Vanishing twin syndrome among ART singletons and pregnancy outcomes

Abstract

STUDY QUESTIONAmong babies born by ART, do singleton survivors of a vanishing twin have lower birth weight than other singletons?SUMMARY ANSWERVanishing twin syndrome (VTS) was associated with lower birth weight among ART singletons; a sibship analysis indicated that the association was not confounded by maternal characteristics that remain stable between deliveries.WHAT IS KNOWN ALREADYPrevious studies indicate that ART singletons with VTS have increased risk of adverse pregnancy outcomes, compared with other ART singletons. The potential contribution of unmeasured maternal background characteristics has been unclear.STUDY DESIGN, SIZE AND DURATIONThis was a Norwegian population-based registry study, including 17 368 mothers with 20 410 ART singleton deliveries between January 1984 and December 2013.PARTICIPANTS/MATERIALS, SETTING, METHODSThe study population included 17 291 ART singletons without VTS, 638 ART singletons with VTS and 2418 ART singletons with uncertain vanishing twin status. We estimated differences in birth weight and gestational age comparing ART singletons with VTS first to all ART singletons without VTS, and subsequently to their ART siblings without VTS, using random- and fixed-effects linear regression, respectively. The corresponding comparisons for the associations with preterm birth and small for gestational age (SGA) were conducted using random-and fixed-effects logistic regression. The sibling analysis of preterm birth included 587 discordant siblings, while the sibling analysis of SGA included 674 discordant siblings.MAIN RESULTS AND THE ROLE OF CHANCEART singletons with VTS had lower birth weight when compared to all ART singletons without VTS, with an adjusted mean difference (95% CI) of −116 g (−165, −67). When we compared ART singletons with VTS to their ART singletons sibling without VTS, the adjusted mean difference was −112 g (−209, −15). ART singletons with VTS also had increased risk of being born SGA, with an adjusted odds ratio (OR) (95% CI) of 1.48 (1.07, 2.03) compared to all ART singletons without VTS, and 2.79 (1.12, 6.91) in the sibship analyses. ART singletons with VTS were also more likely to be born preterm, although this difference did not reach statistical significance.LIMITATIONS REASONS FOR CAUTIONWe did not have information on maternal socio-economic status, but this factor is accounted for in the sibship analyses. We also had no information on whether fresh or frozen embryos were replaced.WIDER IMPLICATIONS OF THE FINDINGSThe reduction in birth weight and increased risk of SGA in ART singletons with VTS may suggest the presence of harmful intrauterine factors with long-term health impact. While vanishing twins are not routinely observed in naturally conceived pregnancies, loss of a twin is potentially a risk factor for the surviving foetus in any pregnancy. This could be further explored in large samples of naturally conceived pregnancies with the necessary information.STUDY FUNDING/COMPETING INTEREST(S)The authors of this study are supported in part b...

Number of embryos transferred and diagnosis of preeclampsia

“…The transfer of multiple embryos may result in multiple implantations with an increased placental mass, or relative placental ischemia, which could increase preeclampsia risk [5]. However, we did not find that the presence of a vanishing twin or triplet by early ultrasound increased the risk of preeclampsia, which may be related to the definition of vanishing twin, which requires fetal cardiac activity by ultrasound [6]. We hypothesized that women having their first ART cycle would have greater risk of preeclampsia than those having subsequent cycles due to reduced exposure to new paternal or fetal antigens, but our data did not support this.…”

“…Vanishing twin or vanishing triplet was identified if the number of fetal heartbeats by ultrasound at 6-8 weeks estimated gestational age was greater than the number of infants born [6]. If early ultrasound information was missing, cases were excluded (0.5% of singletons and 0.4% of twin births).…”

“…Vanishing twin, or fetal resorption, is a fetus in a multi-gestation pregnancy that dies in utero, usually early in pregnancy, and is partially or completely reabsorbed [6]. The surviving infant in a vanishing twin ART pregnancy may be small for gestational age [7], or have greater risk for preterm delivery [8,9] compared to ART pregnancies that were originally singletons.…”

Supraphysiological estradiol level in ovarian stimulation cycles affects the birthweight of neonates conceived through subsequent frozen‐thawed cycles: a retrospective study

“…The same set of covariates was used for all multivariate analyses. The maternal age at ovum pick‐up (OPU), BMI, parity (0 versus ≥1), stage of embryo transfer and presence of vanishing twin were selected as covariates based on the previous information. We included the following covariates regarding ovarian response to the model: basal FSH, basal AFC, type of gonadotropin releasing hormone (GnRH), analogous and starting dose of ovarian stimulation.…”

Birthweight and other perinatal outcomes of singletons conceived after assisted reproduction compared to natural conceived singletons in couples with unexplained subfertility: follow-up of two randomized clinical trials

“…A possible explanation for the lower birthweight in the IUI-OS group might be vanishing twins. The remaining fetus after a vanishing twin has an increased risk for a lower birthweight and being born premature ( Magnus et al , 2017 ). In the absence of viable twin pregnancies, the development of multiple follicles in IUI-OS might still have resulted in vanishing twins, while vanishing twins are not to be expected following IVF-SET.…”