AIUM practice guideline for the performance of an antepartum obstetric ultrasound examination. J Ultrasound Med2003;22:1116-1125.
3.
Strong C: Too many twins, triplets, quadruplets, and so on: a call for new priorities. J Law Med Ethics2003;31:272-282.
4.
Callen PW: Ultrasonography in Obstetrics and Gynecology. 3rd ed.Philadelphia: W. B. Saunders, 1994.
5.
Benacerraf BR: Ultrasound of Fetal Syndromes. Philadelphia: Churchill Livingstone, 1998.
6.
Stenhouse E, Hardwick C, Maharaj S, Webb J, Kelly T, Mackenzie FM: Chorionicity determination in twin pregnancies: how accurate are we? Ultrasound Obstet Gynecol2002;19:350-352.
7.
Machin GA: Why is it important to diagnose chorionicity and how do we do it? Best Pract Res Clin Obstet Gynaecol2004;4:515-530.