Yawn at 27.5 Weeks (image) PLOS Caption This is an ultrasound showing yawn at 27.5 weeks gestation. Credit Citation: Reissland N, Francis B, Mason J (2012) Development of Fetal Yawn Compared with Non-Yawn Mouth Openings from 24-36 Weeks Gestation. PLoS ONE 7(11): e50569. doi:10.1371/journal.pone.0050569 Usage Restrictions With credit to source Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.