Open Journal of Stomatology, 2013, 3, 42-51 OJST
http://dx.doi.org/10.4236/ojst.2013.39A007 Published Online December 2013 (http://www.scirp.org/journal/ojst/)
High birth weight is a risk factor of dental caries increment
during adolescence in Sweden*
Annika Julihn1,2#, Ulrika Molund1, Emma Drevsäter1, Thomas Modéer1
1Division of Pediatric Dentistry, Department of Dental Medicine, Karolinska Institute, Huddinge, Sweden
2Specialist Clinic of Pediatric Dentistry, Specialist Dental Care in Västra Götaland, Göteborg, Sweden
Received 29 October 2013; revised 30 November 2013; accepted 11 December 2013
Copyright © 2013 Annika Julihn et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
This study aimed to assess whether birth weight is
associated with dental caries during the teenage pe-
riod. In this register-based cohort study, all children
of 13 yrs of age (n = 18,142) who resided in the county
of Stockholm, Sweden, in 2000 were included. The
cohort was followed until individuals were 19 yrs of
age. Information regarding dental caries was col-
lected from the Public Health Care Administration in
Stockholm. Data concerning prenatal and perinatal
factors and parental socio-demographic determinants
were collected from the Swedish Medical Birth Reg-
ister and National Registers at Statistics Sweden. The
final logistic regression model showed that birth
weight (≥4000 g), adjusted for potential confounders,
was significantly associated with caries increment
(DMFT ≥ 1) between 13 and 19 yrs of age (OR: 1.29,
95% CI = 1.13 - 1.48). The relatively enhanced risk
OR was further increased from 1.29 to 1.52 in sub-
jects with birth weight (≥4600 g). On the contrary,
subjects with birth weight (<2500 g) exhibited a sig-
nificantly lower risk (OR: 0.67, 95% CI = 0.50 - 0.89)
for exhibiting caries experience (DMFT ≥4) at 19 yrs
of age. In conclusion, birth weight can be regarded as
a predictor for dental caries and birth weight (≥4000
g) is especially a risk factor for caries increment dur-
ing adolescence.
Keywords: Adolescents; Birth Weight; Cohort Study;
Dental Caries; Longitudinal Study; Predictor; Risk
Assessment; Risk Factor
1. INTRODUCTION
Birth weight in children has increased during the last two
decades in many developed countries [1-4] despite an
increased number of preterm births [5,6]. One explana-
tion is an increasing proportion of infants born with high
birth weight [6,7]. In approximately 10% of deliveries,
the fetus exhibits birth weight higher than 4000 grams
[8].
Fetal growth is initially autonomous but later more
dependent on the flow of nutrients across the placenta.
Viral infections as well as various maternal diseases such
as diabetes and hypertension, and maternal life style fac-
tors including smoking have an impact on fetus growth,
thereby affecting the birth weight of the child [9-11]. In
clinical studies, several maternal anthropometric charac-
teristics have been demonstrated to be positively associ-
ated with increased fetal growth, such as a maternal body
mass index (BMI), and excessive weight gain during
pregnancy [11,12].
In recent years, the relationship between birth weight
of the child and the risk for development of chronic dis-
eases as adults has been frequently discussed. It has been
shown that infants born with low birth weight (<2500 g)
have a higher risk later in life of developing diabetes
[13-15] or coronary heart diseases [16]. In addition, chil-
dren with a high birth weight (≥4000 g) are reported to
exhibit a higher prevalence of overweight during adoles-
cence [17] as well as an increased risk of developing
obesity [18,19], diabetes [13,14] or cancer [20-22] later
in life.
The relationship between birth weight and oral condi-
tions has mostly been addressed in infants with low birth
weight. There are several clinical studies demonstrating
enhanced frequency of molar-incisor hypomineralization
(MIH), gingival inflammation and behavioral manage-
ment problems [23-27] in children with low birth weight.
Most of the studies state that there is no relationship be-
tween low birth weight and the development of dental
caries [28-31], although conflicting results are available
[32,33]. The only study to the knowledge of the authors
*Conflicts of Interest: The authors declare no conflict of interest.
#Corresponding author.

A. Julihn et al. / Open Journal of Stomatology 3 (2013) 42-51 43
focused on children with high birth weight and demon-
strated a weak association between dental caries and high
birth weight in 5-year-old children [34]. Furthermore, the
parameter apgar score, which reflects not only labor and
delivery but also the condition during prenatal life, is
reported to be associated with dental caries in 5-year-old
children [35].
In a cohort of teenagers, this study recently identified
maternal overweight in the first trimester as a risk factor
for caries increment in their offspring between 13 to 19
years of age [36]. Overweight mothers and mothers with
high gestational weight gain are at risk to deliver infants
with high birth weight [4,10] who exhibit a higher risk
for developing obesity during childhood [17,18]. In a
cross sectional study, we previously reported a close re-
lationship between obesity and the occurrence of dental
caries in adolescence [37]. The link between obesity and
dental caries might be caused by the lower salivary flow
rate (ml/min) demonstrated in the obese subjects com-
pared with normal weight subjects [37]. In light of these
findings, it was hypothesized that birth weight might be
associated with dental caries later in life. Therefore, the
current register-based cohort study of 13 and 19-year-old
adolescents was undertaken to address whether their
birth weight is associated with dental caries later in life.
2. MATERIAL AND METHOD
2.1. Study Design
The present study was designed as a retrospective longi-
tudinal register-based cohort study and was based on
information collected from data sources at the Public
Health Care Administration in Stockholm, as well as
from National Registers at the National Board of Health
and Welfare and at the Central Bureau of Statistics Swe-
den (SCB). The study was approved by the Regional
Ethical Board in Stockholm, Sweden, and the study pro-
tocol was approved by the Swedish Data Inspection
Board, a Swedish federal agency that serves as an insti-
tutional review board for database linkages. Data was
collected on dental caries, prenatal and perinatal factors,
as well as on socio-demographic determinants.
2.2. Subjects
All 13-yr-old adolescents (n = 18,142) who resided in the
county of Stockholm, Sweden, in the year 2000 were
included in the study. This cohort was followed until the
individuals were 19 yrs of age. During this period, the
subjects received regular dental check-ups either from
the Public Dental Health Service, private practitioners, or
at the Division of Pediatric Dentistry, Department of
Dental Medicine, at the Karolinska Institute, Stockholm.
A total of 15,538 adolescents (7810 boys and 7728 girls)
had clinical as well as radiographic dental examinations
at both 13 and 19 yrs of age. The sample attrition rate
was 14% and the most common reason for sample attri-
tion was that the individual had moved out of the area.
Of the examined subjects (n = 15,538), information
about birth weight or not was collected in 13,808 and
thus constituted the final study cohort.
2.3. Population-Based Registries
The registers’ usefulness in epidemiological research is
facilitated by the Personal Identification Number (PIN),
which is a 10-digit number unique to all residents and
recorded in all health and census registers [38]. The PIN
permits linkage of each individual between different reg-
istries. In the present study, information from the Medi-
cal Birth Register (MBR), the Total Population Register
(TPR), the Total Enumeration Income Register, and the
Education Register were used. Information about the
registers and register linkages have previously been de-
scribed [36].
2.3.1. The Medical Birth Register (MBR)
Mothers-to-be are followed from their first visit at the
public maternity health-care clinic (usually between 8
and 10 weeks gestation), throughout their pregnancy to
delivery and 8 - 12 weeks post delivery. The register’s
quality has been evaluated three times: in 1976, 1988,
and in 2001 [39,40]. The following variables were col-
lected from the MBR; gender, gestational weeks, birth
weight, congenital malformations, parity, maternal age,
smoking habits during early pregnancy, and the mother’s
height and weight at the first visit to the public maternity
health-care clinic as well as at delivery. The Body Mass
Index (BMI) was calculated and analyzed according to
whether the mother was overweight (BMI ≥ 25.00) or
not (BMI < 24.99). On the basis of the mother’s weight
in early pregnancy and at delivery, the variable “gesta-
tional weight gain” was calculated and further dichoto-
mized and analyzed in two groups; ≤20 kg and >20.0 kg.
The variable “birth weight” was categorized into eight
subgroups according to 500 gram intervals. Children
with a birth weight more or equal to 5000 grams (n = 43)
were added to the subgroup of “≥4500 g”. Each sub-
group was then analyzed in relation to caries experience
at 13 and 19 yrs of age as well as total caries increment
between 13 and 19 yrs and presented in Table 1. In the
logistic regression analyses, low birth weight (<2500
grams) and high birth weight (≥4000 grams) were ana-
lyzed separately. A reference group “normal birth
weight” was calculated based on the distribution of birth
weight. The range for normal birth weight was estimated
to be between 25% and 75% of the subjects. Based on
this, the normal birth weight range was found to be be-
tween 3150 and 3815 grams. Remaining variables col-

A. Julihn et al. / Open Journal of Stomatology 3 (2013) 42-51 44
Table 1. Dental caries at 13 and 19 yrs of age in relation to
birth weight.
Birth weight
DMFT
13 yrs
Mean SD
DMFT-increment
13 - 19 yrs
Mean SD
DMFT
19 yrs
Mean SD
<1500 g
n = 86 0.71, 1.23 2.06, 2.94 2.77, 3.25
1500 - 1999 g
n = 127 0.91, 1.60 2.13, 2.82 3.05, 3.51
2000 - 2499 g
n = 408 1.32, 1.84 2.10, 2.77 3.42, 3.41
2500 - 2999 g
n = 1606 1.24, 1.82 2.14, 2.97 3.38, 3.60
3000 - 3499 g
n = 4768 1.26, 1.81 2.00, 2.88 3.19, 3.44
3500 - 3999 g
n = 4682 1.20, 1.77 2.09, 2.88 3.22, 3.43
4000 - 4499 g
n = 1768 1.28, 1.78 2.03, 2.85 3.31, 3.43
≥4500 g
n = 363 1.54, 2.13 2.21, 2.78 3.75, 3.69
DMFT (D = decayed, M = missing, F = filled, T = teeth); SD = standard
deviation; g = gram.
lected from the MBR were dichotomized in the statistical
analyses, see Table 2.
2.3.2. The Register of the Total Population
This register is kept by Statistics Sweden. From the Reg-
ister of the Total Population, the following variables
were collected; maternal country of birth and marital
status in 2005. In the statistical analysis, both variables
were dichotomized (Table 2).
2.3.3. The Total Enumeration Income Register
Data on individuals’ annual income tax, founded on in-
come tax returns and tax-authority decisions, is collected
by the National Swedish Tax Board. The Board then
sends summary statistics to Statistics Sweden. From this
register, information regarding the family’s income and
receipt of social-welfare allowance in 2005 was collected.
Both variables were dichotomized and family income
expressed as low income (less or equal to 25% of the
lowest income range or high income (more than 25% of
the lowest income range) in the statistical analysis (Ta-
ble 2).
2.3.4. The Education Register
Data on education was obtained from the Education
Register. In the statistical analysis, the variable “educa-
tional level” was divided according to years of schooling
as: Low (9 years), intermediate (10 - 12 years) and high
(>12 years), (Table 2).
2.4. Data Collection Concerning Dental Caries
In Stockholm, data on manifest caries lesions (based on
clinical and radiographic examination) in children and
adolescents is sent from the Public Dental Health Service,
private practitioners, and the Division of Pediatric Den-
tistry, Department of Dental Medicine at the Karolinska
Institute to the Public Health Care Administration and is
analyzed at ages 3, 7, 13, and 19 yrs of age. Since the
year 2000, all this data has been linked to the PIN. The
registration sheets of 13 and 19-yr-old children consist of
the following caries counts: DT = Decayed Teeth, MT =
Missing Teeth, FT = Filled Teeth, DSa = Decayed Sur-
faces approximal and FSa = Filled Surfaces approximal.
Manifest caries was recorded on smooth surfaces as the
minimal level that can be verified as a cavity and detect-
able by probing, and in fissures by a catch of the probe
under slight pressure. Approximal caries on the radio-
graphs was recorded as manifest caries when the lesion
clearly extends into the dentin. For this study, the caries
experience at 19 yrs of age and total caries increment
between 13 and 19 yrs of age, using the DFT-indices,
was used as the outcome in the statistical analyses.
The dental caries file of the study cohort was sent
from the Public Health Care Administration to the SCB,
where the data file was linked with the registers from
Statistics Sweden and Swedish National Health and
Welfare. The key to identify individuals was kept within
the SCB and was not disclosed to the investigators.
2.5. Statistical Analysis
Data analyses were carried out using the Statistical
Package for the Social Sciences (SPSS, version 21.0).
For analyzing the data, frequency tables, cross tables and
logistic regression were used. The odds ratios (OR) with
95% CI were used as estimates of the effects.
Total caries increment (DMFT ≥ 1) between 13 and 19
yrs of age and caries experience (DMFT ≥ 1, DMFT ≥ 4)
at 19 yrs of age were used as outcome in the logistic re-
gression analyses.
In a univariate analysis, the key exposure “birth
weight” was analyzed as the continuous variable and
potential confounders as categorical variables. In a mul-
tivariate analysis, “high birth weight” (≥4000) was ana-
lyzed with “normal birth weight” (3150 - 3815 g) as a
reference and total caries increment (DMFT ≥ 1) as the
outcome. To analyze “high birth weight” as a potential
risk factor for total caries increment between 13 and 19
yrs of age, the variable was adjusted for confounders.
The confounders for inclusion in the models were se-
lected using a combination of methods, i.e. based on
their association with the outcome as well as based on
their association with the exposure and subsequently
heir influence on the outcome. All the variables were t

A. Julihn et al. / Open Journal of Stomatology 3 (2013) 42-51 45
Table 2. Univariate logistic regression analysis with pre-, perinatal- and sociodemographic factors as exposure and caries experience
(DMFT ≥ 1) at 19 yrs of age as outcome.
Variables
Subject with DMFT ≥1
(n = 11605)/total number of participants
(n = 15538)
Odds ratio; 95% CI P-value
Child characteristics
Gender Female 5757/7728 1.00
Male 5762/7810 0.96; 0.90 - 1.04 0.298
Gestational weeks >36 weeks 9624/14747 1.00
≤36 weeks 584/791 0.98; 0.84 - 1.16 0.842
Birth weight* 317 - 5760 g 11605/15538 0.013
Congenital malformation
No 9959/15145 1.00
Yes 291/393 0.99; 0.79 - 1.25 0.967
Parity 1 - 2 8112/12877 1.00
≥3 2138/2661 1.54; 1.39 - 1.71 <0.001
Maternal characteris tics
Age ≥29 yrs 5024/8356 1.00
<29 yrs 5226/7182 0.86; 0.80 - 0.93 <0.001
Country of birth Sweden 8164/11526 1.00
Born abroad 3227/4012 1.54; 1.41 - 1.68 <0.001
Marital status 2005 Married 6992/9572 1.00
Not married 4613/5966 1.26; 1.17 - 1.36 <0.001
Smoked in early pregnancy
No 6515/12277 1.00
Yes 2604/3261 1.55; 1.40-1.71 <0.001
BMI in early preg nancy 0 - 24.99 5606/14413 1.00
≥25.00 883/1125 1.39; 1.20 - 1.62 <0.001
BMI at delivery 0 - 24.99 1873/8740 1.00
≥25.00 5063/6798 1.21; 1.10 - 1.34 <0.001
Gestational weight gain 0 - 20.0 kg 6241/14119 1.00
>20.0 kg 1094/1419 1.27; 1.11 - 1.45 <0.001
Educational level 2005 >12 yrs 4694/6677 1.00
10-12 yrs 5087/6705 1.33; 1.23 - 1.43 <0.001
≤9 yrs 1824/2156 2.32; 2.04 - 2.64 <0.001
Income 2005 High income range (>25%) 9043/12338 1.00
Low income range (≤25%) 2562/3200 1.46; 1.33 - 1.61 <0.001
Social welfare allowanc e 2005
No 10775/14568 1.00
Yes 830/970 2.09; 1.74 - 2.51 <0.001
* = continuous variable.
classified (as shown in Table 2), and then entered into
the multivariate analyses as independent variables. The
final logistic regression analysis began with a full model
and the model was then reduced by removing, one by
one, insignificant covariates until only significant co-
variates persisted (Table 3).

A. Julihn et al. / Open Journal of Stomatology 3 (2013) 42-51 46
Table 3. Final multivariate logistic regression analysis with
total caries increment (DMFT ≥ 1) between 13 and 19 yrs of
age as outcome and high birth weight (≥4000 g) as key expo-
sure.
Variables OR
95% CI
Lower Upper P-value
Key variable
High birth weight
3150 - 3815 g
(n = 4318)
1.00
≥4000 g (n = 1391) 1.29 1.13, 1.48 <0.001
Adjusted for
Child characteristics
Parity 1 - 2 1.00
≥3 1.19 1.03, 1.39 0.022
Maternal characteris tics
Country of birth Sweden 1.00
Born abroad 1.17 1.01, 1.37 0.038
Smoked in early pregnancy
No 1.00
Yes 1.29 1.13, 1.49 <0.001
BMI in early preg nancy
0 - 24.99 1.00
≥25.00 1.23 1.04, 1.46 0.016
Marital status 2005
Married 1.00
Not married 1.13 1.01, 1.27 0.037
Educational level 2005
>12 yrs 1.00 <0.001
10 - 12 yrs 1.21 1.07, 1.36 0.002
≤9 yrs 1.64 1.34, 2.02 <0.001
Social welfare allowanc e 2005
No 1.00
Yes 1.63 1.16, 2.30 0.003
The key exposure “birth weight” was also analyzed as
either “low birth weight” (<2500 g) or “high birth
weight” (≥4000) according to the magnitude, with “nor-
mal birth weight” (3150 - 3815 g) as the reference (Ta-
bles 4 and 5). Each cut-off level was analyzed separately
in a multivariate logistic regression analysis with total
caries increment (DMFT ≥ 1), caries experience (DMFT
≥ 1) and caries experience (DMFT ≥ 4) as outcome. In
these analyses, the key exposure was adjusted for poten-
tial confounders (as shown in Table 2).
3. RESULTS
Of the final cohort (n = 13,808), 4.5% (n = 621) were
born with a birth weight less than 2500 grams and 15.4%
(n = 2131) exhibited a birth weight of 4000 grams or
more. In Table 1, the mean value and standard deviation
of caries experience at 13 yrs of age, total caries incre-
ment between 13 and 19 yrs of age, and caries experi-
ence at 19 yrs of age are described in relation to sub-
groups of birth weight. The lowest mean values of caries
experience (DMFT) at both 13 and 19 yrs of age were
seen among subjects born with a birth weight of less than
1500 grams and the highest mean values were seen
among subjects born with a birth weight of 4500 grams
or more (Table 1).
3.1. Univariate Analysis
In the univariate logistic regression analysis, the key ex-
posure “birth weight” was analyzed as a continuous
variable and all covariates as categorical variables. The
analyses were performed with caries experience (DMFT
≥ 1) at 19 yrs of age, as a dependent variable, and
showed that “birth weight”, as a continuous variable, was
significantly associated with the outcome (p = 0.013),
(Table 2). In addition, the following potential confound-
ers were also significantly associated with the outcome:
Parity, maternal age, country of birth, marital status,
smoking during early pregnancy, BMI in early preg-
nancy, BMI at delivery, gestational weight-gain, educa-
tional level, income and receiving social welfare allow-
ance (Table 2).
3.2. Multivariate Analysis
In a multivariate logistic regression analysis, the associa-
tion between high birth weight (≥4000 g) and the total
caries increment (DMFT ≥ 1) between 13 and 19 years
of age was tested. At the start, all variables in Table 2
were included in the model. In the final model, only sig-
nificant covariates persisted. The results showed that
“high birth weight” was significantly associated with the
outcome (OR 1.29; 95% CI = 1.13 - 1.48). Remaining
significant variables in the final model except for “high
birth weight” were parity, country of birth, smoked dur-
ing early pregnancy, BMI in early pregnancy, gestational
weight-gain, marital status, maternal educational level
and family receiving social welfare allowance (Table 3).
3.3. Dental Caries in Relation to the Magnitude
of Low Birth Weight
In this statistical analysis, the total caries increment be-
tween 13 and 19 yrs of age as well as caries experience
at 19 yrs of age in relation to the magnitude of low birth
weight was studied. All analyses were adjusted for pos-
sible confounders presented in Table 2. After adjust-
ents, the results showed that children born with a birth m

A. Julihn et al. / Open Journal of Stomatology 3 (2013) 42-51 47
Table 4. Logistic regression analysis with the magnitude of low birth weight as exposure and caries experience at 19 yrs of age and
total caries increment between 13 and 19 yrs as an outcome.
Caries indices Birth weight < 2500 g
OR 95% CI
Birth weight < 2100 g
OR 95% CI
Birth weight < 2000 g
OR 95% CI
Birth weight < 1800 g
OR 95% CI
Birth weight < 1700 g
OR 95% CI
Caries experience
(DMFT ≥ 1) n = 455 n = 180 n = 148 n = 97 n = 76
Unadjusted 0.97, 0.80 - 1.17 0.84, 0.65 - 1.08 0.80, 0.60 - 1.08 0.76, 0.53 - 1.09 0.75, 0.50 - 1.11
Adjusted 0.84, 0.68 - 1.03 0.75, 0.55 - 1.03 0.69, 0.49 - 0.96 0.63, 0.42 - 0.94 0.60, 0.38 - 0.93
(DMFT ≥ 4) n = 232 n = 83 n = 69 n = 48 n = 36
Unadjusted 0.98, 0.82 - 1.16 0.80, 0.62 - 1.05 0.79, 0.59 - 1.05 0.84, 0.59 - 1.19 0.78, 0.52 - 1.16
Adjusted 0.67, 0.50 - 0.89 0.50, 0.30 - 0.81 0.51, 0.30 - 0.89 0.71, 0.38 - 1.32 0.71, 0.34 - 1.46
Caries increment
(DMFT ≥ 1) n = 398 n = 161 n = 135 n = 90 n = 69
Unadjusted 1.09, 0.92 - 1.29 1.08, 0.83 - 1.40 1.05, 0.79 - 1.40 1.05, 0.75 - 1.49 0.98, 0.67 - 1.43
Adjusted 0.97, 0.81 - 1.17 1.03, 0.77 - 1.37 0.98, 0.72 - 1.35 0.91, 0.62 - 1.34 0.83, 0.54 - 1.26
Adjusted for prenatal and perinatal factors (gender, gestational weeks, congenital malformation, parity, maternal age, maternal smoking during early pregnancy,
BMI in early pregnancy, BMI at delivery, weight-gain during pregnancy), and maternal sociodemographic factors (civil status, maternal country of birth, ma-
ternal educational level, maternal income level and mother receiving social welfare allowance).
Table 5. Logistic regression analysis with the magnitude of high birth weight as exposure and caries experience at 19 yrs of age and
caries increment between 13 and 19 yrs of age as an outcome.
Caries indices Birth weight ≥ 4000 g
OR 95% CI
Birth weight ≥ 4200 g
OR 95% CI
Birth weight ≥ 4400 g
OR 95% CI
Birth weight ≥ 4500 g
OR 95% CI
Birth weight ≥ 4600 g
OR 95% CI
Caries experience
(DMFT ≥ 1) n = 1634 n = 867 n = 416 n = 286 n = 192
Unadjusted 1.16, 1.04 - 1.30 1.20, 1.03 - 1.39 1.22, 0.99 - 1.51 1.31, 1.01 - 1.70 1.54, 1.11 - 2.15
Adjusted 1.24, 1.09 - 1.40 1.24, 1.06 - 1.46 1.28, 1.02 - 1.60 1.35, 1.03 - 1.79 1.50, 1.05 - 2.13
(DMFT ≥ 4) n = 842 n = 458 n = 220 n = 154 n = 103
Unadjusted 1.07, 0.97 - 1.18 1.13, 0.99 - 1.28 1.14, 0.95 - 1.36 1.21, 0.98 - 1.50 1.27, 0.98 - 1.65
Adjusted 1.13, 1.01 - 1.26 1.17, 1.02 - 1.35 1.20, 0.99 - 1.46 1.27, 1.01 - 1.60 1.34, 1.01 - 1.77
Caries increment
(DMFT ≥ 1) n = 1391 n = 743 n = 362 n = 248 n = 166
Unadjusted 1.14, 1.03 - 1.27 1.19, 1.04 - 1.36 1.27, 1.05 - 1.53 1.31, 1.05 - 1.65 1.44, 1.09 - 1.92
Adjusted 1.29, 1.13 - 1.48 1.30, 1.09 - 1.55 1.38, 1.09 - 1.76 1.48, 1.12 - 1.91 1.52, 1.08 - 2.04
Adjusted for prenatal and perinatal factors (gender, gestational weeks, congenital malformation, parity, maternal age, maternal smoking during early pregnancy,
BMI in early pregnancy, BMI at delivery, weight-gain during pregnancy), and maternal sociodemographic factors (marital status, maternal country of birth,
maternal educational level, maternal income level and mother receiving social welfare allowance).
weight less than 2000 grams exhibited a statistically sig-
nificant negative association with caries experience
(DMFT ≥ 1) at 19 yrs of age (OR 0.69; 95% CI = 0.49 -
0.96), (Table 4). When the birth weight was less than
1600 grams, the variable “low birth weight” was no
longer significant in the model. Further, when low birth
weight was analyzed in relation to caries experience
(DMFT ≥ 4), a statistical significant negative association
was found in subjects born with a birth weight less than
2500 grams (OR 0.67; 95% CI = 0.50 - 0.89). Strongest
negative association was seen at low birth weight less
than 2100 grams (OR 0.50; 95% CI = 0.30 - 0.81), (Ta-
ble 4). However, when the birth weight was less than
1800 grams the variable “low birth weight” was no

A. Julihn et al. / Open Journal of Stomatology 3 (2013) 42-51 48
longer significant in the model. Concerning total caries
increment, no significant associations with low birth
weight was found.
3.4. Dental Caries in Relation to the Magnitude
of High Birth Weight
In Table 5, the total caries increment between 13 and 19
yrs of age as well as the caries experience at 19 yrs of
age was analyzed in relation to the magnitude of high
birth weight. All analyses were adjusted for possible
confounders presented in Table 2. After adjustments, the
results showed that children born with a high birth
weight more or equal to 4000 grams, exhibited a statis-
ticcally significant positive association with caries ex-
perience (DMFT ≥ 1) at 19 yrs of age (OR 1.24; 95% CI
= 1.09 - 1.40), (Table 5). When high birth weight was
analyzed at various cut-off levels; ≥4200 g, ≥4400 g,
≥4500 g and ≥4600 g, the positive risk of exhibiting car-
ies experience (DMFT ≥ 1) at 19 yrs of age was still sig-
nificant. Further, the excess risk across the various cut-
off levels increased up to a high birth weight more or
equal to 4600 g (OR 1.50; 95% CI = 1.05 - 2.13), (Table
5). However, when the birth weight was more or equal to
4700 grams the variable “high birth weight” was no
longer significant in the model. High birth weight was
also analyzed in relation to caries experience (DMFT ≥
4). In this analysis, the excess risk of exhibiting caries
was lower compared to the association between high
birth weight and caries experience (DMFT ≥ 1), (Table
5). In the next multivariate model, high birth weight was
tested with total caries increment as the outcome. The
results showed that high birth weight was significantly
positive when associated with the outcome across all
tested cut-off levels of high birth weight. Further, the
excess risk was enhanced as the cut-off levels of high
birth weight increased.
4. DISCUSSION
The novel finding demonstrates that birth weight (≥4000
g) is associated with caries development later in life dur-
ing adolescence. The risk of caries increment (DMFT > 1)
for infants born with a birth weight of 4000 grams or
higher was 1.22 (OR) and increased positively with the
magnitude of birth weight, adjusted for potential con-
founders like maternal and child characteristics including
socioeconomic factors. Regarding infants with birth
weight (<2500 g), we did not demonstrate any enhanced
risk for dental caries development. However, low birth
weight infants reveal a relatively lower risk for exhibit-
ing one or more DMFT at 19 years of age compared with
normal weight infants.
There is a great advantage of using population-based
registers compared with common dental health surveys
when identifying various risk factors for dental caries. In
this study, we used the MBR register as our source of
information. An advantage of using MBR is that it cov-
ers ~97% - 99% of deliveries in Sweden [40]. The qual-
ity of MBR has been evaluated with the conclusion that
it is a valuable source of information for reproduction
epidemiology [39,40]. The validity of information on
prenatal factors used in the statistical analyses is proba-
bly accurate since the information was collected pro-
spectively before birth. Furthermore, all information re-
garding the family was collected independently of the
study outcome, which reduced problems with recall and
interviewer bias. However, we were not able to include
information on the weight of the subjects during the
study period, when the adolescents were between 13 and
19 years of age. Consequently, it was not possible to
adjust for the confounder “weight of the subject” in the
multivariate model with caries increment as outcome.
Dental data was collected at 13 and 19 years of age
from the Public Health Care Administration in the
county of Stockholm and has been used in other register-
based studies with valid results [36,41]. In register-based
studies, there is a risk of random errors because the di-
agnosis of manifest caries can sometimes be under-re-
ported or over-reported due to several examiners. How-
ever, random errors are affected by increasing the size of
the study and will be reduced to zero if a study becomes
infinitely large [42]. In this study, the final study cohort
consisted of 13,808 children and the risk of random error
is, therefore, of minor importance.
We decided on a cut-off point of high caries experi-
ence (DMFT ≥ 4) for both statistical and theoretical rea-
sons. The population in the highest tertile of frequency
distribution are those who attended dental services with
more treatment need [43]. On the other hand, a child
with DMFT equal to one may be considered as accept-
able because dental caries is almost impossible to eradi-
cate.
In a multivariate model, the association between birth
weight and dental caries was controlled for various con-
founders like maternal characteristics in terms of age,
country of birth, marital status, smoking habits, BMI
early in pregnancy and at delivery, gestational weight
gain, social welfare allowance, family income and edu-
cational level as well as the child characteristics like
gestational weeks, congenital malformation and parity.
For the first time, this study demonstrates that birth
weight (≥4000 g) is a risk factor for dental caries devel-
opment later in life. This finding is interesting in light of
previous discussions where dental caries experience
might be biologically programmed in utero or early life
[32], like other chronic diseases [44]. The mechanism
behind the link between birth weight (≥4000 g) and den-
tal caries development is unclear although there might be

A. Julihn et al. / Open Journal of Stomatology 3 (2013) 42-51 49
some factors of importance for predisposing such asso-
ciation. One explanation is that infants born with high
birth weight have an increased risk for developing over-
weight or obesity during childhood [17,18]. Together
with our previous finding of an association between obe-
sity and dental caries in adolescents [37] the link be-
tween birth weight and dental caries found in our study
might be confounded by an overrepresentation of ado-
lescents with overweight or obesity within the group of
infants with birth weight (≥4000 g). As previously pointed
out, there was no information regarding the weight of the
adolescents during the study period. Therefore, it was not
possible to evaluate whether the weight of the subject
was a confounder or not when analyzing the relationship
between birth weight and caries increment in the multi-
variate model. Taken into account previous findings that
obesity subjects might exhibit more dental caries com-
pared to normal weight subjects [37], it is important in
future clinical studies to control for the weight of the
adolescents.
A potential mechanism explaining the link between
obesity and dental caries might be the reduction of the
salivary flow rate seen among obese subjects compared
with normal weight adolescents [37]. The mechanism(s)
behind the association between obesity and dental caries
subjects might also be mediated by an alteration of the
oral microflora during obesity. Due to decreased salivary
flow in obese subjects, the oral biofilm might change in
quality and/or quantity that contribute to an alteration in
balance between demineralization and remineralization
activity on the tooth surface. In a recent paper, we dem-
onstrated that the subgingival microflora differs in obese
teenagers compared with normal weight subjects [45].
We found approximately threefold higher levels of Phy-
lum firmicutes whereas Streptococcus mutans was two-
fold higher in obese adolescents compared with normal
weight adolescents.
One has to consider that we did not have any informa-
tion regarding dietary habits or prevention measures
given to the subjects. We can therefore not eliminate that
the birth weight, as a risk factor for dental caries, can be
biased, to some extent, by decreased prevention proce-
dures, insufficient dietary habits or poorer oral hygiene
among subjects with a high birth weight.
There might also be biological factors that partly can
influence upon a foetus’s immune response like maternal
lifestyle factors [36] that in the long-term influences oral
colonisation of caries related microorganisms [28] and
thereby increase the risk for caries development.
Another interesting finding in this study was the nega-
tive association between low birth weight and caries ex-
perience at 19 yrs of age after taking into account poten-
tial confounding factors. Our finding, that low birth
weight infants run a lower risk of developing caries
compared to normal birth weight infants is in line with
previous studies indicating that caries prevalence in pri-
mary teeth was lower among premature and very low
birth weight infants compared to term and normal weight
infants [46,47]. It is unclear what might causing the de-
creased caries experience (DMFT ≥ 4) in adolescents
with birth weight (<2500 g). One explanation could be
closer monitoring of low birth weight children since in-
fants born both short and thin have been found to be at
greater risk for mortality and hospitalizations [48,49]. In
addition, it has been shown that very low birth weight
infants at 14 years had significantly more functional
limitations and receive more coordinated care than the
term adolescents [26]. In addition, caregivers were pro-
viding brushing assistance/supervision for the very low
birth weight group for a significantly longer period than
for normal birth weight infants [26].
Another possible explanation for the negative associa-
tion between low birth weight and caries experience at
19 yrs of age is more frequent antibiotic use in our low
birth weight group, due to many health problems among
premature and very low birth weight children. The fre-
quent use of antibiotics has been indicated as inhibiting
the colonization of cariogenic bacteria [50] that may
possibly explain the reduced caries experience in our
very low birth weight group. Unfortunately, information
regarding antibiotic use was not available and is there-
fore a limitation of this study.
5. CONCLUSION
In conclusion, birth weight can be regarded as a predictor
for dental caries and birth weight (≥4000 g) is especially
a risk factor for caries increment during adolescence and
should be taken into consideration in the risk assessment.
Furthermore, this study indicates that low birth weight
infants do not run a higher risk of developing caries than
other children in the permanent dentition.
6. ACKNOWLEDGEMENTS
This study was supported by grants from the Skaraborg County Council,
the Swedish Dental Society, and the Swedish Patent Revenue Research
Fund.
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