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Diakses pada 12 Desember 2020What to Expect. https://www.whattoexpect.com/pregnancy/placenta
Diakses pada 12 Desember 2020University of Rochester Medical Center. https://www.urmc.rochester.edu/encyclopedia/content.aspx?ContentTypeID=90&ContentID=P02362#
Diakses pada 12 Desember 2020