Intrapartum fetal blood sampling performed at early cervical dilatation and delivery outcomes

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

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.

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.

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.

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.