Large maternal waist circumference in relation to height is associated with high glucose concentrations in an early-pregnancy oral glucose tolerance test: A population-based study.

INTRODUCTION: To explore the role of maternal anthropometric characteristics in early-pregnancy glycemia, we analyzed the associations and interactions of maternal early-pregnancy waist circumference (WC), height and pre-pregnancy body mass index (BMI) with plasma glucose concentrations in an oral glucose tolerance test (OGTT) at 12-16 weeks' gestation. MATERIAL AND METHODS: A population-based cohort of 1361 pregnant women was recruited in South Karelia, Finland, from March 2013 to December 2016. All participants had their WC, weight, height, HbA1c , and blood pressure measured at 8-14 weeks' gestation and subsequently underwent a 2-h 75-g OGTT, including assessment of fasting insulin concentrations, at 12-16 weeks' gestation. BMI (kg/m2 ) was calculated using self-reported pre-pregnancy weight. Maternal WC ≥80 cm was defined as large. Maternal height ≥166 cm was defined as tall. Data on gestational diabetes treatment was extracted from hospital records. RESULTS: In the total cohort, 901 (66%) of women had an early-pregnancy WC ≥80 cm, which was associated with higher early-pregnancy HbA1c, higher concentrations of  fasting plasma glucose and serum insulin, higher post-load plasma glucose concentrations, higher HOMA-IR indices, higher blood pressure levels, and higher frequencies of pharmacologically treated gestational diabetes, than early-pregnancy WC <80 cm. Maternal height ≥166 cm was negatively associated with 1- and 2-h post-load plasma glucose concentrations. Waist-to-height ratio (WHtR) >0.5 was positively associated with both fasting and post-load plasma glucose concentrations at 12-16 weeks' gestation, even when adjusted for age, smoking, nulliparity, and family history of type 2 diabetes. The best cut-offs for WHtR (0.58 for 1-h plasma glucose, and 0.54 for 2-h plasma glucose) were better predictors of post-load glucose concentrations >90th percentile than the best cut-offs for BMI (28.1 kg/m2 for 1-h plasma glucose, and 26.6 kg/m2 for 2-h plasma glucose), with areas-under-the-curve (95% confidence interval) 0.73 (0.68-0.79) and 0.73 (0.69-0.77), respectively, for WHtR, and 0.68 (0.63-0.74) and 0.69 (0.65-0.74), respectively, for BMI. CONCLUSIONS: In our population-based cohort, early-pregnancy WHtR >0.5 was positively associated with both fasting and post-load glucose concentrations at 12-16 weeks' gestation and performed better than BMI in the prediction of post-load glucose concentrations >90th percentile. Overall, our results underline the importance of evaluating maternal abdominal adiposity in gestational diabetes risk assessment.

Higher pulse wave velocity in young adult offspring of mothers with type 1 diabetes: a case-control study.

BACKGROUND: Offspring of mothers with type 1 diabetes have an increased risk for acquiring early onset cardiovascular disease (CVD). Arterial stiffness, measured as pulse wave velocity (PWV), is a non-invasive biomarker for CVD risk assessment. Our aim is to determine whether PWV is increased in young adult offspring of mothers with type 1 diabetes. METHODS: This is a case-control study carried out in the hospital district of Helsinki and Uusimaa, Finland. 75 offspring of mothers with type 1 diabetes (cases) and 84 offspring of mothers without diabetes (controls), aged 18-23 years, were enrolled in this study. All participants attended clinical assessments, including questionnaires and laboratory tests. Carotid-femoral PWV (cfPWV), carotid-radial PWV (crPWV), and PWV ratio were measured from each participant using the Complior Analyse mechanotransducer (Alam Medical, France). Student's t-test and chi-squared test were used to assess differences between the groups. Stata 17.0, StataCorp LP (College Station, TX, USA) statistical package was used for the analysis. RESULTS: We did not observe any differences in conventional CVD risk factors: systolic blood pressure, LDL, HbA1c, and smoking between cases and controls. We detected higher cfPWV in cases 6.5 (SD ± 1.2) m/s than in controls 6.2 (SD ± 0.7) m/s, p = 0.049, after adjustments for BMI, smoking, mean arterial pressure, height, and pulse rate was made. We did not observe any difference between cases and controls regarding crPWV or PWV ratio. Additionally, we detected no sex differences. CONCLUSIONS: We report a novel finding of signs of increased arterial stiffness already in young adult offspring of mothers with type 1 diabetes compared to matched offspring of mothers without diabetes. Our finding suggests that exposure to an adverse intrauterine environment of type 1 diabetes mothers may affect the vascular health of offspring already in young adulthood. Additional research within this topic is warranted.

Increased variability of fetal heart rate during labour: a review of preclinical and clinical studies.

Increased fetal heart rate variability (FHRV) in intrapartum cardiotocographic recording has been variably defined and poorly understood, limiting its clinical utility. Both preclinical (animal) and clinical (human) evidence support that increased FHRV is observed in the early stage of intrapartum fetal hypoxaemia but can also be observed in a subset of fetuses during the preterminal stage of repeated hypoxaemia. This review of available evidence provides data and expert opinion on the pathophysiology of increased FHRV, its clinical significance and a stepwise approach regarding the management of this pattern, and propose recommendations for standardisation of related terminology.

Intrapartum zigzag pattern of fetal heart rate is an early sign of fetal hypoxia: A large obstetric retrospective cohort study.

INTRODUCTION: The aim of the present study was to identify possible associations of fetal heart rate (FHR) patterns during the last 2 hours of labor with fetal asphyxia expressed by umbilical artery acidemia at birth and with neonatal complications in a large obstetric cohort. MATERIAL AND METHODS: Cardiotocographic recordings from 4988 singleton term childbirths over 1 year were evaluated retrospectively and blinded to the pregnancy and neonatal outcomes in a university teaching hospital in Helsinki, Finland. Umbilical artery pH, base excess and pO2 , low Apgar scores at 5 minutes, need for intubation and resuscitation, early neonatal hypoglycemia, and neonatal encephalopathy were used as outcome variables. According to the severity of the neonatal complications at birth, the cohort was divided into three groups: no complications (Group 1), moderate complications (Group 2) and severe complications (Group 3). RESULTS: Of the 4988 deliveries, the ZigZag pattern (FHR baseline amplitude changes of >25 bpm with a duration of 2-30 minutes) occurred in 11.7%, late decelerations in 41.0%, bradycardia episodes in 52.9%, reduced variability in 36.7%, tachycardia episodes in 13.9% and uterine tachysystole in 4.6%. No case of saltatory pattern (baseline amplitude changes of >25 bpm with a duration of >30 minutes) was observed. The presence of the ZigZag pattern or late decelerations, or both, was associated with cord blood acidemia (odds ratio [OR] 3.3, 95% confidence interval [CI] 2.3-4.7) and severe neonatal complications (Group 3) (OR 3.3, 95% CI 2.4-4.9). In contrast, no significant associations existed between the other FHR patterns and severe neonatal complications. ZigZag pattern preceded late decelerations in 88.7% of the cases. A normal FHR preceded the ZigZag pattern in 90.4% of the cases, whereas after ZigZag episodes, a normal FHR pattern was observed in only 0.9%. CONCLUSIONS: ZigZag pattern and late decelerations during the last 2 hours of labor are significantly associated with cord blood acidemia at birth and neonatal complications. The ZigZag pattern precedes late decelerations, and the fact that normal FHR pattern precedes the ZigZag pattern in the majority of the cases suggests that the ZigZag pattern is an early sign of fetal hypoxia, which emphasizes its clinical importance.

Whole exome sequencing reveals HSPA1L as a genetic risk factor for spontaneous preterm birth.

Preterm birth is a leading cause of morbidity and mortality in infants. Genetic and environmental factors play a role in the susceptibility to preterm birth, but despite many investigations, the genetic basis for preterm birth remain largely unknown. Our objective was to identify rare, possibly damaging, nucleotide variants in mothers from families with recurrent spontaneous preterm births (SPTB). DNA samples from 17 Finnish mothers who delivered at least one infant preterm were subjected to whole exome sequencing. All mothers were of northern Finnish origin and were from seven multiplex families. Additional replication samples of European origin consisted of 93 Danish sister pairs (and two sister triads), all with a history of a preterm delivery. Rare exonic variants (frequency <1%) were analyzed to identify genes and pathways likely to affect SPTB susceptibility. We identified rare, possibly damaging, variants in genes that were common to multiple affected individuals. The glucocorticoid receptor signaling pathway was the most significant (p<1.7e-8) with genes containing these variants in a subgroup of ten Finnish mothers, each having had 2-4 SPTBs. This pathway was replicated among the Danish sister pairs. A gene in this pathway, heat shock protein family A (Hsp70) member 1 like (HSPA1L), contains two likely damaging missense alleles that were found in four different Finnish families. One of the variants (rs34620296) had a higher frequency in cases compared to controls (0.0025 vs. 0.0010, p = 0.002) in a large preterm birth genome-wide association study (GWAS) consisting of mothers of general European ancestry. Sister pairs in replication samples also shared rare, likely damaging HSPA1L variants. Furthermore, in silico analysis predicted an additional phosphorylation site generated by rs34620296 that could potentially affect chaperone activity or HSPA1L protein stability. Finally, in vitro functional experiment showed a link between HSPA1L activity and decidualization. In conclusion, rare, likely damaging, variants in HSPA1L were observed in multiple families with recurrent SPTB.

Correction: Whole exome sequencing reveals HSPA1L as a genetic risk factor for spontaneous preterm birth.

[This corrects the article DOI: 10.1371/journal.pgen.1007394.].

Dissecting maternal and fetal genetic effects underlying the associations between maternal phenotypes, birth outcomes, and adult phenotypes: A mendelian-randomization and haplotype-based genetic score analysis in 10,734 mother-infant pairs.

BACKGROUND: Many maternal traits are associated with a neonate's gestational duration, birth weight, and birth length. These birth outcomes are subsequently associated with late-onset health conditions. The causal mechanisms and the relative contributions of maternal and fetal genetic effects behind these observed associations are unresolved. METHODS AND FINDINGS: Based on 10,734 mother-infant duos of European ancestry from the UK, Northern Europe, Australia, and North America, we constructed haplotype genetic scores using single-nucleotide polymorphisms (SNPs) known to be associated with adult height, body mass index (BMI), blood pressure (BP), fasting plasma glucose (FPG), and type 2 diabetes (T2D). Using these scores as genetic instruments, we estimated the maternal and fetal genetic effects underlying the observed associations between maternal phenotypes and pregnancy outcomes. We also used infant-specific birth weight genetic scores as instrument and examined the effects of fetal growth on pregnancy outcomes, maternal BP, and glucose levels during pregnancy. The maternal nontransmitted haplotype score for height was significantly associated with gestational duration (p = 2.2 × 10-4). Both maternal and paternal transmitted height haplotype scores were highly significantly associated with birth weight and length (p < 1 × 10-17). The maternal transmitted BMI scores were associated with birth weight with a significant maternal effect (p = 1.6 × 10-4). Both maternal and paternal transmitted BP scores were negatively associated with birth weight with a significant fetal effect (p = 9.4 × 10-3), whereas BP alleles were significantly associated with gestational duration and preterm birth through maternal effects (p = 3.3 × 10-2 and p = 4.5 × 10-3, respectively). The nontransmitted haplotype score for FPG was strongly associated with birth weight (p = 4.7 × 10-6); however, the glucose-increasing alleles in the fetus were associated with reduced birth weight through a fetal effect (p = 2.2 × 10-3). The haplotype scores for T2D were associated with birth weight in a similar way but with a weaker maternal effect (p = 6.4 × 10-3) and a stronger fetal effect (p = 1.3 × 10-5). The paternal transmitted birth weight score was significantly associated with reduced gestational duration (p = 1.8 × 10-4) and increased maternal systolic BP during pregnancy (p = 2.2 × 10-2). The major limitations of the study include missing and heterogenous phenotype data in some data sets and different instrumental strength of genetic scores for different phenotypic traits. CONCLUSIONS: We found that both maternal height and fetal growth are important factors in shaping the duration of gestation: genetically elevated maternal height is associated with longer gestational duration, whereas alleles that increase fetal growth are associated with shorter gestational duration. Fetal growth is influenced by both maternal and fetal effects and can reciprocally influence maternal phenotypes: taller maternal stature, higher maternal BMI, and higher maternal blood glucose are associated with larger birth size through maternal effects; in the fetus, the height- and metabolic-risk-increasing alleles are associated with increased and decreased birth size, respectively; alleles raising birth weight in the fetus are associated with shorter gestational duration and higher maternal BP. These maternal and fetal genetic effects may explain the observed associations between the studied maternal phenotypes and birth outcomes, as well as the life-course associations between these birth outcomes and adult phenotypes.

Genetic Associations with Gestational Duration and Spontaneous Preterm Birth.

BACKGROUND: Despite evidence that genetic factors contribute to the duration of gestation and the risk of preterm birth, robust associations with genetic variants have not been identified. We used large data sets that included the gestational duration to determine possible genetic associations. METHODS: We performed a genomewide association study in a discovery set of samples obtained from 43,568 women of European ancestry using gestational duration as a continuous trait and term or preterm (<37 weeks) birth as a dichotomous outcome. We used samples from three Nordic data sets (involving a total of 8643 women) to test for replication of genomic loci that had significant genomewide association (P<5.0×10-8) or an association with suggestive significance (P<1.0×10-6) in the discovery set. RESULTS: In the discovery and replication data sets, four loci (EBF1, EEFSEC, AGTR2, and WNT4) were significantly associated with gestational duration. Functional analysis showed that an implicated variant in WNT4 alters the binding of the estrogen receptor. The association between variants in ADCY5 and RAP2C and gestational duration had suggestive significance in the discovery set and significant evidence of association in the replication sets; these variants also showed genomewide significance in a joint analysis. Common variants in EBF1, EEFSEC, and AGTR2 showed association with preterm birth with genomewide significance. An analysis of mother-infant dyads suggested that these variants act at the level of the maternal genome. CONCLUSIONS: In this genomewide association study, we found that variants at the EBF1, EEFSEC, AGTR2, WNT4, ADCY5, and RAP2C loci were associated with gestational duration and variants at the EBF1, EEFSEC, and AGTR2 loci with preterm birth. Previously established roles of these genes in uterine development, maternal nutrition, and vascular control support their mechanistic involvement. (Funded by the March of Dimes and others.).

Robust increases in erythropoietin production by the hypoxic fetus is a response to protect the brain and other vital organs.

Fetal erythropoietin (EPO), in addition to regulating erythropoiesis, has also tissue-protective properties based on its anti-inflammatory, anti-apoptotic, antioxidant, and neurotrophic effects. Notably, EPO concentrations needed for tissue protection are 100-1000 times higher than concentrations needed for regulating erythropoiesis. This dual effect of EPO is based on EPO-receptor (EPO-R) isoforms, which differ structurally and functionally. We hypothesize in this Integrated Mechanism Review that during severe fetal hypoxia the observed, but poorly understood, marked increases of fetal plasma EPO concentrations occur to protect the brain, heart, and other vital fetal organs. We further hypothesize that the concurrent marked increases of EPO in the amniotic fluid during fetal hypoxia, occur to protect newborn infants from necrotizing enterocolitis. This review presents experimental and clinical evidence in support of these hypotheses and points out unknown or poorly understood functions of EPO in the fetus. If these novel hypotheses are correct, the importance of fetal EPO as an antenatal hypoxia biomarker will become apparent. It will also likely point the way to important diagnostic and therapeutic fetal and neonatal interventions.

CXCR3 Polymorphism and Expression Associate with Spontaneous Preterm Birth.

Spontaneous preterm birth (SPTB) is a major factor associating with deaths and with lowered quality of life in humans. Environmental and genetic factors influence the susceptibility. Previously, by analyzing families with recurrent SPTB in linkage analysis, we identified a linkage peak close to the gene encoding CXCR3. Present objectives were to investigate the association of CXCR3 with SPTB in Finnish mothers (n = 443) and infants (n = 747), to analyze CXCR3 expression levels in human placenta and levels of its ligands in umbilical cord blood, and to verify the influence of Cxcr3 on SPTB-associating cytokines in mice. We detected an association between an intronic CXCR3 polymorphism, rs2280964, and SPTB in infants from families with recurrent preterm births (p = 0.009 versus term controls, odds ratio 0.52, 95% confidence interval 0.32-0.86). The minor allele was protective and undertransmitted to SPTB infants (p = 0.007). In the placenta and fetal membranes, the rs2280964 major allele homozygotes had higher expression levels than minor allele homozygotes; decidual trophoblasts showed strong CXCR3 immunoreactivity. Expression was higher in SPTB placentas compared with those from elective deliveries. Concentration of a CXCR3 ligand, CXCL9, was increased in cord blood from SPTB, and the protective rs2280964 allele was associated with low CXCL9. In CXCR3-deficient mice (Mus musculus), SPTB-associating cytokines were not acutely increased in amniotic fluid after preterm birth-inducing dose of maternal LPS. Our results indicate that CXCR3 contributes to SPTB. Activation of CXCR3 signaling may disturb the maternal-fetal tolerance, and this may promote labor.

White's classification and pregnancy outcome in women with type 1 diabetes: a population-based cohort study.

AIMS/HYPOTHESIS: Our aim was to examine the association of White's classification with obstetric and perinatal risk factors and outcomes in type 1 diabetic patients. METHODS: Obstetric records of a population-based cohort of 1,094 consecutive type 1 diabetic patients with a singleton childbirth during 1988-2011 were studied. The most recent childbirth of each woman was included. RESULTS: The prepregnancy and the first trimester HbA1c increased from White's class B to F (p for trend <0.001). Systolic and diastolic blood pressure and pre-eclampsia frequencies increased stepwise from class B to F (p for trends <0.001). Vaginal deliveries decreased and Caesarean sections and deliveries before 37 weeks increased from class B to F (p for trends <0.001). Fetal macrosomia (p for trend=0.003) decreased and small-for-gestational age infants (p for trend=0.002) and neonatal intensive care unit admissions (p for trend=0.001) increased from class B to F. In logistic regression analysis, White's classes were associated with pre-eclampsia but, with the exception of class R (proliferative retinopathy) and F (nephropathy), not with other adverse outcomes when adjusted for first trimester HbA1c ≥7% (≥53 mmol/mol) and blood pressure ≥140/90 mmHg. First trimester HbA1c ≥7% was associated with pre-eclampsia, preterm delivery, fetal macrosomia and neonatal intensive care unit admission. CONCLUSIONS/INTERPRETATION: White's classification is useful in estimating the risk of pre-eclampsia in early pregnancy independently of suboptimal glycaemic control and hypertension. However, its utility in predicting adverse perinatal outcomes seems limited when information on first trimester HbA1c, blood pressure and diabetic microvascular complications is available.

Obstetric and perinatal outcome in type 1 diabetes patients with diabetic nephropathy during 1988-2011.

AIMS/HYPOTHESIS: Our aim was to analyse possible changes in the glycaemic control, BP, markers of renal function, and obstetric and perinatal outcomes of parturients with diabetic nephropathy during 1988-2011. METHODS: The most recent childbirth of 108 consecutive type 1 diabetes patients with diabetic nephropathy and a singleton pregnancy were studied. Two periods, 1988-1999 and 2000-2011, were compared. RESULTS: The prepregnancy and the first trimester median HbA1c values persisted at high levels (8.2% [66 mmol/mol] vs 8.5% [69 mmol/mol], p = 0.16 and 8.3% [67 mmol/mol] vs 8.4% [68 mmol/mol], p = 0.67, respectively), but decreased by mid-pregnancy (6.7% [50 mmol/mol] vs 6.9% [52 mmol/mol], p = 0.11). Antihypertensive medication usage increased before pregnancy (34% vs 65%, p = 0.002) and in the second and third trimesters of pregnancy (25% vs 47%, p = 0.02, and 36% vs 60%, p = 0.01, respectively). BP exceeded 130/80 mmHg in 62% and 61% (p = 0.87) of patients in the first trimester, and in 95% and 93% (p = 0.69) in the third trimester, respectively. No changes were observed in the markers of renal function. Pre-eclampsia (52% vs 42%, p = 0.29) and preterm birth rates before 32 and 37 gestational weeks (14% vs 21%, p = 0.33, and 71% vs 77%, p = 0.49, respectively) remained high. The elective and emergency Caesarean section rates were 71% and 45% (p = 0.01) and 29% and 48% (p = 0.05), respectively. Neonatal intensive care unit admissions increased from 26% to 49% (p = 0.02). CONCLUSIONS/INTERPRETATION: Early pregnancy glycaemic control and hypertension management were suboptimal in both time periods. Pre-eclampsia and preterm delivery rates remained high in patients with diabetic nephropathy.

Assessing the Causal Relationship of Maternal Height on Birth Size and Gestational Age at Birth: A Mendelian Randomization Analysis.

BACKGROUND: Observational epidemiological studies indicate that maternal height is associated with gestational age at birth and fetal growth measures (i.e., shorter mothers deliver infants at earlier gestational ages with lower birth weight and birth length). Different mechanisms have been postulated to explain these associations. This study aimed to investigate the casual relationships behind the strong association of maternal height with fetal growth measures (i.e., birth length and birth weight) and gestational age by a Mendelian randomization approach. METHODS AND FINDINGS: We conducted a Mendelian randomization analysis using phenotype and genome-wide single nucleotide polymorphism (SNP) data of 3,485 mother/infant pairs from birth cohorts collected from three Nordic countries (Finland, Denmark, and Norway). We constructed a genetic score based on 697 SNPs known to be associated with adult height to index maternal height. To avoid confounding due to genetic sharing between mother and infant, we inferred parental transmission of the height-associated SNPs and utilized the haplotype genetic score derived from nontransmitted alleles as a valid genetic instrument for maternal height. In observational analysis, maternal height was significantly associated with birth length (p = 6.31 × 10-9), birth weight (p = 2.19 × 10-15), and gestational age (p = 1.51 × 10-7). Our parental-specific haplotype score association analysis revealed that birth length and birth weight were significantly associated with the maternal transmitted haplotype score as well as the paternal transmitted haplotype score. Their association with the maternal nontransmitted haplotype score was far less significant, indicating a major fetal genetic influence on these fetal growth measures. In contrast, gestational age was significantly associated with the nontransmitted haplotype score (p = 0.0424) and demonstrated a significant (p = 0.0234) causal effect of every 1 cm increase in maternal height resulting in ~0.4 more gestational d. Limitations of this study include potential influences in causal inference by biological pleiotropy, assortative mating, and the nonrandom sampling of study subjects. CONCLUSIONS: Our results demonstrate that the observed association between maternal height and fetal growth measures (i.e., birth length and birth weight) is mainly defined by fetal genetics. In contrast, the association between maternal height and gestational age is more likely to be causal. In addition, our approach that utilizes the genetic score derived from the nontransmitted maternal haplotype as a genetic instrument is a novel extension to the Mendelian randomization methodology in casual inference between parental phenotype (or exposure) and outcomes in offspring.

Amniotic fluid erythropoietin and neonatal outcome in pregnancies complicated by intrauterine growth restriction before 34 gestational weeks.

OBJECTIVE: High amniotic fluid erythropoietin concentration reflects chronic fetal hypoxia. Our aim was to study amniotic fluid erythropoietin concentration in relation to neonatal outcome in pregnancies complicated by intrauterine growth restriction. DESIGN: Retrospective case series. SETTING: Helsinki University Hospital, Finland. SAMPLE: A total of 66 singleton pregnancies complicated by intrauterine growth restriction. METHODS: Amniocentesis or amniotic fluid sampling at cesarean section was performed between 24 and 34 gestational weeks. Values of amniotic fluid erythropoietin were quantitated with immunochemiluminometric assay. Normal amniotic fluid erythropoietin was defined as <3 IU/L, intermediate as 3-27 IU/L, and abnormal as >27 IU/L. MAIN OUTCOME MEASURES: Adverse neonatal outcome. RESULTS: Abnormal biophysical profile and reversed end-diastolic flow in umbilical artery were associated with abnormal amniotic fluid erythropoietin (p < 0.001 and p = 0.042, respectively). Abnormal amniotic fluid erythropoietin was not associated with absent end-diastolic flow in umbilical artery or with oligohydramnios (p = 0.404 and p = 0.080, respectively). Decreased umbilical artery pH and base excess values were associated with abnormal amniotic fluid erythropoietin (p = 0.027 and p = 0.007, respectively). Composite adverse neonatal outcome defined as intraventricular hemorrhage, periventricular leukomalacia, cerebral infarction and/or necrotizing enterocolitis was associated with abnormal amniotic fluid erythropoietin (p < 0.001). CONCLUSIONS: High amniotic fluid erythropoietin concentrations are associated with decreased umbilical artery pH and base excess and with adverse neonatal outcome in pregnancies complicated by intrauterine growth restriction before 34 gestational weeks. In selected pregnancies complicated by intrauterine growth restriction, determining amniotic fluid erythropoietin could be a useful additional tool in fetal surveillance and possibly in optimizing timing of delivery.

Mapping a new spontaneous preterm birth susceptibility gene, IGF1R, using linkage, haplotype sharing, and association analysis.

Preterm birth is the major cause of neonatal death and serious morbidity. Most preterm births are due to spontaneous onset of labor without a known cause or effective prevention. Both maternal and fetal genomes influence the predisposition to spontaneous preterm birth (SPTB), but the susceptibility loci remain to be defined. We utilized a combination of unique population structures, family-based linkage analysis, and subsequent case-control association to identify a susceptibility haplotype for SPTB. Clinically well-characterized SPTB families from northern Finland, a subisolate founded by a relatively small founder population that has subsequently experienced a number of bottlenecks, were selected for the initial discovery sample. Genome-wide linkage analysis using a high-density single-nucleotide polymorphism (SNP) array in seven large northern Finnish non-consanginous families identified a locus on 15q26.3 (HLOD 4.68). This region contains the IGF1R gene, which encodes the type 1 insulin-like growth factor receptor IGF-1R. Haplotype segregation analysis revealed that a 55 kb 12-SNP core segment within the IGF1R gene was shared identical-by-state (IBS) in five families. A follow-up case-control study in an independent sample representing the more general Finnish population showed an association of a 6-SNP IGF1R haplotype with SPTB in the fetuses, providing further evidence for IGF1R as a SPTB predisposition gene (frequency in cases versus controls 0.11 versus 0.05, P = 0.001, odds ratio 2.3). This study demonstrates the identification of a predisposing, low-frequency haplotype in a multifactorial trait using a well-characterized population and a combination of family and case-control designs. Our findings support the identification of the novel susceptibility gene IGF1R for predisposition by the fetal genome to being born preterm.

An evolutionary genomic approach to identify genes involved in human birth timing.

Coordination of fetal maturation with birth timing is essential for mammalian reproduction. In humans, preterm birth is a disorder of profound global health significance. The signals initiating parturition in humans have remained elusive, due to divergence in physiological mechanisms between humans and model organisms typically studied. Because of relatively large human head size and narrow birth canal cross-sectional area compared to other primates, we hypothesized that genes involved in parturition would display accelerated evolution along the human and/or higher primate phylogenetic lineages to decrease the length of gestation and promote delivery of a smaller fetus that transits the birth canal more readily. Further, we tested whether current variation in such accelerated genes contributes to preterm birth risk. Evidence from allometric scaling of gestational age suggests human gestation has been shortened relative to other primates. Consistent with our hypothesis, many genes involved in reproduction show human acceleration in their coding or adjacent noncoding regions. We screened >8,400 SNPs in 150 human accelerated genes in 165 Finnish preterm and 163 control mothers for association with preterm birth. In this cohort, the most significant association was in FSHR, and 8 of the 10 most significant SNPs were in this gene. Further evidence for association of a linkage disequilibrium block of SNPs in FSHR, rs11686474, rs11680730, rs12473870, and rs1247381 was found in African Americans. By considering human acceleration, we identified a novel gene that may be associated with preterm birth, FSHR. We anticipate other human accelerated genes will similarly be associated with preterm birth risk and elucidate essential pathways for human parturition.

Maternal coding variants in complement receptor 1 and spontaneous idiopathic preterm birth.

Preterm birth (PTB) is a major global public health concern. However, little is known about the pathophysiology of spontaneous idiopathic PTB. We tested the hypothesis that rare variants in families would target specific genes and pathways that contribute to PTB risk in the general population. Whole-exome sequencing was performed on 10 PTB mothers from densely affected families including two mother-daughter pairs. We identified novel variants shared between the two mother-daughter pairs when compared to a 1000 Genomes Project background exome file and investigated these genes for pathway aggregation using the Kyoto Encyclopedia of Genes and Genomes (KEGG). Genes in enriched pathways were then surveyed in the other six PTB exomes and tested for association in a larger number of nuclear families. The KEGG complement and coagulation cascade was one of the most enriched pathways in our two mother-daughter pairs. When the six genes found in this pathway (CFH, CR1, F13B, F5, CR2, and C4BPA) were examined for novel missense variants, half of all the exomes harbored at least one. Association analysis of variants in these six gene regions in nuclear families from Finland (237 cases and 328 controls) found statistically significant associations after multiple test corrections in three CR1 SNPs; the strongest in an exonic missense SNP, rs6691117, p value = 6.91e-5, OR = 1.71. Our results demonstrate the importance of the complement and coagulation cascades in the pathophysiology of PTB, and suggest potential screening and intervention approaches to prevent prematurity that target this pathway.

Investigation of genetic risk factors for chronic adult diseases for association with preterm birth.

Preterm birth (PTB) is the leading cause of infant mortality. PTB pathophysiology overlaps with those of adult cardiovascular, immune and metabolic disorders (CIMD), with mechanisms including inflammation, immunotolerance, thrombosis, and nutrient metabolism. Whereas many genetic factors for CIMD have been identified, progress in PTB has lagged. We hypothesized that highly validated genetic risk factors for CIMD may also be associated with PTB. We conducted case-control study of four female cohorts with spontaneous PTB (n = 673) versus term (n = 1119). Of 35 SNPs genotyped, there were 13 statistically significant associations (P < 0.05), which were more than expected (binomial test; P = 0.02). In US White (307 cases/342 controls), the G allele of HLA-DQA1 (A/G) rs9272346 was protective for PTB in the initial discovery cohort (P = 0.02; OR = 0.65; 95 % CI 0.46, 0.94). This protective association replicated (P = 0.02; OR = 0.85; 95 % CI 0.75, 0.97) nominally in the Danish Cohort (883 cases, 959 controls), but lost significance upon multiple testing correction. We observed more statistically significant associations than expected, suggesting that chance is an unlikely explanation for one or more of the associations. Particularly, a protective association of the G allele of HLA-DQA1 was found in two independent cohorts, and in previous studies, this same allele was found to protect against type-1-diabetes (meta-analysis P value 5.52 × 10(-219)). Previous investigations have implicated HLA phenotypic variation in recurrent fetal loss and in chronic chorioamnionitis. Given the limited sample size in his study, we suggest larger studies to further investigate possible HLA genetic involvement in PTB.

Dietary intervention in infancy and later signs of beta-cell autoimmunity.

BACKGROUND: Early exposure to complex dietary proteins may increase the risk of beta-cell autoimmunity and type 1 diabetes in children with genetic susceptibility. We tested the hypothesis that supplementing breast milk with highly hydrolyzed milk formula would decrease the cumulative incidence of diabetes-associated autoantibodies in such children. METHODS: In this double-blind, randomized trial, we assigned 230 infants with HLA-conferred susceptibility to type 1 diabetes and at least one family member with type 1 diabetes to receive either a casein hydrolysate formula or a conventional, cow's-milk-based formula (control) whenever breast milk was not available during the first 6 to 8 months of life. Autoantibodies to insulin, glutamic acid decarboxylase (GAD), the insulinoma-associated 2 molecule (IA-2), and zinc transporter 8 were analyzed with the use of radiobinding assays, and islet-cell antibodies were analyzed with the use of immunofluorescence, during a median observation period of 10 years (mean, 7.5). The children were monitored for incident type 1 diabetes until they were 10 years of age. RESULTS: The unadjusted hazard ratio for positivity for one or more autoantibodies in the casein hydrolysate group, as compared with the control group, was 0.54 (95% confidence interval [CI], 0.29 to 0.95), and the hazard ratio adjusted for an observed difference in the duration of exposure to the study formula was 0.51 (95% CI, 0.28 to 0.91). The unadjusted hazard ratio for positivity for two or more autoantibodies was 0.52 (95% CI, 0.21 to 1.17), and the adjusted hazard ratio was 0.47 (95% CI, 0.19 to 1.07). The rate of reported adverse events was similar in the two groups. CONCLUSIONS: Dietary intervention during infancy appears to have a long-lasting effect on markers of beta-cell autoimmunity--markers that may reflect an autoimmune process leading to type 1 diabetes. (ClinicalTrials.gov number, NCT00570102.).

Sequence variants in oxytocin pathway genes and preterm birth: a candidate gene association study.

BACKGROUND: Preterm birth (PTB) is a complex disorder associated with significant neonatal mortality and morbidity and long-term adverse health consequences. Multiple lines of evidence suggest that genetic factors play an important role in its etiology. This study was designed to identify genetic variation associated with PTB in oxytocin pathway genes whose role in parturition is well known. METHODS: To identify common genetic variants predisposing to PTB, we genotyped 16 single nucleotide polymorphisms (SNPs) in the oxytocin (OXT), oxytocin receptor (OXTR), and leucyl/cystinyl aminopeptidase (LNPEP) genes in 651 case infants from the U.S. and one or both of their parents. In addition, we examined the role of rare genetic variation in susceptibility to PTB by conducting direct sequence analysis of OXTR in 1394 cases and 1112 controls from the U.S., Argentina, Denmark, and Finland. This study was further extended to maternal triads (maternal grandparents-mother of a case infant, N=309). We also performed in vitro analysis of selected rare OXTR missense variants to evaluate their functional importance. RESULTS: Maternal genetic effect analysis of the SNP genotype data revealed four SNPs in LNPEP that show significant association with prematurity. In our case-control sequence analysis, we detected fourteen coding variants in exon 3 of OXTR, all but four of which were found in cases only. Of the fourteen variants, three were previously unreported novel rare variants. When the sequence data from the maternal triads were analyzed using the transmission disequilibrium test, two common missense SNPs (rs4686302 and rs237902) in OXTR showed suggestive association for three gestational age subgroups. In vitro functional assays showed a significant difference in ligand binding between wild-type and two mutant receptors. CONCLUSIONS: Our study suggests an association between maternal common polymorphisms in LNPEP and susceptibility to PTB. Maternal OXTR missense SNPs rs4686302 and rs237902 may have gestational age-dependent effects on prematurity. Most of the OXTR rare variants identified do not appear to significantly contribute to the risk of PTB, but those shown to affect receptor function in our in vitro study warrant further investigation. Future studies with larger sample sizes are needed to confirm the findings of this study.