Editing Preterm birth (section)

===Ultrasound===
{{Further|Cervical incompetence}}
[[Obstetric ultrasound]] has become useful in the assessment of the [[cervix]] in women at risk for premature delivery. A short cervix preterm is undesirable: A cervical length of less than {{Convert|25|mm|abbr=on}} at or before 24 weeks of [[Gestational age (obstetrics)|gestational age]] is the most common definition of [[cervical incompetence]].<ref>[http://radiopaedia.org/articles/cervical_incompetence Cervical incompetence] {{webarchive|url=https://web.archive.org/web/20140307205141/http://radiopaedia.org/articles/cervical_incompetence |date=7 March 2014 }} from [[Radiopaedia]]. Authors: Dr Praveen Jha and Dr Laughlin Dawes et al. Retrieved Feb 2014</ref>