1. The American College of Obstetricians and Gynecologists (ACOG). 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), 46. Print Edition.

2. The Pregnancy Experts at Mayo Clinic. Medical editors: Roger Harms, MD, Myra Wick, MD, PhD. Mayo Clinic Guide to a Health Pregnancy. (Boston, Massachusetts