1. The Pregnancy Experts at Mayo Clinic. Medical editors: Roger Harms, MD, Myra Wick, MD, Phd. Mayo Clinic Guide to a Health Pregnancy. (Boston, Massachusetts: Mayo Foundation for Medical Education and Research, 2011), 153. Print Edition.

2. American College of Obstetricians and Gynecologists. Women’s Health Care Physicians. Your Pregnancy and Childbirth: Month to Month. Revised 6th edition. (Washington, D.C.: American College of Obstetricians and Gynecologists, 2016), 147. Print Edition.