Non-Invasive Fetal Sex Determination

Introduction

Identifying the sex of a fetus is important in the clinical management of pregnancies where there is a risk of an X-linked genetic disorder or intrauterine treatment is dependent on the sex of the fetus. Fetal sex can be determined by isolating cell free fetal DNA (ffDNA) from maternal blood plasma and testing for the presence or absence of Y chromosome sequences.

Referral information

16ml of blood may be taken into EDTA from pregnant women of at least 9 weeks gestation. Please notify the laboratory at least one week before the sample is to be taken (contact the Duty Scientist on 0161 276 6553 with the patient name, reason for referral, gestation and when the sample will arrive at the laboratory). Testing may be delayed if notice is not provided.  Samples should arrive at the laboratory within 24 hours of collection.

Price & reporting times

NHS referrals to this service are paid for where there is an existing specialist commissioning contract for genetic testing. In other cases prices are shown below.

Test Price (£ ex VAT) TRT *
Fetal sexing by NIPD POA 3 Cd

Test validation & quality assurance - information for users

Auditing of the outcomes from our assay protocol shows a sensitivity, specificity and positive predictive value of 100% (Nov 2010 – 92 tests; 95% confidence interval = 0.033) for samples collected from at least 9 weeks gestation by scan. The failure rate of the assay i.e. where no prediction about fetal sex can be made is currently approximately 4%.  This laboratory participates in the NEQAS quality assessment scheme for this test.

Sample requirements

Minimum 10ml EDTA blood sample

Referral guidelines

Please see our referral guidelines for more information.

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