Perinatal and Peripartum Outcomes in Vanishing Twin Pregnancies Achieved by In Vitro Fertilization

Twin Gestation With Spontaneous Reduction To Singleton

Twin gestations are at increased risk of single intrauterine fetal death. A first-trimester loss is a common complication in twin gestations. The rate of co-twin morbidity and mortality is higher when a single demise occurs in the second and third trimesters. Monochorionicity strongly influences the prognosis for the surviving co-twin. Fetal ultrasound combined with MRI may be able to help predict neurological injury to the surviving co-twin. The rate of co-twin demise decreases with advancing gestation. After single intrauterine fetal demise, monochorionic gestations should be delivered by 34 weeks and dichorionic by 36 to 37 weeks gestation.

Clinical outcomes of vanishing twin syndrome and selective fetal reduction after double embryos transferred in IVF pregnancy: A propensity score matching study

OBJECTIVE

The purpose of this study was to analyze the influence of early vanishing twin syndrome (VTS) and selective fetal reduction (SEFR) on surviving singleton births in in-vitro fertilization (IVF) pregnancy.

METHODS

We collected patients who conceived through IVF and delivered singletons over the past six years. The VT group (n = 194) and SEFR group (n = 144) had underwent double embryos transferred (DET) and only one fetus was born, due to the subsequent one birth reduction. The SET group had one embryo transferred (SET) and gave birth to singleton. Using the propensity score matching (PSM) method to reduce confounding, the VT group and SEFR group were matched and compared with 570 and 576 singleton controls, respectively (SET-I/II group). Obstetric complications and neonatal outcomes were compared. In addition, quantity and quality of transferred embryos of VT (n = 194) and singleton groups (born with singleton after DET and matched with VT group by PSM, n = 554) were compared.

RESULTS

Compared with the SET-I group, VT group had increased incidence of severe obstetric complications, including severe preeclampsia (p = 0.031), oligohydramnios (p = 0.038) and polyhydramnios (p = 0.015). VT group was more likely to show more frequent small for gestational age (SGA) (p = 0.046) and very small for gestational age (VSGA) (p = 0.031). Newborns in the SEFR group had a significantly lower birth weight (p = 0.005) and were more likely to manifest as low birthweight (LBW) (p = 0.009) and very low birthweight (VLBW, birth weight < 1500 g) (p = 0.012), and the incidence of very large for gestational age (VLGA) was lower (p = 0.030), compared with the control group. There were more developmental abnormalities in newborns of VTS, for decreased incidence of SGA (OR 0.156, 95% CI 0.036-0.669), VSGA (OR 0.057, 95% CI 0.006-0.553) and VLGA (OR 0.415, 95% CI 0.212-0.815) in SEFR group. The good quality embryo rate was higher in VT group (72.7% vs. 63.3%, p = 0.001) compared with the singleton group.

CONCLUSIONS

DET with subsequent VTS/SEFR carried a higher rate of adverse clinical outcomes, and the VTS group had worse perinatal outcome compared with SEFR. Therefore, we recommend SET in ART.

Pregnancy outcomes among women with endometriosis and fibroids: registry linkage study in Massachusetts

BACKGROUND

Endometriosis and uterine fibroids are common gynecologic conditions associated with a greater risk for infertility. Previous research has suggested that these conditions are associated with adverse pregnancy outcomes, potentially because of increased utilization of fertility treatments.

OBJECTIVE

Our objective was to investigate whether women with a history of endometriosis or fibroids had a greater risk for adverse pregnancy outcomes and whether this risk varied by infertility history and fertility treatment utilization.

STUDY DESIGN

Deliveries (2013-2017) recorded in Massachusetts' vital records were linked to assisted reproductive technology data, hospital stays, and all-payer claims database. We identified endometriosis and fibroids diagnoses via the all-payer claims database before index delivery. Adjusted relative risks for pregnancy complications were modeled using generalized estimating equations with a log link and Poisson distribution. The influence of subfertility or infertility and assisted reproductive technology was also investigated.

RESULTS

Among 91,825 deliveries, 1560 women had endometriosis and 4212 had fibroids. Approximately 30% of women with endometriosis and 26% of women with fibroids experienced subfertility or infertility without utilizing assisted reproductive technology, and 34% of women with endometriosis and 21% of women with fibroids utilized assisted reproductive technology for the index delivery. Women with a history of endometriosis or fibroids were at a greater risk for pregnancy-induced hypertension, preeclampsia, or eclampsia (endometriosis relative risk, 1.17; fibroids relative risk, 1.08), placental abnormalities (endometriosis relative risk, 1.65; fibroids relative risk, 1.38), and cesarean delivery (endometriosis relative risk, 1.22; fibroids relative risk, 1.17) than women with no history of those conditions. Neonates born to women with a history of endometriosis or fibroids were also at a greater risk for preterm birth (endometriosis relative risk, 1.24; fibroids relative risk, 1.17). Associations between fibroids and low birthweight varied by fertility status or assisted reproductive technology (P homogeneity=.01) and were stronger among noninfertile women.

CONCLUSION

Endometriosis or fibroids increased the risk for adverse pregnancy outcomes, possibly warranting differential screening or treatment.

The vanishing twin: Diagnosis and implications

Vanishing twin syndrome (VTS), defined by first-trimester spontaneous loss of a twin, is a common phenomenon with a reported prevalence of 15-35% of twin pregnancies. The etiology of VTS is obscure. Still, several risk factors have been identified, including an increased number of embryos transferred in pregnancies conceived by in vitro fertilization, an initial increased number of gestational sacs and advanced maternal age. The effect of VTS on obstetric and perinatal outcomes is controversial. Several studies have reported that pregnancies with VTS were associated with increased risk for preterm birth and small for gestational age neonates compared to singleton pregnancies, while others showed no difference in perinatal outcomes. The prevalence of placental vascular and anatomic abnormalities such as small placentas was higher in VTS. These findings lay an essential foundation for understanding how this phenomenon affects obstetric and perinatal outcomes of the surviving pregnancy.

Non-invasive prenatal testing in the management of twin pregnancies

Twin pregnancies are common and associated with pregnancy complications and adverse outcomes. Prenatal clinical management is intensive and has been hampered by inferior screening and less acceptable invasive testing. For aneuploidy screening, meta‐analyses show that non‐invasive prenatal testing (NIPT) through analysis of cell‐free DNA (cf‐DNA) is superior to serum and ultrasound‐based tests. The positive predictive value for NIPT is driven strongly by the discriminatory power of the assay and only secondarily by the prior risk. Uncertainties in a priori risks for aneuploidies in twin pregnancies are therefore of lesser importance with NIPT. Additional information on zygosity can be obtained using NIPT. Establishing zygosity can be helpful when chorionicity was not reliably established early in pregnancy or where the there is a concern for one versus two affected fetuses. In dizygotic twin pregnancies, individual fetal fractions can be measured to ensure that both values are satisfactory. Vanishing twins can be identified by NIPT. Although clinical utility of routinely detecting vanishing twins has not yet been demonstrated, there are individual cases where cf‐DNA analysis could be helpful in explaining unusual clinical or laboratory observations. We conclude that cf‐DNA analysis and ultrasound have synergistic roles in the management of multiple gestational pregnancies.

What's already known about this topic?

In singleton pregnancies, non‐invasive prenatal testing (NIPT) for fetal aneuploidy is more effective than conventional serum and ultrasound‐based screening tests.

NIPT is more complex in dizygotic twin pregnancies due to the presence of two fetal genotypes.

Overall fetal fraction is higher in twin pregnancies but the individual contribution for each fetus is lower.

What does this study add?

A review of cell‐free DNA testing in twin pregnancies.

Individual fetal fractions in dizygotic twin pregnancies can be measured.

Zygosity can be established using NIPT and this can be particularly useful when there are concerns about chorionicity or determining whether one versus two fetuses are affected.

Vanishing twins can be detected through NIPT and this testing could be considered for some apparently singleton pregnancies with complications.

The late vanishing of a co-twin contributes to adverse perinatal outcomes in the surviving singleton

STUDY QUESTION

Is the vanishing of a co-twin after or before the ultrasonic registration of cardiac activity at approximately 6-8 weeks of gestation associated with adverse perinatal outcomes?

SUMMARY ANSWER

The timing of the demise of a co-twin after the registration of cardiac activity is an independent risk factor for adverse perinatal outcomes.

WHAT IS KNOWN ALREADY

A significant body of evidence has confirmed that vanishing twin (VT) pregnancies are associated with higher levels of risk for preterm birth (PTB), low birthweight (LBW), small-for-gestational age (SGA) and perinatal mortality, compared with singleton pregnancy. However, the impact of co-twin vanishing, before or after the presence, of cardiac activity, on perinatal outcomes has yet to be extensively investigated.

STUDY DESIGN, SIZE, DURATION

We retrospectively reviewed the medical records of 38 876 singletons delivered from ART cycles between 2006 and 2018, at the Peking University Third Hospital.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In total, 35 188 singletons were delivered from the singleton pregnancy group, 2256 singletons from the VT pregnancy group after that cardiac activity was noted, and 1432 singletons were delivered from the VT pregnancy group before cardiac activity could be registered. Using the Poisson model, the adjusted risk ratio (aRR) was used to estimate the incidence of PTB, LBW, SGA and perinatal mortality, in the pregnancies of two types of VT compared with singleton pregnancies after correction for potential confounding factors.

MAIN RESULTS AND THE ROLE OF CHANCE

The vanishing of a co-twin after the registration of cardiac activity was associated with an increased risk of perinatal mortality when compared with the group of singleton pregnancies (0.5% vs 0.2%; P = 0.006); this association still existed after adjustment for potential confounders (aRR 2.19, 95% CI 1.12-4.30; P = 0.023). Furthermore, it was significantly associated with a higher risk of PTB (all cycles aRR 2.00, 95% CI 1.77-2.24; P < 0.001; fresh transfer aRR 2.06, 95% CI 1.78-2.38; P < 0.001; frozen transfer aRR 1.87, 95% CI 1.52-2.28; P < 0.001), LBW (all cycles aRR 2.47, 95% CI 2.12-2.88; P < 0.001; fresh transfer aRR 2.50, 95% CI 2.07-3.02; P < 0.001; frozen transfer aRR 2.39; 95% CI 1.83-3.12; P < 0.001) and SGA (all cycles aRR 1.56, 95% CI 1.35-1.80; P < 0.001; fresh transfer aRR 1.53, 95% CI 1.29-1.81; P < 0.001; frozen transfer aRR 1.62, 95% CI 1.24-2.11; P < 0.001). However, prior to the presence of cardiac activity, the vanishing of a co-twin was not associated with a higher risk of perinatal mortality (all cycles aRR 0.71, 95% CI 0.17-2.92; P = 0.636; fresh cycles aRR 0.51, 95% CI 0.07-3.70; P = 0.502; frozen cycles aRR 1.29, 95% CI 0.17-9.66; P = 0.803), PTB (all cycles aRR 1.11, 95% CI 0.91-1.34; P = 0.301; fresh cycles aRR 1.10, 95% CI 0.87-1.39; P = 0.447; frozen cycles aRR 1.13, 95% CI 0.81-1.58; P = 0.467), LBW (all cycles aRR 1.19, 95% CI 0.91-1.55; P = 0.207; fresh cycles aRR 1.08, 95% CI 0.77-1.51; P = 0.668; frozen cycles aRR 1.45, 95% CI 0.93-2.25; P = 0.100) and SGA (all cycles aRR 1.09, 95% CI 0.89-1.35; P = 0.405; fresh cycles aRR 0.97, 95% CI 0.75-1.26; P = 0.839). Pregnancies involving the two types of VT were significantly different in terms of PTB (all cycles aRR 1.80, 95% CI 1.45-2.24; P < 0.001; fresh cycles aRR 1.88, 95% CI 1.44-2.45; P < 0.001; frozen cycles aRR 1.65, 95% CI 1.13-2.40; P = 0.009), LBW (all cycles aRR 2.08, 95% CI 1.55-2.79; P < 0.001; fresh cycles aRR 2.32, 95% CI 1.61-3.36; P < 0.001; frozen cycles aRR 1.65, 95% CI 1.01-2.70; P = 0.046) and SGA (all cycles aRR 1.70, 95% CI 1.36-2.11; P < 0.001; fresh cycles aRR 1.87, 95% CI 1.42-2.45; P < 0.001).

LIMITATIONS, REASONS FOR CAUTION

The present data are not able to differentiate between co-twin demise occurring in the first or second trimester. Because the second trimester ultrasound scan is not an integral aspect of IVF assessment, this information was not available in the database.

WIDER IMPLICATIONS OF THE FINDINGS

Adverse perinatal outcomes in ART babies can be avoided by replacing one embryo at a time. It is possible to apply selective single embryo transfer strategy for all while maintaining acceptable success rates.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the National Natural Science Foundation of China for Young Scholars (Reference number: 31801251). No competing interests to declare.

TRIAL REGISTRATION NUMBER

not applicable.

Risks of nonchromosomal birth defects, small-for-gestational age birthweight, and prematurity with in vitro fertilization: effect of number of embryos transferred and plurality at conception versus at birth

PURPOSE

Excess embryos transferred (ET) (> plurality at birth) and fetal heartbeats (FHB) at 6 weeks' gestation are associated with reductions in birthweight and gestation, but prior studies have been limited by small sample sizes and limited IVF data. This analysis evaluated associations between excess ET, excess FHB, and adverse perinatal outcomes, including the risk of nonchromosomal birth defects.

METHODS

Live births conceived via IVF from Massachusetts, New York, North Carolina, and Texas included 138,435 children born 2004-2013 (Texas), 2004-2016 (Massachusetts and North Carolina), and 2004-2017 (New York) were classified by ET and FHB. Major birth defects were reported by statewide registries within the first year of life. Logistic regression was used to estimate adjusted odds ratios (AORs) and 95% CIs of the risks of a major nonchromosomal birth defect, small-for-gestational age birthweight (SGA), low birthweight (LBW), and preterm birth (≤36 weeks), by excess ET, and excess ET + excess FHB, by plurality at birth (singletons and twins).

RESULTS

In singletons with [2 ET, FHB =1] and [≥3 ET, FHB=1], risks [AOR (95% CI)] were increased, respectively, for major nonchromosomal birth defects [1.13 (1.00-1.27) and 1.18 (1.00-1.38)], SGA [1.10 (1.03-1.17) and 1.15 (1.05-1.26)], LBW [1.09 (1.02-1.13) and 1.17 (1.07-1.27)], and preterm birth [1.06 (1.00-1.12) and 1.14 (1.06-1.23)]. With excess ET + excess FHB, risks of all adverse outcomes except major nonchromosomal birth defects increased further for both singletons and twins.

CONCLUSION

Excess embryos transferred are associated with increased risks for nonchromosomal birth defects, reduced birthweight, and prematurity in IVF-conceived births.

Vanishing Twins Conceived Through Fresh In Vitro Fertilization: Obstetric Outcomes and Placental Pathology

OBJECTIVE

To characterize the obstetric outcomes and placental pathology in live births arising from vanishing twin pregnancies compared with nonreduced in vitro fertilization (IVF) pregnancies.

METHODS

This is a retrospective cohort study of live births resulting from fresh embryo transfers after IVF cycles with autologous oocytes from 2004 through 2017 at a large academic fertility center. Clinical information and pathology reports were reviewed. Placental diagnoses were coded using established nosology by expert placental pathologists. Analysis of variance, Kruskal-Wallis, Pearson's χ, and Fisher exact tests were used, as appropriate, to compare pathology categories between pregnancy outcomes. Mixed effects logistic regression models were generated to reveal the association between pregnancy outcome and placenta pathology, controlling for pregnancies arising in the same woman and various suspected confounders.

RESULTS

Of 905 fresh autologous IVF cycles with placental pathology available for review, we identified 73 vanishing twin pregnancies (8.1%), 556 singleton pregnancies (61.4%), and 276 twin pregnancies (30.5%). Vanishing twin syndrome was not associated with preterm delivery, route of delivery, growth restriction or other obstetric outcomes as compared with IVF singleton pregnancies. However, vanishing twin syndrome pregnancies showed distinctive placental pathologies including an increased rate of small placentas (less than the 10th percentile by weight), with more anatomical abnormalities than IVF singleton pregnancies (odds ratio 1.73, 95% CI 0.94-3.19; adjusted odds ratio 2.15, 95% CI 1.08-4.28). The frequency of placental vascular and inflammatory pathologies associated with IVF vanishing twin syndrome pregnancies were similar to that of IVF singleton pregnancies. Loss of a twin after 8 weeks of gestation was not associated with greater risks of placental pathologies.

CONCLUSION

In vitro fertilization pregnancies affected by vanishing twin syndrome did not have significant differences in obstetric or perinatal outcomes as compared with twin or singleton gestations. However, early twin loss was potentially associated with differences in placental development associated with a higher rate of small placentas and other anatomic pathologies.

Perinatal outcomes in vanishing twin pregnancies following assisted reproductive technology (ART) - a systematic review and meta-analysis

Objectives To compare the fetal and maternal outcomes in surviving singletons of vanishing twin, with singletons or twins, in pregnancies following assisted reproductive technology (ART). Content We searched the PubMed, Embase, Web of Science and Cochrane databases from the time of conception of the database until Dec 2019 to identify relevant published studies. Perinatal outcomes were synthesized with random effects meta-analysis using RevMan 5.3. Summary and Outlook Fifteen studies were included. Dichorionic twin pregnancies conceived by ART wherein the vanishing twin phenomenon occurred had a risk of fetal malformation similar to that of ART singleton pregnancies (OR=1.25; 95% CI 0.87-1.79) and a higher risk of fetal malformation compared with ART twin pregnancies (OR=1.82; 95% CI 1.23-2.70). Moreover, the remaining fetus in ART vanishing twin pregnancy was at a significantly higher risk of preterm birth (<37 weeks) compared to fetuses in ART singleton pregnancies (OR=2.41; 95% CI 1.46-3.99) and a markedly lower risk of preterm birth (<37 weeks) compared to the fetuses in ART twin pregnancies (OR=0.19; 95% CI 0.16-0.22). Meanwhile, the risk of delivery of infants who were small for gestational age (SGA) was significantly higher in ART vanishing twin pregnancies compared to that in ART singleton pregnancies (OR=2.70; 95% CI 1.39-5.24) and similar to that in ART twin pregnancies (OR=0.67; 95% CI 0.27-1.65). The risks of preterm birth and of the infant being SGA is higher for the remaining fetus in an ART vanishing twin pregnancy compared to those for the fetuses in ART singleton pregnancies; the risk of fetal malformation is also higher in such cases compared with ART twin pregnancies.

Is vanishing twin syndrome associated with adverse obstetric outcomes of ART singletons? A systematic review and meta-analysis

PURPOSE

The objective of our meta-analysis was to estimate the effect of VTS on obstetric outcomes of ART singletons.

METHODS

PubMed, Embase, MEDLINE, and ClinicalTrials.gov were searched up to January 2019 to find studies reporting the obstetric outcomes of ART singletons with VTS. Dichotomous data were expressed as odds ratios (OR) with 95% confidence intervals (CI). Continuous data were expressed as weighted mean difference (WMD) with 95% CI.

RESULTS

A total of 17 observational studies encompassing more than 60,000 ART singletons were included in this meta-analysis. The impact of VTS on singletons was highly dependent on the definition of VTS, precisely, the vanishing timing and intrauterine growth stage. When VTS happened at or before 14 weeks, regardless of intrauterine growth stage, there were no differences in terms of gestational age (GA) [WMD = - 0.08, 95% CI = - 0.27, 0.10], preterm birth (< 37 weeks) (PTB) [OR = 1.23, 95% CI = 0.89, 1.70], and low birth weight (< 2.5 kg) (LBW) [OR = 1.56, 95% CI = 1.00, 2.43] in original singletons versus singleton with VTS. On the contrary, VTS occurred after 14 weeks was associated with significantly shorter GW and lower BW, as well as higher risks of PTB and LBW. When the sac reduced in VTS was an empty gestational sac, there would be no differences in GW, PTB, and LBW between singletons versus singletons with VTS, whereas the loss of a fetus with cardiac-activity was associated with adverse obstetric outcomes.

CONCLUSIONS

This meta-analysis suggests whether or not VTS is harmful to obstetric outcomes is highly dependent on the vanishing timing and intrauterine growth stage.

The risk of preterm birth in vanishing twin: A multicenter prospective cohort study

Objective

To evaluate not only the risk of total preterm birth (PTB) but also spontaneous preterm birth (sPTB) and indicated preterm birth (iPTB) in vanishing twin (VT).

Study design

This is a secondary analysis of a multicenter prospective cohort study. In 12 different healthcare institutions, women with singleton pregnancies were enrolled in early pregnancy and followed up till delivery.

Results

A total of 4,746 women were included in the final analysis, and. the frequency of VT was 1.1% (54/4746). VT group had a higher risk for total PTB (PTB<34 weeks, 2.1% vs. 14.8%, p<0.001; PTB<32 weeks, 1.6% vs. 13.0%, p<0.001; PTB<28 weeks, 0.9% vs. 13.0%, p<0.001) than singleton group. The VT group had increased risk for both sPTB and iPTB (<34 weeks, <32 weeks, and <28 weeks), and this increased risk for sPTB and iPTB in VT group remained significant even after controlling for confounders such as maternal age, parity, pre-pregnancy BMI, and mode of conception.

Conclusion

Vanishing twin can be an independent risk factor for both sPTB and iPTB when compared with singleton pregnancy.

Neonatal outcomes of singleton live births with vanishing twin syndrome following double embryos transfer in assisted reproductive technology: a retrospective cohort study

Background

Women with vanishing twin syndrome are associated with increased risks of adverse neonatal outcomes, such as preterm birth (PTB) and low birthweight (LBW), compared with those in singleton live births following single embryo transfer (SET) in assisted reproductive technology (ART).

Methods

Anonymized data on all cycles performed in China were obtained from the Reproductive Medicine Department at the Third Affiliated Hospital of Zhengzhou University, which had involved 127597 cycles following double embryos transfer (DET), including 54585 fresh embryos transfer (ET) cycles and 73012 frozen embryos transfer (FET) cycles. In addition, the obstetric outcomes, such as gestation age, PTB, small for gestation age (SGA), birthweight (BW), LBW, congenital malformation, pediatric admission and Neonatal Intensive Care Unit (NICU) admission in the fresh ET and FET cycles, were analyzed. Moreover, logistic regression analysis was performed to adjust the confounders, including age of women, body weight index (BMI), value of AMH, infertile years, current cycle, antral follicles, cause of infertility, number of oocytes retrieved, endometrial thickness at the date of transplantation, number of high-quality embryos, and embryo stage.

Results

In the fresh ET cycles, the BW and gestational age in study group were lower than those in control group, which were (2962.4 ± 563.1vs. 3104.9 ± 498. 5, p = 0.000) and (262.8 ± 8.4 vs. 268.9 ± 13.9, p = 0.000), respectively. Relative to control group, the study group was linked with increased risks of PTB (adjusted odds ratio (aOR) 2.45, 95% CI:1.98–3.03, adjusted p = 0.000), LBW (aOR2.11, 95% CI:1.67–2.65, adjusted p = 0.000), pediatric admission (aOR 2.55, 95% CI2.07–3.13, adjusted p = 0.000), and NICU admission (aOR 1.98, 95% CI1.32–2.96, adjusted p = 0.001), but there were no statistically significant differences in the risks of SGA (aOR 1.09, 95% CI0.82–1.45, adjusted p = 0.960) and congenital malformation (aOR 0.94, 95% CI0.53–1.68, adjusted p = 0.640) between the two groups. In the FET cycles, the gestational age and BW in study group were lower than those in control group, which were (263.0 ± 15.7vs. 273.0 ± 10.5, p = 0.000) and (3099 ± 662.1vs. 3352 ± 671.5), respectively. The study group was associated with increased risks of PTB (aOR2. 45, 95% CI: 2.23–3.43, adjusted p = 0.000), LBW (aOR 2.67, 95% CI: 2.13–3.34, adjusted p = 0.000), pediatric admission (aOR2.62, 95% CI2.14–3.21, adjusted p = 0.000), and NICU admission (aOR 2.22, 95% CI1.43, 3.46, adjusted p = 0.001) compared with those in control group, but differences in the risks of SGA (aOR 0.98, 95% CI0.71–1.36, adjusted p = 0.730) and congenital malformation (aOR 0.99, 95% CI 0.60,1.63, adjusted p = 0.940) between the two groups were not statistically significant.

Conclusions

Our study finds that singleton live births with VTS have higher risks of LBW, PTB, pediatric admission and NICU admission than those without VTS in both the fresh and frozen cycles, even after adjusting for confounders. However, no increased risks of SGA or congenital malformation are observed in singleton live births in both the fresh and frozen ART cycles following DET.