Baby Due Date Calculator
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3. FamilyDoctor.org. Ultrasound during pregnancy (updated Feb 2011). http://familydoctor.org/familydoctor/en/pregnancy-newborns/fetal-health/ultrasound-during-pregnancy.html (accessed Aug 2015).
4. US National Library of Medicine, National Institutes of Health. MedlinePlus. When you pass your due date (updated 11 Jun 2014). http://www.nlm.nih.gov/medlineplus/ency/patientinstructions/000515.htm (accessed Aug 2015).