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
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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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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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Great Ormond Street Hospital NE Thames Regional Genetics Service Laboratories
Great Ormond Street Hospital for Children
37 Queen Square
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.
3 days from receipt of second sample
Disease / group
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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