[The translation of genetic risk variants to molecular disease mechanisms]

BACKGROUND

Genetic studies have found large numbers of genetic risk variants that increase the risk to develop neuropsychiatric disorders.

AIM

We aim to explain how to investigate the effects of these genetic risk variants on the expression of genes and whether this plays a potential role in neuropsychiatric disorders.

METHOD

We describe the main findings of a study that we recently performed to study the association between genetic risk factors for neuropsychiatric disorders and gene expression in microglia, the immune cells of the brain.

RESULTS

Part of the risk variants for neuropsychiatric disorders could be related to gene expression in microglia. These <br />associations were particularly strong for neurodegenerative disorders.

CONCLUSION

Our study provided more insight into how genetic risk to neuropsychiatric disorders is related to gene expression in microglia. These findings show suggestions for potential new treatment options.

Impact of introduction of 20-week ultrasound scan on prevalence and fetal and neonatal outcomes in cases of selected severe congenital heart defects in The Netherlands

OBJECTIVES

To evaluate in a population-based cohort the effect of the introduction of the 20-week ultrasound scan in 2007 on the time of diagnosis, pregnancy outcome and total prevalence and liveborn prevalence of cases with selected congenital heart defects (CHDs) in The Netherlands.

METHODS

We included children and fetuses diagnosed with selected severe CHD, born in the 11-year period from 2001 to 2011. Two groups of CHD were defined: those associated with an abnormal four-chamber view at ultrasound (Group 1), and those associated with a normal four-chamber view at ultrasound (Group 2). The time of diagnosis, pregnancy outcome and total liveborn prevalence were compared for both groups over two 5-year periods, before and after the introduction of the 20-week ultrasound scan. Trends in total and liveborn prevalence were examined over 2001 to 2011.

RESULTS

Information was collected on 269 children and fetuses. After the introduction of the 20-week ultrasound scan, the prenatal detection rate of CHDs increased in both groups (Group 1, 34.6% in 2001-2005 vs 84.8% in 2007-2011 (P < 0.001); Group 2, 14.3% in 2001-2005 vs 29.6% in 2007-2011 (P = 0.037)). The rate of termination of pregnancy (TOP) increased significantly only for Group 1 (15.4% vs 51.5% (P < 0.001)). The total prevalence of CHD in Group 1 increased over time from 2.9 per 10 000 births in 2001 to 6.4 per 10 000 births in 2011 (P = 0.016). The liveborn prevalence did not show a trend over time. For Group 2, no trends in total or liveborn prevalence could be detected over time.

CONCLUSIONS

Since the implementation of the routine 20-week ultrasound scan in The Netherlands, prenatal detection rate of selected severe CHDs increased significantly. Improved prenatal detection was accompanied by a more than three-fold increase in TOP, although only in those CHDs with an abnormal four-chamber view at prenatal ultrasound.

First-trimester ultrasound

There has been an increase in the use of fetal ultrasound in the first trimester. This article reviews the published literature with emphasis on fetal nuchal translucency (NT). When measured according to well-defined guidelines, increased NT identifies about 80% of chromosomal anomalies for a false-positive rate of about 5%. Increased NT may indicate the presence of structural defects or genetic disorders, and it is relatively frequently seen in monochorionic pregnancies prone to develop twin-twin transfusion syndrome.

Fetal heart rate in chromosomally abnormal fetuses

OBJECTIVES

To determine the effects of chromosomal defects on fetal heart rate at 10-14 weeks of gestation.

METHODS

Fetal heart rate at 10-14 weeks of gestation in 1061 chromosomally abnormal fetuses was compared to that from 25,000 normal pregnancies. The chromosomally abnormal group included 554 cases of trisomy 21, 219 cases of trisomy 18, 95 of trisomy 13, 50 of triploidy, 115 of Turner syndrome and 28 of sex chromosome abnormalities other than Turner syndrome.

RESULTS

In the normal group, fetal heart rate decreased from a mean value of 170 beats per minute (bpm) at 35 mm of crown-rump length to 155 bpm at 84 mm crown-rump length. In trisomy 21, trisomy 13 and Turner syndrome fetal heart rate was significantly higher, in trisomy 18 and triploidy the heart rate was lower and in other sex chromosome defects it was not significantly different from normal. Fetal heart rate was above the 95th centile of the normal range in 10%, 67% and 52% of fetuses with trisomy 21, trisomy 13 and Turner syndrome, respectively. The fetal heart rate was below the 5th centile in 30% of fetuses with triploidy and 19% of those with trisomy 18.

CONCLUSIONS

Trisomy 21, trisomy 13 and Turner syndrome are associated with fetal tachycardia, whereas in trisomy 18 and triploidy there is fetal bradycardia. Inclusion of fetal heart rate in a first-trimester screening program for trisomy 21 by a combination of maternal age and fetal nuchal translucency thickness is unlikely to provide useful improvement in sensitivity.

Some psychometric properties of the Texas Grief Inventory adjusted for miscarriage

The psychometric properties of an adjusted version of the Texas Grief Inventory (Zisook, Devaul & Click, 1982) were evaluated in a sample of 207 women following an early pregnancy loss. Factor structure of the Inventory was examined, and the validity was assessed by comparing the level of grief in women who became pregnant following a miscarriage and those who did not. Factor analysis resulted in a three-factor solution that was theoretically interpretable. The identified subscales were: pure grief, grief-related emotions and perceived adjustment and functioning since miscarriage. Significantly lower levels of grief-related behaviours and feelings were reported in women who became pregnant, which was suggestive of the construct validity of the Inventory. The high reliability coefficient (Cronbach's alpha = .90) obtained with this 17-item version of the Grief Inventory suggests it to be a reliable instrument for the assessment of grief after early miscarriage.

A screening program for trisomy 21 at 10-14 weeks using fetal nuchal translucency, maternal serum free beta-human chorionic gonadotropin and pregnancy-associated plasma protein-A

OBJECTIVE

To examine the potential impact of combining maternal age with fetal nuchal translucency thickness and maternal serum free beta-human chorionic gonadotropin (beta-hCG) and pregnancy-associated plasma protein-A (PAPP-A) in screening for trisomy 21 at 10-14 weeks of gestation.

METHODS

Maternal serum free beta-hCG and PAPP-A were measured by Kryptor, a random access immunoassay analyzer using time-resolved amplified cryptate emission, in 210 singleton pregnancies with trisomy 21 and 946 chromosomally normal controls, matched for maternal age, gestation and sample storage time. In all cases the fetal crown-rump length and nuchal translucency thickness had been measured by ultrasonography at 10-14 weeks of gestation and maternal blood had been obtained at the time of the scan. The distributions (in multiples of the median; MoM) of free beta-hCG and PAPP-A (corrected for maternal weight) and fetal nuchal translucency (NT) were determined in the trisomy 21 group and the controls. Likelihood ratios for the various marker combinations were calculated and these were used together with the age-related risk for trisomy 21 in the first trimester to calculate the expected detection rate of affected pregnancies, at a fixed false-positive rate, in a population with the maternal age distribution of pregnancies in England and Wales.

RESULTS

In a population with the maternal age distribution of pregnancies in England and Wales, it was estimated that, using the combination of maternal age, fetal nuchal translucency thickness and maternal serum free beta-hCG and PAPP-A, the detection of trisomy 21 pregnancies would be 89% at a fixed false-positive rate of 5%. Alternatively, at a fixed detection rate of 70%, the false-positive rate would be 1%. The inclusion of biochemical parameters added an additional 16% to the detection rate obtained using NT and maternal age alone.

CONCLUSIONS

Rapid diagnostic technology like Kryptor, which can provide automated reproducible biochemical measurements within 30 min of obtaining a blood sample, will allow the development of interdisciplinary one-stop clinics for early fetal assessment. Such clinics will be able to deliver improved screening sensitivity, rapidly and more efficiently, leading to reduced patient anxiety and stress.

Using fetal nuchal translucency to screen for major congenital cardiac defects at 10-14 weeks of gestation: population based cohort study

OBJECTIVES

To examine the utility of measuring fetal nuchal translucency thickness in screening for major defects of the heart and great arteries at 10-14 weeks of gestation.

DESIGN

Population based cohort study.

SUBJECTS

29 154 singleton pregnancies with chromosomally normal fetuses at 10-14 weeks of gestation.

SETTING

Fetal medicine centre in London.

MAIN OUTCOME MEASURE

Prevalence of major defects of the heart and great arteries.

RESULTS

Of 50 cases with major defects of the heart and great arteries (prevalence 1.7 per 1000 pregnancies) 28 (56%, 95% confidence interval 42% to 70%) were in the subgroup of 1822 pregnancies with fetal nuchal translucency thicknesses above the 95th centile of the normal range. The positive and negative predictive values for this cut off point of nuchal translucency thickness were 1.5% and 99.9% respectively.

CONCLUSIONS

Measurement of fetal nuchal translucency thickness-traditionally used to identify fetuses at high risk of aneuploidy-at 10-14 weeks of gestation can identify a large proportion of fetuses with major defects of the heart and great arteries.

Lethal congenital arthrogryposis presents with increased nuchal translucency at 10-14 weeks of gestation

This study examines the ultrasonographic features of congenital lethal arthrogryposis. In 27 cases of arthrogryposis diagnosed in the second and third trimesters there was severe bilateral talipes, fixed flexion deformities of the wrists and elbows and either fixed flexion or extension of the knees. In seven (26%) of the cases there was nuchal edema. In two fetuses with arthrogryposis that were examined at 13 weeks of gestation the nuchal translucency thickness was above the 99th centile of the normal range for crown-rump length. In three other women with previously affected pregnancies, ultrasound examination at 10-14 weeks demonstrated normal fetal nuchal translucency thickness and none of these fetuses were subsequently found to have arthrogryposis. These findings suggest that lethal arthrogryposis, which is usually diagnosed by the demonstration of multiple joint contractures during the second or third trimester of pregnancy, may present as increased nuchal translucency thickness at 10-14 weeks of gestation.

Fetal testing in intra-uterine growth retardation

There are three major issues that remain subject to debate in relation to fetal growth retardation: (1) Which method should be used to identify the affected population? (2) Which biophysical test(s) is most appropriate to assess the pregnancy? (3) Which factors are important when considering elective delivery? This review summarizes recent studies investigating the efficacy and accuracy of tests used for the identification and surveillance of pregnancies at risk of growth retardation, and discusses the importance of gestational age in the decision for or against intervention.

Fetal venous, intracardiac, and arterial blood flow measurements in intrauterine growth retardation: relationship with fetal blood gases

OBJECTIVE

Our purpose was to investigate arterial, venous, and intracardiac blood flow in growth-retarded fetuses and to relate the Doppler results to blood gases in umbilical venous blood obtained by cordocentesis.

STUDY DESIGN

A cross-sectional, pulsed-wave color Doppler ultrasonographic study of 23 severely growth-retarded fetuses undergoing cordocentesis and measurement of blood gases was performed. Blood velocity waveforms were recorded from the descending thoracic aorta, middle cerebral artery, inferior vena cava, ductus venosus, and atrioventricular valves.

RESULTS

The Doppler studies demonstrated evidence of redistribution in the arterial system with increased impedance to flow in the aorta and decreased impedance in the cerebral circulation. The velocity of flow in the venous system and across the atrioventricular valves was decreased, whereas pulsatility of waveforms in the inferior vena cava and ductus venosus was increased. The mean umbilical venous blood PO2 and pH were decreased, and there were significant associations between blood gases and Doppler parameters in the thoracic aorta, middle cerebral artery, and ductus venosus.

CONCLUSION

In severe intrauterine growth retardation the degree of fetal acidemia can be estimated from Doppler measurements of pulsatility in both the arterial system and the ductus venosus.

Doppler studies of the fetal circulation in twin-twin transfusion syndrome

This cross-sectional study investigated the circulatory profile of the donor and recipient fetuses in 20 pregnancies with twin-twin transfusion syndrome presenting with acute polyhydramnios at 17-27 (mean, 22) weeks' gestation. Doppler investigations of the arterial vessels and ductus venosus, inferior vena cava, right hepatic vein, tricuspid and mitral ventricular inflow were performed in both fetuses. Mean values of most blood flow velocities on the venous side showed a significant decrease in both groups of fetuses, and a significant increase in mean values for indices describing waveform pulsatility was found in all three venous vessels in the group of recipients, whereas in the donor group this was only the case in the ductus venosus. Mean values of atrioventricular flow velocities showed a significant decrease in the donor group. The most significant findings on the arterial side were an increased mean umbilical artery pulsatility index and a decreased mean value for aortic blood flow velocity in both groups of fetuses. Five recipients and four donors had absence or reversal of blood flow during atrial contraction in the ductus venosus. All these fetuses showed pulsations in the umbilical vein. Tricuspid regurgitation was present in eight recipients. Absence or reversal of end-diastolic velocities in the umbilical artery was found in four donors.(ABSTRACT TRUNCATED AT 250 WORDS)

Fetal venous, arterial, and intracardiac blood flows in red blood cell isoimmunization

OBJECTIVE

To investigate the effect of anemia on fetal venous, arterial, and intracardiac blood flows.

METHODS

Color flow Doppler was used to record flow-velocity waveforms from the atrioventricular valves, ductus venosus, right hepatic vein, inferior vena cava, middle cerebral artery, and descending thoracic aorta from 38 cases of red blood cell isoimmunized pregnancies. Immediately after the Doppler studies, funipuncture was performed and the fetal hemoglobin concentration was measured.

RESULTS

Blood flow velocities in the thoracic aorta, middle cerebral artery, and the ductus venosus were increased compared to reference ranges established previously; however, a significant association with the degree of anemia was found only for the velocity in the thoracic aorta. Pulsatility indices in arteries and veins and the ratio of early to late atrioventricular inflow velocities were not significantly different from normal.

CONCLUSIONS

Fetal anemia is associated with a hyperdynamic circulation in both arterial and venous vessels. Even in severe anemia, there is no evidence of congestive heart failure. Venous and intracardiac Doppler studies do not provide a clinically useful contribution in the management of red blood cell isoimmunization.

Reference ranges for fetal venous and atrioventricular blood flow parameters

This cross-sectional study establishes reference ranges with gestation for Doppler parameters of fetal venous and atrioventricular blood flow. Color flow Doppler was used to examine 143 normal singleton pregnancies at 20-40 weeks' gestation. Flow velocity waveforms were recorded from the ductus venosus, right hepatic vein and inferior vena cava. The waveforms are triphasic, reflecting ventricular systole, early diastole and atrial contraction. Peak velocities for these parameters were measured with pulsed Doppler and a new index, the peak velocity index for veins (PVIV), was calculated. Similarly, time-averaged maximum velocities for the whole cardiac cycle were measured and the pulsatility index for veins (PIV) was calculated. Flow velocity waveforms were also recorded at the level of the atrioventricular valves and the ratios of peak velocities at early diastolic filling (E) and atrial contraction (A) were calculated. Regression analysis was used to define the association of each measured and calculated Doppler parameter with gestational age. Blood flow velocities in the fetal veins and velocities and E/A ratios across the atrioventricular valves increased significantly with gestation, whereas PVIV and PIV decreased. Blood flow velocities were highest in the ductus venosus and lowest in the right hepatic vein, and PVIV and PIV were highest in the hepatic vein and lowest in the ductus venosus. In the ductus venosus, there was always forward flow throughout the heart cycle, whereas in the inferior vena cava and hepatic vein during atrial contraction, flow was away from or towards the heart or there was no flow. Pulsatility of flow velocity waveforms in the venous system is the consequence of changes in pressure difference between the venous system and the heart during the heart cycle. The finding that PVIV and PIV decrease with gestation is consistent with decreasing cardiac afterload and maturation of diastolic ventricular function.

Comparison of chorionic villus sampling and amniocentesis for fetal karyotyping at 10-13 weeks' gestation

We did a prospective study of women with singleton viable pregnancies at 10-13 weeks' gestation who requested first-trimester fetal karyotyping because of advanced maternal age, parental anxiety, or family history of chromosomal abnormality. Women were counselled as to the available options of non-invasive screening or invasive testing by mid-trimester amniocentesis, early amniocentesis (EA), or chorionic villus sampling (CVS), or randomisation to EA or CVS at 10-13 weeks. EA was done in 731 patients (493 by choice and 238 by randomisation) and CVS in 570 (320 by choice and 250 by randomisation). Both procedures were done by transabdominal ultrasound-guided insertion of a 20-gauge needle. The rate of successful sampling was the same for both procedures (97.5%). Spontaneous loss (intrauterine or neonatal death) was significantly higher after EA (total group mean = 5.3%, 95% CI 3.8-7.2; randomised subgroup mean = 5.9%, 3.3-9.7) than after CVS (total group: mean = 2.3%, 1.2-3.9; randomised subgroup: mean = 1.2%, 0.3-3.5). The gestation at delivery and birthweight of the infants after EA and CVS were similar. In the EA group the incidence of talipes equinovarus (1.63%), was higher than in the CVS group (0.56%), but this difference was not significant.

Fetal biophysical profile score. VI. Correlation with antepartum umbilical venous fetal pH

OBJECTIVE

Our objective was to determine the relationship, if any, between the fetal biophysical profile score and antepartum umbilical venous pH.

STUDY DESIGN

This was a prospective observational study conducted concurrently in two centers and involving two discrete high-risk groups of fetuses. Fetal biophysical profile scores were compared with umbilical venous pH values measured in blood obtained by immediate cordocentesis. A total of 493 paired observations of biophysical profile score and pH were made; 104 observations were of fetuses with intrauterine growth retardation and 389 observations were of fetuses with alloimmune anemia.

RESULTS

In both data sets there was a highly significant linear correlation between biophysical profile score and umbilical venous pH. Poor biophysical profile score performance (a score of 0 of 10) was always associated with a pH < 7.20, whereas the pH was always > 7.20 when the biophysical profile score was 10 of 10. Sequenced sensitivity of short-term biophysical variables in the detection of acidemia was observed.

CONCLUSION

The fetal biophysical profile score accurately predicts antepartum umbilical venous pH.

Screening for fetal chromosomal abnormalities by maternal serum biochemistry and ultrasound examination of fetal morphology

The failure of screening studies based on maternal age to reduce substantially the birth incidence of chromosomally abnormal babies has stimulated the search for new methods of screening. In this paper we review the latest literature on the two new approaches to screening for fetal chromosomal abnormalities: maternal blood analysis and examination of the fetal anatomy by ultrasound. Preliminary results from maternal serum biochemistry screening indicate that detection of trisomy 21 is significantly improved, and application of biochemical testing may be expanded to the first trimester of pregnancy. Findings from studies on the association between fetal malformations and chromosomal abnormalities indicate that a high percentage of fetuses with an abnormal karyotype can be detected by ultrasound. In order to improve the detection rate and counsel parents appropriately, prospective studies are needed to determine the sensitivity and specificity of different markers in unselected populations of all ages. Information from such studies will also help us to avoid unnecessary anxiety and keep the fetal loss rate due to invasive procedures as low as possible.

Intra-uterine starvation and fetal leucocyte count

In 104 severely growth-retarded fetuses, the mean white blood cell count (WBC), as well as neutrophil, lymphocyte and monocyte counts were reduced. Furthermore, the severity of the leucopenia was significantly related to the degree of fetal 'smallness' and anaemia. These findings suggest that leucopenia observed in growth-retarded neonates may be a consequence of intra-uterine starvation due to deficiency of haematinics.

Neurotensin induces catalepsy in mice

Intracerebroventricular (i.c.v.) injection of neurotensin (NT) induced catalepsy in mice at doses greater than or equal to 0.02 microgram. The cataleptic effect progressively increased, reaching a maximum at approx. 2 hr after injection. In contrast, the hypothermic effect of neurotensin reached a maximum 1 hr after the injection, and was declining at 2 hr. Not all mice that showed hypothermia also showed catalepsy, and some mice showed catalepsy without hypothermia. Catalepsy induced by intracerebroventricular injection of neurotensin was not significantly correlated with the hypothermia. Furthermore, oxotremorine induced hypothermia without catalepsy. Thus, several lines of evidence indicate that the catalepsy induced by neurotensin is not the consequence of the neurotensin induced hypothermia. Thyrotropin releasing hormone (TRH), injected either intracerebroventricularly with neurotensin, or intraperitoneally before neurotensin abolished the hypothermia but only diminished the catalepsy scores. The cataleptic effect of neurotensin is consistent with its other neuroleptic-like activities.