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Velamentous umbilical cord insertion may be suspected from maternal serum alpha-fetoprotein and hCG.

OBJECTIVE
Patients with unexplained elevations in second trimester maternal serum alpha-fetoprotein or human chorionic gonadotrophin (hCG) concentrations are at increased risk as regards a variety of pregnancy complications and adverse perinatal outcomes. Evidence suggests that elevated alpha-fetoprotein and hCG concentrations may, in some case, be sensitive indicators of underlying placental pathology, either vascular or inflammatory in nature. The present study was carried out to compare these biochemical markers in pregnancies complicated by velamentous umbilical cord insertion (VCI) with normal pregnancies.


DESIGN
An observational study.


PARTICIPANTS
Maternal serum hCG and alpha-fetoprotein concentrations were measured in samples from 76 singleton pregnancies complicated by VCI and from 5200 chromosomally normal controls at 15 weeks of gestation.


RESULTS
Maternal serum hCG concentrations were elevated (mean 1.47 multiples of median (MoM)) in affected pregnancies, whereas alpha-fetoprotein levels were lower (mean 0.88 MoM) in the subjects than in the controls. In relation to Down's syndrome risk assessment, the pattern of the two markers indicated high risk more often in VCI than in pregnancies with normal umbilical insertion. Accordingly, the increased false positive rate (26.3% compared with 6.6%) resulted in a higher rate of invasive techniques for fetal karyotyping in these pregnancies.


CONCLUSIONS
In obstetric practice, elevated maternal serum hCG concentrations may in some cases be explained as being solely the result of abnormal insertion, which provides a link between unexplained hCG elevation and adverse pregnancy outcome. We suggest colour flow Doppler imaging of cord insertion in pregnancies followed because of unexplained hCG elevation or a false positive result in Down's syndrome screening.