1. One child with multiple vertebral anomalies Laurence,1969
2. Carter and Evans (1973) Smith (1973) Wynne-Davies (1975)
3. trimester 2nd trimester 2nd trimester Ist trimester 2nd trimester 3rd trimester Kjessler et al (1975a and b) Nevin and Armstrong;1975) Seller et al (1974a) Weinberg et al (1975,1975
4. Emery et;al (1974) Purdie et al (1975
5. Macri et al (1974) Brock (1975b)