First trimester maternal serum alpha-fetoprotein is not raised in pregnancies with open spina bifida.

BACKGROUND

Two recent studies have suggested that maternal serum alpha fetoprotein (AFP) levels are increased in the first trimester of pregnancies in which the fetus has an open spina bifida. This is contrary to previously published studies. This study assesses further whether maternal serum AFP is elevated in the first trimester in cases with open spina bifida.

METHODS

Cases with open spina bifida were identified from our fetal database, and corresponding first trimester screening samples were retrieved and analysed for maternal serum AFP. A control group was selected by taking three samples matched for gestational age (exact day), ethnicity and smoking status and received in the laboratory on the same day. AFP was measured with the Kryptor platform and free β-hCG and pregnancy-associated plasma protein A results were available from the fetal database.

RESULTS

Thirty-nine open spina bifida cases were identified with a control group of 126 cases. The median multiple of the median AFP in the cases were not significantly different from the controls (0.92 vs 1.06 p = 0.3511) as was the case for free β-hCG (0.87 vs 0.95 p = 0.7146) and pregnancy-associated plasma protein A (1.04 vs 1.04 p = 0.261).

CONCLUSION

Our results confirm that maternal serum biochemical markers in the first trimester are unable to distinguish cases in which the fetus has open spina bifida.