Outcome measures and definitions
Our primary outcome measure was a composite adverse maternal outcome
that included the occurrence of one or more of the following: shoulder
dystocia, obstetrical anal sphincter injury (OASIS), retained placenta,
post-partum hemorrhage (PPH), blood products transfusion, prolonged
duration of hospitalization and puerperal fever.
Even though, the association between lower obstetrician annual volume
and the increased risk for CD has been shown7, we
decided not to include CD or VAVD as an outcome measure as the decision
to perform CD or VAVD in our department is determined by the attending
obstetrician.
CNM practice duration was defined by the time interval between her first
attended delivery and index delivery. Shoulder dystocia was defined as a
protraction of head-to-body delivery time of >60 seconds,
and/or the use obstetrical maneuvers to facilitate safe and rapid
delivery8. OASIS was classified as third-degree
lacerations which involve external ±internal sphincter and fourth-degree
rupture which involves the rectal mucosa. OASIS is diagnosed by an
obstetrician and repaired in the operating room 9.
“Retained placenta” was defined as any third stage of delivery that
included a diagnosis of complete or partial (fragments) remnants of the
placenta10. PPH was defined by one of two means: a
subjective assessment of blood loss (over 500 ml) or hemoglobin drop
>3gr/dL11. Prolonged hospitalization –
length of postpartum hospital stays > 5 days
(routine hospitalization length is 2-3 days). Puerperal febrile
morbidity - temperature of ≥100.4°F [≥38°C] from the second day
after delivery to discharge12.
Secondary outcomes were various maternal and neonatal outcomes. The
maternal outcomes assessed were those that composed the composite
adverse maternal outcome, as described above. The neonatal outcomes
included the following composite adverse neonatal outcomes defined by at
least one of the following: : rates of 1-min Apgar score< 7, 5-min Apgar score < 7, neonatal
asphyxia, meconium aspiration, jaundice, transient tachypnea of the
newborn (TTN), mechanical ventilation, convulsions, neonatal intensive
care unit (NICU) admission, sepsis, hypoxic ischemic encephalopathy
(HIE).