Low-technology assisted reproduction and the risk of preterm birth in a hospital-based cohort

Fertility treatments and the risk of preterm birth among women with subfertility: a linked-data retrospective cohort study

Background

In vitro fertilization (IVF) births contribute to a considerable proportion of preterm birth (PTB) each year. However, there is no formal surveillance of adverse perinatal outcomes for less invasive fertility treatments. The study objective was to describe associations between fertility treatment (in vitro fertilization, intrauterine insemination, usually with ovulation drugs (IUI), or ovulation drugs alone) and preterm birth, compared to no treatment in subfertile women.

Methods

The Fertility Experiences Study (FES) is a retrospective cohort study conducted at the University of Utah between April 2010 and September 2012. Women with a history of primary subfertility self-reported treatment data via survey and interviews. Participant data were linked to birth certificates and fetal death records to asses for perinatal outcomes, particularly preterm birth.

Results

A total 487 birth certificates and 3 fetal death records were linked as first births for study participants who completed questionnaires. Among linked births, 19% had a PTB. After adjustment for maternal age, paternal age, maternal education, annual income, religious affiliation, female or male fertility diagnosis, and duration of subfertility, the odds ratios and 95% confidence intervals (CI) for PTB were 2.17 (CI 0.99, 4.75) for births conceived using ovulation drugs, 3.17 (CI 1.4, 7.19) for neonates conceived using IUI and 4.24 (CI 2.05, 8.77) for neonates conceived by IVF, compared to women with subfertility who used no treatment during the month of conception. A reported diagnosis of female factor infertility increased the adjusted odds of having a PTB 2.99 (CI 1.5, 5.97). Duration of pregnancy attempt was not independently associated with PTB. In restricting analyses to singleton gestation, odds ratios were not significant for any type of treatment.

Conclusion

IVF, IUI, and ovulation drugs were all associated with a higher incidence of preterm birth and low birth weight, predominantly related to multiple gestation births.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12978-022-01363-4.

Infertility treatments such as in vitro fertilization are associated with preterm birth, but less is known about how other less invasive treatments contribute to preterm birth. This study compares different types of fertility treatments and rates of preterm birth with women who are also struggling with infertility but did not use fertility treatments at the time of their pregnancy. 490 women were recruited at the University of Utah between 2010 and 2012. Participants were asked to complete a survey and were linked to birth certificate and fetal death certificate data. Women who used in vitro fertilization were 4.24 times more likely to have a preterm birth than those who used no treatment. Use of intrauterine insemination were 3.17 times more likely to have a preterm birth than those who used no treatment at time of conception. Ovulation stimulating drugs were 2.17 times more likely to have a preterm birth. Having female factor infertility was also associated with higher odds of having preterm birth. For those who are having trouble conceiving, trying less invasive treatments to achieve pregnancy might reduce their risk of preterm birth.

Association of Preterm Singleton Birth With Fertility Treatment in the US

IMPORTANCE

Preterm birth is a global health issue. The association between fertility treatment and preterm singleton births has not been clarified.

OBJECTIVE

To examine the association between fertility treatment and preterm birth.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study used birth data that were submitted by 50 states and the District of Columbia to the National Vital Statistics System database. All mothers in the database who had a singleton live birth from January 1, 2016, to December 31, 2019, were included. Those who had preexisting hypertension or diabetes were excluded.

EXPOSURES

Fertility treatment categorized as assisted reproductive technology (ART) or non-ART treatment.

MAIN OUTCOMES AND MEASURES

The main outcome was a diagnosis of preterm birth, which was defined as birth before 37 complete weeks (<259 days) of gestation. Gestational age was calculated by obstetric estimation at delivery and was collected from the database.

RESULTS

The final sample consisted of 14 370 920 mothers (mean [SD] age, 28.79 [5.79] years) with singleton live births. Of these women, 122 944 (0.9%) conceived by ART and 71 176 (0.5%) received non-ART treatment. The prevalence of preterm birth was 7.6% (n = 1 071 994) in natural conception, 10.7% (n = 13 205) in ART, and 9.3% (n = 6629) in non-ART groups. Compared with neonates who were naturally conceived, newborns who were conceived with ART (adjusted risk difference [aRD], 3.10% [95% CI, 2.93%-3.27%]; adjusted odds ratio [aOR], 1.49 [95% CI, 1.46-1.52]; P < .001) and non-ART treatment (aRD, 2.22% [95% CI, 2.00%-2.44%]; aOR, 1.35 [95% CI, 1.31-1.38]; P < .001) had significantly higher risk for preterm birth after full adjustment. These associations were similar in subgroups of participants as defined by baseline characteristics.

CONCLUSIONS AND RELEVANCE

This study found that singleton neonates who were conceived by fertility treatment had higher rates of preterm birth. Further investigations are warranted into the association between ART or non-ART treatment and the risk of preterm birth in singleton neonates.

Infertility treatment and risk of severe maternal morbidity: a propensity score-matched cohort study

BACKGROUND

The extent to which infertility treatment predicts severe maternal morbidity is not well known. We examined the association between infertility treatment and severe maternal morbidity in pregnancy and the postpartum period.

METHODS

We conducted a cohort study using population-based registries from Ontario between 2006 and 2012. Pregnancies achieved using infertility treatment (ovulation induction, intrauterine insemination or in vitro fertilization with or without intracytoplasmic sperm injection) were compared with unassisted pregnancies using propensity score matching, based on demographic, reproductive and obstetric factors. The primary outcome was a validated composite of severe maternal morbidity or maternal death from 20 weeks' gestation to 42 days postpartum. We also calculated the odds ratio of a woman having 1, 2, or 3 or more severe maternal morbidity indicators in relation to invasive (e.g., in vitro fertilization) or noninvasive (e.g., intrauterine insemination) infertility treatment.

RESULTS

We matched 11 546 infertility treatment pregnancies with 47 553 untreated pregnancies. Severe maternal morbidity or maternal death occurred in 356 infertility-treated pregnancies (30.8 per 1000 deliveries) versus 1054 untreated pregnancies (22.2 per 1000 deliveries); relative risk 1.39 (95% confidence interval [CI] 1.23-1.56). The likelihood of a woman having 3 or more severe maternal morbidity indicators was increased in women who received invasive infertility treatment (odds ratio [OR] 2.28, 95% CI 1.56-3.33) but not in those who received noninvasive infertility treatment (OR 0.99, 95% CI 0.57-1.72).

INTERPRETATION

Women who undergo infertility treatment, particularly in vitro fertilization, are at somewhat higher risk of severe maternal morbidity or death. Efforts are needed to identify patient- and treatment-specific predictors of severe maternal morbidity that may influence the type of treatment a woman is offered.

Obstetric and perinatal outcomes in subfertile patients who conceived following low technology interventions for fertility enhancement: a comprehensive review

PURPOSE

Low technology interventions for fertility enhancement (LTIFE) are strategies that avoid retrieval, handling, and manipulation of female gametes. The definition of LTIFE is yet to be widely accepted and clarified, but they are commonly used in milder cases of infertility and subfertility. Based on these considerations, the aim of the present study was comprehensively to review and investigate the obstetric and perinatal outcomes in subfertile patients who underwent LTIFE.

METHODS

A literature search up to May 2017 was performed in IBSS, SocINDEX, Institute for Scientific Information, PubMed, Web of Science, and Google Scholar. An evidence-based hierarchy was used according to The Oxford Centre for Evidence-Based Medicine to determine which articles to include and analyze, and to provide a level of evidence of each association between intervention and outcome.

RESULTS

This analysis identified preliminary and low-grade evidence on the influence of LTIFE on obstetric and perinatal outcomes in subfertile women.

CONCLUSIONS

LTIFE women should deserve major consideration from Clinicians/Researchers of Reproductive Medicine, because these treatments could be potentially responsible for mothers' and babies' complications. So far, the lack of well-designed and unbiased studies makes further conclusions difficult to be drawn.

Paternal and maternal urinary phthalate metabolite concentrations and birth weight of singletons conceived by subfertile couples

BACKGROUND

Prenatal phthalate exposure has been inconsistently associated with fetal growth and infant birth weight. However, the effect of exposure during the paternal and maternal preconception period remains understudied.

OBJECTIVES

To investigate associations of paternal and maternal preconception and maternal prenatal urinary phthalate metabolite concentrations with birth weight.

METHODS

The study comprised 364 singletons born to 364 mothers and 195 fathers (195 couples) from the EARTH Study, a prospective cohort of couples from Boston, MA. Births were categorized by mode of conception: in-vitro fertilization based (IVF) (n=208) or non-IVF based (n=156, intrauterine insemination or non-medically assisted/natural conception). We measured urinary concentrations of eleven phthalate metabolites in maternal (n=1425) and paternal (n=489) preconception and maternal prenatal (n=781) samples. Birth weight was abstracted from delivery records. Covariate-adjusted associations between loge-phthalate metabolite concentrations and birth weight were evaluated separately by mode of conception using multivariable linear regression.

RESULTS

Each loge-unit increase in paternal urinary concentration of the sum of di(2-ethylhexyl) phthalate (ΣDEHP) metabolites was associated with a 90 gram (95% CI: -165, -15) decrease in birth weight among IVF singletons, but not among non-IVF singletons (18g; 95% CI: -76, 113). Additional adjustment for maternal prenatal ΣDEHP concentrations modestly strengthened findings among IVF singletons. While few associations were found with maternal preconception phthalate metabolites, we observed an inverse relationship between several maternal prenatal urinary phthalate metabolite concentrations and birth weight among IVF singletons in covariate-adjusted models. However, with further adjustment for specific paternal phthalate metabolite concentrations, these associations were attenuated and no longer significant.

CONCLUSIONS

Paternal preconception urinary concentration of ΣDEHP metabolites was associated with a decrease in birth weight among IVF-conceived singletons. These results, if replicated, highlight the importance of preconception health, especially among subfertile couples.

Epidemiologic Approaches for Studying Assisted Reproductive Technologies: Design, Methods, Analysis and Interpretation

PURPOSE

While considerable progress has been made since the advent of assisted reproductive technology (ART), the field remains a complex and challenging one for clinicians and researchers alike. This review discusses some of the most salient issues pertaining to the study of ART and whenever possible suggestions on how to address them.

RECENT FINDINGS

More than 5 million babies have been born through ART to date, representing up to 4% of all births worldwide. While technologies continue to evolve and demand for treatment grows, it is more important than ever to conduct rigorous and timely research to help guide clinical practice that is safe and effective, and that minimizes potential short- and long-term adverse outcomes to mother and child.

SUMMARY

ART research will require exceedingly more sophisticated research methods, designs, and analyses that are rooted in a reproductive epidemiological framework in order to improve future research and ultimately promote better outcomes for all subfertile couples and their children.

Pregnancy complications in spontaneous and assisted conceptions of women with infertility and subfertility factors. A comprehensive review

In the literature, there is growing evidence that assisted reproductive techniques increase the risk of pregnancy complications in subfertile couples. Moreover, many concomitant preconception risk factors for subfertility are frequently present in the same subject and increase the risk of pregnancy complications. This review aimed to summarize in a systematic fashion the best current evidence regarding the effects of preconception maternal factors on maternal and neonatal outcomes. A literature search up to March 2016 was performed in IBSS, SocINDEX, Institute for Scientific Information, PubMed, Web of Science and Google Scholar. An evidence-based hierarchy was used to determine which articles to include and analyse. Available data show that the risk of pregnancy complications in spontaneous and assisted conceptions is likely multifactorial, and the magnitude of this risk is probably very different according specific subgroups of patients. Notwithstanding the only moderate level and quality of the available evidence, available data suggest that the presence and the treatment of specific preconception cofactors of subfertility should be always taken into account both in clinical practice and for scientific purposes.

Methods for a Retrospective Population-based and Clinic-based Subfertility Cohort Study: the Fertility Experiences Study

BACKGROUND

Most cohort-based research for subfertility has been conducted in clinic-based cohorts, which may differ from population-based cohorts.

METHODS

We retrospectively recruited parallel cohorts of subfertile women: one by sampling two specialty fertility clinics in Utah, and one by population-based sampling based on marriage and birth records. The index date (of first clinic visit or subfertility status) was between 2000 and 2009, and we linked the women recruited to subsequent birth certificate records through December 2010.

RESULTS

We enrolled 459 women through clinic-based sampling and 501 women through population-based sampling. Clinic-based women were older, had higher annual household income and more likely to have had a most intensive treatment of intrauterine insemination (31%) or in vitro fertilisation (46%) than women from population recruitment (19% and 14% respectively). Conversely, they were less likely to have received no medical treatment (9%) compared to women from population recruitment (41%). For both types of sampling, prior to eligibility screening, non-responders were less likely to link to a live birth than responders: 51% vs. 58% for clinic-based, and 69% vs. 76% for the population-based with an index date in 2004.

CONCLUSIONS

Population-based sampling for subfertility cohort research identifies women who were more likely to have had less intensive treatment or no treatment. However, in both clinic-based and population-based sampling, women who have had a live birth are more likely to respond to retrospective recruitment.

Obstetric outcome and incidence of congenital anomalies in 2351 IVF/ICSI babies

PURPOSE

The aim of this study was to provide a comprehensive follow-up of fetal and perinatal outcome and the incidence of congenital anomalies in babies born after fresh embryo transfers compared to those conceived spontaneously in infertile couples.

METHODS

Retrospective comparative analysis of all clinical pregnancies from fresh cleavage-stage embryo transfer cycles (IVF and ICSI) compared with infertile patients who conceived spontaneously in the same time period (control). Congenital anomalies were classified following the European Surveillance of Congenital Anomalies (EUROCAT) classification.

RESULTS

A total of 2414 assisted reproductive technology (ART) pregnancies were compared to 582 spontaneous conceptions in the control infertile group representing 2306 deliveries. No significant differences were found in pregnancy outcome between the two groups (delivery rate, abortion rate, ectopic pregnancies, medical abortions for fetal anomalies, single and twins mean gestational age, and weight at delivery). A significant difference (p < 0.001) was found in the twin (21.3 vs 2.3 %) and triplet rates (2.3 vs 0 %). A total of 2351 babies were delivered in the ART group and 449 in the control group. A total of 90 babies (3.8 %) were diagnosed with a major congenital anomaly in the ART group and 15 (3.3 %) in the control group (p = ns). The overall rate of major congenital anomalies (105/2800) in ART and spontaneous pregnancies in infertile couples was significantly higher when compared to the EUROCAT 2.0 versus 3.75 % (p = 0.0002).

DISCUSSION

Babies born after ART treatments and from spontaneous conception in infertile couples had rates of congenital anomalies higher than those recorded by the EUROCAT. However, the rates of anomalies were not different within the infertile population whether conceived by ART or spontaneously. These data suggest that the diagnosis of infertility in itself is the common denominator for the increase in the rates of anomalies seen in both ART and spontaneous conceptions.

Differential effect of mode of conception and infertility treatment on fetal growth and prematurity

Objectives To examine perinatal outcomes in pregnancies conceived by different methods: fertile women with spontaneous pregnancies, infertile women who achieved pregnancy without treatment, pregnancies achieved by ovulation induction (OI) and in vitro fertilization or intra-cytoplasmic sperm injection (IVF/ICSI). Methods Retrospective single-center cohort study including 200 fertile and 748 infertile women stratified according to infertility treatment. The outcome measurements were preterm delivery (PTD), small-for-gestational-age (SGA), gestational diabetes, placenta previa or preeclampsia. Results The overall rate of pregnancy complications was significantly increased in all infertility groups regardless of the infertility treatment (adjusted odds ratio (OR): infertile without treatment 2.3 versus OI 2.2 versus IVF/ICSI 3.4). While PTD was mainly associated to IVF/ICSI (adjusted OR: infertile without treatment 1.3 versus OI 1.6 versus IVF/ICSI 3.3), SGA was significantly associated to both OI and IVF/ICSI (adjusted OR: infertile without treatment 1.9 versus OI 2.7 versus IVF/ICSI 2.6). All these associations remained statistically significant after adjusting by maternal age and twin pregnancy. Conclusions This study confirms the higher prevalence of pregnancy complications in infertile women irrespectively of receiving infertility treatment or not, and further describes a preferential association of prematurity with IVF/ICSI, and SGA with treated infertility (OI and IVF/ICSI).

Fertility treatments and adverse perinatal outcomes in a population-based sampling of births in Florida, Maryland, and Utah: a cross-sectional study

OBJECTIVE

To investigate perinatal outcomes associated with fertility treatments, including assisted reproductive technology (ART), intrauterine insemination with ovulation stimulation (IUI), and ovulation stimulation alone (OS).

DESIGN

Population-representative cross-sectional survey of women with live births, 2004-2008.

SETTING

Florida, Maryland, and Utah, USA.

SAMPLE

21 803 women, weighted to represent 1 022 597 women.

METHODS

Survey and birth certificate data were analysed with logistic regression models adjusted for age, education, race, income, and parity, using separate models for singletons and all births. We used two referent groups: (1) women who never used fertility treatment and (2) subfertile women conceiving without treatment.

MAIN OUTCOME MEASURES

Preterm birth (<37 weeks), very preterm birth (<34 weeks), low birthweight (<2500 g), and very low birthweight (<1500 g).

RESULTS

Referent group 1: In singletons, ART was associated with preterm birth (OR 3.28; 95% CI 1.74, 6.20) and low birthweight (OR 2.91; 95% CI 1.99, 4.26). OS was also associated with low birthweight (OR 1.62; 95% CI 1.19, 2.19). Including all births, treatment was associated with preterm birth and low birthweight: ART (OR 6.21; 95% CI 4.21, 9.16 and OR 6.51; 95% CI 4.85, 8.73); IUI (OR 2.10; 95% CI 1.24, 3.56 and OR 2.41; 95% CI 1.54, 3.76); OS (OR 1.40; 95% CI 1.01, 1.94 and OR 2.10; 95% CI 1.60, 2.75), respectively. Referent group 2: ART was associated with both outcomes in all births, but not singletons.

CONCLUSIONS

Preterm birth and low birthweight associated with fertility treatments are largely attributable to multiple gestation, but are also related to underlying subfertility.

TWEETABLE ABSTRACT

Preterm birth is associated with subfertility, and with fertility treatments through multiple gestation.

Do the causes of infertility play a direct role in the aetiology of preterm birth?

BACKGROUND

It is well established that singletons born of assisted reproductive technology are at higher risk of preterm birth and other adverse outcomes. What remains unclear is whether the increased risk is attributable to the effects of the treatment alone or whether the underlying causes of infertility also play a role. The aim of this study was to examine whether any of the six categories of causes of infertility were associated with a direct effect on preterm birth using causal mediation analysis.

METHODS

We assembled a hospital-based cohort of births delivered at a large tertiary care hospital in Montreal, Canada between 2001 and 2007. Causes of infertility were ascertained through a clinical database and medical chart abstraction. We employed marginal structural models (MSM) to estimate the controlled direct effect of each cause of infertility on preterm birth compared with couples without the cause under examination.

RESULTS

The final study cohort comprised 18,598 singleton and twin pregnancies, including 1689 in couples with ascertained infertility. MSM results suggested no significant direct effect for any of the six categories of causes. However, power was limited in smaller subgroup analyses, and a possible direct effect for uterine abnormalities (e.g. fibroids and malformations) could not be ruled out.

CONCLUSION

In this cohort, most of the increased risk of preterm birth appeared to be explained by maternal characteristics (such as age, body mass index, and education) and by assisted reproduction. If these findings are corroborated, physicians should consider these risks when counselling patients.