Oestriol

Keywords: Estriol

Specimen:

5 mL blood in plain tube.

Method:

Immunoassay.

Reference Interval:

Depends on gestational age and whether total (free and conjugated) or free oestriol is measured.

Levels should increase progressively during pregnancy.

Application:

Although it has been used for monitoring placental function and fetal status in high risk pregnancies from 26 weeks gestation, the test is now considered to be of little value and is rarely used.

Unconjugated oestriol is, however, one of the components of the 'triple test' used for assessment of Down syndrome risk, see Down syndrome antenatal risk test.

Urine oestriol can be measured, but is also unreliable.

Interpretation:

Trends in levels are more reliable than single values.

Decreasing levels suggest placental insufficiency and/or fetal problems.

Low levels are found in anencephaly, congenital adrenal hyperplasia, placental sulphatase deficiency (X-linked ichthyosis), adrenal hypoplasia and steroid therapy.

Impaired maternal liver function decreases clearance of oestriol from plasma and may make interpretation impossible.

Reference:

Beischer N et al. Aust NZ J Obstet Gynaecol 1995; 35: 151-159.