presentation
Association of assisted reproductive technology and multiple pregnancies with the risks of birth defects and stillbirth: A retrospective cohort study 1SCiENtiFiC REPORTS | (2018) 8:8296 | DOI:10.1038/s41598-018-26567-2 www.nature.com/scientificreports Association of assisted reproductive technology and multiple pregnancies with the risks of birth defects and stillbirth: A retrospective 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 reported 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 2.10 (95% 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 0.54 (0.32–0.92). These findings clearly show that ART is associated with an increased risk of birth 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 born17. 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 embryos 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="" retrospective="" 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.="" correspondence="" and="" requests="" for="" materials="" should="" be="" addressed="" to="" j.-n.w.="" (email:="" wjnhmm@126.com)="" or="" j.-m.w.="" (email:="" wjm8219@163.com)="" received:="" 8="" december="" 2017="" accepted:="" 14="" may="" 2018="" published:="" xx="" xx="" xxxx="" open="" http://orcid.org/0000-0002-3625-7145="" mailto:wjnhmm@126.com="" mailto:wjm8219@163.com="" www.nature.com/scientificreports/="" 2scientific="" reports="" |="" (2018)="" 8:8296="" |="" doi:10.1038/s41598-018-26567-2="" (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="" based="" 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="" be="" 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="" birth="" 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="" 201528.="" the="" 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="" 2.52="" (95%="" ci,="" 2.00="" to="" 3.18),="" and="" the="" risk="" was="" reduced="" but="" remained="" significant="" after="" adjusting="" for="" potential="" confounders,="" with="" an="" adjusted="" or="" of="" 2.10="" (1.63="" to="" 2.69).="" the="" 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="" 2.38="" (1.34="" to="" 4.21)="" and="" 2.17="" (1.51="" to="" 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="" 1.44="" (0.95="" to="" 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="" 3.44).="" however,="" 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,="" respectively)="" 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="">< 0.001). compared with the infants conceived naturally, the art-conceived infants had a higher like- lihood of stillbirth, with a crude or of 3.70 (95% ci, 2.59 to 5.28). however, 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 2.22 (95% ci, 1.75 to 2.81). the 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 been 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 1.35 (94% ci, 1.19 to 1.53) (table 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 1.86 (1.37 to 2.52) and 3.37 (1.13 to 10.12), respectively, compared with those for singleton infants 0.001).="" compared="" with="" the="" infants="" conceived="" naturally,="" the="" art-conceived="" infants="" had="" a="" higher="" like-="" lihood="" of="" stillbirth,="" with="" a="" crude="" or="" of="" 3.70="" (95%="" ci,="" 2.59="" to="" 5.28).="" however,="" 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="" 2.22="" (95%="" ci,="" 1.75="" to="" 2.81).="" the="" 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="" been="" 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="" 1.35="" (94%="" ci,="" 1.19="" to="" 1.53)="" (table 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="" 1.86="" (1.37="" to="" 2.52)="" and="" 3.37="" (1.13="" to="" 10.12),="" respectively,="" compared="" with="" those="" for="" singleton="">