Trends in delivery and neonatal outcome after in vitro fertilization in Sweden: data for 25 years.

BACKGROUND: Marked changes have occurred in in vitro fertilization (IVF) methodology during the past 25 years but also in characteristics of couples undergoing treatment. METHODS: This study was based on 27 386 women undergoing IVF treatment from 1982 to 2006 and giving birth to 31 850 infants. Outcomes of deliveries were studied using Swedish health registers. Comparisons were made with all deliveries in the population (n = 2 603 601). Adjusted odds ratios were calculated when important changes in background rates had occurred. RESULTS: There was a substantial increase in the use of intracytoplasmatic sperm injection (ICSI) and the transfer of cryopreserved embryos. Among all ICSI cases, the proportion using epididymal or testicular sperm varied between 5 and 10%. Maternal characteristics changed during the observation period but the median age remained relatively constant in spite of the increasing maternal age in the population. There was a decline in the rate of some maternal pregnancy diagnoses (notably pre-eclampsia, premature rupture of membranes) and some neonatal diagnoses (notably preterm births, low birthweight, cerebral hemorrhage, respiratory diagnoses, use of continuous positive airway pressure and mechanical ventilation, sepsis/pneumonia). Up till 1992, the twinning rate increased to a maximum of about 30% and then declined to 5% towards the end of the period whereas higher order multiples nearly disappeared. The total rate of infants with congenital malformations changed only little. CONCLUSIONS: The decrease in unwanted outcomes can, to a large extent, be explained by the reduced rate of multiple births but was seen also among singletons. Other explanations can be sought in changes in the characteristics of patients undergoing IVF.

Maternal and neonatal factors and mortality in children with Down syndrome born in 1973-1980 and 1995-1998.

AIMS: To investigate maternal and neonatal factors in Down syndrome (DS) at birth, the impact of a congenital heart defect (CHD) on these factors and changes over time. METHODS: Medical data of children with DS born in northern Sweden in the periods 1973-1980 (n = 219) and 1995-1998 (n = 88) obtained from the Swedish Medical Birth Register were compared. A comparison with the general population on a group level was also made. RESULTS: The main finding was a reduction in infant mortality in DS, from 14.2% to 2.3% in 1995-1998 (p < 0.001), but this was still significantly higher than in the general population. The rate of Caesarean sections increased over time (from 14.5% to 27.3%, p < 0.05) even after adjustment for increased maternal age. No change over time was detected in the following rates: premature birth (gestational age < or = 36) (25%); asphyxia (5-min Apgar score < or = 6) (8%); low birthweight (< 2500 g) (14%); or small for gestational age (SGA) (14%); all rates were significantly higher than those of the general population. A CHD did not seem to influence the rates of these factors in a logistic regression model. CONCLUSION: Infant mortality decreased substantially over time in the DS group, whereas there was no reduction in the rate of asphyxia, SGA, low birthweight or prematurity. The presence of a CHD did not influence any of the neonatal factors studied.

Neurosensory outcome and growth at three years in extremely low birthweight infants: follow-up results from the Swedish national prospective study.

A prospective national investigation comprising 633 extremely low birthweight (ELBW) infants born alive in the 2-y period 1990-1992 with a birthweight of < or = 1000 g and gestational age of > or = 23 completed weeks was conducted regarding neurosensory outcome and growth. Three-hundred and sixty-two (98%) surviving ELBW infants were assessed at a median age of 36 months, using a specially designed protocol. At follow-up, mean height, weight and head circumference in both boys and girls were significantly lower than the reference values. The incidence of cerebral palsy was 7% among all children and 14%, 10% and 3% in children born at 23-24, 25-26 and > or = 27 gestational weeks, respectively. At least one obvious handicap was present in 14%, 9% and 3% of these three groups of children, respectively. After adjustment for gestational age, a significantly increased risk of handicap was found in children with intraventricular haemorrhage grade > or = 3 and/or periventricular leucomalacia and in children with retinopathy of prematurity stage > or = 3. The results show that more than 90% of ELBW children born at > or = 25 completed gestational weeks were without neurosensory handicap at 36 months of corrected age. In infants born at 23-24 weeks of gestation, both survival and long-term outcome were less favourable.

Infant mortality in Norway and Sweden 1975-88: a cause-specific analysis of an increasing difference.

In a previous article, a high infant mortality was reported in the 1980s in Norway compared with Sweden. The aim of the present study was to assess secular trends in this difference, and to clarify whether the difference was confined to particular causes of death. Mortality rates, ratios of mortality rates and numbers of excess deaths were calculated on the basis of birth records comprising all livebirths in Norway and Sweden during the two periods 1975-79 and 1985-88. From the first to the second period, the infant mortality ratio for Norway to Sweden increased from 1.22 to 1.45 for single births, and from 1.23 to 1.54 for twin births. Increasing mortality ratios were observed for all ages at death. These were lowest in the early neonatal period (1.09 and 1.20 respectively) and highest in the postneonatal period (1.53 and 1.78 respectively). Within each cause of death category, the mortality rate in Norway was equal to or higher than the rate in Sweden. The highest mortality rate ratios were observed for sudden infant death syndrome (SIDS), 2.44 and 2.46 respectively, for the two time periods. SIDS was also the single cause of death that gave the largest contribution to the Norwegian excess mortality (45% and 53% overall, 65% and 78% for postneonatal deaths, and 65% and 79% for birthweights above 2500 g). In the second period, the excess SIDS mortality in Norway pertained mainly to infants of young mothers, infants of birth order two or more and twin births. An adverse trend for infants of young mothers in Norway was also observed in non-SIDS deaths. This suggests that in Norway, preventive health care should be improved, particularly for young mothers and their infants.

Sudden infant death syndrome in Sweden, 1983-1990: season at death, age at death, and maternal smoking.

Several risk factors for sudden infant death syndrome (SIDS) have been consistently reported, while results regarding seasonality and age at death of SIDS victims are conflicting. In the present population-based cohort study, single births in Sweden from 1983 through 1990 were used to estimate the relative and absolute risks for SIDS associated with season at death, age at death, and maternal smoking. In the winter period, 283 SIDS deaths occurred, while only 98 infants died during summer (winter/summer ratio = 2.9). Taking person-time at risk into account and restricting the analysis to infants aged 7-180 days, the authors determined the relative risk for SIDS to be 3.5 times higher in winter than in summer. When comparing incidence rate differences, they found a more noticeable seasonal variation for early SIDS (7-90 days at death) than for late SIDS (91-180 days at death). For early SIDS, the incidence rate was 0.6 cases per 100,000 person-days higher among smokers than among nonsmokers; for late SIDS, the corresponding difference was 0.3. The effect of smoking on SIDS was not associated with seasonality. Since exposure to passive smoking is likely to vary by season, the results suggest that the effect of smoking on SIDS is prenatal rather than the result of passive smoking after birth.

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.

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.