 kg.

CONCLUSIONS:

Fetal fraction in maternal plasma cf-DNA is affected by maternal and fetal characteristics.

PMID:
23108725
DOI:
10.1002/uog.12331
[Indexed for MEDLINE]
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