Twin Rate Research Articles

Changes in the perinatal outcomes of twin pregnancies delivered at a tertiary referral center in Korea during a 24-year period from 1995 to 2018.

ObjectiveTo analyze the changes in the clinical characteristics and perinatal outcomes of twin pregnancies delivered at a tertiary referral center in Korea during a 24-year period.MethodsThis was a retrospective cohort study of twin pregnancies delivered at 24–40 weeks of gestation, from 1995 to 2018. The subjects were divided into 4 groups according to the year of delivery: 1995–2000, 2001–2006, 2007–2012, and 2013–2018. The trends in the changes in the twin birth rate, maternal age, assisted reproductive technology (ART) pregnancy rate, chorionicity, obstetric complications, delivery outcomes, and neonatal outcomes over the periods were analyzed.ResultsA total of 2,133 twin pregnancies were included in the study. The twin birth rate increased from 16.7/1,000 in 1995–2000 to 42.2/1,000 in 2001–2006, 49.5/1,000 in 2007–2012, and 61.8/1,000 in 2013–2018. The maternal age and ART pregnancy and dichorionic twin rates increased, while the monochorionic twin rate decreased over the periods. The incidence of fetal congenital anomalies, cervical incompetence, gestational diabetes mellitus, preeclampsia, and placental abruption increased over the periods. The preterm birth (PTB) rate significantly decreased owing to the decreasing elective late-PTB rate; however, the early-PTB rate significantly increased.ConclusionThis study found that twin pregnancies increased steadily over the last 24 years and that the increase was related to increased maternal age and ART pregnancy rate. The incidence of obstetric complications increased over the periods; however, the neonatal intensive care unit admission rate decreased, along with decreases in the elective late-PTB rate.

Fracture behavior of twinning-induced plasticity steel during wire drawing

The present study focuses on the effects of strain and temperature distribution on the fracture behavior in twinning-induced plasticity (TWIP) steel during wire drawing in order to understand the fracture mechanism of drawn TWIP steel wire. The deformation and fracture behaviors of a wire subjected to the reduction of area (RA) per pass of 10% (lower reduction, LR) and 20% (higher reduction, HR) were analyzed. The deformation temperature of the wire had a linear relationship with RA per pass during wire drawing, which means that the HR wire exhibited higher temperature compared to the LR wire. The maximum effective and shear strains occurred at the near surface area, i.e., at the relative distance of 0.9 from center to surface of the wire, leading to the maximum twinning rate and geometrically necessary dislocation density at the near surface area. Also, the near surface area had a lower temperature than that of the surface area. Therefore, cracks were initiated at the near surface area in TWIP steel during wire drawing, which was well observed from the fractography by scanning electron microscopy. The HR wire had a higher drawability compared to that of the LR wire because the HR wire had a lower twinning rate at the near surface area due to the higher stacking fault energy and the lower effective and shear strains. This unique fracture phenomenon of drawn wire is presented for the first time in this study since it rarely occurs in general metals during wire drawing.

Observational retrospective study of UK national success, risks and costs for 319,105 IVF/ICSI and 30,669 IUI treatment cycles

ObjectiveTo compare success rates, associated risks and cost-effectiveness between intrauterine insemination (IUI) and in vitro fertilisation (IVF).DesignRetrospective observational study.SettingThe UK from 2012 to 2016.ParticipantsData from Human Fertilisation and Embryology Authority’s...

Single blastocyst transfer yields similar pregnancy rates compared with multiple cleavage embryo transfer, with reduced twin rate, in patients with low number of fertilized oocytes

BackgroundIn patients with low numbers of embryos, there is not yet consensus on whether to extend culture to the blastocyst stage, especially due to the risk that some or all of the embryos will not make it to the blastocyst stage. The objective of our study was to evaluate pregnancy outcomes in patients with a low number of fertilized oocytes (< 4), comparing single blastocyst transfer to one or more cleavage embryo transfer.ResultsWe analyzed 6795 cycles from the 2014–2105 Society for Assisted Reproductive Technology (SART) registry. All patients were ≤ 38 years old, had less than four fertilized oocytes, and were undergoing first fresh in vitro fertilization (IVF) transfer. Primary outcomes were clinical pregnancy (CP), live birth (LB), and miscarriage rate in both cleavage stage transfer and single blastocyst transfer. A secondary outcome was the rate of twin gestation. The comparison of interest in day of transfer included (1) single blastocyst vs single cleavage and (2) single blastocyst vs multiple cleavage stage. The association between day of transfer and primary outcome was investigated using logistic regression, controlling for the age, race/ethnicity, BMI, smoking, gravidity, parity, infertility diagnoses, and assisted hatching.Single blastocyst transfer was associated with an increased odds of CP (adjusted OR 2.03) and LB (adjusted OR 1.86) when compared to single cleavage transfer, and no statistically significant association was observed when comparing single blastocyst transfer to multiple cleavage embryo transfer for CP (adjusted OR 0.94) and LB (adjusted OR = 0.88). The odds of having twins among single blastocyst transfer was significantly lower compared to those odds that among multiple cleavage stage transfer (unadjusted OR 0.09).ConclusionsWhile pregnancy outcomes are similar between single blastocyst and multiple cleavage embryo transfer, the twin rate is reduced significantly among the single blastocyst transfers in patients with a low number of fertilized oocytes.

The effect on twinning rate of transferring double vitrified-warmed embryos in women of advanced reproductive age: a retrospective study.

Twin pregnancies are associated with greater risk of neonatal morbidity and mortality than a singleton. This study was performed to investigate the twin pregnancy rate when two vitrified-warmed embryos are transferred in women of advanced reproductive age (≥35 years at the time of oocyte retrieval) and to evaluate the implications of findings in selecting candidates for elective single embryo transfer (eSET). A retrospective analysis of data which included 2,038 women aged 35–45 years, who underwent vitrified-warmed double embryo transfer (DET), from January 2013 to December 2016 was undertaken. Pregnancy and twin rates were estimated after stratifying by prognostic profile. The twin pregnancy rate was lower in women with poor prognosis (12/96, 12.5%) as compared with that in women with favorable prognosis (102/374, 27.3%) and average prognosis (78/346, 22.5%) with significant differences (P < 0.05). The twin rate for women with favorable prognosis was 29.2% (70/240) in the cycles of women aged 35–37 years, 26.8% (26/97) in the cycles of women aged 38–40 years and 16.2% (6/37) in the cycles of women >40 years. The twin rate for women with average prognosis was 25.8% (51/198) in the cycles of women aged 35–37 years, 22.0% (22/100) in the cycles of women aged 38–40 years and 10.4% (5/48) in the cycles of women >40 years. The twin rate for women with poor prognosis was 15.3% (9/59) in the cycles of women aged 35–37 years, 10.3% (3/29) in the cycles of women aged 38–40 years and 0% (0/8) in the cycles of women >40 years. From these results, it was concluded that women with a favorable or average prognosis have a high risk of twin pregnancies. The finding can be used to guide future practice: that is, performing eSET in women with favorable or average prognosis and DET in women with poor prognosis.

Temporal Trends in the Rates of Singletons, Twins and Higher-order Multiple Births Over Five Decades Across Racial Groups in the United States.

We analysed Natality data obtained from the National Vital Statistics System from 1971 through 2018. Overall, the rates of singletons declined among all racial groups over the five decades of the study. However, the rates of twins and higher-order multiples increased over the same period although for the past two decades, the rates of higher-order multiples had substantially plummeted. The global health implication of these findings is that policy changes in the US in the form of professional practice guidelines have succeeded in reducing the birth of vulnerable populations (i.e., higher-order multiples) who are predominantly created using assisted reproductive technology.

Twinning rate is not genetically correlated with production and reproduction traits in Iranian dairy cows

Context Any interruption to the reproductive system can negatively influence animal performance, and suitable animal-management practices should be adopted that will decrease the occurrence of reproductive problems such as may be the case with twinning. Aims The study was designed to estimate genetic parameters for twinning rate (TR) and to estimate genetic correlations between twinning rate and production and reproductive performances in the first lactation of Iranian Holstein cows. Methods The dataset used in this study was collected by the Animal Breeding Center of Iran during 1991–2013 and consisted of 273742 records of calving type (singleton or twin), 435742 records of 305-day milk yield, 424175 records of milk fat percentage, 253901 records of milk protein percentage, 251558 records of first calving interval, and 153632 records of number of days to first service. A single Gibbs sampling chain with 500000 rounds was generated to run linear and threshold animal models. Key results Posterior mean estimates of heritabilities for traits were: TR 0.0028, milk yield 0.28, milk fat percentage 0.33, milk protein percentage 0.38, first calving interval 0.064, and days to first service 0.061. Genetic correlations between TR and performance traits were negligible and varied from –0.08 (between TR and milk yield) to 0.04 (between TR and protein percentage). Conclusions Diminishing TR by genetic selection is a slow task owing to its low heritability. Negligible genetic correlation between TR and performance traits suggests that selection for decreased TR would not cause a significant decrease in milk production, nor is it likely to have a negative impact on the reproductive performance of dairy cows. Implications Dairy cattle breeders should follow genetic selection programs, especially for milk-production traits, without concern for an increase in twinning rate.

A rare case of heteropaternal twin calves after natural mating in Brazil.

Twin birth is a complex condition observed in most livestock animals, when the female gives birth to two or more offspring, generally out of the same mating. In cattle, it is a rare condition (3 to 5%) and depends on the genetic background and environmental factors. Twin birth is a result of multiple ovulations, being more common in dairy rather than in beef cattle. Calves could be monozygous or dizygous, with the same or of different sexes. When twins are born with different sexes, a sexual condition called Freemartinism occurs in between 90 to 97% of pregnancies, causing infertility in the female calf. Knowing that the twin rate is rare in commercial beef cattle, here we present an even rarer case of twin birth from two different sires after natural mating, also called heteropaternal superfecundation.

Fetomaternal Outcome in Twin Pregnancies: A Retrospective Analysis from a Tertiary Care Centre

Introduction: Twin pregnancies are among the major challenges faced by obstetricians globally. Increased maternal and foetal morbidity is observed with an increase in the incidence of twin pregnancies. Due to elevated rates of complications, a larger number of caesarean sections are performed in twin pregnancies in comparison to singleton gestation. Aim: The study aimed to find out the incidence of twin pregnancy with associated maternal risk factors and foetal outcome in the study population. Materials and Methods: This retrospective observational study was carried out at JNU Hospital and Medical College, Jaipur for a period of 4 years from December 2015 to December 2019. A total of 70 mothers, who presented with twin pregnancy, were included in this study. Data were collected from hospital records regarding maternal age, parity, whether spontaneous or assisted conception, gestational age, pregestational Body Mass Index (BMI) and family history. Details of maternal and foetal complications that occurred during the antenatal period and labour as well as the mode of delivery were collected and analysed. Statistical significance was considered if the p-value was ≤0.05. Qualitative data were represented as rate and proportions, while quantitative data were represented as mean and standard deviation. Results: A total of 70 mothers with twin births, resulting in 140 babies during the 4 years study period were included. A total of 4240 deliveries overall during the study period, gave a twin pregnancy incidence rate of 16.5 in 1000 deliveries. Preterm labour (25.4%), anaemia (26.8%) and hypertension (22.5%) were common problems. The most common indication for caesarean delivery was foetal malpresentation (37.8%) The mean weight of the first twin was 2.12±0.35 kg while the mean weight of the second twin was 1.97±0.30 kg. Among foetal complications, Intrauterine Growth Restriction (IUGR) was seen in 11.4% and birth weight discordance in 21.4% of children. A low Appearance, Pulse, Grimace, Activity, and Respiration (APGAR) score was noted in 21.4% of babies, while 12.9% of babies died in the early neonatal period. Conclusion: Maternal complications during twin pregnancy were mainly preterm labour, diabetes, hypertension and anaemia. Caesarean section was the main mode of delivery in this study with significant association with hypertension and preterm labour. Foetal complications were in the majority related to IUGR. More vigilance during the antenatal period and labour is needed for proper selection of mode of delivery. Active foetal surveillance and intervention with appropriate neonatal care can improve fetomaternal outcome.

ART in Europe, 2015: results generated from European registries by ESHRE.

STUDY QUESTIONWhat are the European trends and developments in ART and IUI in 2015 as compared to previous years?SUMMARY ANSWERThe 19th ESHRE report on ART shows a continuing expansion of treatment numbers in Europe, and this increase, the variability in treatment modalities and the rising contribution to the birth rates in most participating countries all point towards the increasing impact of ART on European society.WHAT IS KNOWN ALREADYSince 1997, the ART data generated by national registries have been collected, analysed and reported in 18 manuscripts published in Human Reproduction.STUDY DESIGN, SIZE, DURATIONCollection of European data by the European IVF-Monitoring Consortium (EIM) for ESHRE. The data for treatments performed between 1 January and 31 December 2015 in 38 European countries were provided by national registries or on a voluntary basis by clinics or professional societies.PARTICIPANTS/MATERIALS, SETTINGS, METHODSFrom 1343 institutions in 38 countries offering ART services a total of 849 811 treatment cycles, involving 155 960 with IVF, 385676 with ICSI, 218098 with frozen embryo replacement (FER), 21 041 with preimplantation genetic testing (PGT), 64 477 with egg donation (ED), 265 with IVM and 4294 with FOR were recorded. European data on IUI using husband/partner’s semen (IUI-H) and donor semen (IUI-D) were reported from 1352 institutions offering IUI in 25 countries and 21 countries, respectively. A total of 139 050 treatments with IUI-H and 49 001 treatments with IUI-D were included.MAIN RESULTS AND THE ROLE OF CHANCEIn 18 countries (14 in 2014) with a population of approximately 286 million inhabitants, in which all institutions contributed to their respective national registers, a total of 409 771 treatment cycles were performed, corresponding to 1432 cycles per million inhabitants (range: 727–3068 per million). After IVF the clinical pregnancy rates (PRs) per aspiration and per transfer were slightly lower in 2015 as compared to 2014, at 28.5 and 34.6% versus 29.9 and 35.8%, respectively. After ICSI, the corresponding PR achieved per aspiration and per transfer in 2015 were also slightly lower than those achieved in 2014 (26.2 and 33.2% versus 28.4 and 35.0%, respectively). On the other hand, after FER with own embryos the PR per thawing continued to rise from 27.6% in 2014 to 29.2% in 2015. After ED a slightly lower PR per embryo transfer was achieved: 49.6% per fresh transfer (50.3% in 2014) and 43.4% for FOR (48.7% in 2014). The delivery rates (DRs) after IUI remained stable at 7.8% after IUI-H (8.5% in 2014) and at 12.0% after IUI-D (11.6% in 2014). In IVF and ICSI together, 1, 2, 3 and ≥4 embryos were transferred in 37.7, 53.9, 7.9 and in 0.5% of all treatments, respectively (corresponding to 34.9, 54.5, 9.9 and in 0.7% in 2014). This evolution towards the transfer of fewer embryos in both IVF and ICSI resulted in a proportion of singleton, twin and triplet DR of 83.1, 16.5 and 0.4%, respectively (compared to 82.5, 17.0 and 0.5%, respectively, in 2014). Treatments with FER in 2015 resulted in twin and triplet DR of 12.3 and 0.3%, respectively (versus 12.4 and 0.3% in 2014). Twin and triplet delivery rates after IUI-H were 8.9 and 0.5%, respectively (in 2014: 9.5 and 0.3%), and 7.3 and 0.6% after IUI-D (in 2014: 7.7 and 0.3%).LIMITATIONS, REASONS FOR CAUTIONThe methods of data collection and reporting vary among European countries. The EIM receives aggregated data from various countries with variable levels of completeness. Registries from a number of countries have failed to provide adequate data about the number of initiated cycles and deliveries. As long as incomplete data are provided, the results should be interpreted with caution.WIDER IMPLICATIONS OF THE FINDINGSThe 19th EIM report on ART shows a continuing expansion of treatment numbers in Europe. The number of treatments reported, the variability in treatment modalities and the rising contribution to the birth rates in most participating countries point towards the increasing impact of ART on reproduction in Europe. Being the largest data collection on ART worldwide, detailed information about ongoing developments in the field is provided.STUDY FUNDING/COMPETING INTEREST(S)The study has no external funding and all costs are covered by ESHRE. There are no competing interests.

Monozygotic twinning following embryo biopsy at the blastocyst stage.

Objective:Monozygotic twinning incidence following preimplantation genetic testing in embryos at cleavage-stage does not appear to increase; however, data regarding the possible impact of the blastocyst-stage preimplantation genetic testing is lacking. We compared the incidence of monozygotic twinning in preimplantation genetic testing cycles performed at the blastocyst-stage, versus cycles without PGT, following single embryo transfer.Methods:In this retrospective cohort study, we analyzed the incidence of twin pregnancies in patients undergoing intracytoplasmic sperm injection and blastocyst-preimplantation genetic testing (253 cycles), versus a period-matched control population of patients undergoing intracytoplasmic sperm injection and single embryo transfer without preimplantation genetic testing (606 cycles).Results:The overall monozygotic twinning rate was 14/859 (1.6%) per clinical pregnancy. The incidence of zygotic splitting following intracytoplasmic sperm injection and preimplantation genetic testing was 3.5% (95% Confidence interval 1.8%-6.6%) versus 0.8% (95% Confidence interval 0.3%-1.9%) following intracytoplasmic sperm injection without preimplantation sperm injection. After adjusting for potential confounders, preimplantation genetic testing cycles were associated with an increase in the incidence of monozygotic twinning when compared to cycles without embryo biopsy (Odd ratio 3.44, 95% Confidence interval 1.05-11.27, p=0.041).Conclusions:Our findings indicate that embryo biopsy for preimplantation genetic testing performed at the blastocyst stage is associated to an increase in the incidence of monozygotic twinning. Further validation in larger sample size studies is warranted. Patients undergoing preimplantation genetic testing must receive proper counselling about the potential risks of the technique.

Effects of letrozole combined with human menopausal gonadotrophin in ovarian stimulation for intrauterine insemination cycles.

The effects of letrozole plus human menopausal gonadotropin (HMG) on ovarian stimulation (OS) of intrauterine insemination (IUI) cycles were examined. In all, 1,005 IUI cycles were included in this study. Couples underwent natural cycle (NC) IUI (n=150) or IUI after OS with letrozole (n=207) or IUI after OS with letrozole + HMG (n=648). The clinical pregnancy rates were 9.0%, 13.0%, and 17.0%, and the live birth rates were 7.0%, 9.0%, and 14.0% in the NC, letrozole, and letrozole + HMG IUI groups, respectively. The twin pregnancy rate of the letrozole + HMG group (11.0%) was higher than that of the NC (7.0%) and letrozole groups (4.0%). To date, the only triplet pregnancies to occur were in the letrozole + HMG group. On the day of human chorionic gonadotropin (hCG), the number of follicles with an average follicle diameter greater than 18 mm in the letrozole + HMG group (1.21±0.56) and letrozole group (1.14±0.48) was greater than that in the NC group (0.85±0.36). The thickness of the endometrium in the letrozole + HMG group (8.8±2.1 mm) was significantly greater than that in the letrozole group (7.3±1.6 mm). The letrozole + HMG protocol of OS in IUI can improve follicular development, increase the thickness of endometrium, significantly increase the live birth rate, but not significantly increase the multiple pregnancy rate.

Does assisted hatching affect live birth in fresh, first cycle in vitro fertilization in good and poor prognosis patients?

To assess the effect of assisted hatching (AH) on live birth rate (LBR) in first cycle, fresh in vitro fertilization (IVF) in good and poor prognosis patients. Retrospective cohort using cycles reported to the Society for Assisted Reproductive Technology Clinic Outcomes Reporting System. Live birth rate was compared in women who underwent first cycle, autologous, fresh IVF cycles with (n = 48,858) and without (n = 103,413) AH from 2007 to 2015. The propensity-weighted LBR was 39.2% with AH versus 43.9% without AH in all patients. The rate difference (RD) with AH was - 4.7% ([CI - 0.053, - 0.040], P < 0.001) with the calculated number needed to harm being 22. AH affected live birth in both good prognosis and poor prognosis patients. The propensity-weighted monozygotic twinning (MZT) rate was 2.3% in patients treated with AH as compared to 1.2% patients that did not receive AH. The RD with AH on MZT in fresh, first IVF cycles was 1.1% ([0.008, 0.014], P < 0.001). AH may affect LBR across all patients and in poor prognosis patients in fresh IVF cycles. Caution should be exercised when applying this technology. More prospective research is needed.

Factors Affecting Twinning and the Impacts of Twinning in Cattle

Efforts to increase cattle production can be done through increasing the population and productivity of cattle, one of which is through the birth of two offsprings per parent (twin). The incidence of twinning in cattle ranged 1-10%, and influenced by genetic/breed, parity, management, season of breeding. This paper presented factors and technology that increase twinning rate and the impacts of twin births in cattle. There are genetic and non genetic factors affecting twinning rate. Increased twin births can be done through some technologies such as selection, reproduction and management. The problems in twinnings are the high incidence of abortion, early embryonic loss, distochia, retained placenta, metabolic disorders, and ketosis resulting in longer calving interval. Intensive management to dam bearing twins can reduce the problems. Economically, the profits of twinning are different between beef and dairy cattle. Twin births give benefit to beef cattle farming through the increase in total weaning per cattle. The pros and cons of twin births occur in dairy cows farming, especially on milk production.

Reproductive performance of goats treated with free gonadorelin or nanoconjugated gonadorelin at estrus

The reproductive performance of goats that received a GnRH analog (gonadorelin) fabricated with or without chitosan-sodium tripolyphosphate (TPP) nanoparticles on the day of estrus (day 0) was evaluated. The chitosan-TPP polymer was conjugated with gonadorelin using an ionic gelation method. Thirty-three multiparous Zaraiebi goats were synchronized for estrus with 2 intramuscular (im) injections of 125 μg prostaglandin F2α 14 d apart. Goats showing signs of estrus were divided equally into 3 experimental groups and received a single im injection of 1 mL physiological saline (placebo; control), 50 μg/mL gonadorelin (GnRH), or 12.5 μg (quarter of GnRH dose)/mL chitosan-TPP–conjugated gonadorelin nanoparticles (NGnRH). Each goat underwent ultrasound imaging of their ovaries at day 0 and at day 10 after mating, and pregnancy was diagnosed 28 and 45 d after mating. The concentrations of estradiol (E2) and progesterone (P4) were determined at day 0 and at days 7, 14, 21, and 42 after mating. NGnRH size, polydispersity, and zeta potential were 93.91 nm, 0.302, and 11.6 mV, respectively. Chitosan-TPP nanoparticles showed 91.2% entrapment efficiency for GnRH. No differences in estrus rate, interval to estrus, or ovarian structure at day 0 were observed among the experimental groups, but the GnRH and NGnRH treatments significantly decreased the duration of estrus compared with the control. At day 10 after mating, both GnRH and NGnRH increased (P = 0.011) the number of corpora lutea compared with the control. Treatment with GnRH increased (P = 0.023) serum E2 concentrations from day 7 to 42 after mating compared with NGnRH and control treatments. The highest (P = 0.043) serum P4 concentration was observed in the GnRH group, followed by the NGnRH and control groups. The increase in serum P4 concentration started earlier a on day 7 in the GnRH group but later on day 14 in the NGnRH group. Compared with the control, GnRH resulted in a higher (P = 0.041) P4-to-E2 ratio, followed by NGnRH. Both gonadorelin treatments significantly increased the twinning rate, the number of embryos at days 28 and 42, and prolificacy and decreased pregnancy losses compared with the control. In conclusion, the administration of GnRH at the time of estrus improved the prolificacy of goats by increasing both the ovulation rate and the number of embryos. In addition, the nanoformulation developed in this study allowed a 75% reduction in the conventional dose of gonadorelin without affecting the fertility and prolificacy of goats, indicating the bioavailability of the reduced GnRH dose after conjugation with developed nanoformula.

Assisted reproductive techniques in Latin America: the Latin American Registry 2016.

What was the utilization, effectiveness and perinatal outcome of assisted reproductive technologies (ART) performed in Latin America during 2016? Retrospective collection of multinational data on ART performed in 178 institutions from 15 Latin American countries. This paper reports on 85,474 initiated cycles, 15,070 deliveries and 18,182 babies born in this period. Of all fresh autologous IVF/intracytoplasmic sperm injection (ICSI) cycles, 40.9% were performed in women aged 35-39 years, and 31.1% in women aged ≥40 years. After removing freeze-all cycles, delivery rate per oocyte retrieval was 20.31% for ICSI and 21.85% for IVF. Fresh single embryo transfer including all age categories represented 22.96%, with a 15.35% delivery rate per transfer. Double embryo transfer represented 61.58% of transfers, with a 27.62% delivery rate per transfer. Multiple births included 18.12% twins and 0.55% triplets and higher. In oocyte donation, delivery rate per transfer was 32.89%, with a twin and triplet rate of 23.48% and 0.73%, respectively. Overall, preterm deliveries reached 17.11% in singletons, 65.69% in twins and 95.51% in triplets. Perinatal mortality was 8.0‰ in singletons, 19.0‰ in twins, and 62.3‰ in high-order multiples. The number of initiated cycles continues to increase. Compared with previous years, the number of embryos transferred decreased while the proportion of single embryo transfers increased with a drop in multiple births. It is vital to motivate health care providers and consumers to continue this trend.

Secular Trends of Multiple Birth Rate in Korea: 1981–2017

Purpose To determine the secular trend of the multiple birth rate in Korea from 1981 to 2017. Methods This study used birth certificate data covering the years 1981-2017 (20,948,901 births), provided by Statistics Korea. The impact of assisted reproductive technologies (ART) on multiple birth was analyzed by examining data prior to and after the introduction of ART and the national support program for infertile couples in South Korea. The odds ratio (OR) and 95% confidence intervals were calculated to describe the secular trend in the multiple birth rate per 100 births. Results During this period, the multiple birth rate per 100 births increased by 277 percent from 1.031 to 3.891, the twin birth rate increased from 1.013 to 3.807 (275%), and the triplet birth rate increased from 0.018 to 0.084 (363%). The secular trend of the multiple birth rate remained in the 1.000 level during 1981-1991, but has been rising steadily since 1992. The average increment of the multiple birth rate was 3.9% annually from 1981 through 2017 (peaking at more than 10 percent during 2006-2007). Prior to the introduction of ART in Korea (1981-1984), the multiple birth rate was 1.007, but after its introduction, the multiple birth rate was 1.005 in 1985-1989 (OR, 0.998; 95% confidence interval, 0.982-1.014), 1.084 in 1990-1994 (1.007; 1.060-1.094), 1.891 in 2000-2004 (1.894; 1.866-1.922), 3.127 in 2010-2014 (3.173; 3.129-3.217), and 3.811 in 2015-2017 (3.893; 3.835-3.952). Conclusion Over the past three decades, multiple births have risen dramatically in Korea, primarily due to the increasingly widespread use of fertility therapies, and the delayed age of childbearing. There is a need for more research to understand the factors contributing to multiple births, and the national birth registration systems ought to be reformed to monitor whether multiple births originated spontaneously or from assisted-conception. Key Words: Multiple birth rate, Twin and triplet birth rate, Secular trend

The Guinea-Bissau Twin Registry Update: A Platform for Studying Twin Mortality and Metabolic Disease.

Sub-Saharan Africa has the highest natural twinning rate in the world. Unfortunately, due to lack of adequate care during pregnancy, labor and postnatally, twin mortality in Sub-Saharan Africa also remains very high. Thus, it has been estimated that one in five twins dies during the childhood years. In spite of this, surprisingly few twin studies have been conducted in the region, making additional epidemiological data much needed. In 2009, we established one of the first twin registries in Sub-Saharan Africa at the Bandim Health Project in Guinea-Bissau. The registry had two main objectives. First, we wanted to describe the twinning rate and mortality patterns among newborn twins, including mortality risk factors and hospitalization patterns. Such studies can help the local clinicians improve twin health by identifying the most vulnerable children. Second, and in light of the rapidly increasing diabetes rates in Africa, we wanted to use the registry to particularly focus on metabolic disorders. Twins are often born with low birth weight, which according to the 'thrifty phenotype hypothesis' could predispose them to metabolic disorders later in life. Yet, no such 'fetal programming' data have previously been available from African twins despite the fact that nutritional patterns and influences from other factors (e.g., infections) could be markedly different here compared to high-income settings. In this article, we summarize the findings and current status of the Guinea-Bissau twin registry.

DNA methylation signatures of monozygotic twins clinically discordant for multiple sclerosis

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system with a modest concordance rate in monozygotic twins, which strongly argues for involvement of epigenetic factors. We observe highly similar peripheral blood mononuclear cell-based methylomes in 45 MS-discordant monozygotic twins. Nevertheless, we identify seven MS-associated differentially methylated positions (DMPs) of which we validate two, including a region in the TMEM232 promoter and ZBTB16 enhancer. In CD4 + T cells we find an MS-associated differentially methylated region in FIRRE. Additionally, 45 regions show large methylation differences in individual pairs, but they do not clearly associate with MS. Furthermore, we present epigenetic biomarkers for current interferon-beta treatment, and extensive validation shows that the ZBTB16 DMP is a signature for prior glucocorticoid treatment. Taken together, this study represents an important reference for epigenomic MS studies, identifies new candidate epigenetic markers, and highlights treatment effects and genetic background as major confounders.

Discordance in monozygotic Parkinson's disease twins - continuum or dichotomy?

Differences in concordance rates between monozygotic and dizygotic twin pairs with Parkinson's disease (PD) have been used to estimate genetic influences in PD pathogenesis. We hypothesized that “discordance” may not in all cases adequately reflect the multifaceted disease manifestation of PD that involves a continuum from prodromal to definite PD. Deep clinical phenotyping, combining motor, nonmotor, and imaging modalities in five monozygotic, seemingly discordant twin pairs revealed motor and/or nonmotor features and/or nigral hyperechogenicity in all of the five putatively unaffected twins. In conclusion, our data suggest that concordance rates in monozygotic twins may be higher than previously appreciated.