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.