Description
Free fetal DNA may be detected in maternal plasma from early in gestation and used for determination of fetal gender. Total cell-free DNA reflecting both maternal and fetal material is extracted from maternal plasma collected from 7 weeks gestation. Molecular analysis is performed using real time PCR and Taqman MGB probes for the Y-specific SRY and control-CCR5 markers. The presence of SRY marker in duplicate samples is used to indicate the presence of a male fetus and reduce false positives. In the case of detection of total cell free DNA but absence of the SRY marker, indicative of a female fetus we rely on results from repeated analysis at gestation beyond 7 weeks and the cfDNA control marker to discriminate between a true and false negative result.
Also known as
NIPD, NIPT, cffDNA, cell-free fetal DNA sex determination
Request a test
When requesting this test please use the referral form provided. Please also refer to any additional information provided for this test.
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Additional information
Please notify laboratory in advance of sending a sample, samples should arrive within 48 hours. Gestation as determined by ultrasound scan is mandatory information to perform this test. This test is not applicable before 7 weeks gestation or in multiple pregnancies including vanishing twin. Testing is only offered to females at risk of having a child with a severe X-linked disorder.
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Sending address
Great Ormond Street Hospital NE Thames Regional Genetics Service Laboratories
Great Ormond Street Hospital for Children
Barclay House
37 Queen Square
London
WC1N 3BH
Laboratory service
Genetics
Sample requirements
20ml blood (EDTA) from mother. Post 9 weeks this can be obtained in one sampling. At 7-9 weeks gestation 2 x 10ml sample should be taken one week apart.
Reference range
Not applicable
Turnaround time
3 days from receipt of second sample
Disease / group
SRY
Cost
Upon request
Call in advance?
All referrals should be made via a Clinical Genetics Department, please contact the laboratory in advance of sending a sample.� Advance notice is required so samples can be processed rapidly upon receipt