Computed tomography analysis of radiostereometric data to determine flexion axes after total joint replacement: application to the elbow joint

Kinematic analysis for in vivo assessment of elbow endoprostheses requires knowledge of the exact positions of motion axes relative to bony landmarks or the prosthesis. A prosthesis-based reference system is required for comparison between individuals and studies. The primary aim of this study was to further develop an earlier described algorithm for fusion of radiostereometric analysis (RSA) data and data obtained in 3D computed tomography (CT) for application to the elbow after total joint replacement. The secondary aim was to propose a method for marking of prostheses in 3D CT, enabling definition of a prosthesis-based reference system. Six patients with elbow endoprostheses were investigated. The fusion of data made it possible to visualize the motion axes in relation to the prostheses in the 3D CT volume. The differences between two repeated positioning repetitions of the longitudinal prosthesis axis were less than 0.6 degrees in the frontal and sagittal planes. Corresponding values for the transverse axis were less than 0.6 degrees in the frontal and less than 1.4 degrees (in four out of six less than 0.6 degrees ) in the horizontal plane. This study shows that by fusion of CT and RSA data it is possible to determine the accurate position of the flexion axes of the elbow joint after total joint replacement in vivo. The proposed method for implant marking and registration of reference axes enables comparison of prosthesis function between patients and studies.

The effects of capsaicin on gastrin secretion in isolated human antral glands: before and after ingestion of red chilli

BACKGROUND

Capsaicin is known to have regulatory effects on gastrointestinal functions via the vanilloid receptor (VR1). We reported previously that endocrine-like cells in the human antrum express VR1.

AIM

To identify VR1-expressing endocrine-like cells in human antral glands and to examine whether stimulation with capsaicin causes release of gastrin, somatostatin, and serotonin. Further, to investigate the effects of a chilli-rich diet.

METHODS

Gastroscopic biopsies were received from 11 volunteers. Seven of the 11 subjects agreed to donor gastric biopsies a second time after a 3-week chilli-rich diet containing 1.4-4.2 mg capsaicin/day. VR1-immunoreactive cells were identified by double-staining immunohistochemistry against gastrin, somatostatin, and serotonin. For the stimulation studies, we used an in vitro method where antral glands in suspension were stimulated with 0.01 mM capsaicin and physiological buffer was added to the control vials. The concentrations of secreted hormones were detected and calculated with radioimmunoassay (RIA). Results The light microscopic examination revealed that VR1 was localized in gastrin cells. The secretory studies showed an increase in release of gastrin and somatostatin compared to the control vials (P = 0.003; P = 0.013). Capsaicin-stimulation caused a consistent raise of the gastrin concentrations in the gland preparations from all subjects. A chilli-rich diet had an inhibitory effect on gastrin release upon stimulation compared to the results that were obtained before the start of the diet.

CONCLUSION

This study shows that capsaicin stimulates gastrin secretion from isolated human antral glands, and that a chilli-rich diet decreases this secretion.

Fusion of radiostereometric analysis data into computed tomography space: application to the elbow joint

Improvement of joint prostheses is dependent upon information concerning the biomechanical properties of the joint. Radiostereometric analysis (RSA) and electromagnetic techniques have been applied in previous cadaver and in vivo studies on the elbow joint to provide valuable information concerning joint motion axes. However, such information is limited to mathematically calculated positions of the axes according to an orthogonal coordinate system and is difficult to relate to individual skeletal anatomy. The aim of this study was to evaluate the in vivo application of a new fusion method to provide three-dimensional (3D) visualization of flexion axes according to bony landmarks. In vivo RSA data of the elbow joint's flexion axes was combined with data obtained by 3D computed tomography (CT). Results were obtained from five healthy subjects after one was excluded due to an instable RSA marker. The median error between imported and transformed RSA marker coordinates and those obtained in the CT volume was 0.22 mm. Median maximal rotation error after transformation of the rigid RSA body to the CT volume was 0.003 degrees . Points of interception with a plane calculated in the RSA orthogonal coordinate system were imported into the CT volume, facilitating the 3D visualization of the flexion axes. This study demonstrates a successful fusion of RSA and CT data, without significant loss of RSA accuracy. The method could be used for relating individual motion axes to a 3D representation of relevant joint anatomy, thus providing important information for clinical applications such as the development of joint prostheses.

Variation in the position and orientation of the elbow flexion axis

We analysed the axis of movement in the normal elbow during flexion in vivo using radiostereometric analysis (RSA). The results show an intraindividual variation in the inclination of the axis ranging from 2.1 degrees to 14.3 degrees in the frontal and from 1.6 degrees to 9.8 degrees in the horizontal plane analysed at 30 degrees increments. The inclination of the mean axis of rotation varied within a range of 12.7 degrees in the frontal and 4.6 degrees in the horizontal plane. In both planes, the mean axes were located close to a line joining the centres of the trochlea and capitellum. The intra- and interindividual variations of the axes of flexion of the elbow were greater than previously reported. These factors should be considered in the development of elbow prostheses.

Hospital care utilization of infants born after IVF

BACKGROUND

Infants born after IVF are often twins, and singleton IVF babies have an increased risk for preterm birth. Both conditions are likely to increase morbidity. We examined the frequency and duration of hospitalization required by babies born after IVF, and compared this information with all infants born in Sweden during the same time period.

METHODS

We used a nationwide registration of IVF pregnancies from 1984 to 1997 and a nationwide register of all in-patient care up to the end of 1998. We identified 9056 live born infants after IVF treatment and compared them with 1 417 166 non-IVF live born infants.

RESULTS

The highest odds ratio (OR approximately 3) was seen for neonatal hospitalization, but an increased OR (1.2-1.3) was noted for children up to 6 years of age. The OR for being hospitalized after IVF was 1.8, but when the analysis was restricted to term infants it was 1.3 and this excess was then explainable by maternal subfertility. Statistically significant increased ORs were seen for hospitalization for cerebral palsy (1.7), epilepsy (1.5), congenital malformation (1.8) or tumour (1.6), but also for asthma (1.4) or any infection (1.4). When information from the Swedish Cancer Registry was used, no excess risk for childhood cancer was found. The average number of days spent in hospital by IVF and non-IVF children was 9.5 and 3.6 respectively.

CONCLUSIONS

The increased hospitalization of IVF children is, to a large extent, due to the increased incidence of multiple births. Therefore, the increased costs associated with this may be reduced by the use of single embryo transfers, with the savings in health care costs being offset against the increased number of embryo transfer cycles required to maintain the pregnancy rate.

Neurological sequelae in children born after in-vitro fertilisation: a population-based study

BACKGROUND

There is an absence of population-based long-term studies on the risk of neurological sequelae in children born after in-vitro fertilisation (IVF). Our aim was to compare the frequency of such problems between IVF-born children and controls.

METHODS

We did a population-based retrospective cohort study in which we compared development of neurological problems in 5680 children born after IVF, with 11360 matched controls. For 2060 twins born after IVF, a second set of controls (n=4120), all twins, were selected. We obtained data on neurological problems from the records of the Swedish habilitation centres.

FINDINGS

Children born after IVF are more likely to need habilitation services than controls (odds ratio 1.7, 95% CI 1.3-2.2). For singletons, the risk was 1.4 (1.0-2.1). The most common neurological diagnosis was cerebral palsy, for which children born after IVF had an increased risk of 3.7(2.0-6.6), and IVF singletons of 2.8 (1.3-5.8). Suspected developmental delay was increased four-fold (1.9-8.3) in children born after IVF. Twins born after IVF did not differ from control twins with respect to risk of neurological sequelae. Low-birthweight and premature infants were more likely to need habilitation than fullterm babies. Maternal age did not affect risk.

INTERPRETATION

Our study suggests that children born after IVF have an increased risk of developing neurological problems, especially cerebral palsy. These risks are largely due to the high frequency of twin pregnancies, low birthweight, and prematurity among babies born after IVF. To limit these risks, we recommend that only one embryo should be transferred during IVF.

Nonsteroidal anti-inflammatory drugs in early pregnancy

A study was performed of congenital malformations in infants whose mothers used nonsteroidal anti-inflammatory drugs (NSAIDs) in early pregnancy. Data were obtained from an ongoing prospective recording of drug use during the first trimester. During the period July 1, 1995 through December 31, 1998, 2557 infants were born to women who reported the use of NSAIDs in early pregnancy. The OR (after consideration of maternal age, parity, and smoking habits) for any congenital malformation was 1.04 (95%CI 0.84-1.29), but the OR for cardiac defects reported to the Medical Birth Registry was 1.86 (1.32-2.62) based on 36 instances, and for orofacial clefts 2.61 (1.01-6.78) based on only six instances. By using other information sources, another four infants with cardiac defects were identified. There was no drug specificity for cardiac defects but among six mothers of infants with orofacial clefts, five had used naproxen.

Use of multivitamins and folic acid in early pregnancy and multiple births in Sweden

Folic acid is recommended to reduce the risk of neural tube defects and other congenital malformations. Data from the Swedish Medical Birth Registry were used to study frequency of twinning in women who in early pregnancy reported the use of folic acid. Women (n = 2,569) who in early pregnancy reported the use of folic acid had an increased rate of twin deliveries after consideration of maternal age and of length of involuntary childlessness, both variables being significant confounders. The effect of folic acid was seen also in women who did not report involuntary childlessness. A similar but not statistically significant trend was seen after use of multivitamins without simultaneous use of folic acid tablets (n = 1,979). The increased risk seems to be limited to dizygotic twinning (relative risk = 2.13, 95% CI 1.64-2.74). If this association is causal, wide-spread supplementation with folic acid may represent a hazard larger than the postulated beneficial effect on neural tube defects, at least in low-risk areas.

Congenital malformations in infants born after IVF: a population-based study

The presence of congenital malformations in infants born after IVF was studied from a register consisting of practically all infants born in Sweden after IVF, 1982--1997 (n = 9111). A further 64 infants were studied using only medical records. It is a nation-wide study and has a population-based control group (n = 1,690,577) and relevant potential confounders have been taken into account. There was an excess of congenital malformations registered in the Medical Birth Registry (n = 516, odds ratio = 1.47) but this excess disappeared when confounders were taken into consideration: year of birth, maternal age, parity, and period of unwanted childlessness (odds ratio = 0.89). For some specific conditions, an approximately 3-fold excess risk was seen: neural tube defects, alimentary atresia, omphalocele, and hypospadias (after intracytoplasmatic sperm injection). No excess risk for hypospadias was seen after standard IVF. Various explanations for these findings are discussed. It is postulated that the excess risk for alimentary atresia, like the excess risk for monozygotic twinning after IVF, is a direct consequence of the IVF procedure. The excess risk for hypospadias after ICSI may be related to paternal subfertility with a genetic background. The absolute risk for a congenital malformation in association with IVF is small.

Blood transfusion at delivery and risk of subsequent malignant lymphoma in the mother

BACKGROUND AND OBJECTIVES

Blood transfusion has been shown to be a risk factor for non-Hodgkin's lymphoma (NHL).

MATERIALS AND METHODS

In a cohort of 77,928 women with bleeding complications at delivery in the period of 1973-1986, subsequent NHL cases were identified and the number was compared with the number expected from national incidence rates. In a case-control study the proportion of transfused NHL cases was compared with the proportion of transfused controls.

RESULTS

The observed number of NHL in the cohort was 18 versus 22.0 expected. Information on transfusion was obtained for 15 of the NHL cases and none (0%) was transfused versus 32 out of 136 controls (23%).

CONCLUSIONS

Blood transfusion at delivery is not a risk factor for NHL. The immune tolerance induced by pregnancy may reduce the risk of NHL associated with the transfusion of allogeneic blood cells.

Deliveries and children born after in-vitro fertilisation in Sweden 1982-95: a retrospective cohort study

BACKGROUND

In-vitro fertilisation is an effective treatment for infertility, but there is concern about the health of children. We investigated, in a retrospective registry study, malformations, cancers, and deaths in the complete Swedish in-vitro-fertilisation birth cohort compared with the general population.

METHODS

We collected data from all in-vitro-fertilisation clinics in Sweden and compared the obstetric outcomes of babies (n=5856) born between 1982 and 1995 with all babies born in the general population (n=1,505,724) during the same period, according to data from the Swedish Medical Birth Registry and the Registry of Congenital Malformations. We investigated the incidence of childhood cancer through the Swedish Cancer Registry. Data were stratified for maternal age, parity, previous subfertility, year of birth, and multiple of pregnancies.

FINDINGS

Multiple births occurred in 27% of pregnancies compared with 1% in the control group. In the in-vitro-fertilisation group, more babies were born preterm (<37 weeks) than controls (30.3 vs 6.3%) and more had low birthweights (<2500 g, 27.4 vs 4.6%). The perinatal mortality was 1.9% in the in-vitro fertilisation group and 1.1% in the controls. For in-vitro-fertilisation singletons, the risk ratios, adjusted for year of birth, for very preterm birth (<32 weeks) and very low birthweight (<1500 g) were 3.54 (95% CI 2.90-4.32) and 4.39 (3.62-5.32), respectively. Malformations occurred in 5.4% of all babies in the in-vitro-fertilisation group (1.39 [1.25-1.54]), and the rates of neural-tube defects and oesophageal atresia were higher than those in the controls. There was no increase in childhood cancer in the in-vitro-fertilisation group.

INTERPRETATION

A high frequency of multiple births and maternal characteristics were the main factors that led to adverse outcomes, and not the in-vitro-fertilisation technique itself. The clinical practice of in-vitro-fertilisation needs to be changed to lower the rate of multiple pregnancy.

[Health care registries a community asset. Centralized registries of health care data can save life and improve quality of life]

The article is a review of how national epidemiological data bases in Sweden can be used for research and statistical purposes. Over 500 major applications from research groups and others are dealt with annually by the National Cancer, Hospital discharge, Medical birth, and Cause-of-death registries, providing essential data for studies which have yielded well over a thousand peer-reviewed scientific papers. In over 40 years' Swedish experience of administering the registration of sensitive patient-specific information on diseases, there has not been a single case of data misuse. It is concluded that the benefits of national epidemiological registries far outweigh the risks and marginal costs of maintaining them.

Delivery outcome after the use of antidepressants in early pregnancy

OBJECTIVES

To investigate delivery outcome after the use of antidepressants in early pregnancy.

METHODS

Using an ongoing prospective recording of drug use in early pregnancy, 969 women were identified who reported the use of antidepressants: 531 used only SSRI (selective serotonin re-uptake inhibitor) drugs (mostly citalopram, 375 exposures), 423 used only other antidepressants, and 15 used both. Outcome was compared with all births in the population.

RESULTS

Women using these drugs were older and smoked more than three times as often as other women. There seemed to be an excess of high parity women. The frequency of multiple births was lower than expected, resulting from too few twin births in women who had used SSRI. Gestational duration among singletons was shorter but it did not affect infant survival and was similar after the use of SSRI or non-SSRI antidepressants, perhaps the result of uncompensated for confounding or related to the underlying disease. Infants were somewhat heavier than expected, notably after non-SSRI treatment. No increase was seen in congenital abnormalities, observable in the perinatal period.

CONCLUSIONS

Based on this database, the use of antidepressants in early pregnancy does not seem to carry any significant risk for the infant that is detectable during the newborn period.

Very low birthweight boys at the age of 19

Using linked data from the Swedish Medical Birth Registry and the National Service Enrollment Register, long term follow up (to 18-19 years age) was made of 260 surviving singleton boys whose birthweight was less than 1500 g from a total of 150 229 boys born between 1973-5. These boys were shorter and lighter than boys who weighed more at birth, they had more visual and hearing impairments, were at much higher risk of cerebral palsy and other signs of mental impairment, evident as lower intelligence test scores and shorter schooling. No significant excess of asthma, back problems, or headaches were found.

Long-term clinical results after treatment with conical crown-retained dentures

The clinical outcome of treatment using conical crown-retained dentures was evaluated. Of the initial 25 patients provided with 26 conical crown-retained dentures, 18 patients with 18 restorations could be examined after a time ranging between 73 and 92 months. Of the eight restorations lost, four had been changed as a result of factors that might have been related to the prosthodontic care. Most of the patients were very satisfied with the restorations both functionally and esthetically and found their chewing comfort to be better after treatment with conical crown-retained dentures. However, 50% of the patients reported speech problems related to treatment. Technical failures were not insignificant but were treatable. The survival rate after 73 to 92 months was 78.3%.

Preterm birth and low birthweight among children of Swedish and immigrant women between 1978 and 1990

The aim of the study was to estimate the occurrence of low birthweight (LBW) and preterm birth among immigrant and Swedish women in Sweden. Eligible for analysis were all 1,270,407 singleton births in Sweden between 1978 and 1990 to mothers aged between 15 and 44 years, whose own country of birth was known. The mothers of the children were born in Sweden (88.2%), or had immigrated from Finland (4.4%), other Scandinavian countries (1.2%), Western Europe or North America (1.3%), Eastern Europe (1.8%), the Middle East and North Africa (1.7%), Central and South America (0.6%), Asia and the Pacific Islands (0.6%), or Sub-Saharan Africa (0.2%). Multiple logistic regression was used to model LBW and preterm birth categorical outcomes. Each immigrant group was compared with the Swedish group. Odds ratios (ORs) for LBW were 1.13 (95% CI 1.04, 1.22) for Asia and the Pacific Islands, 1.21 (1.05, 1.38) for Sub-Saharan Africa and 0.89 (0.86-0.93) for Finland. Odds ratios for preterm birth were 1.15 (1.08-1.23) for immigrants from Asia and the Pacific Islands and 1.08 (1.04, 1.13) for immigrants from Eastern Europe. Remarkably small differences were found between immigrant women and native Swedish women.

Pregnancy outcome in Sweden after the Chernobyl accident

OBJECTIVE

To study pregnancy outcome including development of childhood cancer in areas within Sweden with the highest radioactive fallout after the Chernobyl accident in 1986.

METHODS

Various Swedish health registries were used in order to identify all pregnancies and their outcome in Sweden according to the measured radioactive fallout.

RESULTS

A reduction in conception rate occurred after the accident, as well as possible increase in induced abortion rate during the fall after the accident. No changes in the rate of spontaneous abortions or congenital malformations occurred in pregnancies exposed at the time of the accident. There was a temporary increase in low birth weight which could well be random. Among infants conceived after the accident, a slight excess of Down syndrome infants was found in the most exposed areas but this observation is based on small numbers. No certain excess of childhood cancer was seen in the most exposed areas, but three infants, in utero at the time of the accident, developed leukemia.

CONCLUSIONS

No major effects on pregnancy outcome were seen but the indicated increase in Down syndrome and childhood leukemia--if not random--could be a result of radioactive exposure.

Infant survival in Norway and Sweden 1985-88

In recent years, considerable attention has been attached to the disquieting fact that infant survival is much lower in Norway than in Sweden. In the present study, comprising all live single births in Norway and Sweden during 1985-88, the observed infant mortality was 1.5 times higher in Norway than in Sweden. The largest difference between Norway and Sweden was found in infants of young mothers with high birth order. Thus for the second births of mothers aged less than 20 years the observed mortality ratio of Norway to Sweden was 1.8. The infant mortality ratio decreased with increasing maternal age for all birth orders, and for the second births of mothers aged 35 years or more the mortality ratio was 1.0. The higher infant mortality in Norway was evident throughout the first year of life, with the highest mortality ratio observed at 6-8 months of life. Adjustment for maternal age, birth order and geographical region did not alter the observed infant mortality ratios. In both countries, the highest risk was found among infants of young mothers. this suggests a need for a more extensive preventive health care system directed at young mothers during their pregnancy and the infancy period.

High adenosine content in human uterine smooth muscle compared with striated skeletal muscle

We determined the concentrations of adenosine and some of its catabolic products in biopsy specimens from predetermined loci of human myometrium under different functional conditions to compare uterine muscle with rectus abdominis muscle from the same individuals. In order to achieve a good resolution in the separation of nucleosides and purine bases, a preseparation procedure was developed prior to analysis of these compounds on high performance liquid chromatography. Adenosine occurred in a nearly 70-fold higher concentration in smooth uterine muscle in comparison with striated skeletal muscle. Similarly, myometrial inosine and hypoxanthine were 7- and 2.4-times in excess over the rectus muscle, whereas xanthine was scarcely and rather evenly represented in the two types of muscles. The uterine content of adenosine and inosine was distinctly higher in pregnant women compared to non-pregnant ones. A regional difference existed for adenosine, with 3.3 times higher concentration in fundus uteri compared to the isthmic part. A reverse pattern was observed for hypoxanthine and inosine, being 2-3 times more frequent in the isthmic part. The orthophosphate concentration was not stoichiometrically related to the adenosine concentration in a simple way, being 2-3 times lower in uterine muscle compared to the skeletal muscle. A significant correlation existed between uterine contents of AMP and adenosine and similarly, significant inverse correlations were apparent between uterine ATP and ADP contents and energy charge on one hand and adenosine content on the other.

A clinical evaluation of conical crown retained dentures

In an uncontrolled retrospective recall study of 57 patients treated with conical crown retained dentures, 60 restorations (37 in the maxillae and 23 in the mandible jaw) with a mean wearing time of 30.1 months (range 4 to 76) were evaluated. Of the 248 abutments, eight (3.2%) had been lost. Clinically healthy mucosa was seen in 35 jaws. The marginal fit of the copings was judged to be good. No caries or new restorations were observed in 44 patients. Thirteen patients had 19 surfaces with new restorations and 20 surfaces with caries lesions. Of these 39 surfaces, 38 were located subgingivally.

Methods for the evaluation of social effects on birth weight-- experiences with Swedish population registries

All births in Sweden in 1986, registered in the Medical Birth Registry, were analyzed with linked data from the November 1985 census in order to identify variables which could be used as proxy variables for the socio-economic situation of the women, using birth weight as outcome variable. Two phenomena appear to be strong socio-economic indices of significance for birth weight: whether the woman co-habited or not at the census and whether she had a long education (> 14 years) and an "academic" work. The two variables interacted, however: when the woman had a long education, cohabitation status played no significant role. Maternal education as judged from occupation seemed to play a more important role than paternal education or job. To some extent, the effects of the socio-economic variables could be explained by different smoking habits but a residual effect existed which may have different explanations. Cohabitation status and education may be used as estimates of socio-economic level of significance for birth weight and perhaps other pregnancy outcome in the analysis of, for instance, the effect of various occupational exposures on pregnancy outcome.

Secular trends in the effect of socio-economic factors on birth weight and infant survival in Sweden

Time trends in the effect of socio-economic factors on low birth weight, stillbirth, perinatal deaths and deaths up to the age of one were studied using a medical birth registry linked to census information from 1975, 1980, and 1985. For each census year, delivery outcome the following year was studied. Two socio-economically different groups of women were studied, defined by occupation/education, cohabitation, and citizenship--one privileged and one under-privileged group. A difference in birth weight distribution was found between the two groups which is only partly explainable by different smoking habits in early pregnancy and did not substantially change during the ten year observation period. In 1976, there was virtually no difference in infant mortality between the two groups. In 1981 and 1986, infant mortality had decreased in both groups but more strongly so in the privileged group, and a difference between the groups therefore appeared.

Maternal and perinatal risk factors for Wilms' tumor: a nationwide nested case-control study in Sweden

This report describes maternal and perinatal risk factors for Wilms' tumor analyzed in a case-control study nested in a nationwide cohort in Sweden. The Swedish National Cancer Registry ascertained 110 cases from among successive birth cohorts from 1973 through 1984, identified by the Swedish Medical Birth Registry, the latter based on medical records. From the Birth Registry, we matched 5 controls without cancer to each case by sex and date of birth. Wilms'-tumor children were more likely to have mothers who had been exposed to penthrane (methoxyflurane) anesthesia during delivery than mothers of controls (odds ratio (OR) = 2.4; 95% confidence interval (CI) 1.1 to 5.1); this excess risk was higher in females than males and increased with age at diagnosis. Wilms'-tumor cases were also more likely to have had physiologic jaundice (OR = 2.3; 95% CI 1.1 to 5.0). Higher parity of the mother decreased the risk of Wilms' tumor among females (OR = 0.7; 95% CI 0.5 to 1.0). We were unable to confirm the reported increased risks of Wilms' tumor for those with high birth weights or with a maternal history of hypertension or fluid retention during pregnancy, nor did we find any association with mother's age at delivery, previous stillbirth, previous live birth, gestational length or height of the child.

A registry study of very low birthweight liveborn infants in Sweden, 1973-1988

Very low birthweight liveborn infants (less than 1,500 g, VLBW) born in Sweden 1973-88 were identified from the Medical Birth Registry and efforts were made to remove wrongly recorded birthweights--9% of infants with a registered birth weight below 1,500 g were removed. Some VLBW infants were not recorded in the register and the estimate of the prevalence at birth of VLBW infants is therefore slightly underestimated. It increased from about 5.5 per 1,000 during the period 1973-84 to 6.7 per 1,000 during 1987-88. 18% of VLBW infants were involved in multiple births. Median Apgar score at 5 min increased for each 100 g birthweight class. Even at a birthweight between 1,400 and 1,499 g, a low Apgar score at 5 min was seen in 20%. The rate of cesarean section increased between 1973 and 1983 from about 10% to 60%. One-year survival for infants with a birthweight less than 1,000 g increased from less than 20% in 1973-75 to 50% in the 1986-88 cohorts. Corresponding figures for infants with a birthweight between 1,000 and 1,499 g were 60% and 90%. A markedly better one-year survival is already evident in the 600-699 g class. On stratifying for 100 g birthweight class, perinatal death risk was higher in boys than in girls and higher in multiple births than in singletons. An increased rate of congenital malformations was seen in the 1,000-1,499 g class but not in the less than 1,000 g class.

Maternal smoking in pregnancy: does it increase the risk of childhood cancer?

Experimental studies show that some compounds in tobacco smoke are transplacental carcinogens, but epidemiological data on maternal smoking and childhood cancer are inconclusive. Using the national Swedish Medical Birth and Cancer Registries, the incidence of cancer was followed through 1987 in a cohort of 497,051 children born 1982-1987 for whom information was available on maternal smoking at 2-3 months of pregnancy. A total of 327 cancers appeared including 198 solid tumours and 129 cancers of the lymphatic and haematopoietic system. The overall relative risk for cancer in children with mothers reporting smoking during pregnancy was 0.99 (95% confidence interval (CI): 0.78-1.27). Corresponding risks for solid tumours and cancers of the lymphatic/haematopoietic system were 0.96 (0.70-1.32) and 1.04 (0.71-1.52), respectively. There was no consistent increase in risk for cancer of different sites or in relation to number of cigarettes smoked per day.

An update of the Swedish reference standards for weight, length and head circumference at birth for given gestational age (1977-1981)

An update of the Swedish reference standards for weight, length, and head circumference at birth, for each week of gestational age, is presented. It is based on the total Swedish cohorts of infants born 1977-1981 (n = 475,588). A "healthy population" (79%) was extracted, using prospectively collected data. Weekly (28-42 weeks) grouped data for length and head circumference were well approximated by the normal distribution, but the distributions for birthweight were positively skewed. The original skewed distributions for birthweight were transformed, using the square root, resulting in distributions close to the Gaussian. For smoothing purposes, the weakly values for the mean and the standard deviation were both fitted by a third degree polynomial function. These functions also make possible the calculation of the continuous variable, standard deviation score, for individual newborn infants as well as a comparison of distributions between groups of infants. The reference values and charts presented here have two major advantages over the current Swedish ones: the sample size used is now sufficiently large at the lower gestational ages, so that empirically found variations can be used, and the skewness of the birth weight distribution has been taken into account. The use of the reference standards presented here improves and facilitates evaluation of size deviation at birth.

Maternal and perinatal risk factors for childhood leukemia

This report describes an exploratory population-based study of maternal and perinatal risk factors for childhood leukemia in Sweden. The Swedish National Cancer Registry ascertained 411 cases in successive birth cohorts from 1973 through 1984 recorded in the Swedish Medical Birth Registry. Using the latter, we matched five controls without cancer to each case by sex and month and year of birth. Mothers of children with leukemia were more likely to have been exposed to nitrous oxide anesthesia during delivery than mothers of controls [odds ratio (OR) = 1.3; 95% confidence interval (CI) = 1.0, 1.6]. Children with leukemia were more likely than controls to have Down's syndrome (OR = 32.5; 95% CI = 7.3, 144.0) or cleft lip or cleft palate (OR = 5.0; 95% CI = 1.0, 24.8); to have had a diagnosis associated with difficult labor but unspecified complications (OR = 4.5; 95% CI = 1.1, 18.2) or with other conditions of the fetus or newborn (OR = 1.5; 95% CI = 1.1, 2.1), specifically, uncomplicated physiological jaundice (OR = 1.9; 95% CI = 1.2, 2.9); or to have received supplemental oxygen (OR = 2.6; 95% CI = 1.3, 1.3, 4.9). Because multiple potential risk factors were analyzed in this study, future studies need to check these findings. We did not confirm the previously reported higher risks for childhood leukemia associated with being male, having a high birth weight, or being born to a woman of advanced maternal age.

Storage of saline-adenine-glucose-mannitol-suspended red cells in a new plastic container: polyvinylchloride plasticized with butyryl-n-trihexyl-citrate

Blood collection and component preparation have been performed in integrally connected multiple plastic containers made with a new plastic. This polyvinylchloride (PVC) container plasticized with butyryl-n-trihexyl-citrate (BTHC) is a new material for blood storage; it contains no di(2-ethylhexyl)phthalate (DEHP). After removal of plasma and buffy coat, the red cells were suspended in saline-adenine-glucose-mannitol (SAGM) medium. After 42-day refrigerator storage, the total adenine nucleotide concentration remained the same as the initial concentration in the red cells, whereas ATP levels had decreased to 61 percent of the initial value. The 2,3 DPG concentration was 62 percent of normal on Day 7 and 21 percent on Day 14. Glucose consumption, lactate production, potassium leakage from red cells, and pH levels were similar to those found after storage in DEHP-plasticized containers under the same conditions. After 42 days, hemolysis levels were 0.56 +/- 0.21 percent and 0.42 +/- 0.17 percent in two series of units mixed weekly and 0.70 +/- 0.27 percent in units stored unmixed. Although even higher levels of hemolysis were observed in the units stored unmixed and used for 24-hour posttransfusion survival, the autologous red cell recovery results were excellent (83.2 +/- 5.1%, n = 8). BTHC-plasticized PVC is found to be a suitable material for 42-day storage of red cells in SAGM solution.

Incidence of legal abortion in Sweden after the Chernobyl accident

The number of legal abortions in Sweden increased around the time of the Chernobyl accident, particularly in the summer and autumn of 1986. Although there was no recording of reasons for legal abortions, one might have suspected this increase to be a result of fear and anxiety after the accident. However, seen over a longer time perspective, the increase in the number of abortions started before and continued far beyond the time of the accident. There was also a simultaneous and pronounced increase in the number of births during the years subsequent to the accident. Therefore, it seems unlikely that fear of the consequences of radioactive fall-out after the Chernobyl accident resulted in any substantial increase of the number of legal abortions in Sweden.

Surveillance of smoking during pregnancy in Sweden, 1983-1987

Since 1982, prospective information on smoking during early pregnancy is reported to the Swedish Medical Birth Registry for nearly all (93%) women who give birth. The present paper studies the validity of this information: effects on birthweight and perinatal mortality are very similar to those described previously in the literature. For each parity class, smoking decreases in inverse proportion to increasing maternal age; for each maternal age class, smoking increases with parity. A slight reduction in smoking rate is observed between 1983 and 1987, most pronounced for young women. There are marked geographic and social differences in the rate of smoking during pregnancy. This dataset can be used in the future to monitor the prevalence of smoking, and to study various factors associated with smoking and the impact of countermeasures taken against smoking during pregnancy. It can also be used to study possible associations between maternal smoking and rare events like congenital malformations and child cancer.

Clinical results in patients provided with conical crown retained dentures

During 1985 and 1986, 25 patients were treated with conical crown retained dentures, 26 in the maxillary arch and four in the mandible. The primary indication for having used these dentures was the presence of only a few teeth, mostly in unfavorable positions. Clinical findings after 24 to 43 months are reported and considered promising. Patients were generally satisfied and only comparatively small tissue changes were found.

Socio-economic variables and pregnancy outcome. 2. Infant and child survival

The effects of various social indicators on infant and child mortality were studied in Sweden with the use of a medical birth register to which census information was linked. Two years were studied: 1976 births linked to the 1975 census, and 1981 births linked to the 1980 census. Survival was followed to the age of 5 by linkage of the birth register with the death certificate register. The only statistically significant effect of a single socio-economic variable was that of housing conditions on perinatal death rate and postperinatal death rate up to the age of one. The family situation (e.g., cohabitation or not) had some effect, although it was not statistically significant. On the basis of cohabitation status and other social indicators, including housing conditions, we selected two groups: one privileged and the other underprivileged. Using crude mortality rates, we found no definite difference. There was evidence that the mortality rate had decreased more between 1976 and 1981 in the privileged than in the underprivileged group, but the difference may have been coincidental. After standardization for maternal age and parity, however, a difference appeared with a ratio of 1.14 between the underprivileged and the privileged groups, which was valid for deaths up to the age of one. After that age, no difference was seen. Following standardization for birthweight, the opposite was found: a higher weight-specific mortality rate in the privileged group than in the underprivileged group. The interpretation of these findings is discussed.

A quality study of a medical birth registry

A quality control study was made of the Swedish Medical Birth Registry. This registry used one mode of data collection during 1973-1981 and another from 1982 onwards. The number of errors in the register was checked by comparing register information with a sample of the original medical records, and the variability in the use of diagnoses between hospitals was studied. Different types of errors were identified and quantified and the efficiency of the two methods of data collection evaluated.

Lack of success with a combination of alanine and phosphoenolpyruvate as an additive for liquid storage of red cells at 4 degrees C

Red cells were stored at 4 degrees C in a storage solution containing alanine or alanine plus phosphoenolpyruvate (PEP). The intention was to investigate whether alanine and PEP might act synergistically to maintain a normal level of both red cell ATP and 2.3 diphosphoglycerate (2.3 DPG) under normal liquid storage conditions. Storage in the presence of alanine kept the red cell concentration of 2.3 DPG higher than the reference solution for an extended period of time, provided the initial pH was about 7.0 (37 degrees C). When the pH of the storage solution containing alanine plus PEP was lowered to facilitate the transport of PEP into the red cells, the concentration of 2.3 DPG was lowered to a rate equal to that in the reference solution. The level of ATP was also about the same as in the reference solution. The majority of the added PEP was continuously converted to 2 phosphoglycerate and 3 phosphoglycerate in the extracellular fluid. A small amount of unconverted PEP penetrated the red cell membrane when the pH went below 6.5; this occurred after 3 weeks of storage. The intracellularly located PEP, however, was not metabolized to 2.3 DPG to any significant extent within the first 6 weeks of storage. These findings indicate that PEP is not suitable as an additive for liquid storage of red cells at 4 degrees C. The combination of alanine and PEP that theoretically could be a suitable additive for liquid storage of red cells was not satisfactory in practice.

Socio-economic variables and pregnancy outcome. Birthweight in singletons

The effect of various social indicators on birthweight in singletons was studied in Sweden with the use of a medical birth registry to which census information was linked. Two years were studied: 1976 births linked to the 1975 census, and 1981 births linked to the 1980 census. The strongest social indicator affecting birthweight was family situation: whether the woman cohabited or not. After standardization for this variable, effects were still seen for occupation and type of housing. They were not secondary to maternal age or parity. By using cohabitation status, enhanced with other social indicators, two groups were selected: one privileged and one underprivileged. Distributions of birthweight and pregnancy duration in the two groups were compared with those formed in women being neither privileged nor under privileged and also working outside the home (because occupation entered the definitions of the two former groups). There were marked differences: underprivileged women had shorter pregnancy duration and, at term, their infants weighed slightly less than those of privileged women. These differences remain after standardization for maternal age and parity.

Pregnancy outcome in women working as dentists, dental assistants or dental technicians

Pregnancy outcome in women with work in dentistry was studied using various central health registries. A total of 8157 infants born of dentists, dental assistants, or dental technicians in 1976 or 1982-1986 in Sweden were studied with respect to perinatal survival, low birthweight, and malformations and compared with all births. The only deviating finding was that of a significantly low perinatal death rate. Specifically, no increase in a risk for spina bifida was seen and the upper 95% confidence limit for the risk ratio was 2.1. A study was also made of hospitalized spontaneous abortions in women with these occupations in the years 1980-1981. No significant deviations from expected values were found. In a small study of only 78 such pregnancies in 1964-1965, no increase in spontaneous abortion rate was seen. Only one infant was malformed (anencephaly): both its parents worked as dental technicians. None of the mothers of 220 infants with a neural tube defect born in 1965-1967 in Sweden was a dentist. We find no indications that this occupation represents a significant reproduction hazard at the present time in Sweden.

Modelling of reference values for size at birth

Data from the Swedish Medical Birth Registration, 1977-1981 were used to apply methods of constructing reference standards for size at birth. Using clinical information a 'healthy' sub-population was extracted. The conditional distributions of birthweight (BW) and birthlength (BL) for each week of Gestational age, and the conditional distribution of birthweight given birthlength were modelled using truncated Normal distributions, after making use of Box-Cox power transformations. Spline functions were then used in conjunction with a multiplicative method to obtain appropriate percentage point curves. Examples of this analysis are given.

Deaths and tumors among workers grinding stainless steel

This study examined a cohort of 1,164 males who, during the period 1927-1981, had been employed for 3 months or more in an industry that produced objects from stainless steel. These workers were exposed to the dust of grinding materials, grinding agents, and stainless steel. From 1975 to 1980, measurements of the total dust in the workroom air have shown levels of about one mg/m3 (consisting of chromium at about 0.1 mg/m3 and nickel at about 0.05 mg/m3) during grinding and several mg/m3 (chromium at about 0.01 mg/m3 and nickel at about 0.005 mg/m3) during polishing. Before 1950, the concentrations were probably considerably higher. Compared to a local reference population, a decrease in mortality (63 observed deaths, standardized mortality (SMR) = 0.79, 95% confidence limits CL = 0.61, 1.01) took place during the 1951-1983 observation period among 318 subjects who had been employed for at least five years, allowing a latency period of at least 20 years. Mortality from cancer of the colon/rectum increased (observed deaths = 6, SMR = 2.47, CL = 0.97, 5.58). The mortality from nonmalignant pulmonary disease did not increase (SMR = 0.29, CL = 0.01, 1.81). During the observation period (1958-1983), there was no significant overall excess of tumors (observed cases = 33, standardized morbidity [SMR] = 1.09, CL = 0.76, 1.54). However, tumor morbidity of the colon/rectum (observed 11, SMR = 2.83, CL = 1.47, 5.19) significantly increased. There were no cases of respiratory cancer (expected 4.7, CL = 0, 0.21). Thus, the results indicate an increased risk of intestinal cancer.(ABSTRACT TRUNCATED AT 250 WORDS)

Purine metabolism in normal and ITP-pyrophosphohydrolase-deficient human erythrocytes

Fresh and stored erythrocytes from normal and ITP-pyrophosphohydrolase (ITP-ase, EC 3.6.1.19) deficient individuals were incubated with hypoxanthine, guanine, allopurinol, and inosine. Differences in the purine metabolism between the normal and the ITP-ase deficient erythrocytes were observed only in the IMP-ITP cycle. Hypoxanthine, guanine and allopurinol were converted to nucleotides at the same rate. Hypoxanthine (2.5 mumol/l) inhibited the salvage of allopurinol (40 mumol/l). A slow decrease (0.7%/day) in salvage rate was observed in both types of cells upon storage at +4 degrees C. Erythrocyte ITP-ase activity was measured in a reference sample group of 48 healthy volunteers. Two distinct groups were found with mean activities equal to 48.3 +/- 13.1 nkat/g Hb (means +/- SD, n = 38) and 11.4 +/- 4.3 nkat/g Hb (n = 10). In two previously selected subjects, the ITP-ase activity was 0.2 and 2.4 nkat/g Hb. A hypothetical genetic mechanism is discussed. The maximal energy turnover in the IMP-ITP cycle during hypoxanthine incubation was found to be less than 10% of the basal erythrocyte energy turnover.

Studies on the mechanism of human red cell loss of viability during storage at +4 degrees C in vitro. III. Effects of mixing during storage

Red cells supended in saline-adenine-glucose-mannitol solution were stored for 42 days at +4 degrees C. One portion was packed by centrifugation and stored unmixed; the other portion was mixed once a week. Red cell fluidity and adenine nucleotide concentration were significantly lower in unmixed than in mixed units and also differed within the packed layer, showing a decrease towards the bottom. Hemolysis was 2.5-fold and microvesiculation 5-fold higher in cells stored unmixed. It is suggested that, during liquid storage, an early accumulation of acid metabolites in the bottom part of packed red cells may play an important role both for adenylate loss and microvesiculation, but lack of membrane-stabilizing action of diethylhexylphthalate may in part explain the latter. Both of these two changes are factors associated with impaired red cell viability. Mixing appears essential to optimize storage conditions for red cells.

Maternal occupation and delivery outcome: a study using central registry data

The outcome of all deliveries in Sweden in 1981 has been studied. The occupation of each mother was obtained by record linkage using census data from November 1980. Rates of perinatal deaths or congenital malformations did not vary according to maternal occupation, more than might be expected to happen by chance, which indicated that maternal occupation is not a major factor in the outcome of these deliveries. There was variation in the rates of low birth weight infants, according to maternal occupation, which may have been an effect of socioeconomic factors associated with the occupation. Within occupational groups, working situations may exist which entail an increased teratogenic risk, but in order to reveal such risks, studies with a different design must be carried out.

Birth weight distribution as an indicator of environmental effects on fetal development

A medical birth registry was used for a geographical analysis of birth weight distribution. Nearly 900,000 Swedish singleton births, 1973-1981, were used for an analysis of the effect of some variables and for standardization for these variables. A marked change in the rate of low birth weight infants (LBW, less than 2,500 g) was seen in the country between 1976 and 1977. A U-formed effect of maternal age and of parity was demonstrated. A marked interaction between the effects of these two variables existed. Two social groups were compared and the well-known high rate of LBW infants associated with low socioeconomic conditions was demonstrated. Standardization for the variables mentioned influenced this effect only little but reduced the difference between the social groups concerning infants above 3.5 kg weight. The background data were used for analysis of restricted geographical areas.