Falling perinatal mortality in twins in the UK: organisational success or chance?

Maternal and perinatal outcomes in twin pregnancies following assisted reproduction: a systematic review and meta-analysis involving 802 462 pregnancies

BACKGROUND

ART is associated with higher rates of twin pregnancies than singleton pregnancies. Whether twin pregnancies conceived following ART have additional maternal and neonatal complications compared with non-ART twin pregnancies is not known.

OBJECTIVE AND RATIONALE

The objective was to quantify the risk of adverse maternal and perinatal outcomes among twin pregnancies conceived following ART compared with non-ART and natural conception. Existing reviews vary in the reported outcomes, with many studies including triplet pregnancies in the study population. Therefore, we aimed to perform an up-to-date review with an in-depth analysis of maternal and perinatal outcomes limited to twin pregnancies.

SEARCH METHODS

We searched electronic databases MEDLINE and EMBASE from January 1990 to May 2023 without language restrictions. All cohort studies reporting maternal and perinatal outcomes following ART compared with non-ART twin pregnancies and natural conception were included. Case-control studies, case reports, case series, animal studies, and in vitro studies were excluded. The Newcastle-Ottawa Scale was used to assess the methodological quality of the studies. Using random-effects meta-analysis, the estimates were pooled and the findings were reported as odds ratios (OR) with 95% CI.

OUTCOMES

We included 111 studies (802 462 pregnancies). Twin pregnancies conceived following ART were at higher risk of preterm birth at <34 weeks (OR 1.33, 95% CI 1.14-1.56, 29 studies, I2 = 73%), <37 weeks (OR 1.26, 95% CI 1.19-1.33, 70 studies, I2 = 76%), hypertensive disorders in pregnancy (OR 1.29, 95% CI 1.14-1.46, 59 studies, I2 = 87%), gestational diabetes mellitus (OR 1.61, 95% CI 1.48-1.75, 51 studies, I2 = 65%), and caesarean delivery (OR 1.80, 95% CI 1.65-1.97, 70 studies, I2 = 89%) compared with non-ART twins. The risks for the above maternal outcomes were also increased in the ART group compared with natural conception. Of the perinatal outcomes, ART twins were at significantly increased risk of congenital malformations (OR 1.17, 95% CI 1.05-1.30, 39 studies, I2 = 59%), birthweight discordance (>25% (OR 1.31, 95% CI 1.05-1.63, 7 studies, I2 = 0%)), respiratory distress syndrome (OR 1.32, 95% CI 1.09-1.60, 16 studies, I2 = 61%), and neonatal intensive care unit admission (OR 1.24, 95% CI 1.14-1.35, 32 studies, I2 = 87%) compared with non-ART twins. When comparing ART with natural conception, the risk of respiratory distress syndrome, intensive care admissions, and birthweight discordance >25% was higher among the ART group. Perinatal complications, such as stillbirth (OR 0.83, 95% CI 0.70-0.99, 33 studies, I2 = 49%), small for gestational age <10th centile (OR 0.90, 95% CI 0.85-0.95, 26 studies, I2 = 36%), and twin-twin transfusion syndrome (OR 0.45, 95% CI 0.25-0.82, 9 studies, I2 = 25%), were reduced in twin pregnancies conceived with ART versus those without ART. The above perinatal complications were also fewer amongst the ART group than natural conception.

WIDER IMPLICATIONS

ART twin pregnancies are associated with higher maternal complications than non-ART pregnancies and natural conception, with varied perinatal outcomes. Women seeking ART should be counselled about the increased risks of ART twin pregnancies and should be closely monitored in pregnancy for complications. We recommend exercising caution when interpreting the study findings owing to the study's limitations.

The Contribution of Multiple Pregnancies in Stillbirths in Greece: A Time-Trend Analysis

Introduction Multiple pregnancy is an established risk factor for fetal death. This study aimed to examine the impact of multifetal pregnancies on stillbirth rates (SBRs) in the Greek population. Methods Data on live births and stillbirths by multiplicity were derived from the Hellenic Statistical Authority, covering a 65-year period from 1957 to 2021. The SBR for multiple and single gestations, and the population attributable risk (%) (PAR (%)) stillbirth attributable to multifetal gestations were calculated, and temporal trends were assessed using joinpoint regression analysis, with annual percentage changes (APC) and 95% confidence interval (95% CI). Results In the period 1957-2021, multiple pregnancies accounted for 9.4% of total stillbirths in Greece and the overall relative risk of fetal death among multifetal gestations was 3.34, in comparison with singletons. The SBR in multiple births remained unchanged from 1957 to 1976 and showed downward trends from 1976 to 2021 (APC = -3.0, 95% CI: -3.4 to -2.7, p < 0.001). PAR (%), after two decades of stability, showed an increasing trend over the period 1975-2011 (APC = 3.4, 95% CI: 2.8 to 4.0, p < 0.001), which was reversed in the more recent decade 2011-2021 (APC = -6.1, 95% CI: -9.6 to -2.5, p = 0.001), with PAR (%) decreasing from a historical high of 19.3% in 2012 to 8.6% in 2021. Conclusion The high incidence of multiple births has a considerable impact on stillbirth rates in the Greek population. The recent downward trends of SBR and PAR (%) of multiple gestations are encouraging, however more measures and targeted interventions are needed to improve perinatal outcomes in multifetal gestation.

Risk factors for adverse outcomes in twin pregnancies: a narrative review

PURPOSE

Globally, the incidence of twin pregnancies is rising owing to the use of assisted reproductive technologies (ART), emigration and deferment of pregnancy until advanced maternal age (AMA). While twin pregnancies have higher absolute risks of adverse outcomes, including miscarriage, stillbirth, neonatal death and preterm delivery, the impact of specific exposures and risk factors related to these outcomes may differ between twin pregnancies and singleton pregnancies. Regarding modifiable factors, data are sometimes based on evidence extrapolated from singleton or whole obstetric populations. Therefore, targeted evidence is required to provide care tailored to twin pregnancies to prevent adverse outcomes. We aimed to comprehensively review the association between different risk factors and adverse outcomes in twin pregnancies, including data on chorionicity, and to compare these to singletons.

MATERIALS AND METHODS

This review examines the risks associated with chorionicity, AMA, body mass index (BMI), socioeconomic and ethnic inequalities, maternal smoking, use of ART, maternal perception of fetal movement, and maternal comorbidities, including hypertensive disorders of pregnancy (HDP) and gestational diabetes mellitus (GDM). Adverse outcomes reported were preterm birth, admission to the neonatal intensive care unit (NICU), stillbirth and neonatal mortality. As such, fetal mortality and morbidity will be under-represented, as pregnancy loss before 22-24 weeks is omitted.

RESULTS

Monochorionicity increases the risk of stillbirth, NICU admission, and preterm delivery in twin pregnancy. AMA predisposes twin pregnancies to higher risks of mortality, admission to the NICU, and preterm birth than singleton pregnancies do. Conversely, the impact of BMI, socioeconomic inequalities, smoking, ART, and HDP on adverse outcomes appears to be lower in twin pregnancies than in singleton pregnancies. This attenuation might be explained by the higher baseline risk of adverse outcomes such as preterm birth in twin pregnancies. Some exposures, such as ART use and GDM, appear to be "protective" against perinatal mortality in twin pregnancies, despite being established risk factors for adverse outcomes in singleton pregnancies, potentially related to access to specialist care. There is a paucity of evidence available to counsel mothers of twin pregnancies regarding reduced fetal movement.

CONCLUSIONS

Overall, the risk factors for adverse pregnancy outcomes differ between twin and singleton pregnancies. This highlights the need for further studies to examine the association between risk factors and adverse outcomes in twin pregnancies. The resulting data would facilitate tailored guidance for twin pregnancies, contribute to improved antenatal care, and inform wider public health strategies.

Clinical practice guidelines for the antenatal management of dichorionic diamniotic twin pregnancies: a systematic review

OBJECTIVE

This review aimed to identify guidelines with recommendations applicable to the antenatal management of dichorionic diamniotic twin pregnancies within high-income countries, appraise their methodological quality, and discuss the similarities and variability across guidelines.

METHOD

A systematic literature review of electronic databases was performed. Manual searches of guideline repositories and websites of professional organisations were performed to identify additional guidelines. The protocol for this systematic review was registered on PROSPERO (CRD42021248586, 25 June 2021). AGREE II and AGREE-REX tools were applied to assess the quality of eligible guidelines. A narrative and thematic synthesis described and compared the guidelines and their recommendations.

RESULTS

Twenty-four guidelines were included, from which 483 recommendations were identified across 4 international organisations and 12 countries. Guidelines addressed eight themes and recommendations were classified accordingly: chorionicity and dating (103 recommendations), fetal growth (105 recommendations), termination of pregnancy (12 recommendations), fetal death (13 recommendations), fetal anomalies (65 recommendations), antenatal care (65 recommendations), preterm labour (56 recommendations) and birth (54 recommendations). Guidelines showed significant variability in recommendations, with conflicting recommendations regarding non-invasive preterm testing, definitions surrounding selective fetal growth restriction, screening for preterm labour and the timing of birth. Guidelines lacked a focus on standard antenatal management of DCDA twins, management of discordant fetal anomaly and single fetal demise.

CONCLUSIONS

Specific guidance for dichorionic diamniotic twins is overall indistinct and access to guidance regarding the antenatal management of these pregnancies is currently difficult. Management of discordant fetal anomaly or single fetal demise needs greater consideration.

Trend and causes of maternal death, stillbirth and neonatal death over seven decades in Hong Kong

BACKGROUND

Reducing maternal and perinatal mortality is a global objective. Hong Kong is a city with low maternal and perinatal mortality but little is known about the trend and causes of these deaths in this high-income city. We analyzed the maternal death, stillbirth and neonatal death since 1946 in Hong Kong.

METHODS

Data were extracted from vital statistics, based on the number of registered deaths and births, provided by the Department of Health, the Government of the HKSAR. The annual change rate of mortality was evaluated by regression analysis. Contextual factors were collected to assess the association with mortality.

FINDINGS

Between 1946 and 2017, the stillbirth rate (per 1,000 total births) reduced from 21·5 to 2·4; early and late neonatal deaths (per 1,000 live births) reduced from 14·1 and 18·1 to 0·7 and 0·4 in 2017, respectively. The maternal mortality ratio (per 100,000 live births) declined from 125 to 1·8.The causes of maternal and perinatal deaths were available since 1981 and 1980 respectively. The leading causes of death were thromboembolism (37·0%) and obstetric haemorrhage (30·4%) for maternal death; congenital problem (30·1%) and prematurity (29·0%) for neonatal death. No data on causes of stillbirth were available. No specific shift of pattern was observed in the causes of maternal and neonatal death with time. There were no cases of maternal death due to sepsis and only 2 cases (2·2%) of maternal deaths due to indirect cause.

INTERPRETATION

The maternal and perinatal death have reduced significantly in Hong Kong and maintained at the lowest level globally. Indirect maternal death and sepsis were unusual causes of maternal deaths. Use of ICD-PM stillbirth classification, setting up a maternal death confidential enquiry and adding pregnancy checkbox could be the next step to identify and categorize hidden burden.

FUNDING

Nil.

Temporal trends and adverse perinatal outcomes of twin pregnancies at differing gestational ages: an observational study from China between 2012–2020

Background

With the development of assisted reproductive technology, the twinning rate in China has been increasing. However, little is known about twinning from 2014 onwards. In addition, previous studies analysing optimal gestational times have rarely considered maternal health conditions. Therefore, whether maternal health conditions affect the optimal gestational time remains unclear.

Methods

Data of women delivered between January 2012 and December 2020 were collected through China’s National Maternal Near Miss Surveillance System. Interrupted time series analysis was used to determine the rates of twinning, stillbirth, smaller than gestational age (SGA), and low Apgar scores (< 4) among twins in China. To estimate the risk of each adverse perinatal outcome for separate gestational weeks, a multivariate generalised linear model was used. Infants born at 37 weeks of gestational age or foetuses staying in utero were used as reference separately. The analyses were adjusted for the sampling distribution of the population and the cluster effect at the hospital and individual levels were considered.

Results

There were 442,268 infants enrolled in this study, and the adjusted rates for twinning, stillbirth, SGA, and low Apgar scores were 3.10%, 1.75%, 7.70%, and 0.79%, respectively. From 2012 to 2020, the twinning rate showed an increasing trend. Adverse perinatal outcomes, including stillbirth, SGA, and low Apgar scores showed a decreasing trend. A gestational age between 34 and 36 weeks decreased most for rate of stillbirth (average changing rate -9.72%, 95% confidence interval [CI] -11.41% to -8.00%); and a gestational age of between 37 and 38 weeks decreased most for rates of SGA (average changing rate -4.64%, 95% CI -5.42% to -3.85%) and low Apgar scores (average changing rate -17.61%, 95% CI -21.73% to -13.26%). No significant difference in changes in twinning rate or changes of each perinatal outcome was observed during periods of different fertility policies. Infants born at 37 weeks of gestation had a decreased risk of stillbirth, SGA, and low Apgar scores. Maternal antepartum or medical complications increased the risk of SGA and low Apgar scores in different gestational weeks.

Conclusion

China’s twinning rate showed an increasing trend, while adverse perinatal outcomes decreased from 2012 to 2020. Fertility policy changes have had little effect on the twinning rate or the rate of adverse perinatal outcomes such as stillbirth, SGA, or low Apgar scores. The optimal gestational age for twins was 37 weeks. Women pregnant with twins and with antepartum or medical complications should be cautious due to an increased risk of SGA and low Apgar scores.

Reduction in twin stillbirth following implementation of NICE guidance

OBJECTIVE

There has been an unprecedented fall in the rate of stillbirth in twin pregnancy in the UK. It is contested whether implementation of the National Institute for Health and Care Excellence (NICE) guidance on the antenatal management of uncomplicated twin pregnancies has contributed to this change. The aim of this study was to investigate whether the implementation of NICE guidance was associated with a reduction in the rate of stillbirth in twin pregnancies delivered in a large UK hospital.

METHODS

This was a retrospective cohort study including all twin pregnancies delivered at St George's Hospital, London, UK, between 2000 and 2018. Data were analyzed according to two time periods: before implementation of the NICE guidance on twins (before June 2013; pre-NICE) and after its implementation (after June 2013; post-NICE). The exclusion criteria were higher-order multiple gestations, pregnancies of unknown chorionicity, pregnancies complicated by miscarriage, those that underwent termination and those diagnosed with vanishing twin. The main outcome was stillbirth. Other outcomes included neonatal death (NND), admission to the neonatal intensive care unit (NICU) and emergency Cesarean section. We planned a priori a sensitivity analysis according to chorionicity. The chi-square test and Mann-Whitney U-test were used to compare outcomes between the study groups.

RESULTS

We included in the analysis 1666 twin pregnancies (3332 fetuses), of which 1114 pregnancies (2228 fetuses) were delivered before and 552 pregnancies (1104 fetuses) after June 2013. Of those, 1299 were dichorionic and 354 were monochorionic diamniotic. The incidence of stillbirth was significantly lower in the post-NICE than in the pre-NICE group (3.6 per 1000 births vs 13.5 per 1000 births; P = 0.008). The reduction in stillbirth rate was from 8.5 to 3.6 per 1000 births (P = 0.161) in dichorionic and from 33.6 to 3.8 per 1000 births (P = 0.011) in monochorionic diamniotic twin pregnancies. There was no significant difference in the rates of NND (P = 0.625), NICU admission (P = 0.506) or emergency Cesarean section (P = 0.820) between the two groups. The median gestational age at delivery was significantly lower in the post-NICE than in the pre-NICE group (median 36.3 vs 36.9 weeks; P < 0.001), as a consequence of a significant increase in preterm birth between 34 and 37 weeks' gestation (39.3% vs 27.0%; P = 0.002), but not before 34 weeks (P = 0.473).

CONCLUSIONS

A significant reduction of > 70% in the stillbirth rate in twin pregnancies was noted after implementation of the NICE guidance. This reduction was statistically significant in monochorionic, but not dichorionic, twin pregnancies. The improvement in twin pregnancy outcome was achieved without a concomitant increase in NND, admission to the NICU or emergency Cesarean section. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

The incidence, maternal, fetal and neonatal consequences of single intrauterine fetal death in monochorionic twins: A prospective observational UKOSS study

Objective

Report maternal, fetal and neonatal complications associated with single intrauterine fetal death (sIUFD) in monochorionic twin pregnancies.

Design

Prospective observational study.

Setting

UK.

Population

81 monochorionic twin pregnancies with sIUFD after 14 weeks gestation, irrespective of cause.

Methods

UKOSS reporters submitted data collection forms using data from hospital records.

Main outcome measures

Aetiology of sIUFD; surviving co-twin outcomes: perinatal mortality, central nervous system (CNS) imaging, gestation and mode of delivery, neonatal outcomes; post-mortem findings; maternal outcomes.

Results

The commonest aetiology was twin-twin transfusion syndrome (38/81, 47%), “spontaneous” sIUFD (22/81, 27%) was second commonest. Death of the co-twin was common (10/70, 14%). Preterm birth (<37 weeks gestation) was the commonest adverse outcome (77%): half were spontaneous and half iatrogenic. Only 46/75 (61%) cases had antenatal CNS imaging, of which 33 cases had known results of which 7/33 (21%) had radiological findings suggestive of neurological damage. Postnatal CNS imaging revealed an additional 7 babies with CNS abnormalities, all born at <36 weeks, including all 4 babies exhibiting abnormal CNS signs. Major maternal morbidity was relatively common, with 6% requiring ITU admission, all related to infection.

Conclusions

Monochorionic twin pregnancies with single IUD are complex and require specialist care. Further research is required regarding optimal gestation at delivery of the surviving co-twin, preterm birth prevention, and classifying the cause of death in twin pregnancies. Awareness of the importance of CNS imaging, and follow-up, needs improvement.

Effect of delayed interval delivery of remaining fetus(es) in multiple pregnancies on survival: a systematic review and meta-analysis

BACKGROUND

The management of the pregnancy after delivery of the first fetus during a second-trimester miscarriage or very early preterm birth has not been well defined.

OBJECTIVE

The objective of the study was to evaluate whether delayed interval delivery of the remaining fetus(es) in twins/triplets is associated with improved survival, when compared with immediate delivery, after miscarriage or very preterm birth of the first fetus in multiple pregnancy.

DATA SOURCES

PubMed, MEDLINE, and Cochrane Library were systematically searched through January 2019. STUDY ELIGIBILITY CRITERIA (STUDY DESIGN, POPULATIONS, AND INTERVENTIONS): The following eligibility criteria applied: full-text original article; included at least 5 cases of delayed interval delivery for remaining fetus(es); and reported the survival rate of the first-born and the remaining fetus(es).

STUDY APPRAISAL AND SYNTHESIS METHODS

K.W.C. and W.W. searched, screened, and reviewed the articles. The quality of the studies was assessed according to the Strengthening the Reporting of Observational studies in Epidemiology checklist. If possible, data were stratified for assigned chorionicity. Effect sizes were pooled through a meta-analysis.

RESULTS

A total of 2295 published article and abstracts were identified. Only 16 studies met inclusion criteria. Meta-analysis of 492 pregnancies (432 twins [88%], 56 triplets [11%], 3 quadruplets and 1 quintuplets) showed that delayed interval delivery significantly improved the perinatal survival of remaining fetus(es) compared with the first born (odds ratio, 5.22, 95% confidence interval, 2.95-9.25, I² = 53%), before 20+0 weeks (odds ratio, 6.32, 95% confidence interval, 1.99-20.13, I² = 0%), between 20+0 and 23+6 weeks (odds ratio, 3.31, 95% confidence interval, 1.95-5.63, I² = 0%), and after 24+0 weeks (odds ratio, 1.92, 95% confidence interval, 1.21-3.05, I² = 0%), in dichorionic twin pregnancy (odds ratio, 14.89, 95% confidence interval, 6.19-35.84, I² = 0%), and unselected triplet pregnancy (odds ratio, 2.33, 95% confidence interval, 1.02-5.32, I² = 0%. ). Among the survivors, there were no significant differences in the short-term and long-term neonatal morbidities between the first-born and the remaining fetus(es). Serious maternal morbidity was reported in 39% of pregnancy after delayed interval delivery (71 of 183). In addition, 2 cases were managed by postpartum hysterectomy and 1 reported postoperative uterovaginal fistula. There were no recorded cases of maternal mortality.

CONCLUSION

Delayed interval delivery when a fetus has delivered in a multiple pregnancy is an effective management option to increase the survival rate of the remaining fetus(es). About 39% of women may experience morbidity following this management option.

Updated guidance for the management of twin and triplet pregnancies from the National Institute for Health and Care Excellence guidance, UK: What's new that may improve perinatal outcomes?

In September 2019, NICE published updated guidance on the management of multiple pregnancy (NG 137). Many of the previous recommendations for care are upheld but there have been important changes: increased frequency of combined ultrasound/specialist antenatal care appointments for pregnancies containing a monochorionic placenta (twins and triplets), increased frequency of ultrasound monitoring in all triplet pregnancies, changes in the definition of selective growth restriction and its subsequent referral pathways, the introduction of some monitoring for twin (or triplet) anemia polycythemia sequence in monochorionic pregnancies (albeit in complex pregnancies or at an advanced stage), and a recommended timing of birth for any pregnancy with monoamniotic fetuses. New recommendations have been made for mode of delivery, fetal monitoring in labor, maternal analgesia, and the prevention of postpartum hemorrhage. The absence of any recommendation relating to the prevention of preterm birth is notable. The basis and implications of the updates that may improve perinatal outcomes are discussed.