2Bronshte in M , Blumenfeld Z. Transvaginal sonography - detection of findings suggestive of fetal chromosomal anormalies in the first and early second trimesters[J]. Prenat Diagn, 1992,12:587- 593.
8Bonalti C, Briard ML, Feingold Jet al. An epidemiological and genetic study of facial clefting in France. I. epidemiology and frequence in relatives[J]. Med Genet, 1982, 19 (1): 8.
9Chan A, Robertson EF, Han EA et al. The sensitivity of ultrasound and serum alpha - fetoprotein in population - based antenatal screening for neural tube defects, South Australia, 1986 - 1991 [J] . Br J Obstet Gynaecol, 1995, 102:370.
