Moro response is usually described as
normal/abnormal or present/absent. However, deviant
responses like, vigorous, weak and asymmetric responses have
been shown to be closely linked with developmental outcome
[1] and neurological impairment in newborns [2]. Studies on
duration and quality of different events in normal response
like the latency interval, optimal response and total
duration of reflex response are few, and standard values for
these durations are not available. The present study was
undertaken to evaluate Moro response qualitatively, and
determine normative values for latency interval and other
components of a normal response
Latency interval of Moro reflex was
defined as the time taken for onset of first sign of reflex
response. Arc like embracing movement of arms following
initial abduction was considered as Optimal response. The
total time taken for a complete response was labeled as
Completion. 91 healthy full term newborns, who remained
asymptomatic for the first 48 hours after birth, were
included in this prospective observational study. The study
was carried on newborns after 48 hours (time for
physiological stabilization) of birth. Head drop method was
used to elicit Moro response [3] while the baby was alert,
active and moving the limbs but not crying. Video recording
was done simultaneously, and the investigator analyzed the
video-clippings and calculated the various parameters with
the help of a stop watch. Mean values were calculated for
latency interval, optimization and total duration of
response. Upper and lower limit was obtained by calculating
the 95 % confidence interval for the means.
TABLE I Values of Various Parameters of moro Reflex in Healthy term Newborns (n=91)
Parameter |
Values (s), mean (SD) |
|
Male |
Female
|
Overall |
|
(n=48)
|
(n=43)
|
|
Latency interval |
0.42 (0.172) |
0.48 (0.197)
|
0.45 (0.186)
|
Time taken for optimal response |
0.97 (0.226) |
1.02 (0.292) |
0.998(0.259) |
Duration of complete response |
2.55 (0.59) |
2.38 (0.625)
|
2.47 (0.61) |
The range for latency interval of Moro
response was found to be 0.41-0.49 seconds. The time taken
for optimal Moro response was 0.91-1.04 seconds and the
total duration for Moro response was 2.34-2.59 s. The values
were similar for males and females. The mean values of
newborn delivered through cesarean section were longer than
babies delivered vaginally but was found to be statistically
significant only for time taken for optimal response.
In view of these findings, a better
assessment is possible by a standardized grading of Moro
reflex in the form of an ordinal scale, as follows: 0 -
Absent reflex; 1 - Long latency (>0.49 s); 2 - Normal range
(0.41 -0.49s); and 3 - Short latency (< 0.41s).
For day-to-day use, the time taken to
pronounce the word "thousand and one" is approximately
0.4-0.5 sec and will be a fair estimate of latency interval.
Say "thousand and one" with the head drop. Onset of response
both before and after the completion of the word "thousand
and one" shall be considered as abnormal.
Hyperexcitability (short latency) may
indicate behavior problems in later life like short
concentration span, mood instability and learning difficulty
while delayed excitability (long latency) may indicate
severe nervous system pathology[4]. Results of our study are
comparable with other studies [5,6], taking in to
consideration the difference in methods and analysis.
Contributors: BS : conducted the
study under the supervision of HPS & JS and wrote the first
draft of the manuscript. HPS and JS: conceived and designed
the study and revised the manuscript for important
intellectual content. They will act as guarantors of the
study. The final manuscript was approved by all the authors.
Funding: None; Competing interests:
None stated.
References
1. Sohn M, Ahn Y, Lee S. Assessment of
primitive reflexes in high-risk newborns. J Clin Med
Res. 2011;3:285-90.
2. Zafeiriou DI. Primitive reflexes and
postural reactions in the neurodevelopmental examination.
Pediatr Neurol. 2004; 31:1-8.
3. Nair MKC, Russell P. Illingworth’s The
development of the infant and young child: Normal and
abnormal, Tenth edition. New Delhi: Elsevier; 2012.
4. Prechtl H. The neurological
examination of the full-term newborn infant. In: Clinics In
Developmental Medicine, Vol. 63, 2nd
ed. Spastics International Medical Publications;1977.
5. Ronnqvist L, Hopkins B, Van Emmerik R,
De Groot L. Lateral biases in head turning and the Moro
response in the human newborn: are they both vestibular in
origin? Dev Psychobiol.1998;33:339-49.
6. Ronnqvist L. A critical examination of the Moro
response in newborn infants—symmetry, state relation,
underlying mechanisms. Neuropsychologia. 1995;33:713-26.