Nataša Tul

Cross-Country Individual Participant Analysis of 4.1 Million Singleton Births in 5 Countries with Very High Human Development Index Confirms Known Associations but Provides No Biologic Explanation for 2/3 of All Preterm Births.

Background Preterm birth is the most common single cause of perinatal and infant mortality, affecting 15 million infants worldwide each year with global rates increasing. Understanding of risk factors remains poor, and preventive interventions have only limited benefit. Large differences exist in preterm birth rates across high income countries. We hypothesized that understanding the basis for these wide variations could lead to interventions that reduce preterm birth incidence in countries with high rates. We thus sought to assess the contributions of known risk factors for both spontaneous and provider-initiated preterm birth in selected high income countries, estimating also the potential impact of successful interventions due to advances in research, policy and public health, or clinical practice. Methods We analyzed individual patient-level data on 4.1 million singleton pregnancies from four countries with very high human development index (Czech Republic, New Zealand, Slovenia, Sweden) and one comparator U.S. state (California) to determine the specific contribution (adjusting for confounding effects) of 21 factors. Both individual and population-attributable preterm birth risks were determined, as were contributors to cross-country differences. We also assessed the ability to predict preterm birth given various sets of known risk factors. Findings Previous preterm birth and preeclampsia were the strongest individual risk factors of preterm birth in all datasets, with odds ratios of 4.6–6.0 and 2.8–5.7, respectively, for individual women having those characteristics. In contrast, on a population basis, nulliparity and male sex were the two risk factors with the highest impact on preterm birth rates, accounting for 25–50% and 11–16% of excess population attributable risk, respectively (p<0.001). The importance of nulliparity and male sex on population attributable risk was driven by high prevalence despite low odds ratios for individual women. More than 65% of the total aggregated risk of preterm birth within each country lacks a plausible biologic explanation, and 63% of difference between countries cannot be explained with known factors; thus, research is necessary to elucidate the underlying mechanisms of preterm birth and, hence, therapeutic intervention. Surprisingly, variation in prevalence of known risk factors accounted for less than 35% of the difference in preterm birth rates between countries. Known risk factors had an area under the curve of less than 0.7 in ROC analysis of preterm birth prediction within countries. These data suggest that other influences, as yet unidentified, are involved in preterm birth. Further research into biological mechanisms is warranted. Conclusions We have quantified the causes of variation in preterm birth rates among countries with very high human development index. The paucity of explicit and currently identified factors amenable to intervention illustrates the limited impact of changes possible through current clinical practice and policy interventions. Our research highlights the urgent need for research into underlying biological causes of preterm birth, which alone are likely to lead to innovative and efficacious interventions.

Risk factors for preeclampsia in twin pregnancies: a population-based matched case-control study.

Abstract Objective: To evaluate associated factors for preeclampsia in twin gestations and to compare incidences of pregnancy complications among twin pregnancies with vs. without preeclampsia. Patients and methods: We performed a case-control study using a population dataset of twin pregnancies delivered after 24 weeks of gestation, in Slovenia, between 1997 and 2009. Cases were twin gestations complicated by preeclampsia and controls were cases matched by gestational age, parity, and chorionicity. Results: We identified 181 cases (4.7%) of preeclampsia among 3885 twins and 542 matched controls. High pre-pregnancy body mass index (BMI) and gestational diabetes were significantly associated with preeclampsia [odds ratio (OR) 1.8, 95% CI 1.26, 2.77 for overweight (BMI 25.0–29.9); OR 4.72, 95% CI 2.83, 7.89 for obese (BMI≥30), and OR 2.19, 95% CI 1.03, 4.68 for gestational diabetes]. The association was not significant for preexisting hypertension, maternal age, smoking, and pregnancy following assisted reproduction. Placental complications (previa, abruption, or adherent placenta) were more common, and low birth weight less common in the preeclampsia group (P=0.03 and P=0.01, respectively). Conclusions: High pre-pregnancy BMI carries an especially high risk for the development of preeclampsia and its complications in twin gestation.

Impact of pre-gravid body mass index and body mass index change on preeclampsia and gestational diabetes in singleton and twin pregnancies

Abstract Objective: To examine pre-gravid body mass index (BMI) and gestational BMI change impact on preeclampsia and gestational diabetes mellitus (GDM). Methods: Retrospective population-based cohort study. Data from Slovenian National Perinatal Information System were analyzed for the period 2002–2011. Three singleton controls were matched by parity and maternal age to each twin pregnancy delivered at >36 weeks. Student’s t test was used to compare pre-gravid BMI and gestational BMI change in different groups (p < 0.05 significant). Results: 2046 twin and 6138 singleton pregnancies were included. Twin and singleton patients with preeclampsia or GDM had higher pre-gravid BMI (p < 0.001). Gestational BMI change was smaller in twins with GDM (p < 0.001), and not associated with preeclampsia (p = 0.07). Smaller gestational BMI change in singleton pregnancies was associated with GDM (p < 0.001), and greater BMI change with preeclampsia (p = 0.004). Conclusions: Pre-gravid BMI is more strongly associated with preeclampsia and GDM in twin and singleton pregnancies than gestational BMI change. Smaller gestational BMI change in GDM pregnancies reflect the importance of dietary counseling.

Changes in incidence of iatrogenic and spontaneous preterm births over time: a population-based study

Abstract Objective: To examine the proportion of iatrogenic births among all preterm births over a 26-year period. Patients and methods: A registry-based survey of preterm deliveries between 1987 and 2012 analyzed by the onset of labor: spontaneous with intact membranes, preterm premature rupture of membranes (PPROM) or iatrogenic. Stratification into categories by gestation (22 weeks to 27 weeks and 6 days, 28 weeks to 31 weeks and 6 days, 32 weeks to 33 weeks and 6 days, 34 weeks to 36 weeks and 6 days) was performed. Preterm birth rates were analyzed using the Mantel-Haenszel linear-by-linear association χ2-test (P<0.05 significant). Logistic regression was used to account for potential confounders. Results: Overall preterm birth rate was 5.9% (31328 deliveries) including 2358 (0.4%) before 28 completed weeks, 3388 (0.6%) between 28 weeks and 31 weeks 6 days, 3970 (0.8%) between 32 weeks and 33 weeks and 6 days, and 21611 (4.1%) between 34 weeks and 36 weeks and 6 days There was an increase in overall preterm birth rate (P<0.001). The rate of iatrogenic preterm births and PPROM increased over time (P<0.001 and P<0.014, respectively). Rates of spontaneous preterm birth decreased (P<0.001). After accounting for potential confounders, year of birth remained an independent risk factor for iatrogenic preterm delivery in all four gestational age categories (P<0.001). Conclusion: The incidence of iatrogenic preterm birth is increasing with a concomitant decrease in the incidence of spontaneous preterm birth. Attempts to analyze, interpret and decrease preterm birth rates should consider spontaneous and iatrogenic preterm births separately.

Maternal obesity in singleton versus twin gestations: a population-based matched case–control study

Abstract Objective: To examine the impact of pre-pregnancy obesity on adverse outcomes in twin compared to singleton pregnancies. Methods: Dichorionic twin gestations with maternal body mass index >30 were matched to three singleton controls. Both obese groups were matched (1:3) with non-obese controls. Rates of preeclampsia, gestational diabetes, cesarean section, and preterm birth were compared. Results: One hunder eighty-nine dichorionic twin pregnancies in obese mothers were matched to 567 twin pregnancies in non-obese mothers, and to 567 singleton pregnancies in obese mothers. The latter were matched to 1701 non-obese mothers with singletons. Preeclampsia was more common in obese mothers with both twins and singletons (odds ratio (OR) 3.95, 95% confidence interval (CI) 2.18–7.16 and OR 6.53, 95% CI 3.75–11.4, respectively) as was gestational diabetes (OR 4.35, 95% CI 2.18–8.69; OR 5.53 95% CI 3.60–8.50). Obese mothers with singletons were more likely to deliver abdominally, but the cesarean rates were obesity independent in twins. Obese mothers were more likely to deliver at < 34 weeks in both twin and singleton groups (OR 1.65, 95% CI 1.10–2.48, and OR 2.41, 95% CI 1.21–4.77, respectively). Conclusion: Obesity-attributable adverse outcomes are lower in twins compared to singletons. Obesity increases the risk of preterm birth regardless of plurality.

No “masculinization” effect of a male on birth weight of its female co-twin

Abstract Objective: To test the hypothesis that the presence of a male affects birth weight of its female co-twin. Patients and methods: We evaluated a large population dataset of bichorionic twins after exclusion of potential confounders and after controlling for parity and gestational age. We tested the hypotheses that males (M) are heavier than females (F) irrespective of gender mix, parity and gestational age, and the hypothesis that birth weight of twins might be influenced by the gender of the co-twin. Results : There were 819 MM pairs, 777 FF pairs and 1097 MF sets, for a total of 2735 males and 2651 female twins. Male twins were heavier than female twins, irrespective of parity or gestational age; twins born to multiparas were heavier than twins born to nulliparas, except for very preterm births (≤32 weeks); males from MF pairs were heavier than males from MM pairs, but the mean birth weight of females from MF was not different from that of females from FF sets suggesting no “masculinization” effect of the male on birth weight of its female co-twin, irrespective of parity and gestational age. Conclusions: After exclusion of potential confounders and controlling for chorionicity, parity, and gestational age, our data do not support the presence of a “masculinization” effect on birth weight.

Lung and cardiac ultrasound for hemodynamic monitoring of patients with severe pre-eclampsia

To evaluate lung and cardiac ultrasound for the assessment of fluid tolerance and fluid responsiveness before and after delivery in pregnant women with severe pre‐eclampsia (PE).

Simpson–Golabi–Behmel syndrome: a prenatal diagnosis in a foetus with GPC3 and GPC4 gene microduplications

To the Editor: Mutations and genomic rearrangements involving the GPC3 gene lead to an X-linked overgrowth syndrome called Simpson–Golabi–Behmel type I (SGBS1) (1). One case of a GPC4 duplication linked to SGBS1 has been reported in the literature (2); however, no point mutations or deletions have been described so far. We present a male foetus and his mother with two microduplications involving the GPC3 and GPC4 genes. The foetus presented with a full-blown SGBS1 with severe brain malformations, whereas the mother was diagnosed with the Wilms’ tumour as a toddler. To our knowledge, this is the first report of a SGBS1 carrier with Wilms’ tumour. Our patient was a 28 year old primigravida, who had undergone a unilateral nephrectomy at 18 months of age because of the Wilms’ tumour, had no other medical problems and was of normal stature and intelligence. In her pregnancy, the second trimester scan detected foetal overgrowth, polyhydramnios, an enlarged placenta and an abnormal development of the central nervous system. At 24 weeks 6 days gestation, she gave birth to a boy weighing 1235 g with the head circumference of 27 cm (>99th percentile) who died a few minutes later. A foetal examination showed macrosomy, hypertelorism, short nose, broad nasal bridge, macrostomia, macroglossia (Fig. 1c), and 13 ribs on the left side (Fig. 1d). Hepatomegaly, nephromegaly, thymic hyperplasia, ventricular septal defect (VSD), complete agenesis of the corpus callosum, cerebellar hypoplasia, dilatation of lateral ventricles, and histological abnormalities of renal tissue were noted at autopsy. Molecular karyotyping of the amniotic fluid revealed a male karyotype with two maternally inherited interstitial microduplications at Xq26.2. Larger microduplication encompasses four genes: HS6ST2, USP26, TFDP3, and GPC4. Smaller microduplication is located within the GPC3 gene and contains exons 6 and 7 of its longest transcript (Fig. 1a). Both duplications were confirmed by the multiplex ligation-dependent probe amplification (Fig. 1b). The mother had a skewed chromosome X inactivation pattern (retaining approximately 12% of non-shared human androgen receptor (HUMARA) gene allele) (Fig. 1b). HS6ST2 and TFDP3 have been associated with various tumours in the literature, but never with the Wilms’ tumour. At present, there is also no indication that rearrangements of USP26 and TFDP3 cause brain malformations. HS6ST2 is expressed in the brain and believed to play a role in embryonic development. 3-O-sulphated heparan sulphates produced by a similar sulfotransferase, HS3ST2, have been reported to act as molecular chaperones allowing the abnormal phosphorylation of tau in Alzheimer’s disease (3). Considering that the structure of this gene is disrupted by the larger duplication in our case, its potential pathological effect on brain development cannot be ruled out. Glypicans are involved in signalling pathways associated with cell division and growth regulation (1). The loss of functional GPC3 probably leads to hyperactivation of Hedgehog signalling which could explain overgrowth and increased tumour risk seen in SGBS1 (4). GPC4 gene presumably has a similar biological role to GPC3 (2). Mapping of GPC3 and GPC4 showed that these two genes are tandemly arrayed. Because SGBS1 patients have variable clinical features, it was proposed that GPC3-GPC4 gene cluster might be reciprocally expressed, whereby loss of GPC3 function leads to loss of GPC4 function, which could, in turn, lead to a more severe clinical presentation in some SGBS1 patients. Thus, screening for mutations in both genes was proposed in SGBS patients, especially in cases where no mutations in GPC3 gene were detected (5). In silico prediction showed that duplication of exons 6 and 7 of the GPC3 gene disrupts its transcription and causes loss of functional protein, thereby causing the SGBS1 phenotype in the foetus. However, it does not fully explain the mother’s Wilms’ tumour, which has never been reported in GPC3 mutation carriers and the brain malformations in the foetus, which are rare in this syndrome (6, 7). Considering the close association of GPC4 with GPC3, it remains possible that the duplication of GPC4 contributed to the development of these two features. Even if GPC4 is not important in SGBS1 pathogenesis, the larger duplication could further disrupt the expression of GPC3 as it flanks its 3′ end (5). Also, aberrant expression of the other three genes, encompassed by the larger duplication, could alter the phenotypic presentation in the foetus and its mother. Our findings also raise the important question whether carriers of SGBS1 are at an increased risk of certain malignancies. Further studies of tissue expression of GPC3, GPC4, and the other three genes involved are

Functional Polymorphisms of Matrix Metalloproteinases 1 and 9 Genes in Women with Spontaneous Preterm Birth

Objective. The aim of this study was to investigate the association of functional MMP-1-1607 1G/2G and MMP-9-1562 C/T gene polymorphisms with spontaneous preterm birth (SPTB; preterm birth with intact membranes) in European Caucasian women, as well as the contribution of these polymorphisms to different clinical features of women with SPTB. Methods and Patients. A case-control study was conducted in 113 women with SPTB and 119 women with term delivery (control group). Genotyping of MMP-1-1607 1G/2G and MMP-9-1562 C/T gene polymorphisms was performed using the combination of polymerase chain reaction and restriction fragment length polymorphism methods. Results. There were no statistically significant differences in the distribution of neither individual nor combinations of genotype and allele frequencies of MMP-1-1607 1G/2G and MMP-9-1562 C/T polymorphisms between women with SPTB and control women. Additionally, these polymorphisms do not contribute to any of the clinical characteristics of women with SPTB, including positive and negative family history of SPTB, gestational age at delivery, and maternal age at delivery, nor fetal birth weight. Conclusion. We did not find the evidence to support the association of MMP-1-1607 1G/2G and MMP-9-1562 C/T gene polymorphisms with SPTB in European Caucasian women.

P31.05: Incidence of Down syndrome in Slovenia in the last 15 years

Introduction: First trimester screening for aneuploidy has been proposed as a major improvement because of higher detection rates and an earlier gestational age at diagnosis. Objectives: To evaluate the possible influence of first trimester examination on the time of diagnosis in cases with trisomy 21 in a referral center. Methods: Retrospective database analysis of all cases with trisomy 21 over a 4-year period (2003–2006). The studied population consisted of patients referred for targeted ultrasound examinations at different weeks, including patients with suspected or externally diagnosed aneuploidies. Results: A total of 160 fetuses with trisomy 21 were identified. Of those, 40 (25%), 37 (23.1%), 37 (23.1%) and 46 (28.8%) were diagnosed < 13 + 6 weeks, at 15 to 18 weeks, 19 to 22 weeks and > 22 weeks, respectively. Maternal age in the first three groups was significantly higher than in the group with late referral (37.1 vs. 34.9 years). In the first trimester, 38% of cases were diagnosed after screening in our center and 62% were referred for suspicious findings or confirmed trisomy 21. Second trimester diagnosis was 21.6% and 13.6% after screening, compared to 78.4% and 86.4% referred for suspected or diagnosed trisomy 21 at 15 to 18 weeks and 19 to 22 weeks, respectively. All cases with late referral had ultrasound abnormalities. Conclusion: Despite an increasing proportion of first trimester examinations performed at centers and by local obstetricians, the vast majority of cases with trisomy 21 are still diagnosed in the second trimester. Cases in the high risk population are detected earlier, as these patients receive targeted ultrasound examination in the first and early second trimester.