Reference
- Beard RW: Prevention of Handicap Through Antenatal Care. Amsterdam, Excerpta Medica Foundation, 1976, p 163
- Chamberlain R, Chamberlain G, Howlett B, et al: British Births 1970. London, William Heinemann Medical Books, Ltd, 1975, p 98
- Renou P, Wood C: Clinics in Obstetrics and Gynaecology. Philadelphia & London, WB Saunders Co, 1974, p 197
- Beard RW: Fetal Health. London, Hospital Medicine Publications, 1971, p 55