Association of assisted reproductive technology and multiple pregnancies with the risks of birth defects and stillbirth: A retrospective cohort study
1SCiENtiFiC REPORTS | XXXXXXXXXX:8296 | DOI:10.1038/s XXXXXXXXXX
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Association of assisted
eproductive technology and
multiple pregnancies with the risks
of birth defects and stillbirth: A
etrospective cohort study
Min Yang 1, Xiao-Bo Fan1, Jiang-Nan Wu2 & Ji-Mei Wang1
Assisted reproductive technology (ART) has been widely used among women with infertility. However,
the association of ART with birth defects and stillbirth remains controversial and has rarely been
eported in China. A retrospective cohort study of 112,043 pregnant women and 114,522 newborns
from 2006 to 2016 was performed. Compared to spontaneously conceived infants, ART-conceived
infants had a higher likelihood of any birth defect, with an adjusted odds ratio (OR) of XXXXXXXXXX%
confidence interval, 1.63–2.69). ART-conceived infants also had a significantly increased risk for
subcategories of cardiovascular, musculoskeletal, urogenital, gastrointestinal, and respiratory defects.
Most (62.25%) of the effect of ART on birth defects was a direct effect, whereas 37.75% of the effect of
ART on birth defects was due to multiple pregnancies (i.e., an indirect effect). Compared with naturally
conceived singletons, the combined effect of ART and twins on the risk of birth defects was lower than
that of the sum of the individual effects of ART and twins on the risk of birth defects, with an adjusted
OR of XXXXXXXXXX–0.92). These findings clearly show that ART is associated with an increased risk of
irth defects in China and may provide guidance to couples and obstetricians in selecting numbers of
pregnancies and in identifying organs at a high risk of birth defects.
Assisted reproductive technology (ART), including in vitro fertilization (IVF) and intracytoplasmic sperm injec-
tion (ICSI), has been widely used among women with infertility1–4. However, whether ART is associated with an
increased risk of birth defects remains controversial5–8. Even though several cohort studies and multiple system-
atic reviews or meta-analyses have found that ART treatment may be associated with an increased risk of birth
defects4,9–12, some other studies have concluded that the observed increase in the risk of birth defects after ART
may be attributed to infertility-related maternal characteristics13–16.
Since the first infant conceived by ART in China was born in 1988, many ART-conceived infants have been
orn17. To strengthen the management of ART treatment, the Ministry of Health of the People’s Republic of
China released ART regulations in 2001 stipulating that the total number of eggs, zygotes and em
yos per trans-
plant cycle is limited to ≤3 for women aged 35 years and ≤2 for women aged <35 years18. Some studies have
investigated the association between ART and birth defects in Chinese populations. In a national hospital-based
etrospective study, ART-conceived infants were estimated to account for approximately 1.01% of total deliveries
in China in 2011, and the author further found that ART was associated with an increased risk of maternal and
neonatal complications (e.g., premature delivery, placenta previa, gestational diabetes mellitus, low birth weight,
and infant mortality)15. Another multi-centre study of 15,405 ART-conceived infants found that 1.23% of the
subjects had one or more major birth defects6. Several studies have compared the risk of birth defects between
children conceived by IVF and children conceived by ICSI6,19–22. Liu et al. studied the risk of birth defects among
ART-conceived children compared with that among spontaneously conceived children in a small sample size
1Department of Neonatology, Obstetrics and Gynecology Hospital of Fudan University, Shanghai, China.
2Department of Clinical Epidemiology, Obstetrics and Gynecology Hospital of Fudan University, Shanghai, China.
Jiang-Nan Wu and Ji-Mei Wang contributed equally to this work. Co
espondence and requests for materials should
e addressed to J.-N.W. (email: XXXXXXXXXX) or J.-M.W. (email: XXXXXXXXXX)
Received: 8 December 2017
Accepted: 14 May 2018
Published: xx xx xxxx
OPEN
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2SCiENtiFiC REPORTS | XXXXXXXXXX:8296 | DOI:10.1038/s XXXXXXXXXX
(8,240 naturally-conceived singletons and 567 ART-conceived births) and concluded that no statistically signif-
icant association existed23. However, little is known about the association of ART with the risk of birth defects
ased on a large sample size in China.
Similarly, the relationship between ART and the risk of stillbirth also remains controversial. A large Nordic
cohort study did not find a significant association between ART and stillbirth24, but other studies have indicated
that ART is associated with an increased risk of stillbirth25,26. However, few studies on the association of ART with
stillbirth have been conducted in China.
Furthermore, multiple gestations seem to be more common among pregnancies conceived by ART compared
to those conceived naturally1–4. In the United States, 1.7% of infants were conceived with ART, but more than 19%
of twins and 25% of triplets or higher multiples were conceived with ART4. Multiple gestations are considered to
e involved in the causal pathway between ART and birth defects27 and have been used to explain why the associ-
ations between ART and birth defects appear to be weaker among infants from multiple births than among those
from singleton births11. However, few studies have investigated the relationship between multiple gestations and
irth defects among infants from natural and ART-assisted conceptions.
China has abolished the “one child” policy and has allowed two children to be born in each family since 2015,
which resulted in a substantial increase in the number of infants born to 18.46 million people in 2016, reflecting
an 11.5% increase in births compared to that in XXXXXXXXXXThe change in the birth policy may have increased the
demand for ART. Therefore, determining the associations of ART with birth defects and stillbirth and identifying
the extent to which the association between ART and the risk of birth defects may be mediated by multiple ges-
tations are important. We hypothesized that ART may be associated with slightly increased risks of birth defects
and stillbirth and that the impact of ART on birth defects may be greater for infants from singleton births versus
infants from multiple births. Therefore, we conducted a retrospective cohort study to evaluate these hypotheses.
Results
ART and birth defects. A total of 112,043 pregnant women and 114,522 newborns were included in the
analysis. Among the pregnant women, 2.22% (2,484) had received ART treatment. Pregnant women who received
ART treatment were older and were less likely to be nulliparous. A lower proportion of these women had single-
ton births compared to women who conceived spontaneously. Moreover, the women in the ART group were likely
to have an abnormal pregnancy history and were at a higher risk for poor pregnancy conditions and developing
pregnancy complications compared to women in the spontaneous conception group (Table 1).
Among the newborns included in the analysis, 1,108 infants (1.0%) were diagnosed with at least one birth
defect. The infants conceived by ART had an increased likelihood of developing any birth defect compared to
infants conceived by natural means (2.3%, vs. 0.9%, P < 0.001); the crude OR was XXXXXXXXXX% CI, 2.00 to 3.18),
and the risk was reduced but remained significant after adjusting for potential confounders, with an adjusted
OR of XXXXXXXXXXto XXXXXXXXXXThe association between assisted conception and any birth defect among infants from
singleton births was similar to that among all newborns, with crude and adjusted ORs of XXXXXXXXXXto 4.21) and
XXXXXXXXXXto 3.13), respectively. However, the relationship between ART and any birth defect among infants from
multiple births was weaker than that among infants from singleton births, with crude and adjusted ORs of 1.49
(1.01 to 2.22) and XXXXXXXXXXto 2.17), respectively (Table 2).
Infants conceived by ART also had a significantly increased likelihood of subcategories of cardiovascular,
urogenital, and gastrointestinal defects compared to all infants (ORs ranging from 2.13 to XXXXXXXXXXHowever, no
significant associations were found between ART and musculoskeletal and respiratory defects, central nervous
system defects, chromosomal defects, ear and facial deformations, and cleft lip and/or cleft palate. In the strata of
multiplicity analyses, the associations between ART and cardiovascular and gastrointestinal defects disappeared,
whereas ART was significantly associated with musculoskeletal and respiratory defects (ORs of 2.38 and 11.19,
espectively) among singleton births, but no significant associations were observed between ART and all subcat-
egories of birth defects in the subgroup of multiple births (Table 2).
ART and stillbirth. The incidence of stillbirth among the women in the assisted conception group was sig-
nificantly higher than that among the women in the spontaneous conception group (34 cases, 1.0% vs. 308 cases,
0.3%, P < XXXXXXXXXXCompared with the infants conceived naturally, the ART-conceived infants had a higher like-
lihood of stillbirth, with a crude OR of XXXXXXXXXX% CI, 2.59 to XXXXXXXXXXHowever, no significant association between
ART and the risk of stillbirth was observed after adjusting for potential confounders in all births (OR = 0.96, 95%
CI, 0.64 to 1.44) or in the subgroups of singleton and multiple births (Table 2).
Multiple gestations, ART, and birth defects. ART was associated with a significant increase in the like-
lihood of birth defects in the logistic regression analysis using path analysis models, with an adjusted OR (total
effect of ART on birth defects) of XXXXXXXXXX% CI, 1.75 to XXXXXXXXXXThe ART-conceived newborns would have had a
1.64-higher likelihood of birth defects than spontaneously conceived births if the risk of multiple pregnancies had
een kept constant at the level of spontaneously conceived births (OR = 1.64, 95% CI, 1.27 to 2.12, direct effect
of ART on birth defects). Approximately 37.75% of the total effect of ART on birth defects was mediated by the
association between ART and multiple pregnancies (indirect effect), with an adjusted OR of XXXXXXXXXX% CI, 1.19
to XXXXXXXXXXTable 3).
Multiple gestations were associated with a significantly increased likelihood of birth defects among infants
conceived by spontaneous conception, with prevalence rates of birth defects among infants from singleton, twin,
and triplet births of 0.9%, 1.7%, and 3.3%, respectively. The adjusted ORs of birth defects for twin and triplet
infants were XXXXXXXXXXto 2.52) and XXXXXXXXXXto 10.12), respectively, compared with those for singleton infants