Comparison of meconium and neonatal hair analysis for
detection of gestational exposure to drugs of abuse
B Bar-Oz, J Klein, T Karaskov, G Koren
Arch Dis Child Fetal Neonatal Ed 2003;88:F98–F100
Dr Koren, Director,
Division of Clinical
Toxicology, Hospital for
Sick Children, 555
University Avenue, Toronto,
Ontario M5G 1X8,
Accepted 22 July 2002
Background: Meconium and hair are two biological markers of in utero exposure to illicit drugs.
Objective: To compare the sensitivity of the two tests for different drugs.
Setting: Motherisk laboratory which tests in utero drug exposure in Toronto.
Methods: Cocaine, benzoylecgonine, opiates, cannabis, benzodiazepines, methadone, and barbiturates
were measured in pairs of hair and meconium samples from the same neonates.
Results: Meconium was marginally more sensitive than neonatal hair for detection of cocaine and
cannabis, possibly because it may detect second trimester exposure whereas hair grows only during
the third trimester of pregnancy. There was a significant correlation between hair and meconium concentrations
of cocaine, cannabis, and opiates.
Conclusion: In cases of clinical suspicion and a negative neonatal urine test, both meconium and hair
are effective biological markers of in utero illicit drug exposure. Meconium may be more sensitive, but
neonatal hair is available for three months whereas meconium is available for only one or two days. In
contrast, the use of meconium, being a discarded material, is more acceptable to some parents than
hair testing, which entails cutting scalp hair from the newborn.
During the past two decades, illicit drug use has reached
epidemic proportions in North America.1 In the United
States, 10–45% of the women cared for at urban teaching
hospitals use cocaine during pregnancy.2 As women of
reproductive age constitute a large segment of the drug using
population, the effects of their drug use on the fetus has been
studied extensively. Prenatal cocaine use has been associated
with placental abruption and premature labour,3–5 as well as
with increased rates of low birth weight, microcephaly,
congenital anomalies, and necrotising enterocolitis.6 7 However,
because of multiple other reproductive risk factors in
women using illicit drugs, it is possible that many of the
adverse effects attributed to drugs are caused by other
factors.5 Similarly, it is not clear whether cocaine per se, or
other risk factors, leads to adverse neurobehavioural effects.8
Of importance, maternal addiction itself is a determinant of
serious postnatal risk for the infant. Newborns exposed to
opioids, barbiturates, benzodiazepines, or alcohol in utero may
experience withdrawal symptoms, often requiring
Estimated rates of infants exposed prenatally to cocaine
range between 2.6% and 11% of all live births.11 A prevalence
study of cocaine use during pregnancy conducted by our
group in 1990–1991 in three Metropolitan Toronto hospital
nurseries (one inner city, two suburban) found 37 out of 600
(6.25%) infants tested positive for cocaine.12 In the Metropolitan
Toronto area, there has been a steady increase in the
number of newborns affected by maternal drug use.13
It has been shown thatmaternal reporting of drug use is far
from accurate.12 14 Fearing legal consequences and embarrassment
from admitting illicit substance use, most users tend to
deny or to under-report drug consumption.
A major problem in studying the adverse effects of illicit
drugs is the lack of standardised techniques to ascertain fetal
exposure. The validity of blood and urine tests depends on the
elimination half life of the compound in question. In the case
of cocaine, which has a short elimination half life of less than
one hour, the drug and its metabolites are not likely to be
detected for more than a few days in either blood or urine.14
Other drugs, such as cannabis and opioids, have longer elimination
half lives, but even these drugs can be detected for only
a maximum of three to four weeks after use.15
These facts have highlighted an urgent need for a biological
marker which will still be sensitive weeks after the end of
exposure and which may yield a cumulative reflection of long
term exposure to illicit drugs.
In 1989, we first reported the use of hair analysis as a biological
marker for gestational cocaine exposure in seven
neonates whose mothers were known cocaine users.16 This test
is widely used at present. Meconium testing has proved to be
another very effective tool for verifying gestational drug
exposure.14 No formal comparison of the sensitivities of meconium
and hair analysis for different drugs of abuse has as yet
The aim of this study was to estimate the sensitivity and
correlation between neonatal hair and meconium testing in
185 infants suspected of being exposed in utero to one or more
illicit substances, namely cocaine, opiates, and cannabis.
SUBJECTS AND METHODS
Between 1999 and September 2001 the Motherisk laboratory
at the Hospital for Sick Children in Toronto, Canada received
thousands of neonatal hair and meconium samples for analysis.
Among them were 185 pairs of hair and meconium
samples collected from the same babies in various hospitals in
Ontario. Based on clinical suspicion of maternal drug abuse,
the testing of hair and/or meconium was requested by either a
doctor or the Children’s Aid Societies. Most of the requests
were for analysis for cocaine, opiates, and cannabinoids. We
report on measurements of cocaine, its metabolite benzoylecgonine,
heroin, morphine, cannabis, methadone, benzodiazepines,
Hair was analysed by well established methods.17 It was not
washed before testing unless external contamination was
suspected. If washing of the hair sample was included in the
procedure, a previously described method was followed.18
Briefly, 2–5 mg finely cut hair, unwashed or previously
washed, was sonicated in 1 ml methanol/5 M HCl (20:1, v/v)
for 30 minutes and incubated overnight at 45°C. On the next
day, the methanol was pipetted off, and the hair rinsed briefly
with an additional 1 ml methanol. After evaporation of the
methanol at 40°C under a stream of nitrogen, 200 ml
phosphate buffered saline at pH 7.0–7.4 was added, and the
individual drugs were analysed by enzyme linked immunosorbent
assay using kits manufactured by Immunalysis (San
Diego, California, USA).
For quantification, standards were prepared in blank hair
extract to control for matrix effect. Different blank hair
extracts were used to match the age and hair colour of the
subject. The limit of detection for each drug was 0.2 ng/mg
hair when 2 mg hair was used. Positive results were confirmed
using gas chromatography/mass spectrometry with the mass
selective detector operating in selective ion monitoring mode.
For meconium testing, approximately 0.2 g wet meconium
was extracted with methanol. After centrifugation, the supernatant
was diluted 1:5 with phosphate buffered saline, and an
aliquot was analysed for cocaine, benzoylecgonine, opiates,
and/or cannabinoids. Standards were prepared in blank meconium
extract similarly to the hair samples. Similar immunoassays
were used to those for the hair analysis described
above. Here too, positive results were confirmed by gas
chromatography/mass spectrometry. The limit of detection for
each drug was 50 ng/g meconium when 0.2 g meconium was
used for testing. The coefficient of variation of these tests in
our laboratory is less than 5%.
Assuming a false positive rate of zero for all the drugs
analysed—that is, a specificity of 100%—the estimated sensitivity
of the test was calculated for each drug, with the rate of
positive hair plus meconium in neonates estimated to
represent 100% of positive cases.
Linear regression and Spearman rank order correlation
were used whenever appropriate.
Of 185 pairs of hair and meconium samples assayed, 75 were
negative for all the drugs analysed. Table 1 shows the distributions
of cocaine, benzoylecgonine, opiates, and cannabis in the
positive hair and meconium samples. A total of 173 pairs were
tested for cocaine, 172 pairs for benzoylecgonine, 136 pairs for
opiates, and 141 pairs for cannabis. Additional tests were performed
for benzodiazepines (two pairs), methadone (two
pairs), and barbiturates (one pair).
The total number of positive samples for cocaine (hair, meconium
or both) was 53, of which 51 were positive in meconium
whereas 43 were positive in hair. The calculated sensitivity for
cocaine testing was 96% in meconium and 84% for hair (table 2)
The total number of positive samples for benzoylecgonine
was 53, of which 50 were positive in meconium (sensitivity of
95%), and 38 were positive in hair (sensitivity of 78%).
There was a significant correlation between hair and meconium
levels of cocaine (r0 = 0.83, p < 0.001) and benzoylecgonine
(r0 = 0.56, p < 0.001).
The total number of positive samples was 27, of which 23 were
positive in both or one of the matrices studied (sensitivity
87%). There was a highly significant correlation between hair
and meconium levels (r0 = 0.69, p < 0.0001).
The total number of positive samples was 55, of which 54 were
positive in meconium and 34 were positive in hair. The calculated
sensitivity for cannabis in meconium was 98%, and for
hair it was 71%. There was a highly significant correlation
between hair and meconium measures (ro = 0.73,
p < 0.0001).
Two hair-meconium pairs were positive for benzodiazepines in
both matrices, methadone was positive in hair and in
meconium in two pairs tested, and one pair was positive for
barbiturates (table 3).
As illicit drug use reaches epidemic proportions, protecting the
wellbeing of the fetus and offspring of drug users is a serious
challenge for health professionals and social services. A positive
meconium test can reflect maternal use of illicit drugs
from the second trimester of pregnancy onwards. Only meconium
collected during the first 1 or 2 days of life or for the first
three stools can be used to document in utero drug exposure.
In contrast, neonatal hair, which grows during the third
trimester, may reflect exposure of drugs during the last
trimester of pregnancy, and can stay positive for up to three
months after birth.
This study shows the correlation between meconium-hair
pairs for cocaine, benzoylecgonine, opiates, and cannabis. For
cocaine, benzoylecgonine, and cannabis, meconium testing
seems to be more sensitive (95% and above) than hair testing.
This may be partly explained by the earlier formation of
meconium compared with hair (roughly the second trimester
compared with the third trimester). The limitation of using
meconium for routine testing is the narrow time frame for
obtaining the sample. In all the cases in which meconium
tested negative whereas the hair tested positive, although the
documents specified the sample to be meconium, in fact it was
a mixture of meconium and stool, confirming that, for the test
to be accurate, meconium has to collected not later than one or
two days after birth.
Chiriboga et al19–21 have shown a concentration-response
effect of cocaine, as measured in maternal hair, on newborn
head circumference and abnormalities in muscle tone, movement,
and posture. Our study is the first to document significant
correlation between meconium and hair levels of different
illicit drugs, which enables the use of either meconium or
neonatal hair for assessment of the magnitude of exposure
and therefore the expected neurological impairment to the
exposed newborn. It is possible that a combination of negative
hair test and positive meconium test reflects second trimester
exposure to drugs, with no third trimester exposure.
Benzodiazepines are thought to be human teratogens, possibly
causing oral clefts.22 Although meconium forms only in
the second trimester, it is important to document the pattern
of benzodiazepine use in cases of oral cleft. Both meconium
and hair can be used for this purpose.
Maternal abuse of barbiturates can cause abstinence
syndrome in the newborn infant. Sampling either meconium
or hair, or both, can help to establish the diagnosis when the
maternal history is not accurate or available.
Both meconium and hair analysis have advantages and disadvantages.
Meconium may be more sensitive. However, it is
available for only two days after birth, whereas hair may be
available for up to three months. Because meconium production
begins in weeks 14–16, meconium testing may detect
second trimester exposure to drugs, whereas the hair present
at birth only develops in the third trimester. Although this
may increase the sensitivity of the meconium test, third
trimester exposure, evidenced by hair testing, reflects drug
abuse long after pregnancy was detected and hence is
diagnostic of maternal addiction, which has important implications
for neonatal care. Some parents resist hair cutting,
whereas meconium is a discarded material. Equally as important,
some babies are born with very little hair or no hair at all.
Another problem with hair analysis is that hair levels of drugs
are affected by the amount of melanin in the shaft.23 The
dose-response characteristics of deposition of drugs in hair
and meconium have been documented.19 20 24
To improve the yield of both matrices involved, we propose
to initiate clinical investigations with urine testing in
suspected cases. If the urine test is negative, meconium or hair
testing will be used depending on postnatal age. In cases with
a high index of suspicion, both matrices should be used, rendering
higher sensitivity. Because of the strong correlation between their measured levels, both matrices can be used to
estimate the extent and timing of fetal exposure and the
resulting neurological impairment.
This work was supported by a grant from The Canadian Institute for
Health Research (CIHR), and the Research Leadership in Better Pharmacotherapy
During Pregnancy and Lactation. BB-O was a recipient
of a Fellowship award by the Research Training Center, The Hospital
for Sick Children. GK is a Senior Scientist of CIHR.
. . . . . . . . . . . . . . . . . . . . .
B Bar-Oz, J Klein, T Karaskov, G Koren, The Motherisk Program,
Division of Clinical Pharmacology and Toxicology, Hospital for Sick
Children and University of Toronto, Toronto, Canada
B Bar-Oz, Department of Neonatology, Hadassah Medical Center and
The Hebrew University, Jerusalem, Israel
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Source: Comparison of meconium and neonatal hair analysis for detection of gestational exposure to drugs of abuse