Background
Intrapartum fetal blood sampling (FBS) is a fetal well‐being diagnostic test for cardiotocogram abnormalities.

Aim
The aim of this study was to determine whether women who had their first FBS at <4 cm cervical dilation had an increased risk of operative delivery (caesarean section, instrumental delivery) compared to those women who had their first FBS ≥ 4 cm dilation. Materials and methods Retrospective cohort study involving labouring women who underwent FBS in a tertiary centre between 2015 and 2017. Women who had their first FBS at <4 cm dilation were compared to those who had their first FBS at ≥4 cm. The primary outcome was operative delivery (caesarean, instrumental delivery); secondary outcomes were neonatal complications. Univariate logistic regression was used to assess the association between degree of cervical dilation at first FBS and study outcomes. Results Among 591 women, 39 (6.6%) had their first FBS at <4 cm cervical dilation. Women in the ≥4 cm group were less likely to have a total of ≥2 FBS (P = 0.003). There was no difference in the primary outcome between the two groups. Women who had the first FBS at <4 cm dilation were twice as likely to have a caesarean section delivery (odds ratio 2.06, 95% confidence interval 1.06–3.98), although 41% had a vaginal birth (instrumental and spontaneous). There were no differences in rates of resuscitation or admission to nursery between groups. Conclusion Women who had their first FBS < 4cm cervical dilation were twice as likely to have a caesarean section compared to women who had their first FBS ≥ 4 cm. However, 41% had a vaginal birth, and there were no differences in fetal outcomes.