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\begin{document}

\title{Prenatal antibiotic exposure and the risk of atopic dermatitis in
children: a nationwide population-based cohort study.}



\author[1]{Yu Chuan Chang}%
\author[2]{Meng-Che Wu}%
\author[1]{Hsing-Ju Wu}%
\author[3]{Pei-Lun Liao}%
\author[4]{James Wei}%
\affil[1]{Chang Bing Show Chwan Memorial Hospital}%
\affil[2]{Taichung Veterans General Hospital}%
\affil[3]{Chung Shan Medical University Hospital}%
\affil[4]{Chung Shan Medical University}%


\vspace{-1em}



  
  \date{May 20, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
\textbf{Background:} Atopic dermatitis (AD) contributes to substantial
social and financial costs in public health care systems. Antibiotic
exposure during pregnancy has been proposed as a risk factor, but
findings remain inconsistent. The aim of this study was to investigate
the association between prenatal antibiotic use and childhood AD.
\textbf{Methods:} We performed a population-based cohort study using
data collected from the Taiwan Maternal and Child Health Database from
2009 to 2016. Associations were determined using Cox proportional
hazards model and were adjusted for several potential covariates,
including maternal atopic disorders and gestational infections. Subgroup
analyses evaluated the influence of postnatal infant
antibiotic/acetaminophen use on the association between prenatal
antibiotic exposure and childhood AD diagnosed after 1 year of age.
\textbf{Results:} A total of 1288343 mother-child pairs were identified
and 39.5\% received antibiotics prenatally. Maternal antibiotic use
during pregnancy was slightly positively associated with childhood AD
(aHR 1.05, 95\% CI 1.04-1.06), especially in the first and second
trimesters. An apparent dose-response pattern was observed with an 11\%
increased risk when the exposure was [?]5 courses prenatally (aHR 1.11,
95\% CI 1.09-1.14). Subgroup analysis showed the positive association
remained significant regardless of postnatal antibiotic use; however, a
negative association was found in children without postnatal infant
acetaminophen use (aHR 1.02, 95\% CI 0.97-1.07). \textbf{Conclusion:}
Maternal antibiotic use during pregnancy was associated with increased
risk of childhood AD in a dose-related manner. Possible confounders
existed between prenatal antibiotics and postnatal infant acetaminophen
use in the subgroup analysis. Further research may be warranted to
investigate this variable using a prospectively designed study, and also
to examine whether or not this association is specifically related to
pregnancy.%
\end{abstract}%



\sloppy


\textbf{Article type} : Original article

\textbf{Title} : Prenatal antibiotic exposure and the risk of atopic
dermatitis in children: a nationwide population-based cohort study.

\textbf{Running title} : Prenatal antibiotics and risk of atopic
dermatitis.

\textbf{Keywords} : Antibiotics, atopic dermatitis, gestational
infection, acetaminophen, microbial dysbiosis

\textbf{Authors} :

Yu-Chuan Chang,\textsuperscript{1} MD, Meng-Che
Wu,\textsuperscript{2-4}MD, PhD, Hsing-Ju Wu\textsuperscript{5-7}, PhD,
Pei-Lun Liao, MS\textsuperscript{8}, James Cheng-Chung
Wei\textsuperscript{3, 9, 10}MD, PhD

\textsuperscript{1}Department of Pediatrics, Chang Bing Show Chwan
Memorial Hospital, Changhua;

\textsuperscript{2}Division of Gastroenterology, Children's Medical
Center, Taichung Veterans General Hospital, Taichung;

\textsuperscript{3}Institute of Medicine, Chung Shan Medical University,
Taichung;

\textsuperscript{4}College of Medicine, National Chung Hsing University,
Taichung;

\textsuperscript{5}Department of Biology, National Changhua University
of Education, Changhua;

\textsuperscript{6}Research Assistant Center, Show Chwan Memorial
Hospital, Changhua;

\textsuperscript{7}Department of Medical Research, Chang Bing Show Chwan
Memorial Hospital, Changhua;

\textsuperscript{8}Department of Medical Research, Chung Shan Medical
University Hospital, Taichung;

\textsuperscript{9}Division of Allergy, Immunology and Rheumatology,
Chung Shan Medical University Hospital, Taichung;

\textsuperscript{10}Graduate Institute of Integrated Medicine, China
Medical University, Taichung

All in Taiwan.

Yu-Chuan Chang and Meng-Che Wu contributed equally.

\textbf{Corresponding author} :

James Cheng-Chung Wei, M.D., Ph.D.,

Department of Allergy, Immunology \& Rheumatology, Chung Shan Medical
University Hospital

No. 110, Sec. 1, Jianguo N. Rd., South District, Taichung City 40201,
Taiwan

TEL: +886 4 24739595 \#34718, 34308

FAX: +886 4 24734323

Email: jccwei@gmail.com

\textbf{Manuscript word count} : 3165

\textbf{Abstract word count} : 271

\textbf{References} : 33

\textbf{Figures} : 1

\textbf{Supplementary figures} : 1

\textbf{Tables} : 5

\textbf{Supplementary tables} : 1

\textbf{Funding sources} : This study was supported by the DryLab Team
of Chung Shan Medical University, Taichung, 47 Taiwan.

\textbf{Conflicts of interest} : The authors have no conflicts of
interest that are directly relevant to the content of this article.

\textbf{IRB approval status} : Reviewed and approved by the ethical
review board of Chung Shan Medical University Hospital (No. CS1-21022).

\textbf{Author contributions} : Study concept and design: Y-C C, M-C W,
H-J W. Statistical analysis: P-L L. Analysis and interpretation of data:
Y-C C, M-C W. Drafting of the manuscript: Y-C C, M-C W. Critical
revision of the manuscript for important intellectual content: M-C W,
H-J W, J-C W. All authors read and approved the final manuscript.

\textbf{Abstract}

\textbf{Background:} Atopic dermatitis (AD) contributes to substantial
social and financial costs in public health care systems. Antibiotic
exposure during pregnancy has been proposed as a risk factor, but
findings remain inconsistent. The aim of this study was to investigate
the association between prenatal antibiotic use and childhood AD.

\textbf{Methods:} We performed a population-based cohort study using
data collected from the Taiwan Maternal and Child Health Database from
2009 to 2016. Associations were determined using Cox proportional
hazards model and were adjusted for several potential covariates,
including maternal atopic disorders and gestational infections. Subgroup
analyses evaluated the influence of postnatal infant
antibiotic/acetaminophen use on the association between prenatal
antibiotic exposure and childhood AD diagnosed after 1 year of age.

\textbf{Results:} A total of 1288343 mother-child pairs were identified
and 39.5\% received antibiotics prenatally. Maternal antibiotic use
during pregnancy was slightly positively associated with childhood AD
(aHR 1.05, 95\% CI 1.04-1.06), especially in the first and second
trimesters. An apparent dose-response pattern was observed with an 11\%
increased risk when the exposure was [?]5 courses prenatally (aHR 1.11,
95\% CI 1.09-1.14). Subgroup analysis showed the positive association
remained significant regardless of postnatal antibiotic use; however, a
negative association was found in children without postnatal infant
acetaminophen use (aHR 1.02, 95\% CI 0.97-1.07).

\textbf{Conclusion:} Maternal antibiotic use during pregnancy was
associated with increased risk of childhood AD in a dose-related manner.
Possible confounders existed between prenatal antibiotics and postnatal
infant acetaminophen use in the subgroup analysis. Further research may
be warranted to investigate this variable using a prospectively designed
study, and also to examine whether or not this association is
specifically related to pregnancy.

\textbf{Key message:}

Prenatal antibiotic use was positively associated with atopic dermatitis
in childhood in a dose-response manner. Further research should be
conducted to examine whether or not this association was specific to
during pregnancy.

\textbf{Introduction}

Atopic dermatitis (AD) is an inflammatory skin disorder characterized by
recurrent pruritic eczematous lesions. The prevalence of AD varies among
different geographic areas, with a rate of up to 20\% in the pediatric
population.\textsuperscript{1} AD manifests mostly in infancy with an
age of onset before 6 years in about 80\% of
patients.\textsuperscript{2} Dermatitis, including AD, is responsible
for the majority of the global skin disease burden, leading to
substantial social and financial costs.\textsuperscript{3}

The cause of AD may be multifactorial, including genetic susceptibility,
environmental exposure, immune dysregulation, and
inflammation.\textsuperscript{4,5} Among the environmental variables,
antibiotic use during pregnancy and in early life are thought to be risk
factors of AD and have been discussed in several studies and
meta-analyses. Antibiotics account for nearly 80\% of prescribed
medications during pregnancy and the estimated rate of antibiotic use
during this period was reported to be 20-25\%.\textsuperscript{6} The
changes in gut microbiota and dysbiosis after antibiotic use may be one
of the reasons for subsequent AD development.\textsuperscript{7}

Tsakok el al. conducted the first systematic review and meta-analysis of
the effects of prenatal antibiotic exposure on AD. The pooled odds ratio
(OR), which was 1.3 (95\% CI: 0.86-1.95), indicated there was no
association, although the estimate was elevated.\textsuperscript{8}Three
subsequent meta-analysis showed a positive
association.\textsuperscript{9-11} In a study by Cait et al., the risk
of eczema/dermatitis was increased in their pooled data (RR 1.28; 95\%
CI: 1.06 --1.53). However, high heterogeneity among the data was also
mentioned by the authors. Similar findings were also noted in the other
2 meta-analyses. The reasons for the high heterogeneity may be the
different methods of data collection (some were by questionnaire or
telephone interviews), inconsistent outcome measurements, and
differences in methods used to control the variables among studies.

This study employed a cohort study design with a large sample from
Taiwan's national healthcare system and aimed to examine the association
between maternal antibiotic use during pregnancy and childhood AD,
taking the timing of exposure during pregnancy into account.

\textbf{Methods}

\textbf{2.1 Data source}

The data used in this study were from the Taiwan Maternal and Child
Health Database (TMCHD), which consists of four linked nationwide
databases, namely the National Health Insurance Research Database
(NHIRD), the Birth Certificate Application (BCA) database, Birth
Registration Database (BRD), and the National Register of Death (NRD) in
Taiwan.

The NHI (National Health Insurance) program was launched in Taiwan in
1995 and covers over 99\% of the nation's population of approximately 23
million residents, with medical claims data on all outpatients and
inpatients. Information regarding demographic data, dates of visits,
disease diagnoses, prescriptions, and medical orders are included in the
NHIRD. Information related to birth of children and nationality of
mother are included in the BCA database, whereas the NRD contains the
survival status of infants. Using the unique personal identification
numbers of residents in Taiwan, we were able to confirm the
relationships between parents and children through the BRD and link
individuals across the four databases. The diagnosis of diseases was
based on the \emph{International Classification of Diseases, 9th}
and\emph{10th Revision, Clinical Modification} (\emph{ICD-9-CM}
and\emph{ICD-10-CM} ). The study was approved by the ethical review
board of Chung Shan Medical University Hospital.

\textbf{2.2 Study population and design}

We conducted a retrospective cohort study by analyzing data from
children born between 2009 and 2016 from the TMCHD. A total of 1459093
labor events were identified initially. After excluding mothers with
foreign nationality (\emph{n =}88837), stillbirths or miscarriages
(\emph{n =} 14639), and newborns with missing identification numbers
(\emph{n =} 67274), there were 1288343 mother-child pairs (Figure S1).
The exposure of antibiotics during pregnancy, as well as the dose and
timing, was identified by using Anatomical Therapeutic Chemical
Classification (ATC) code J01. The index date was set as the birth date.
The trimester in which antibiotic exposure occurred was defined as
follows: first, 1-91 days; second, 92-189 days; third, [?]190 days. The
outcome variable was defined as outpatient visits at least 3 times or
one hospitalization with a diagnosis of atopic dermatitis (ICD-9-CM: 691
or ICD-10-CM: L20) after the index date. Maternal comorbidities were
defined as comorbidities occurring two years before the index date and
at least 3 outpatient visits or one hospitalization, whereas gestational
infections, gestational diabetes, and preeclampsia were defined as at
least one outpatient visit or hospitalization. The exposure and
non-exposure group were followed up until the onset of atopic
dermatitis, death, or 31 December 2019, whichever occurred first.

\textbf{2.3 Potential confounders or covariates}

We considered the following covariates for potential association with
exposure and outcome based on previous
studies.\textsuperscript{2,12}Maternal factors included maternal age,
urbanization, insurance property, mode of delivery, type of pregnancy,
acetaminophen use during pregnancy, maternal atopic disorders,
gestational infections, and maternal comorbidities, including
hypertension, diabetes mellitus, hyperlipidemia, malignancy, urinary
tract infection, maternal asthma, rheumatoid arthritis, systemic lupus
erythematosus, Sj\selectlanguage{ngerman}ögren syndrome, endometriosis, gestational diabetes,
and preeclampsia. Infant factors included birth year, child's sex,
length of gestation, birth weight, and APGAR score at birth. In
addition, postnatal antibiotic and acetaminophen exposure in the first
year of life were also selected as variables based on previous reports.

\textbf{2.4 Statistical analysis}

We used absolute standardized differences (ASD) to measure the effect
size of baseline covariates between groups. When the ASD was
\textless{}0.1, the characteristics between two groups were considered
similar. In addition, Kaplan-Meier analysis was used to calculate the
cumulative incidence of AD and a log-rank test was used to measure the
significance between groups. We used a Cox proportional hazards model to
estimate the associations of maternal antibiotic use during pregnancy
with childhood AD and associated covariates, which were reported as
crude and adjusted hazard ratios (HR and aHR, respectively) and 95\%
confidence intervals. To consider the effect of infant
antibiotic/acetaminophen use on prenatal antibiotic exposure and avoid
reverse causation (AD occurred before antibiotic/acetaminophen use), we
performed an analysis with exclusion of AD diagnosed before 1 year of
age, as shown in the subgroup analysis. All calculations were performed
using SAS version 9.4 (SAS Institute, Cary, NC, USA).

\textbf{Results}

\textbf{3.1 Demographic data of the study subjects}

A total of 1288343 mother-child pairs were included in our study with a
median follow-up time of 61 months, and the mean (SD) age of AD
diagnosis was 0.81 ± 1.1 years old. The mean maternal age was 31.38 ±
4.6 years and 508647 (39.5\%) received antibiotics during pregnancy. The
prevalence of AD in our cohort was 22.3\%, corresponding to the
incidence rate of 3.69 (95\% CI 3.68-3.71) per 1000 person-months. The
frequency of maternal antibiotic use varied slightly during pregnancy,
from 17.9\% in the first trimester to 19.0\% in the second and 14.6\% in
the third trimester.

As shown in Table 1, the infants of mothers exposed to prenatal
antibiotics were more likely to be born preterm than infants of
unexposed mothers, but there was no association with increased risk of
AD (aHR 0.98, 95\% CI 0.96-0.99) (Table 3). In contrast, prenatal
acetaminophen exposure, gestational infections, and maternal atopic
disorders, such as allergic rhinitis, and AD were positively associated
with prenatal antibiotic use and AD risk (Table 1, Table 3). The
exposure and unexposed groups were similar regarding childbirth year,
sex distributions, birth weight, Apgar scores at birth, maternal age,
urbanization, insurance properties, mode of delivery, type of pregnancy,
and paternal age (Table 1). Infants born to mothers with prenatal
antibiotic exposure were more likely to be exposed to postnatal
antibiotics and acetaminophen than those born to unexposed mothers in
the first year of life (Table 1). We performed a subgroup analysis that
only included AD diagnosed after 1 year of age, as shown in Table 5,
which still showed a positive association with AD in the prenatal
exposure group, but the estimate was attenuated after adjusting for
potential covariates and was even reduced to null in children who were
not exposed to postnatal acetaminophen (aHR 1.02, 95\% CI 0.97-1.07).

\textbf{3.2 Relationship between prenatal antibiotic exposure and atopic
dermatitis}

In the present study, prenatal antibiotic exposure was associated with
higher rates of AD (4 per 1000 person-months, 95\% CI 3.98-4.03)
compared to unexposed groups (3.5 per 1000 person-months, 95\% CI
3.48-3.52) (HR 1.13, 95\% CI 1.12-1.14) (Table 2). After adjusting for
covariates, the association still persisted in the Cox proportional
hazards model (HR 1.05, 95\% CI 1.04-1.06) (Table 2). The cumulative
probability of AD was significantly higher in the prenatal antibiotic
exposure group than in the non-exposure group (log-rank test
\emph{P}\textless{}0.001, Figure 1).

\textbf{3.3 Timing of prenatal antibiotic exposure and AD risk}

Regarding the timing of prenatal antibiotic exposure and AD risk, the
risk was slightly higher in the first trimester (aHR 1.04, 95\% CI
1.03-1.05) and second trimester (aHR 1.03, 95\% CI 1.01-1.04) than in
the third trimester (aHR 1, 95\% CI 0.99-1.01), in which the risk became
non-significant. When the reference group was set as ``no antibiotic use
during the whole pregnancy'', the risk of AD was slightly increased in
all three trimesters (first trimester: aHR 1.06, 95\% CI 1.05-1.08,
second trimester: aHR 1.06, 95\% CI 1.05-1.07, and third trimester: aHR
1.04, 95\% CI 1.02-1.05) (Table 4).

\textbf{3.4 Cumulative prenatal antibiotic courses and AD risk}

We observed a significant dose-response association between number of
prenatal antibiotic courses and AD. With a mean of 2.1 courses of
antibiotic use during pregnancy, the adjusted HRs were 1.05 (95\% CI
1.04-1.06) for 1-2 courses of antibiotic use, 1.08 (95\% CI 1.06-1.1)
for 3-4 courses of antibiotic use, and 1.11 (95\% CI 1.09-1.14) for \selectlanguage{english}[?]5
courses of antibiotic use (Table S1).

\textbf{Discussion}

In this population-based study, we found a positive association between
prenatal antibiotic exposure in all trimesters and development of AD in
childhood. This association remained significant after adjusting for
several established AD risk factors in the hazards model analysis. The
positive association remained significant in the subgroup analysis
regardless of postnatal antibiotic use after excluding AD diagnosed
before 1 year of age, but the association did not persist in children
who were not exposed to postnatal acetaminophen. We also found an
apparent dose-response relationship with an 11\% increased risk when
exposed to \selectlanguage{english}[?]5 courses prenatally. To our knowledge, this is the largest
study to date to investigate the relationship between maternal
antibiotic use during pregnancy and offspring AD.

The gut microbiome and the intestinal immune system develop in parallel
in the first trimester, which is also when enrichment of innate immune
cells in skin takes place.\textsuperscript{13,14} Studies have reported
that intrauterine samples/placenta harbor bacterial DNA or biomass and
its colonization may begin in utero.\textsuperscript{7,14-16} However,
whether the bacterial DNA are present in the placenta is still a matter
of debate, as some studies have suggested the presence of DNA may be
caused by contamination during the DNA purification
process.\textsuperscript{16} Nevertheless, the maternal microbiome can
potentially influence fetal immune maturation through agonists of
toll-like receptors (TLRs), short-chain fatty acids (SCFAs) or
lipopolysaccharides (LPS) via the placenta.\textsuperscript{16,17}Proper
differentiation, specification and complete development of adaptive
immunity rely on the interactions between gastrointestinal-associated
lymphoid tissue (GALT) and the gut microbiome.\textsuperscript{14}
Dysbiosis, which refers to imbalances in gut microflora and changes in
their functional composition, local distribution, and metabolic
activities,\textsuperscript{18} may potentially lead to allergy and
atopic diseases.\textsuperscript{14,19}Dysbiosis that occurs during the
critical time window of immune development, even within a short-term
period, may have a long-term impact on immune
health.\textsuperscript{14}

\textbf{Comparison with other studies}

Our results are consistent with a cross-sectional study by McKeever et
al., who used a birth cohort of 24690 children derived from the General
Practice Research Database in the United Kingdom, and found a positive
association between prenatal antibiotic use and doctor-diagnosed eczema
in a dose-related manner.\textsuperscript{20} In line with our results,
their study also revealed that infections during pregnancy increased the
risk of allergic diseases and adjusting for them did not notably affect
the estimates. Dom et al. conducted a prospective birth cohort study of
773 children in Belgium. A questionnaire was used to investigate
parent-reported eczema, and the results revealed that prenatal
antibiotic exposure was strongly positively associated with eczema in
children up to 4 years old after adjusting for post-natal
antibiotics.\textsuperscript{21} Conversely, two Danish cohort studies
that used a prospective design were conducted by Stensballe et al. and
the results showed that prenatal antibiotic use did not influence the
risk of eczema in 411 and 30675 children,
respectively.\textsuperscript{22} However, their follow-up period was
shorter and did not take exposure in all trimesters into account. In
addition, a study by Sasaki et al. who used a Japanese nationwide
dataset to conduct a prospective birth cohort study showed no
association between prenatal antibiotic exposure and diagnosed or
observed AD at 1 year old in 70408 children (aOR 1.01, 95\% CI
0.97-1.06).\textsuperscript{23} Similar to the study by Stensballe et
al., their follow-up period was also shorter and excluded children born
through cesarean delivery, which may influence the risk of prenatal
antibiotic exposure in AD.

A recent prospective cohort study performed by Mubanga et al.
investigated 722767 singleton children and 74663 discordant siblings in
Sweden. In line with our results, they found the risk of AD was greater
in children exposed to prenatal antibiotics than in those who were not
exposed (aHR 1.10, 95\% CI 1.09-1.12), whereas no such increased risk
was found in the sibling-control analysis, suggesting some familial
confounders.\textsuperscript{24} Based on the covariates they adjusted
for, we further adjusted the maternal comorbidities, maternal AD,
maternal allergic rhinitis, gestational infections, and maternal
acetaminophen use during pregnancy, which may be potential risk factors
according to previous studies.\textsuperscript{12,25,26} In addition,
their study revealed an apparent dose-response relationship, and the
category of infection did not modify the association of maternal
antibiotic use and child AD, which was consistent with our results. In
terms of the trimester-specific association between antibiotic exposure
during pregnancy and childhood AD, their results were comparable with
our results in that the risk increased in all trimesters; however, our
data showed a slightly higher risk in the first and second trimesters
compared with the third trimester, which might be explained by
antibiotics-related dysbiosis or immunomodulatory effects, phenomena
that are known to have a greater impact during early pregnancy.

Several studies and meta-analyses revealed that post-natal antibiotics
and acetaminophen exposure were associated with an increased risk of AD,
especially within the first year of
life.\textsuperscript{27-29}Antibiotics and acetaminophen are frequently
used to treat infection. However, reverse causation must be taken into
consideration, so we performed a subgroup analysis by independently
examining the effects of these two medications on AD. After excluding AD
diagnosed before 1 year of age, the positive association was still
present in the prenatal antibiotic exposure group regardless of
postnatal antibiotic use, but the adjusted hazards reduced to null in
children who were not exposed to postnatal acetaminophen, suggesting
that some confounders common to both prenatal antibiotics and postnatal
acetaminophen use existed (e.g., infection, fever, or AD itself).
However, the majority (87\%) of AD patients in our cohort were diagnosed
before 1 year of age, so this negative association could only represent
the minority (13\%) of AD patients diagnosed after 1 year of age. Our
results are consistent with a study by Dom et al. that found adjusting
for post-natal antibiotics did not significantly change the result
showing prenatal antibiotic use increased the risk of childhood
AD.\textsuperscript{21}

Even though our results showed a positive association between maternal
use of antibiotics during pregnancy and childhood AD, this does not
necessarily imply a causal link between the two. A registry-based cohort
study conducted by Stokholm et al. investigated the temporal association
between maternal antibiotic use and childhood asthma and showed that the
risk of asthma was similar among 80 weeks before pregnancy, during
pregnancy, and 80 weeks after pregnancy.\textsuperscript{30} The authors
suspected that maternal antibiotic use is a surrogate marker of maternal
propensity for infection, which is the true cause of childhood asthma.
Loewen et al. replicated their results in a retrospective cohort study
and proposed that some unmeasured factors, such as healthcare
utilization patterns, shared familial factors, and maternal deficiency
of vitamin D or other immunomodulatory nutrients may explain both the
increased risk of maternal antibiotic use/infection and the increased
risk of asthma in offspring.\textsuperscript{31} While we could not
address the temporal association between maternal antibiotic use before
and after pregnancy, our results were unchanged after adjusting for
three common infections during pregnancy. Furthermore, maternal
antibiotic use may also be a surrogate marker of infant antibiotic use,
which is associated with asthma and AD.\textsuperscript{31} Our data
showed that infants born to mothers who received antibiotics during
pregnancy were indeed more likely to be exposed to postnatal
antibiotics; however, the positive association between maternal
antibiotic use during pregnancy and childhood AD remained significant in
the subgroup analysis independent of infant antibiotic use.

\textbf{Strengths and Limitations}

The major strengths of this study were its large sample size, long
follow-up period, and its population-based sample, which was
representative of Taiwanese residents. The diagnosis of AD in our study
was given by board-certified pediatricians or dermatologists, and
therefore recall bias and detection bias was likely minimal. In
addition, we were able to adjust for some covariates, including
gestational infections and maternal acetaminophen use during pregnancy,
which were not addressed in previous studies. Our analysis of the effect
of prenatal antibiotic exposure on AD diagnosed after 1 year of age and
its relationship with infant antibiotic/acetaminophen use may have
partly taken confounding by indication (increased infection or fever
that led to increases in both AD and antibiotic/acetaminophen exposure)
into account in our study, which has not been mentioned previously.

The major limitation of our study is that some covariates, which may
influence the risk of AD due to maternal antibiotic use during
pregnancy, such as maternal smoking, patients' consulting behavior or
healthcare utilization patterns, dietary habits, environment exposures
(e.g., climate conditions, air pollution, etc.) and some unmeasured
factors shared by families,\textsuperscript{2,24,32} were not adjusted
for in our analysis. It is also possible that mild cases of AD who did
not seek medical help were not identified in our analysis. However, the
Taiwan NHI is an easily accessible, low-cost medical insurance system.
Finally, we were not able to analyze the effect of prenatal antibiotics
on AD by types of antibiotic use, which may have influenced the risk in
patients with asthma.\textsuperscript{10,11} However, to our knowledge,
this effect did not exist when investigating the influence of antibiotic
exposure during pregnancy on offspring AD.\textsuperscript{9,20,24,33}

In conclusion, this cohort study revealed that maternal antibiotic use
during pregnancy was associated with a slightly increased risk of
childhood AD. This association was similar among trimesters during
pregnancy and an apparent dose-response pattern was observed, although
the association may have been partly confounded by postnatal
acetaminophen use in AD diagnosed after 1 year of age. Further research
should be conducted to investigate this confounder in a prospectively
designed study and to explore the timing before or after pregnancy in
order to elucidate whether or not this association was specific to
during pregnancy. Nevertheless, we believe that antibiotics should be
used prudently during pregnancy and that this potential effect should be
taken into account.

\textbf{References}

1. Odhiambo JA, Williams HC, Clayton TO, Robertson CF, Asher MI, Group
IPTS. Global variations in prevalence of eczema symptoms in children
from ISAAC Phase Three. \emph{J Allergy Clin Immunol} 2009;124:1251-1258
e1223.

2. Weidinger S, Beck LA, Bieber T, Kabashima K, Irvine AD. Atopic
dermatitis. \emph{Nat Rev Dis Primers} 2018;41.

3. Karimkhani C, Dellavalle RP, Coffeng LE, et al. Global Skin Disease
Morbidity and Mortality: An Update From the Global Burden of Disease
Study 2013. \emph{JAMA Dermatol} 2017;153:406-412.

4. Narla S, Silverberg JI. The Role of Environmental Exposures in Atopic
Dermatitis. \emph{Curr Allergy Asthma Rep} 2020;2074.

5. Langan SM, Irvine AD, Weidinger S. Atopic dermatitis. \emph{The
Lancet} 2020;396:345-360.

6. Bookstaver PB, Bland CM, Griffin B, Stover KR, Eiland LS, McLaughlin
M. A Review of Antibiotic Use in Pregnancy.
\emph{Pharmacotherapy}2015;35:1052-1062.

7. Pascal M, Perez-Gordo M, Caballero T, et al. Microbiome and Allergic
Diseases. \emph{Front Immunol} 2018;91584.

8. Tsakok T, McKeever TM, Yeo L, Flohr C. Does early life exposure to
antibiotics increase the risk of eczema? A systematic review. \emph{Br J
Dermatol} 2013;169:983-991.

9. Huang FQ, Lu CY, Wu SP, Gong SZ, Zhao Y. Maternal exposure to
antibiotics increases the risk of infant eczema before one year of life:
a meta-analysis of observational studies. \emph{World J
Pediatr}2020;16:143-151.

10. Zhong Y, Zhang Y, Wang Y, Huang R. Maternal antibiotic exposure
during pregnancy and the risk of allergic diseases in childhood: A
meta-analysis. \emph{Pediatr Allergy Immunol} 2021;32:445-456.

11. Cait A, Wedel A, Arntz JL, et al. Prenatal antibiotic exposure,
asthma, and the atopic march: A systematic review and
meta-analysis.\emph{Allergy} 2022.

12. Lloyd-Lavery A, Solman L, Grindlay DJC, Rogers NK, Thomas KS, Harman
KE. What's new in atopic eczema? An analysis of systematic reviews
published in 2016. Part 2: Epidemiology, aetiology and risk
factors.\emph{Clin Exp Dermatol} 2019;44:370-375.

13. Reynolds G, Vegh P, Fletcher J, et al. Developmental cell programs
are co-opted in inflammatory skin disease. \emph{Science} 2021;371.

14. Vangay P, Ward T, Gerber JS, Knights D. Antibiotics, pediatric
dysbiosis, and disease. \emph{Cell Host Microbe} 2015;17:553-564.

15. Tamburini S, Shen N, Wu HC, Clemente JC. The microbiome in early
life: implications for health outcomes. \emph{Nat Med} 2016;22:713-722.

16. Sanidad KZ, Zeng MY. Neonatal gut microbiome and immunity.\emph{Curr
Opin Microbiol} 2020;56:30-37.

17. Vuillermin PJ, Macia L, Nanan R, Tang ML, Collier F, Brix S. The
maternal microbiome during pregnancy and allergic disease in the
offspring. \emph{Semin Immunopathol} 2017;39:669-675.

18. DeGruttola AK, Low D, Mizoguchi A, Mizoguchi E. Current
Understanding of Dysbiosis in Disease in Human and Animal
Models.\emph{Inflamm Bowel Dis} 2016;22:1137-1150.

19. Kim J, Kim BE, Leung DYM. Pathophysiology of atopic dermatitis:
Clinical implications. \emph{Allergy Asthma Proc} 2019;40:84-92.

20. McKeever TM, Lewis SA, Smith C, Hubbard R. The importance of
prenatal exposures on the development of allergic disease: a birth
cohort study using the West Midlands General Practice Database. \emph{Am
J Respir Crit Care Med} 2002;166:827-832.

21. Dom S, Droste JH, Sariachvili MA, et al. Pre- and post-natal
exposure to antibiotics and the development of eczema, recurrent
wheezing and atopic sensitization in children up to the age of 4
years.\emph{Clin Exp Allergy} 2010;40:1378-1387.

22. Stensballe LG, Simonsen J, Jensen SM, Bonnelykke K, Bisgaard H. Use
of antibiotics during pregnancy increases the risk of asthma in early
childhood. \emph{J Pediatr} 2013;162:832-838 e833.

23. Sasaki M, Sakurai K, Shimojo N, Yamamoto M, Mori C, Japan
Environment Children's Study G. No association between prenatal
antibiotic exposure and atopic dermatitis among Japanese
infants.\emph{Pediatr Allergy Immunol} 2020;31:218-221.

24. Mubanga M, Lundholm C, D'Onofrio BM, Stratmann M, Hedman A, Almqvist
C. Association of Early Life Exposure to Antibiotics With Risk of Atopic
Dermatitis in Sweden. \emph{JAMA Netw Open} 2021;4e215245.

25. Earp E, Tsianou Z, Grindlay DJC, Rogers NK, Olabi B. What's new in
atopic eczema? An analysis of systematic reviews published in 2019. Part
1: Risk factors and prevention. \emph{Clin Exp
Dermatol}2021;46:1205-1210.

26. Hale G, Davies E, Grindlay DJC, Rogers NK, Harman KE. What's new in
atopic eczema? An analysis of systematic reviews published in 2017. Part
2: epidemiology, aetiology and risk factors. \emph{Clin Exp
Dermatol}2019;44:868-873.

27. Metzler S, Frei R, Schmausser-Hechfellner E, et al. Association
between antibiotic treatment during pregnancy and infancy and the
development of allergic diseases. \emph{Pediatr Allergy
Immunol}2019;30:423-433.

28. Wang JY, Liu LF, Chen CY, Huang YW, Hsiung CA, Tsai HJ.
Acetaminophen and/or antibiotic use in early life and the development of
childhood allergic diseases. \emph{Int J Epidemiol} 2013;42:1087-1099.

29. Duong QA, Pittet LF, Curtis N, Zimmermann P. Antibiotic exposure and
adverse long-term health outcomes in children: A systematic review and
meta-analysis. \emph{J Infect} 2022;85:213-300.

30. Stokholm J, Sevelsted A, Bonnelykke K, Bisgaard H. Maternal
propensity for infections and risk of childhood asthma: a registry-based
cohort study. \emph{The Lancet Respiratory Medicine} 2014;2:631-637.

31. Loewen K, Monchka B, Mahmud SM, t Jong G, Azad MB. Prenatal
antibiotic exposure and childhood asthma: a population-based
study.\emph{Eur Respir J} 2018;52.

32. Baiz N, Just J, Chastang J, et al. Maternal diet before and during
pregnancy and risk of asthma and allergic rhinitis in
children.\emph{Allergy Asthma Clin Immunol} 2019;1540.

33. Timm S, Schlunssen V, Olsen J, Ramlau-Hansen CH. Prenatal
antibiotics and atopic dermatitis among 18-month-old children in the
Danish National Birth Cohort. \emph{Clin Exp Allergy} 2017;47:929-936.

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