Kristin Melheim Strand

Mediators of the association between pre-eclampsia and cerebral palsy: population based cohort study

Objective To test the hypothesis that pre-eclampsia is a risk factor for cerebral palsy mediated through preterm birth and being born small for gestational age. Design Population based cohort study. Setting Clinical data from the Norwegian Cerebral Palsy Registry were linked with perinatal data prospectively recorded by the Medical Birth Registry of Norway. Participants All singleton babies who survived the neonatal period during 1996-2006 (849 children with cerebral palsy and 616 658 control children). Main outcome measures Cerebral palsy and cerebral palsy subtypes. Results Children exposed to pre-eclampsia had an excess risk of cerebral palsy (unadjusted odds ratio 2.5, 95% confidence interval 2.0 to 3.2) compared with unexposed children. Among children born at term (≥37 weeks), exposure to pre-eclampsia was not associated with an excess risk of cerebral palsy in babies not born small for gestational age (1.2, 0.7 to 2.0), whereas children exposed to pre-eclampsia and born small for gestational age had a significantly increased risk of cerebral palsy (3.2, 1.5 to 6.7). Non-small for gestational age babies born very preterm (<32 weeks) and exposed to pre-eclampsia had a reduced risk of cerebral palsy compared with unexposed children born at the same gestational age (0.5, 0.3 to 0.8), although the risk was not statistically significantly reduced among children exposed to pre-eclampsia and born small for gestational age (0.7, 0.4 to 1.3). Exposure to pre-eclampsia was not associated with a specific cerebral palsy subtype. Conclusions Exposure to pre-eclampsia was associated with an increased risk of cerebral palsy, and this association was mediated through the children being born preterm or small for gestational age, or both. Among children born at term, pre-eclampsia was a risk factor for cerebral palsy only when the children were small for gestational age.

Changing patterns of cytomegalovirus seroprevalence among pregnant women in Norway between 1995 and 2009 examined in the Norwegian Mother and Child Cohort Study and two cohorts from Sør-Trøndelag County: a cross-sectional study

Objectives To examine cytomegalovirus (CMV) seroprevalence and associated risk factors for CMV seropositivity in pregnant Norwegian women. Design Cross-sectional study. Setting The Norwegian Mother and Child Cohort Study (MoBa) in addition to two random samples of pregnant women from Sør-Trøndelag County in Norway. Participants Study group 1 were 1000 pregnant women, randomly selected among 46 127 pregnancies in the MoBa (1999–2006) at 17/18 week of gestation. Non-ethnic Norwegian women were excluded. Study groups 2 (n=1013 from 1995) and 3 (n=979 from 2009) were pregnant women at 12 weeks of gestation from Sør-Trøndelag County. Outcome measures CMV seropositivity in blood samples from pregnant Norwegian women. Results CMV-IgG antibodies were detected in 59.9% and CMV-IgM antibodies in 1.3% of pregnant Norwegian women in study group 1. Women from North Norway demonstrated a higher CMV-IgG seroprevalence (72.1%) than women from South Norway (58.5%) (OR 1.83, 95% CI 1.17 to 2.88). The CMV-IgG seroprevalence was higher among women with low education (70.5%) compared to women with higher education (OR 2.20, 95% CI 1.24 to 3.90). Between 1995 and 2009 the CMV-IgG seroprevalence increased from 63.1% to 71.4% in pregnant women from Sør-Trøndelag County (study groups 2 and 3; p<0.001). The highest CMV-IgG seroprevalence (79.0%) was observed among the youngest pregnant women (<25 years) from Sør-Trøndelag County in 2009 (study group 3). Conclusions The CMV-IgG seroprevalence of pregnant Norwegian women varies with geographic location and educational level. Additionally, the CMV-IgG seroprevalence appears to have increased over the last years, particularly among young pregnant women.

Association of placental weight with cerebral palsy: population-based cohort study in Norway

To study the risk of cerebral palsy (CP) associated with placental weight, and also with placental weight/birthweight ratio and placental weight/birth length ratio.

Growth during infancy and early childhood in children with cerebral palsy: a population-based study

To describe growth in infancy and early childhood in children with cerebral palsy (CP).

Refined phenotyping identifies links between preeclampsia and related diseases in a Norwegian preeclampsia family cohort

Objective: Preeclampsia is a complex genetic disease of pregnancy with a heterogenous presentation, unknown cause and potential severe outcomes for both mother and child. Preeclamptic women have increased risk for atherothrombotic cardiovascular disease. We aimed to identify heritabilities and phenotypic correlations of preeclampsia and related conditions in the Norwegian Preeclampsia Family Biobank. Methods: By applying a variance components model, a total of 493 individuals (from 138 families with increased occurrence of preeclampsia) were classified according to 30 disease-related phenotypes. Results: Of parous women, 75.7% (263/338) had experienced preeclampsia and 35.7% of women with and 22.4% without preeclampsia delivered children small for gestational age (SGA). We identified 11 phenotypes as heritable. The increased occurrence of preeclampsia was reflected by the presence [heritability (H2r) = 0.60)] and severity (H2r = 0.15) of preeclampsia and being born in a preeclamptic pregnancy (H2r = 0.25). Other heritable phenotypes identified included SGA (H2r = 0.40), chronic hypertension (H2r = 0.57), severity of atherothrombotic cardiovascular disease (H2r = 0.31), BMI (H2r = 0.60) and pulmonary disease (H2r = 0.91). The heritable phenotype preeclampsia overlapped with SGA (P = 0.03), whereas pulmonary disease was phenotypically correlated with atherothrombotic cardiovascular disease (P < 0.01), SGA (P = 0.02) and BMI (P = 0.02). Conclusion: This is the first study identifying the H2r of a range of health-related conditions in preeclamptic families. Our study demonstrates how refinement of phenotypes leads to better H2r estimation and the identification of a biological relationship between preeclampsia and related traits.

Cytomegalovirus antibody status at 17–18 weeks of gestation and pre-eclampsia: a case–control study of pregnant women in Norway

Please cite this paper as: Strand K, Odland M, Iversen A, Nordbø S, Vik T, Austgulen R. Cytomegalovirus antibody status at 17–18 weeks of gestation and pre‐eclampsia: a case–control study of pregnant women in Norway. BJOG 2012;119:1316–1323.

Congenital anomalies and the severity of impairments for cerebral palsy

To study the prevalence of congenital anomalies among children with cerebral palsy (CP) born at term or late preterm, and if CP subtypes and clinical manifestations differ between children with and without congenital anomalies.

OP006. A preeclampsia genome-wide linkage scan in norwegian families

INTRODUCTION Several maternal susceptibility loci for preeclampsia (PE) have been discovered amongst Icelandic, Australian/New Zealand, Dutch and Finnish family cohorts, implicating locus heterogeneity. Through candidate gene studies, allele-specific heterogeneity in different populations is also evident. It is therefore likely that numerous population specific PE susceptibility variants exist, differing in their effect size. Despite on-going efforts to identify susceptibility genes for PE, the causal genetic variants still remain obscure. OBJECTIVES The aim of this study is to interrogate the genetic architecture of PE susceptibility by performing a genome-wide linkage scan in a novel familial cohort from Norway. METHODS A total of 480 DNA samples from The Norwegian PE Family Biobank were genotyped at Genomic Core Facility at NTNU. Genome-wide genotyping was performed with the Infinium HumanExome BeadChip (>240,000 markers) (Illumina, USA) that delivers focused coverage of exonic regions of the human genome. RESULTS A total of 137 families are represented with 222 women with a valid PE diagnosis (SBP⩾140mmHg DBP⩾90mmHg, ⩾2 measurements at least 4h apart with documented proteinuria at ⩾2 occasions occurring after 20weeks of pregnancy), 44 with self-reported PE and 72 women with a healthy pregnancy. The genotyping has just recently been completed with an average call rate of 99.96%. Data and statistical analysis is now underway using MERLIN, R and SOLAR. A description of the Norwegian PE familial cohort plus preliminary results will be presented at the Congress. CONCLUSION To our knowledge this is the first SNP-based genome-wide linkage study on PE, and the first performed in a novel Norwegian PE family cohort. By using an approach focusing on functionally relevant markers we anticipate the identification of susceptibility loci that are of substantial importance for disease development.

The Placenta in Neonatal Encephalopathy: A Case–Control Study

Objective We assessed whether specific histologic placental lesions were associated with risk for neonatal encephalopathy, a strong predictor of death or cerebral palsy. Study design Case–control study of singletons with gestational ages ≥35 weeks. Data were abstracted from a prospectively collected database of consecutive births at a hospital in which placental samples from specified sites are collected and stored for all inborn infants. Placentas of infants with neonatal encephalopathy were compared with randomly selected control infants (ratio of 1:3). Placental histologic slides were read by a single experienced perinatal pathologist unaware of case status, using internationally recommended definitions and terminology. Findings were grouped into inflammatory, maternal, or fetal vascular malperfusion (FVM) and other lesions. Results Placental samples were available for 73 of 87 (84%) cases and 253 of 261 (97%) controls. Delivery complications and gross placental abnormalities were more common in cases, of whom 4 died. Inflammation and maternal vascular malperfusion did not differ, and findings consistent with global FVM were more frequent in case (20%) than control (7%) placentas (P = .001). There was a trend toward more segmental FVM and high‐grade FVM (fetal thrombotic vasculopathy) among cases. Some type of FVM was observed in 24% of placentas with neonatal encephalopathy. In infants with both neonatal encephalopathy and placental FVM, more often than in infants with neonatal encephalopathy without FVM, electronic fetal monitoring tracings were considered possibly or definitely abnormal (P = .028). Conclusions Vascular malperfusion of subacute or chronic origin on the fetal side of the placenta was associated with increased risk of neonatal encephalopathy.