Birth defects after assisted reproductive technology according to the method of treatment in Japan: nationwide data between 2004 and 2012
Environ Health Prev Med
Birth defects after assisted reproductive technology according to the method of treatment in Japan: nationwide data between 2004 and 2012
Syuichi Ooki 0 1
0 Department of Health Science, Ishikawa Prefectural Nursing University , 1-1 Gakuendai, Kahoku, Ishikawa 929-1210 , Japan
1 & Syuichi Ooki
Objectives The purpose of the present study was to analyze birth defects (congenital anomalies) after assisted reproductive technology (ART) according to the method of treatment, namely in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI) and frozen-thawed embryo transfer (FET). Methods Individual lists of all ART pregnancies resulting in birth defects from birth year 2004 to 2012 presented in the annual reports by the Japan Society of Obstetrics and Gynecology were used as the initial sources of information. Relative risks (RRs) with the corresponding 95 % confidence intervals (CIs) were calculated with IVF as the reference group when calculating RR of ICSI for IVF, and with FET as the reference group when calculating the RR of fresh embryo transfer for FET. Results In total, 2725 stillbirths or live births with birth defects were analyzed. The prevalence of birth defects was slightly yet significantly higher in ICSI compared with IVF throughout the study period (RR = 1.15, 95 % CI 1.02-1.29) and in the 2004-2006 period (RR = 1.26, 95 % CI 1.00-1.58). The prevalence of birth defects was significantly higher for fresh embryo transfer compared with FET in the 2004-2006 period (RR = 1.39, 95 % CI 1.12-1.72). The prevalence of birth defects in multiple births was significantly lower in fresh embryo transfer compared with FET (RR = 0.70, 95 % CI 0.55-0.90, live births of 2007-2012).
Birth defects; In vitro fertilization (IVF); Intracytoplasmic sperm injection (ICSI); Frozen-thawed embryo transfer (FET); Nationwide multi-year data
Conclusions The present descriptive epidemiological
study suggests that the impacts of different ART methods
on birth defects might differ.
According to Japanese vital statistics, the percentage of
live births attributable to assisted reproductive techniques
(ART) has increased rapidly, from 0.22 % in 1992 and
1.32 % in 2002 to 3.66 % in 2012. Thus, the use of ART is
becoming widespread in Japan.
According to Mayor [
], the risk of congenital
malformation in children born after ART is higher than previously
thought, and has become a public health issue. There are
many epidemiological studies on the relationship between
birth defects (also known as ‘congenital anomalies’ or
‘congenital disorders’ according to the definition of fact
sheets presented by the World Health Organization [
ART. Data from meta-analyses consistently suggest that the
overall risk of major birth defects in children born after ART
is about 30 % higher than in children conceived
]. A more recent systematic review and
metaanalysis, which analyzed 45 cohort studies, similarly showed
that ART infants, including both singletons and multiple
births (i.e., twins and triplets/?), had a 32 % higher risk of
birth defects compared with naturally conceived infants .
Thus, the risk of ART in total on birth defects compared
with natural conception is highly probable.
Most of these studies use data from countries where
large population-based or hospital-based registries are
available, for example Scandinavian counties or Australia.
On the other hand, data collection of ART, birth defects
and births records (vital statistics) are not systematically
managed in Japan, and record linkage is virtually
]. With this background, the author performed
secondary data analyses of published information in Japan.
The purpose of the present study was to analyze
ARTassociated birth defects according to the method of
treatment, namely in vitro fertilization (IVF), intracytoplasmic
sperm injection (ICSI) and frozen-thawed embryo transfer
Materials and methods
Outline of ART-associated birth defect data in Japan
The method for collecting data has been described
]. Almost all medical institutions performing ART
are registered with the Japan Society of Obstetrics and
Gynecology (JSOG). The JSOG administers questionnaire
surveys for these medical institutions. Some of the survey
data such as number of treatment cycles, transfers,
pregnancies, deliveries, stillbirths, and live births according to
the types of treatment are presented in simple annual
reports of aggregate, not individual, data (in Japanese).
Fresh embryo transfer was reported according to the two
major techniques, IVF and ICSI. FET was reported only as
total numbers, including both IVF and ICSI. These annual
reports do not include the data on simple ovulation
stimulation/enhancement. From birth year 2004 to 2012 (the
latest), lists of all ART pregnancies resulting in birth
defects have been presented in these annual reports. The
presented data include method of treatment (IVF, ICSI and
FET), maternal age, perinatal outcome
(spontaneous/artificial abortion (\22 weeks), stillbirths (C22 weeks), and
live births) and gestational week, plurality (singleton,
twins, triplets/?, and unknown), sex (male, female,
unknown), early neonatal infant death up to day 6 (yes, no,
unknown), and names of birth defects and so on. The
response rate for ART surveillance between 2004–2012
was 97.7–99.5 %, and the mean response rate throughout
the 9 years was 99.1 % (5400/5449), meaning that an
almost-complete database reflecting the current situation of
ART and birth defects in Japan could be constructed.
The author used these case report data as initial
information for the present study. The names of birth defects
provided in the above annual JSOG lists were carefully
checked and reclassified according to the International
Classification of Diseases, tenth edition (i.e., ICD-10, 2003
version). Diseases that were classified in the category of
ICD-10 code Q00–Q99 (i.e., congenital malformations,
deformations and chromosomal abnormalities) were
identified as birth defects, and selected and analyzed in the
present study. Other congenital diseases not classified in
Q00–Q99 were excluded.
This study was designed to compare the risk of birth
defects associated with the various micromanipulations
of different ART methods, since data on natural
conception were not available. First, basic information and
perinatal outcome data according to the treatment were
presented. Then, the crude prevalence of birth defects
calculated as percentage after each ART method per
births (stillbirths and live births) were calculated
according to three birth year periods (2004–2006,
2007–2009 and 2010–2012). And relative risks (RRs)
with the corresponding 95 % confidence intervals (CIs)
were calculated with IVF as a reference group when
calculating the RR of ICSI for IVF, and with FET as a
reference group when calculating RR of fresh embryo
transfer for FET.
Singletons and multiple births were combined in the
above analysis, since the number of stillbirths according to
plurality was not reported in the JSOG data. RRs were
calculated according to plurality for live births from 2007
to 2012; this was the only available data on the plurality of
Statistical analysis was conducted using SAS for
Windows ver 9.3.
Demographic and perinatal outcome data of ART
pregnancies according to the method of treatment are
summarized in Table 1. In the process of reclassification of birth
defects, 273 out of 3468 (7.9 %) were excluded, since these
cases were not classified as ICD-10 code Q00–Q99.
Moreover, 470 birth defect cases were excluded because
the pregnancy outcome was abortion. In total, 2725
stillbirths or live births with birth defects were included.
Crude prevalence of birth defects and RR with 95 % CI
according to the method of treatment (ICSI vs. IVF and
fresh embryo transfer vs. FET) by birth year period are
shown in Table 2. The prevalence of birth defects was
slightly yet significantly higher in ICSI compared with IVF
(RR = 1.15, 95 % CI 1.02–1.29) in the total period. Most
of this significance disappeared when the time-periods
were divided into three classes; only ICSI in the
2004–2006 period showed a significantly higher prevalence
(RR = 1.26, 95 % CI 1.00–1.58). The prevalence of birth
defects was significantly higher for fresh embryo transfer
compared with FET in the 2004–2006 period (RR = 1.39,
95 % CI 1.12–1.72).
Crude prevalence of birth defects and RR with 95 % CI
according to plurality and the method of treatment by birth
year period are shown in Table 3. The prevalence of birth
defects in multiple births was significantly lower in fresh
embryo transfer compared with FET throughout the study
period (RR = 0.70, 95 % CI 0.55–0.90) and in the
2010–2012 period (RR = 0.60, 95 % CI 0.40–0.91).
The present author analyzed birth defects as a short-term
outcome indicator of ART, since this was the only
available (presented/published) data reflecting the ART
outcome for all of Japan. As far as the author knows, this study
is the first descriptive epidemiological study in Japan to
analyze the relationship between each ART method and
birth defects using nationwide multi-year data. The total
number of ART-associated deliveries or births was over
200,000 during 9 years of observation.
The present percentage of total birth defects after ART,
irrespective of method, may be lower overall compared
with other studies mentioned in the reviews [
Moreover, the percentage of birth defects after ART is clearly
higher in the recent period (2010–2012) than in the earlier
period (2004–2006). This is likely not because the
frequency of birth defects themselves has rapidly increased,
but because reporting bias may have existed
(underreporting in the earlier period). Nevertheless, the main
objective of this study was to evaluate the prevalence of
birth defect according to the ART method, and not to
2 5 7
2 5 7
46 59 ,
compare the prevalence of birth defect across different
time-periods or populations. Therefore, the comparison of
birth defects in different treatments is biased only if there
is differential reporting according to the method of
treatment, which is not likely to occur this type of national data.
The main results of the present study were the
following. First, regarding fresh embryo transfer, ICSI might
have more risk of birth defects compared with IVF, at least
this was true in the earlier period (2004–2006). There are
two meta-analyses of whether birth defects are more
common in ICSI compared with IVF infants [
] and both
suggest no significant difference in risk between the two
methods. Lie et al.  combined the results of four studies
to obtain pooled estimates of birth defect risk in ICSI
compared with IVF infants of 1.12 (95 % IC 0.97–1.28).
According to Wen et al. [
], 24 studies were performed
regarding birth defects in children conceived by IVF
compared with those by ICSI. Overall no difference in risk
for birth defects was found between IVF and ICSI groups
(RR = 1.05, 95 % CI 0.91–1.20). On the other hand, two
recent reports [
] suggested a higher risk for ICSI
compared with IVF. A recent survey in South Australia
 showed an increased risk for birth defects after ICSI,
even adjusting for possible confounding factors, such as
year of birth, maternal age, and parity. A Chinese study
with a 3-year follow-up [
] showed the same tendency,
especially for boys. The risk of IVF vs. ICSI is thus
confusing. The present result suggested that the elevated risk
of ICSI compared with IVF might exist in some periods in
Japan for whatever reason. According to the Pinborg study
], recent data may show a lower birth defect risk for
ICSI because the technique is now used to treat a broader
range of infertile couples rather than being restricted to
those with severe male infertility.
Second, fresh embryo transfer might also have greater
risk than FET in the earlier period (2004–2006). In this
point, although the risks of preterm birth, small for
gestational age, and low birthweight were all lower for FET
compared with fresh transfer in the meta-analysis [
significant differences were seen between FET and fresh
embryo transfers for birth defects in other meta-analysis
]. Other single studies [
] also reported no increase
in risk of birth defects after FET compared with fresh IVF/
ICSI. On the other hand, a recent Chinese study 
suggested a lower rate of birth defects in FET children
compared with fresh IVF/ICSI. Moreover, a recent study
by Davies et al. [
] found regarding ICSI a significant
increase in the risk of birth defects associated with fresh
embryo cycles but not with frozen-embryo transfer cycles,
compared to unassisted conception. These results are often
explained by a reduced likelihood that developmentally
compromised embryos will survive the thawing process
] or only the most robust embryos survive the initial
selection process, leading to superior quality embryos
being frozen [
]. When discussing the present results,
caution is needed because the total number of FET
increased rapidly during the observation period
(2004–2012), while that of fresh IVF slightly decreased
and that of fresh ICSI remained relatively constant, as
shown in Table 2. This difference in observation numbers
may provide a simple mathematical explanation for the
increase of birth defects in fresh embryo transfer compared
Third, in the case of multiple births, FET pregnancies,
however, have elevated risk compared with fresh embryo
transfer, as shown in Table 3. This tendency was not
observed in singletons. Although the data were limited to
live births in the present study, multiple births in FET may
be more vulnerable than singletons. The studies on ART’s
effects according to the method of treatment and plurality
are very limited and suffer from small sample sizes. Of
them, Olson et al. [
] reported that cryopreservation of
embryos did not seem to have an effect on birth defect rates
in singletons as compared with singletons conceived after
the transfer of fresh embryos with IVF. There was,
however, a higher incidence of birth defects in twins born after
transfer of cryopreserved embryos as compared with twins
born after the transfer of fresh embryos (RR = 2.11, 95 %
CI 1.02–4.33) [
]. On the other hand, Belva et al. [
reported that only cryo-ICSI singletons as compared with
fresh ICSI singletons had significantly higher malformation
rates, and this tendency was not observed regarding
multiple births. Although the percentage of multiple pregnancy
in ART is dramatically decreased because of the
widespread adoption of the single-embryo transfer policy [
the present result suggested that plurality should be
considered when analyzing the relationship between the effect
of the each ART treatment on birth defects.
This study has the following limitations, most of which
could be attributed to the dataset: namely, the fact that
individual information was obtained only from subjects
with birth defects after ART, not the total ART
The first and greatest limitation is that the author could
not control for confounding factors that can affect ART
and/or birth defects, such as maternal age, parity, smoking,
and socioeconomic status, medical history, and prenatal
care, since these data on general ART populations are not
available. Therefore, whether the results were attributable
to the characteristics of patients, other descriptive
epidemiological factors (regarding time, place, and person)
and/or ART techniques themselves was unclear. Therefore,
present results should be considered as the total effects of
ART on birth defects.
Second, the author could not check the reliability of the
data directly. Several misspellings or misclassifications of
diseases were found in the annual report. This is the
essential limitation of secondary data analyses.
Third, follow-up after birth was limited to the early
neonatal period, and was incomplete. The prevalence of
birth defects increases with the growth of children, since
some birth defects are not obvious within a few days after
Even with all these limitations, the present results
overviewed some characteristics of births defects after
ART according to the type of treatment using nationwide
multi-year data in Japan. As mentioned earlier, the
percentage of children born after ART is now about 4 % in
Japan. This value is nearly the same as the percentage of
women who smoke during pregnancy. However, the study
of ART’s influence on later life, especially for the
longterm influence of children, is still limited in Japan.
Considering the widespread use of fertility treatment, the
method of pregnancy, namely spontaneous conception vs.
medically assisted reproduction (MAR), including both
ovulation induction and ART (each method of ART
treatment, if possible), would become more important factors
when analyzing intrauterine environmental, or in some
cases genetic/epigenetic factors that influence or modify
the later development of children. This would be especially
important when verifying fetal origin of adult disease
(FOAD) or developmental origin of health and disease
(DOHaD) hypotheses. In conclusion, the present study
suggested that the impacts of different ART methods on
birth defects might differ. Proper registration and long-term
follow-up after ART and population-based epidemiological
researches are needed.
Acknowledgments I would like to thank Toshimi Ooma for
assistance with data analysis. This work was supported by JSPS
KAKENHI Grant Number 15H04785.
Compliance with ethical standards
Conflict of interest The authors declare no conflict of interest.
This article does not contain any studies with human participants
performed by any of the authors.
1. Mayor S. Risk of congenital malformations in children born after assisted reproduction is higher than previously thought . BMJ . 2010 ; 340 :c3191. doi: 10 .1136/bmj.c3191.
2. http://www.who.int/mediacentre/factsheets/fs370/en/. Accessed 17 July 2015 .
3. Rimm AA , Katayama AC , Diaz M , Katayama KP . A metaanalysis of controlled studies comparing major malformation rates in IVF and ICSI infants with naturally conceived children . J Assist Reprod Genet . 2004 ; 21 ( 12 ): 437 - 43 .
4. Hansen M , Bower C , Milne E , de Klerk N , Kurinczuk JJ . Assisted reproductive technologies and the risk of birth defects-a systematic review . Hum Reprod . 2005 ; 20 ( 2 ): 328 - 38 .
5. Hansen M , Kurinczuk JJ , Milne E , de Klerk N , Bower C . Assisted reproductive technology and birth defects: a systematic review and meta-analysis . Hum Reprod Update . 2013 ; 19 ( 4 ): 330 - 53 . doi: 10 .1093/humupd/dmt006.
6. Ooki S. Birth defects in singleton versus multiple ART births in Japan ( 2004 - 2008 ). J Pregnancy . 2011 ; 2011 :285706. doi: 10 . 1155/ 2011 /285706.
7. Ka¨lle´n B, Finnstro¨ m O , Lindam A , Nilsson E , Nygren KG , Otterblad PO . Congenital malformations in infants born after in vitro fertilization in Sweden . Birth Defects Res A Clin Mol Teratol . 2010 ; 88 ( 3 ): 137 - 43 . doi: 10 .1002/bdra.20645.
8. Lie RT , Lyngstadaas A , Ørstavik KH , Bakketeig LS , Jacobsen G , Tanbo T. Birth defects in children conceived by ICSI compared with children conceived by other IVF-methods; a meta-analysis . Int J Epidemiol . 2005 ; 34 ( 3 ): 696 - 701 .
9. Wen J , Jiang J , Ding C , Dai J , Liu Y , Xia Y , et al. Birth defects in children conceived by in vitro fertilization and intracytoplasmic sperm injection: a meta-analysis . Fertil Steril . 2012 ; 97 ( 6 ): 1331 - 7 . doi: 10 .1016/j.fertnstert. 2012 . 02 .053.
10. Davies MJ , Moore VM , Willson KJ , Van Essen P , Priest K , Scott H , et al. Reproductive technologies and the risk of birth defects . N Engl J Med . 2012 ; 366 ( 19 ): 1803 - 13 . doi: 10 .1056/ NEJMoa1008095.
11. Yin L , Hang F , Gu LJ , Xu B , Ma D , Zhu GJ . Analysis of birth defects among children 3 years after conception through assisted reproductive technology in China . Birth Defects Res A Clin Mol Teratol . 2013 ; 97 ( 11 ): 744 - 9 . doi: 10 .1002/bdra.23116.
12. Pinborg A , Loft A , Henningsen AK , Ziebe S. Does assisted reproductive treatment increase the risk of birth defects in the offspring? Acta Obstet Gynecol Scand . 2012 ; 91 ( 11 ): 1245 - 6 . doi: 10 .1111/j.1600- 0412 . 2012 . 01500 .x.
13. Wennerholm UB , So¨derstro¨ m-Anttila V , Bergh C , Aittoma¨ki K , Hazekamp J , Nygren KG , et al. Children born after cryopreservation of embryos or oocytes: a systematic review of outcome data . Hum Reprod . 2009 ; 24 ( 9 ): 2158 - 72 . doi: 10 .1093/humrep/ dep125.
14. Maheshwari A , Pandey S , Shetty A , Hamilton M , Bhattacharya S. Obstetric and perinatal outcomes in singleton pregnancies resulting from the transfer of frozen thawed versus fresh embryos generated through in vitro fertilization treatment: a systematic review and meta-analysis . Fertil Steril . 2012 ; 98 ( 2 ): 368 - 77 . doi: 10 .1016/j.fertnstert. 2012 . 05 .019.
15. Olson CK , Keppler-Noreuil KM , Romitti PA , Budelier WT , Ryan G , Sparks AE , et al. In vitro fertilization is associated with an increase in major birth defects . Fertil Steril . 2005 ; 84 ( 5 ): 1308 - 15 .
16. Belva F , Henriet S , Van den Abbeel E , Camus M , Devroey P , Van der Elst J , et al. Neonatal outcome of 937 children born after transfer of cryopreserved embryos obtained by ICSI and IVF and comparison with outcome data of fresh ICSI and IVF cycles . Hum Reprod . 2008 ; 23 ( 10 ): 2227 - 38 . doi: 10 .1093/humrep/ den254.