An official website of the United States government
The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before
sharing sensitive information, make sure you’re on a federal
government site.
The site is secure.
The https:// ensures that you are connecting to the
official website and that any information you provide is encrypted
and transmitted securely.
Wang LJ, Brännström M, Robertson SA, Norman RJ.Wang LJ, et al. Among authors: norman rj.Fertil Steril. 1992 Nov;58(5):934-40. doi: 10.1016/s0015-0282(16)55438-7.Fertil Steril. 1992.PMID: 1426379Free article.