References: Williams Obstetrics 24th edition.
Embryogenesis and Fetal Morphological Development (Chapter 7, 127-144). In: Cunningham FG, Lenovo KJ, Bloom SL, Spong CY, Dashe JS, Hoffman BL, Casey BM, Sheffield JS (eds.). Williams Obstetrics. 24th edition. 2014, McGraw Hill Education.