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Fetal head position was determined using transabdominal ultrasound and station as head\u2010perineum distance (\n                      <jats:styled-content style=\"fixed-case\">HPD<\/jats:styled-content>\n                      ) from transperineal ultrasound prior to an instrument. The primary outcome was duration of vacuum and forceps to vaginal delivery and was analysed as survival expressed by hazard ratio (\n                      <jats:styled-content style=\"fixed-case\">HR<\/jats:styled-content>\n                      ). Secondary outcomes were delivery mode and immediate neonatal outcome.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      In the study population of 54 women, the primary instrument was vacuum for 36 and forceps for 18. Four women were delivered by Caesarean section. Estimated median duration for forceps deliveries was 5\u00a0min (95%\n                      <jats:styled-content style=\"fixed-case\">CI<\/jats:styled-content>\n                      4.0\u20136.0) vs. 9\u00a0min (95%\n                      <jats:styled-content style=\"fixed-case\">CI<\/jats:styled-content>\n                      7.3\u201310.6) for vacuum deliveries (P\u00a0=\u00a00.17; Log\u2010rank test). The\n                      <jats:styled-content style=\"fixed-case\">HR<\/jats:styled-content>\n                      for vaginal delivery was 2.02 (95%\n                      <jats:styled-content style=\"fixed-case\">CI<\/jats:styled-content>\n                      1.04\u20133.91, P\u00a0=\u00a00.038) after adjusting for\n                      <jats:styled-content style=\"fixed-case\">HPD<\/jats:styled-content>\n                      , maternal age and\n                      <jats:styled-content style=\"fixed-case\">BMI<\/jats:styled-content>\n                      .\n                      <jats:styled-content style=\"fixed-case\">OP<\/jats:styled-content>\n                      position had minor influence on the primary outcome (\n                      <jats:styled-content style=\"fixed-case\">HR<\/jats:styled-content>\n                      changed from 2.02 to 2.08). The first instrument failed in 11\/31 (35.5%) where\n                      <jats:styled-content style=\"fixed-case\">HPD<\/jats:styled-content>\n                      \u00a0&gt;\u00a035\u00a0mm vs. 2\/21 (9.5%) where\n                      <jats:styled-content style=\"fixed-case\">HPD<\/jats:styled-content>\n                      \u00a0\u2264\u00a035\u00a0mm (P\u00a0&lt;\u00a00.05). There were no cases of Apgar score &lt;7 at 5\u00a0min or umbilical artery\n                      <jats:styled-content style=\"fixed-case\">pH<\/jats:styled-content>\n                      \u00a0&lt;\u00a07.1.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>In prolonged second stage, delivery with forceps was achieved more quickly than by vacuum when matched for ultrasound determined head station. Irrespective of which was the primary instrument, the failure rate was greater at higher head stations.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/ajum.12121","type":"journal-article","created":{"date-parts":[[2019,1,21]],"date-time":"2019-01-21T05:44:55Z","timestamp":1548049495000},"page":"111-117","update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Time to delivery based on sonographic assessment prior to forceps and vacuum"],"prefix":"10.1002","volume":"22","author":[{"given":"Sana","family":"Usman","sequence":"first","affiliation":[{"name":"Department of Cancer and Surgery Institute of Reproductive Developmental Biology Hammersmith Campus Du Cane Road London W12 ONN UK"},{"name":"Centre for Fetal Care Imperial College Healthcare NHS Trust Du Cane Road London W12 0HS UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Birgitte","family":"Kahrs","sequence":"additional","affiliation":[{"name":"National Center for Fetal Medicine St Olavs Hospital Trondheim University Hospital Prinsesse Kristinas Gate 3, 7030 Trondheim Norway"},{"name":"Department of Clinical and Molecular Medicine Norwegian University of Science and Technology NO\u20107491 Trondheim Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Helen","family":"Barton","sequence":"additional","affiliation":[{"name":"Department of Cancer and Surgery Institute of Reproductive Developmental Biology Hammersmith Campus Du Cane Road London W12 ONN UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kjell","family":"Salvesen","sequence":"additional","affiliation":[{"name":"National Center for Fetal Medicine St Olavs Hospital Trondheim University Hospital Prinsesse Kristinas Gate 3, 7030 Trondheim Norway"},{"name":"Department of Clinical and Molecular Medicine Norwegian University of Science and Technology NO\u20107491 Trondheim Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Torbjorn","family":"Moe Eggebo","sequence":"additional","affiliation":[{"name":"National Center for Fetal Medicine St Olavs Hospital Trondheim University Hospital Prinsesse Kristinas Gate 3, 7030 Trondheim Norway"},{"name":"Department of Clinical and Molecular Medicine Norwegian University of Science and Technology NO\u20107491 Trondheim Norway"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2104-5561","authenticated-orcid":false,"given":"Christoph","family":"Lees","sequence":"additional","affiliation":[{"name":"Department of Cancer and Surgery Institute of Reproductive Developmental Biology Hammersmith Campus Du Cane Road London W12 ONN UK"},{"name":"Centre for Fetal Care Imperial College Healthcare NHS Trust Du Cane Road London W12 0HS UK"},{"name":"KU Leuven Oude Markt 13 3000 Leuven Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2019,1,21]]},"reference":[{"issue":"1","key":"e_1_2_9_2_1","first-page":"1","article-title":"Births: final data for 2015","volume":"66","author":"Martin JA","year":"2017","journal-title":"Natl Vital Stat Rep"},{"key":"e_1_2_9_3_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ijgo.2005.05.016"},{"key":"e_1_2_9_4_1","unstructured":"BahlR StrachanB MurphyD.RCOG Green\u2010Top Guideline Number 26: Operative Vaginal Delivery;2011."},{"key":"e_1_2_9_5_1","doi-asserted-by":"publisher","DOI":"10.1053\/beog.2000.0146"},{"key":"e_1_2_9_6_1","doi-asserted-by":"publisher","DOI":"10.1097\/GRF.0000000000000104"},{"key":"e_1_2_9_7_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.ajog.2017.03.006"},{"issue":"9","key":"e_1_2_9_8_1","first-page":"819","article-title":"Failed vacuum extraction. 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