The origin of alpha-fetoprotein in first-trimester anembryonic pregnancies.

OBJECTIVE

Our purpose was to evaluate the origin of alpha-fetoprotein in the maternal circulation and coelomic fluid of pregnancies with an empty gestational sac on first-trimester ultrasonographic examination.

STUDY DESIGN

The alpha-fetoprotein level and the affinity of alpha-fetoprotein for concanavalin A Sepharose was measured between 8 and 11 weeks of gestation in the maternal serum and coelomic fluid of nine pregnancies complicated by an empty gestational sac and of 27 normal pregrancies.

RESULTS

The maternal serum alpha-fetoprotein level in patients with an empty gestational sac was high in seven cases and normal in two cases. In these cases the median level was significantly (p < 0.01) higher in the serum and lower in the coelomic fluid compared with normal pregnancies. In eight cases of the nine pregnancies with an empty sac, > 50% of alpha-fetoprotein molecules in the coelomic fluid were of the concanavalin A nonreactive fraction, whereas in one case the coelomic fluid sample contained < 5% of this fraction. A similar distribution was found in the corresponding serum samples.

CONCLUSION

Normal or high maternal serum AFP levels and alpha-fetoprotein molecules predominantly of yolk sac origin in the coelomic fluid of pregnancies with an empty gestational sac on ultrasonography provide further evidence that the most likely explanation for this feature is the early death of the embryo with persistence of the placental tissue.