Methods
We performed a longitudinal cohort study using the nationwide registry. Details about our registry were summarized in our previous report.4 In brief, the subjects included children with CP who were approved for disability support by the age of 5 after a review of the Operating Organization of the Japan Obstetric Compensation System for Cerebral Palsy (JOCSC). The JOCSC covers more than 99% of delivery institutions throughout Japan.
Patients eligible for inclusion in the present study were children born from January 2009 to July 2014, with a birth weight of ≥2000 g, gestational age of ≥33 weeks, and disability due to CP independent of congenital causes or factors during the neonatal period or later. We defined severe CP as the first- or second-degree of disability according to the definitions in the Act on Welfare of Physically Disabled Persons,4 which are equivalent to level 3 to 5 of the Gross Motor Function Classification System-Expanded and Revised.6 Multiple pregnancies and cases with poor FHR tracings were excluded from the present study. Among the eligible patients, those associated with umbilical cord troubles were retrieved from reports of the Operating Organization of the JOCSC.
In each case, the FHR strips were obtained and retrospectively analyzed by four authors (J.H., M.N., T.I., and E.J.). The FHR class was determined after careful discussions. The National Institute of Child Health and Human Development guidelines7,8 were applied when interpreting the FHR patterns. We categorized all the FHR patterns into the following five groups based on the guidelines between the time of admission and delivery, as advocated by Phelan et al.9
When an abnormal FHR pattern was observed on admission for delivery or at labor onset, we defined the following two groups. (i) The Persistent bradycardia (P-Brady) group consists of fetuses with severe bradycardia (<80 beats/min) or absent variability with persistent severe decelerations on admission. (ii) The persistently non-reassuring (P-NR) group comprises fetuses with late or variable decelerations or decreased variability without bradycardia on admission test, which persisted until delivery.
In contrast, when the admission test showed a reassuring pattern (moderate variability on a normal baseline rate without late or variable decelerations), the following three groups were defined. (iii) Hon’s pattern (Hon) group comprises fetuses with a reassuring FHR pattern on admission and subsequent recurrent severe decelerations with or without an increased baseline rate and decreased variability. Finally, prolonged deceleration (PD) or terminal bradycardia was observed before delivery. (iv) A reassuring-PD (R-PD) group consists of the fetuses with a reassuring FHR pattern on admission; however, an abrupt change to severe PD or bradycardia occurred before delivery. (v) A persistently reassuring group indicates fetuses with a reassuring FHR that remains within ordinary throughout the entire course (Figure 1).
Umbilical cord troubles analyzed in the present study included umbilical cord prolapse, marginal/velamentous cord insertion, multiple cord entanglement, a true knot, umbilical cord constriction, hyper-coiled cord, hypo-coiled cord, and a single umbilical artery. We assessed frequencies of the FHR evolution patterns in patients with CP associated with umbilical cord troubles.