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Indian Pediatr 2009;46: 791-793 |
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Determinants of Lead Level in Umbilical Cord
Blood |
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AB Patel and AS Prabhu
From the Department of Pediatrics, Indira Gandhi
Government Medical College, Nagpur, India.
Correspondence to: Dr Archana B Patel, 125, Raj Nagar,
Katol Road, Nagpur 440 013, India.
Email: [email protected]
Manuscript received: February 19, 2008;
Initial review: March 18, 2008;
Accepted: July 31, 2008.
Published online 2009 April 1. PII: S001960610800105-2
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Abstract
Lead levels were measured by atomic absorption
spectrophotometry in umbilical cord blood samples of 205 consecutively
born neonates and venous blood in 62 of the mothers. The mean (±
SD) cord blood lead level was 4.7 ± 12.1 µg/dL. In the sub sample
of 62 mother-baby pairs, the mean (±
SD) cord blood lead levels were 1.6
±
2.5 µg/dL and 2.0
± 2.1 µg/dL, respectively. According
to CDC risk categories, 92% babies were in Class I of which 87% had lead
levels below 5 µg/dL. The mean (±
SD) birthweight in <5 µg/dL category was 2640
± 445 grams as compared to 2617 ±
408 grams in >5 µg/dL category. The mean (±
SD) gestational ages were 39.1 ±
2.0 weeks and 38.1±2.0 weeks,
respectively in the two groups (P=0.014). On multivariate linear
analysis, lower gestational age significantly correlated with higher
cord blood lead level.
Keywords: India, Lead poisoning, Neonate, Umbilical cord.
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Low birthweight, prematurity and
retardation of cognitive development have been associated with exposure to
lead in utero(1). High maternal blood lead level is an important
indicator of risk to the fetus(2). The umbilical cord blood lead levels (UCBLL)
indicate the degree of lead exposure to the fetus. In this study, we
determined UCBLL and its clinical, social and environmental correlates in
babies born at a tertiary care center in Nagpur, India. We also determined
the venous blood lead levels (BLL) in the mothers of 62 of these newborns
and correlated it with the mean UCBLL.
Methods
This hospital based cross sectional study was conducted
at Nagpur, India. Ethical clearance and informed consent were obtained.
UCBLL estimation was done in 205 consecutive births. Besides baseline
maternal and neonatal characteristics, records were made of habits such as
use of eye cosmetic "surma" and exposure to house paint by
interviewing the mothers of the newborns. Concomitant maternal venous
blood levels were also estimated in a simple random sample of 62 neonates.
Cord and maternal blood were collected in lead free EDTA vacutainers. The
lead levels were analyzed at the National Environmental Engineering
Research Institute (NEERI), Nagpur within 48 hours of sample collection by
flameless atomic absorption spectro-photometry (Hitachi Z-8000) in parts
per billion at a wavelength of 283.3 nm with a slit width of 1.3 nm using
the method described by Lagesson, et al.(3).
The detection rate of lead for the instrument was 1µg/L, with an average
error rate of 5% for reproducibility of results.
UCBLL were classified in the different Center for
Disease Criteria (CDC) risk categories(4). The ratio of means of UCBLL and
maternal venous BLL was calculated in 62 cases. Univariate and the multi-variate
linear regression was used to determine the sociodemographic and
environmental correlates of lead levels (sex of newborn, caste, education
level of mother, birthweight, gestational age, head circum-ference,
premature rupture of membranes, alcohol or tobacco use in mother, use of
surma by mother and the presence of house paint in homes).
Results
The mean ( ±
SD) gestational age, birthweight and head circumference of 205 neonates
(56% males and 44% females) were 39±2
weeks, 2637±440
grams and 32.6+1.5 cm, respectively. 30% of the enrolled neonates
were low birth weight (<2500 grams). The mean (±SD)
UCBLL of all 205 neonates was 4.7±12.1
µg/dL (range 0 to 81.2 µg/dL). According to CDC categorization of risk
level(4), 92% belonged to Class I, of which 87% were in
³5
µg/dL category and 5 % were in >5 to
£10
µg/dL category. Only six percent of the neonates were in the CDC risk
category class IIIB. The risk categories of 62 concomitant maternal BLL
were 98% in Class I and rest in Class II. In the cord blood samples from
these randomly selected 62 cases, the mean UCBLL was 1.6±2.5
µg/dL (range 0 to 19.1 µg/dL) and the mean mother’s BLL was 2.0±2
µg/dL (range 0 to 13.5 µg/dL) with a ratio of mean UCBLL to maternal BLL
of 0.8 which was significantly corrlelated (R2=0.6, P=0.000).
On univariate analysis, UCBLL was significantly
associated with gestational age, house paint, and maternal education but
not associated with caste, use of eye cosmetic, tobacco or use of alcohol.
The mean UCBLL in those homes that had no paint (n=119) was 3 ±6.9
µg/dl as compared to 6.9±16
µg/dl in those that had some or complete paint (n=86). In those
with UCBLL >5 µg/dL, the mean gestational age was 38 weeks compared to 39
weeks in those with £5
µg/dL. On multivariate linear regression, gestational age reduced by a
week for every 1 µg/dl increase in mean UCBLL.
Discussion
In our study, a low prevalence of toxic lead levels was
seen in the cord blood samples and the maternal venous samples. Although
different populations have different environmental exposures, it is
possible that a global awareness regarding lead toxicity has brought about
a consistent decrease in the toxic lead levels over the years across
different studies. In a study conducted at Mumbai, it was found that there
was a reduction in pediatric blood lead levels in 2002 as compared to 1997
after phasing out of leaded petrol(5). This emphasizes the role of
environment friendly legislations.
The correlation of UCBLL to mother’s venous BLL, as
found in our study, is in agreement to other studies which report that
maternal lead level is an important determinant of fetal lead exposure and
that the cord lead level is a good indicator of maternal levels(1).
Therefore the demographic and environmental factors contributing to
elevated maternal lead levels need to be examined. In this study, house
paint and higher maternal education were associated with high UCBLL but
the results did not reach statistical significance. The use of house paint
was observed in the family of two-thirds (69%) of neonates with UCBLL >10
µg/dL. Other correlates such as caste and use of surma (eye
cosmetic) by mother did not have significant impact on the umbilical cord
lead levels. In another study conducted in Nagpur, in 1997-98, house paint
was found to be a major determinant of lead levels in children(6). In our
study, there was a significant correlation found between the UCBLL and
gestational age in multivariate linear regression. It showed that one
microgram increase in mean UCBLL was associated with reduction in
gestational age by a week. An earlier study has also shown increased
incidence of early deliveries in women with high blood lead levels where
the mean BLL was 11.2 µg/dL at parturition and there were 5.3% preterm
deliveries(1).
To conclude, this is the first report of the mean lead
levels in cord blood of apparently healthy newborns and their mothers’
environmental correlates from India. The most interesting finding was
reduction in gestational age with high cord lead levels. The effect of
toxic levels of lead on infant’s birth weight and gestational age requires
further exploration by well-controlled studies from diverse settings.
Funding: This study was supported by grant
1004-94-6305 from International Clinical Epidemiology Network (INCLEN),
Philadelphia, USA.
Competing interest: None stated.
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What This Study Adds?
• Umbilical cord blood lead levels correlate
significantly with maternal blood lead levels and a lower
gestational age.
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References
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ATSDR-HE-CS-2001-0001, Oct 2000.
3. Lagesson V, Andrasko L. Direct determination of lead
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Preventing Lead Poisoning in Young Children. Washington DC: US Department
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