Excerpts from the papers by Baskett et al. (2006) and Milsom et al.
(2002) are provided below. Both papers tried to identify maternal
and/or fetal factors associated with failure to breathe right away at
birth. Baskin et al. stated that the rate of respiratory depression at
birth was low (6.2 per 1000), but the similar statistic (2 to 6 per 1000)
is high when considering numbers of children with autism.
Note in both articles:
- "Respiratory depression" is defined as delay in initiating and
maintaining respiration after birth or as a low Apgar score five
minutes after birth.
- All infants were born alive. Thus "respiratory depression" at
birth includes infants who did not make the transition from
placental to pulmonary respiration immediately after birth,
before the umbilical cord was clamped.
An infant born alive is receiving oxygen (an urgent ongoing need)
from the placenta -- until the cord is clamped.
How many prospective parents have any idea that placental
respiration is to be cut off so abruptly at birth?
Baskett et al. (2006)
"Respiratory depression at birth was defined as delay in initiating and maintaining
respiration after birth" [1, p770]
Measures were: (a) resuscitation by mask and/or endotracheal tube for 3 minutes
or more, (b) 5-minute Apgar score of 3 or less, or (c) neonatal seizures.
"Since 1996, neonatal cord arterial pH results have been coded in the Atlee
database; therefore, from 1996 to 2002" [1, p770]
To obtain cord blood samples, a segment of cord (between two clamps) is obtained
per ACOG protocol [2]
"The rate of respiratory depression at birth with delay in respiration was 5.2/1000,"
[1, p770]
With 5-minute Apgar score less than or equal to 3, the rate was 1.0/1000, and
with neonatal seizures 0.7/1000
"The rate of respiratory depression at birth with the composite outcome of at least
one of the defining variables was 6.2/1000." [1,770]
"In the study population, 20 765 pregnancies (16.4%) had cord pH recorded" [1,
p770]
Cord pH less than or equal to 7.0 was found in 152 infants (only 0.7%). Of the 34
infants with seizures, 13 (38.2%) had a cord arterial pH less than or equal to 7.0.
"Respiratory depression at birth was most commonly associated with placental
abruption, intrapartum infection, operative delivery in labour, small for gestational
age <3rd percentile, and birthweight > 4500 g." [1, p771]
"Overall, the rate of respiratory depression at birth was low (6.2/1000) and the rate
of the serious manifestation of seizures was less than 1 in 1000. Of the three
clinical markers of respiratory depression at birth used in this study, seizures had
the strongest relationship with fetal acidosis (cord arterial pH < 7.0)." [1, p772]
Milsom et al. (2002)
"Asphyxia was defined by a low Apgar score and according to the development of
hypoxic-ischemic encephalopathy (HIE) and asphyxia-related death/damage
(disability), which were ascertained on clinical grounds after excluding other
possible causes."
"During the 7-year period from 1985 to 1991, 42,203 live infants were born to
mothers residing in the city of Göteborg. Infants born during this period with a
gestational age (GA) of 37weeks, and Apgar scores <7 at 5min were identified via
the MBR." [3, p910] (MBR = Medical Birth Register)
"A total of 292 infants with a 5-min Apgar score 7 were identified." [3, p910]
Infants with opiod/anesthesia or congenital abnormalities were excluded. Of the
remaining infants (n=227), 136 were boys and 91 were girls (60%/40%).
"During the 7-year period 1985–91, the incidences of low Apgar score (<7 at 5min),
pure birth asphyxia and birth asphyxia with HIE in this population were 6.9, 5.4 and
1.8 per 1000 live born infants," [3, p911]
"There was no difference in placenta weight between the asphyxia group and the
control group." [3, p913]