Very low alpha-fetoprotein in Down syndrome maternal serum screening.
OBJECTIVE
To establish the frequency of very low maternal serum AFP and to differentiate congenital AFP deficiency from those diseases known to be associated with low AFP.


METHODS
AFP values below 2 microg/L and borderline values up to 3 microg/L were retrospectively analysed in 839 773 singleton pregnancies included in a programme for routine screening of trisomy 21 maternal serum markers.


RESULTS
Serum AFP was undetectable (< or =2 microg/L) in 8 cases, giving a frequency of 1/105 000. The calculated risk of Down syndrome was > or =1/250 in 5 cases. Fetal karyotype was normal. Seven of these pregnancies went to term (39-41 weeks) uneventfully, and birth weight was normal (3050-4110 g). In the 8th case, fetal death occurred at 35 weeks due to severe maternal diabetes. AFP levels between 2.1 and 3.0 microg/L were noted in 7 other cases. The calculated risk of Down syndrome was > or =1/250 in 5 cases, and fetal karyotype was normal. Pregnancies went to term in 4 cases (33-41 weeks), and birth weight was normal (3000-3380 g). In 3 cases, low hCG (<0.6 MoM) was associated with low AFP, and fetal death occurred at 15 to 16 weeks.


CONCLUSIONS
Once technical errors have been excluded (repeat assay in a second run, calcium assayed to exclude the interference of EDTA for fluorimetric methods, dilution to exclude interfering antibodies, running on an alternative analyser, checking a second sample), very low second-trimester maternal serum AFP should prompt ultrasound examination in order to check fetal viability. Congenital AFP deficiency, an extremely rare disorder (1/100 000), should be suspected. It has no consequences for fetal and infant development, and parents should be reassured.
Muller
Françoise
F
Service de Biochimie, Hôpital Ambroise Paré, 92104 Boulogne, France. francoise.muller@apr.ap-hop-paris.fr
Dreux
Sophie
S
Sault
Corinne
C
Galland
Armelle
A
Puissant
Hugues
H
Couplet
Gisèle
G
Lemay
Catherine
C
Larcher
Marie-Estelle
ME
Renom
Gilles
G
D000328:Adult; D015331:Cohort Studies; D003677:Deficiency Diseases / Q000097:blood* / Q000151:congenital / Q000175:diagnosis / Q000453:epidemiology*; D004314:Down Syndrome / Q000175:diagnosis; D005260:Female; D005315:Fetal Diseases / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology*; D005602:France / Q000453:epidemiology; D006801:Humans; D008403:Mass Screening / Q000379:methods; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011296:Prenatal Diagnosis; D012189:Retrospective Studies; D000509:alpha-Fetoproteins / Q000172:deficiency* / Q000378:metabolism*
D000509:alpha-Fetoproteins