Name Info Provider Link
subscription/membership/fee required Elsevier Science https://linkinghub.elsevier.com/retrieve/pii/0020-7292(90)90718-Z
Pregnancy free resource MedlinePlus Health Information https://medlineplus.gov/pregnancy.html
subscription/membership/fee required Wiley https://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=0020-7292&date=1990&volume=31&issue=2&spage=175