Inter-pregnancy Weight Change and Risks of Severe Birth-Asphyxia-Related Outcomes in Singleton Infants Born at Term: A Nationwide Swedish Cohort Study

<div><p>Background</p><p>Maternal overweight and obesity are associated with increased risks of birth-asphyxia-related outcomes, but the mechanisms are unclear. If a change of exposure (i.e., maternal body mass index [BMI]) over time influences risks, this would be consistent with a causal relationship between maternal BMI and offspring risks. Our objective was to investigate associations between changes in maternal BMI between consecutive pregnancies and risks of birth-asphyxia-related outcomes in the second offspring born at term.</p><p>Methods and Findings</p><p>This study was a prospective population-based cohort study that included 526,435 second-born term (≥37 wk) infants of mothers with two consecutive live singleton term births in Sweden between January 1992 and December 2012.</p><p>We estimated associations between the difference in maternal BMI between the first and second pregnancy and risks of low Apgar score (0–6) at 5 min, neonatal seizures, and meconium aspiration in the second-born offspring. Odds ratios (ORs) were adjusted for BMI at first pregnancy, maternal height, maternal age at second delivery, smoking, education, mother´s country of birth, inter-pregnancy interval, and year of second delivery. Analyses were also stratified by BMI (<25 versus ≥25 kg/m²) in the first pregnancy.</p><p>Risks of low Apgar score, neonatal seizures, and meconium aspiration increased with inter-pregnancy weight gain. Compared with offspring of mothers with stable weight (BMI change of −1 to <1 kg/m²), the adjusted OR for a low Apgar score in the offspring of mothers with a BMI change of 4 kg/m² or more was 1.33 (95% CI 1.12–1.58). The corresponding risks for neonatal seizures and meconium aspiration were 1.42 (95% CI 1.00–2.02) and 1.78 (95% CI 1.19–2.68), respectively. The increased risk of neonatal seizures related to weight gain appeared to be restricted to mothers with BMI < 25 kg/m² in the first pregnancy. A study limitation was the lack of data on the effects of obstetric interventions and neonatal resuscitation efforts.</p><p>Conclusions</p><p>Risks of birth-asphyxia-related outcomes increased with maternal weight gain between pregnancies. Preventing weight gain before and in between pregnancies may improve neonatal health.</p></div

Maternal inter-pregnancy weight change and risks of low Apgar score (0–6) at 5 min, neonatal seizures, and meconium aspiration: live singleton second term infants of women in Sweden 1992–2012.

<p>Maternal inter-pregnancy weight change and risks of low Apgar score (0–6) at 5 min, neonatal seizures, and meconium aspiration: live singleton second term infants of women in Sweden 1992–2012.</p

Maternal characteristics and rates of low Apgar scores (0–6), meconium aspiration, and neonatal seizures: live-born singleton second term infants of women in Sweden 1992–2012.

<p>Maternal characteristics and rates of low Apgar scores (0–6), meconium aspiration, and neonatal seizures: live-born singleton second term infants of women in Sweden 1992–2012.</p

Maternal body-mass index and odds ratios for low Apgar scores at 5 and 10 minutes: live singleton term births in Sweden 1992–2010.

<p>In addition to regression models used in <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1001648#pmed-1001648-t003" target="_blank">Table 3</a>, odds ratios are further adjusted for mode of delivery.</p

Maternal characteristics and rates of low Apgar scores at 5 and 10 minutes in live singleton term births in Sweden 1992–2010.

<p>Maternal characteristics and rates of low Apgar scores at 5 and 10 minutes in live singleton term births in Sweden 1992–2010.</p

Maternal body-mass index and odds ratios for meconium aspiration and neonatal seizures; live singleton term births in Sweden 1992–2010.

<p>In addition to regression models used in <a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1001648#pmed-1001648-t003" target="_blank">Table 3</a>, odds ratios are further adjusted for mode of delivery.</p

Functional Properties of Rare Missense Variants of Human <i>CDH13</i> Found in Adult Attention Deficit/Hyperactivity Disorder (ADHD) Patients

<div><p>The <i>CDH13</i> gene codes for T-cadherin, a GPI-anchored protein with cell adhesion properties that is highly expressed in the brain and cardiovascular system. Previous studies have suggested that <i>CDH13</i> may be a promising candidate gene for Attention Deficit/Hyperactivity Disorder (ADHD). The aims of this study were to identify, functionally characterize, and estimate the frequency of coding <i>CDH13</i> variants in adult ADHD patients and controls. We performed sequencing of the <i>CDH13</i> gene in 169 Norwegian adult ADHD patients and 63 controls and genotyping of the identified variants in 641 patients and 668 controls. Native and green fluorescent protein tagged wild type and variant CDH13 proteins were expressed and studied in CHO and HEK293 cells, respectively. Sequencing identified seven rare missense <i>CDH13</i> variants, one of which was novel. By genotyping, we found a cumulative frequency of these rare variants of 2.9% in controls and 3.2% in ADHD patients, implying that much larger samples are needed to obtain adequate power to study the genetic association between ADHD and rare CDH13 variants. Protein expression and localization studies in CHO cells and HEK293 cells showed that the wild type and mutant proteins were processed according to the canonical processing of GPI-anchored proteins. Although some of the mutations were predicted to severely affect protein secondary structure and stability, no significant differences were observed between the expression levels and distribution of the wild type and mutant proteins in either HEK293 or CHO cells. This is the first study where the frequency of coding <i>CDH13</i> variants in patients and controls is reported and also where the functional properties of these variants are examined. Further investigations are needed to conclude whether <i>CDH13</i> is involved in the pathogenesis of ADHD or other conditions.</p></div

Schematic description of the CDH13 proteins expressed in CHO and HEK293 cells.

<p>CDH13 was expressed with or without a C-terminal tGFP tag in HEK293 and CHO cells, respectively. The location of the identified variants is also shown (A). According to the general model of processing of GPI anchored proteins in the ER, a C-terminal transmembrane domain is cleaved off and is then replaced by a GPI anchor. The protein with the attached GPI anchor is then directed to the external side of the plasma membrane (B). Wild type and variant CDH13 proteins were expressed on the cell membrane in HEK293 and CHO cells. In HEK293 cells, the C-terminal GFP tag of the GFP-CDH13 fusion proteins was cleaved off as a result of GPI anchoring at the c- terminal of CDH13 and the fully processed protein was subsequently transferred to the cell membrane.</p

<i>In silico</i> analysis of the effect of CDH13 variants.

<p>The analysis was based on the protein sequence. SIFT scores below 0.05 were considered damaging. I-mutant-3.0 predicted the effects of the variants on protein stability by calculating the unfolding Gibbs free energy value of the mutant proteins minus that of the wild type protein (ΔΔG = ΔG mutant – ΔG wild type), given in kcal/mol. A negative change indicates decreased stability. The reliability index (RI) for a large decrease (ΔΔG<−0.5) ranged from 0–10. For the G113R* a reliability index for a neutral stability change was given. Ternary classification (SVM3) −0.5< = ΔΔG< = 0.5 corresponds to neutral stability, ΔΔG<−0.5 to large decrease of stability and ΔΔG >0.5 to a large increase of stability.</p

Frequency of <i>CDH13</i> variant alleles identified in Norwegian adult patient and control groups.

<p>Seven <i>CDH13</i> variants were identified in the sequencing study, three of which were only detected in patients. All variants were genotyped in a larger sample. Two-tailed P-values for genotype frequencies were calculated by Fisher’s exact test in a 2×2 contingency table.</p