The role of fetal growth restriction in the association between Down syndrome and perinatal mortality

Copy number variants and fetal growth in stillbirths

BACKGROUND

Fetal growth abnormalities are associated with a higher incidence of stillbirth, with small and large for gestational age infants incurring a 3 to 4- and 2 to 3-fold increased risk, respectively. Although clinical risk factors such as diabetes, hypertension, and placental insufficiency have been associated with fetal growth aberrations and stillbirth, the role of underlying genetic etiologies remains uncertain.

OBJECTIVE

This study aimed to assess the relationship between abnormal copy number variants and fetal growth abnormalities in stillbirths using chromosomal microarray.

STUDY DESIGN

A secondary analysis utilizing a cohort study design of stillbirths from the Stillbirth Collaborative Research Network was performed. Exposure was defined as abnormal copy number variants including aneuploidies, pathogenic copy number variants, and variants of unknown clinical significance. The outcomes were small for gestational age and large for gestational age stillbirths, defined as a birthweight <10th percentile and greater than the 90th percentile for gestational age, respectively.

RESULTS

Among 393 stillbirths with chromosomal microarray and birthweight data, 16% had abnormal copy number variants. The small for gestational age outcome was more common among those with abnormal copy number variants than those with a normal microarray (29.5% vs 16.5%; P=.038). This finding was consistent after adjusting for clinically important variables. In the final model, only abnormal copy number variants and maternal age remained significantly associated with small for gestational age stillbirths, with an adjusted odds ratio of 2.22 (95% confidence interval, 1.12-4.18). Although large for gestational age stillbirths were more likely to have an abnormal microarray: 6.2% vs 3.3% (P=.275), with an odds ratio of 2.35 (95% confidence interval, 0.70-7.90), this finding did not reach statistical significance.

CONCLUSION

Genetic abnormalities are more common in the setting of small for gestational age stillborn fetuses. Abnormal copy number variants not detectable by traditional karyotype make up approximately 50% of the genetic abnormalities in this population.

Accelerated epigenetic aging in newborns with Down syndrome

Accelerated aging is a hallmark of Down syndrome (DS), with adults experiencing early-onset Alzheimer's disease and premature aging of the skin, hair, and immune and endocrine systems. Accelerated epigenetic aging has been found in the blood and brain tissue of adults with DS but when premature aging in DS begins remains unknown. We investigated whether accelerated aging in DS is already detectable in blood at birth. We assessed the association between age acceleration and DS using five epigenetic clocks in 346 newborns with DS and 567 newborns without DS using Illumina MethylationEPIC DNA methylation array data. We compared two epigenetic aging clocks (DNAmSkinBloodClock and pan-tissue DNAmAge) and three epigenetic gestational age clocks (Haftorn, Knight, and Bohlin) between DS and non-DS newborns using linear regression adjusting for observed age, sex, batch, deconvoluted blood cell proportions, and genetic ancestry. Targeted sequencing of GATA1 was performed in a subset of 184 newborns with DS to identify somatic mutations associated with transient abnormal myelopoiesis. DS was significantly associated with increased DNAmSkinBloodClock (effect estimate = 0.2442, p < 0.0001), with an epigenetic age acceleration of 244 days in newborns with DS after adjusting for potential confounding factors (95% confidence interval: 196-292 days). We also found evidence of epigenetic age acceleration associated with somatic GATA1 mutations among newborns with DS (p = 0.015). DS was not associated with epigenetic gestational age acceleration. We demonstrate that accelerated epigenetic aging in the blood of DS patients begins prenatally, with implications for the pathophysiology of immunosenescence and other aging-related traits in DS.

Growth charts for Mexican children with Down syndrome

We present the results of a prospective, observational, descriptive, cross-sectional study performed on a Mexican population of 1867 children, aged 0-18 years, with Down syndrome (DS), observed between 2013 and 2019. A total of 9968 measurements of height, weight, and head circumference, as well as calculation of body mass index (BMI) were used to create growth charts and tables of percentiles. Growth curves were elaborated using Cole's LMS method. The mean weight and length at birth did not differ by sex: the weight was 2750 g for boys and 2710 g for girls (p > 0.05), and the length was 48.2 cm for boys and 47.9 cm for girls (p > 0.05). The mean final height at 18 years was different by sex: 149.6 cm for boys and 141.2 cm for girls. The average BMI at 18 years was 24.2 kg/m² for boys and 21.9 kg/m² for girls. In a comparison with U.S. growth charts, we find that the Mexican population has lower height and weight. These are the first growth curves for the Mexican population with DS. They can be used by health care providers to optimize preventive care by monitoring children with DS for the early identification of factors that affect individual growth.

The Effect of Fetal Trisomy 21 on Adverse Perinatal Obstetrical Outcomes in Nova Scotia, 2000-2019

OBJECTIVE

To understand the risks associated with trisomy 21 in pregnancy in order to inform obstetrical care and improve outcomes.

METHODS

A population-based retrospective cohort study was undertaken of all pregnancies involving a fetus with trisomy 21 in Nova Scotia, Canada, from 2000 to 2019. Cases were identified from the provincial laboratory genetics database, linked to the Nova Scotia Atlee Perinatal Database for pregnancy outcomes, and compared with the general obstetrical population.

RESULTS

A total of 350 pregnancies were identified, of which 23% were ongoing pregnancies in which trisomy 21 was diagnosed prenatally and 24% involved diagnoses made after delivery. Compared with the general obstetrical population, women with ongoing pregnancies affected by trisomy 21 were more likely to be older (mean age 34 vs. 29 y), multiparous (67% vs. 55%), and in a relationship (79% vs. 68%). Trisomy 21 was associated with a significantly increased risk of preterm birth (<37 weeks; 24.1% vs. 8.3%); small for gestational age (<10th percentile; 21.7% vs. 8.2%); cesarean delivery (31.5% vs. 27.1%); and combined perinatal/neonatal mortality (8.0% vs. 0.8%) (P < 0.001 for all).

CONCLUSION

Trisomy 21 is associated with significant adverse perinatal and neonatal risks. Population screening to identify trisomy 21 can be used to optimize perinatal outcomes with appropriate fetal surveillance in these pregnancies.