Down syndrome among primiparae at older maternal age: A test of the relaxed filter hypothesis

More twins expected in low-income countries with later maternal ages at birth and population growth

STUDY QUESTION

How are the changing maternal age structure and population growth expected to shape future twinning rates in low-income countries?

SUMMARY ANSWER

With maternal age at birth projected to shift toward older ages, twinning rates are also estimated to increase in most low-income countries by 2050 and even more by 2100.

WHAT IS KNOWN ALREADY

Many of the sub-Saharan African and South Asian countries are undergoing, and projected to further experience, the shift of maternal age at birth to older ages. Advanced maternal age is a well-established predictor of multiple births at the individual level, but currently, it is unknown how the changes in maternal age distribution are associated with the changes in twinning rates at the population level in low-income countries.

STUDY DESIGN, SIZE, DURATION

We first estimated age-specific twinning probability based on Demographic Health Surveys and World Fertility Surveys data. We then scaled up the age-specific twinning probability at the population level to estimate changes in the number of twin births in 2050 and 2100 attributable to the estimated shifts in maternal age toward older ages as projected by the UN World Population Prospects (WPP).

PARTICIPANTS/MATERIALS, SETTING, METHODS

We analyzed ∼3.19 million births that occurred within 10 years before the interview. Majority of the births in our data took place between 1980 and 2015 across 39 countries, where the uptake of medically assisted reproduction (MAR) is known to have been low during the observation period. We estimated country fixed-effects models to obtain country-specific twinning rates and age-specific twinning probability. We applied these estimates to the future number of births projected by the UN WPP, to estimate the number of twin births in 2050 and 2100.

MAIN RESULTS AND THE ROLE OF CHANCE

With maternal age at birth projected to shift toward older ages, twinning rates are also estimated to increase in most countries by 2050 compared to 2010 (increases from 0.3% to 63% depending on countries), and even more in all studied countries by 2100 (increases from 3.5% to 79%). Due to its large population size, India will continue to have among the largest share of twin births despite its estimated decline of twin births by 10.5% by 2100. Nigeria, due to its not only large and growing population size but also high twinning rate, is expected to contribute the second largest number of twin births.

LIMITATIONS, REASONS FOR CAUTION

Although the accuracy in maternal recall of multiple births tends to be high, our use of data based on recalled births from the past nonetheless imply a potential bias in our estimation of twinning rates.

WIDER IMPLICATIONS OF THE FINDINGS

The present study suggests that, even if the spread of MAR remains slow in many low-income countries, twinning rates and number of twin births are expected to grow as an increase in maternal age at birth and population growth continue. Our findings call for more public health attention and societal support to be paid to twins and their families in low-income countries, given that twins are at higher risk of developmental challenges and health disadvantages.

STUDY FUNDING/COMPETING INTEREST(S)

D.S.L. was supported by the European Union (ERC, BIOSFER, 101071773). K.J.B. was supported by a Pro Futura Scientia XIV Fellowship awarded by the Swedish Collegium for Advanced Study and Riksbankens Jubileumsfond. There are no competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

Chromosomal and cellular therapeutic approaches for Down syndrome: A research update

In individuals with Down syndrome (DS), an additional HSA21 chromosome copy leads to the overexpression of a myriad of HSA21 genes, disrupting the transcription of the entire genome. This dysregulation in transcription and post-transcriptional modifications contributes to abnormal phenotypes across nearly all tissues and organs in DS individuals. The array of severe clinical symptoms associated with trisomy 21 poses a considerable challenge in the quest for a cure for DS. Fortunately, a wealth of research suggests that chromosome therapy, hinging on cutting-edge genome editing technologies, can potentially eliminate the extra copy of the human chromosome 21. Genome editing tools have demonstrated their efficacy in restoring trisomy to a normal diploid state in vitro DS cell models. Furthermore, we delve into the noteworthy findings in cellular therapy for DS, with recent studies showcasing the increasing feasibility of strategies involving stem cells and CAR T-cells to address corresponding clinical phenotypes.

Risk factors characterisation for CHD: a case-control study in Bogota and Cali, Colombia, 2002-2020

OBJECTIVE

CHDs correspond to 28% of all congenital anomalies, being the leading cause of infant mortality in the first year of life. Thus, it is essential to explore risk factors for CHDs presentation, allowing the detection of probable cases within a population.

METHODS

We identified newborns with CHDs within a cohort from the Program for the Prevention and Monitoring of Congenital Defects in Bogota and Cali, 2002-2020. Cases were classified as isolated, complex isolated, polymalformed, and syndromic. Variables were analysed by comparing case and control averages with Student's t test using a 95% confidence level.

RESULTS

Prevalence obtained was 19.36 per 10 000 live births; non-specified CHD, ventricular septal defect, and atrial septal defect were the most prevalent. As risk factors were found: paternal and maternal age above 45 years, pregestational diabetes, mother's body mass index above 25, low educational level, and socio-economic status. As protective factors: folic acid consumption within the first trimester and pregestational period.

CONCLUSION

Different risk and protective factors associated with the presentation of CHDs have been described. We consider that public health strategies should be aimed to reduce risk factors exposure. Also, improving diagnosis and prognosis by having a close monitoring on high-risk patients.

Congenital anomalies and maternal age: A systematic review and meta-analysis of observational studies

INTRODUCTION

Several studies have reported on the maternal age-associated risks of congenital anomalies. However, there is a paucity of studies with comprehensive review of anomalies. We aimed to quantify the risk of birth defects in children born to middle-aged mothers compared with that in children born to young or older mothers.

MATERIAL AND METHODS

We classified maternal ages into three groups: young (<20 years old), middle (20-34 years old) and older age (≥35 years old). Observational studies that met our age criteria were eligible for inclusion. The articles searched using the Embase and MEDLINE databases were those published from 1989 to January 21, 2021. The Newcastle-Ottawa scale was used to assess the risk of bias. If heterogeneity exceeded 50%, the random effect method was used; otherwise, the fixed-effect method was used. Prospero registration number: CRD42021235229.

RESULTS

We included 15 cohort, 14 case-control and 36 cross-sectional studies. The pooled unadjusted odds ratio (95% CI) of any congenital anomaly was 1.64 (1.40-1.92) and 1.05 (0.95-1.15) in the older and young age groups, respectively (very low quality of evidence). The pooled unadjusted odds ratio of chromosomal anomaly was 5.64 (5.13-6.20) and 0.69 (0.54-0.88) in the older and young age groups, respectively. The pooled unadjusted odds ratio of non-chromosomal anomaly was 1.09 (1.01-1.17) and 1.10 (1.01-1.21) in the older and young age groups, respectively (very low quality of evidence). The incidence of abdominal wall defects was increased in children of women in the young maternal age group.

CONCLUSIONS

We identified that very low quality evidence suggests that women in the older maternal age group had increased odds of having children with congenital anomalies compared with those in the 20-34 year age group. There was no increase in odds of children with congenital anomalies in women of <20 year age group except for abdominal defects compared with those in the 20-34 year age group. The results stem from very low quality evidence with no adjustment of confounders.