The survival of extremely-low-birthweight infants in Victoria: 1982-1985

Regionalized long-term follow-up

The importance of population-based long-term follow-up studies of geographically determined cohorts to evaluate the effectiveness, efficiency and availability of a regionalized perinatal-neonatal care programme is demonstrated by the Victorian Infant Collaborative Study Group. The survival and quality of survival of consecutively born extremely-low-birthweight infants below 1000 g or extremely preterm infants below 28 weeks' gestation in the state of Victoria were assessed up to 14 years of age over four distinctive eras: 1979-1989, 1985-1987, 1991-1992 and 1997. Both survival and quality-adjusted survival rates rose progressively in all birth weight and gestation subgroups, associated with progressively more such infants being born in level III perinatal centres. Cost-effectiveness and cost-utility ratios remained stable overall, with efficiency gains in the smaller infants over time. Regionalized long-term follow-up provides unique information that is not available from institution-based studies, which is vital to the regional organization of perinatal-neonatal care.

Trends in place of birth for preterm infants in New South Wales, 1992-2001

OBJECTIVE

To examine trends in preterm births, especially those less than 33 weeks gestation, occurring in perinatal centres in New South Wales (NSW) from 1992 to 2001.

METHODS

Population data were obtained from the NSW Midwives' Data Collection. Trends in the proportion of births in perinatal centres by gestation and by type of preterm birth (spontaneous or elective), and in Apgar scores and neonatal mortality were determined.

RESULTS

The preterm birth rate increased from 6.1% in 1992 to 6.7% in 2001. Factors contributing to the increase in preterm births were multiple births and elective preterm deliveries. Births less than 33 weeks gestation in perinatal centres increased from 76% to 83% and for multiple births from 77% to 87%. This coincided with a decrease in 1-minute Apgar scores less than 4 but no significant change in 5-minute Apgar scores or neonatal mortality.

CONCLUSIONS

Progress has been made towards the National Health and Medical Research Council guideline that births less than 33 weeks gestation occur in perinatal centres. Preterm births are increasing, creating greater demands for neonatal intensive care unit care and ventilation services.

Évaluation des risques en anténatal, information des parents et prise en charge de l’accouchement

Perinatal networks, antenatal administration of glucosteroids, postnatal administration of surfactant, and new techniques for mechanical ventilation, have considerably improved the prognosis of extremely preterm infants. Such recent progress in perinatology had enabled neonatologists to provide intensive care for infants born after 24 and 28 weeks of gestation. This practice raises serious medical and ethical issues. The optimal mode of delivery of such newborns is not well established mainly because available studies are retrospective and subjected to biases. Moreover, perinatologists are implicated in the continuing discussion on ethical issues that modify clinical practices.

Population-based study of infants born at less than 28 weeks' gestation in New South Wales, Australia, in 1992-3. New South Wales Neonatal Intensive Care Unit Study Group

The aims of the study were to use the population base of New South Wales (NSW) to study all births from 20 to 27 weeks' gestation in 1992-3 and to compare two data sources for perinatal deaths. The prospective population-based statewide audit (NICUS) of infants admitted to tertiary neonatal intensive care units (NICUs) in NSW was used to collect data on infants less than 28 weeks' gestation registered in 1992-3. This audit also surveyed the 160 obstetric hospitals in NSW to ascertain information on stillbirths and early neonatal deaths in the study period. The NSW midwives data collection (MDC) was the other source of information on stillbirths and labour ward deaths. Data were analysed using SAS. In 1992-3 in NSW 1170 infants were born at 20-27 weeks' gestation. There were 556 stillbirths and 614 live births, of whom 180 (29.3%) died in the labour ward and 434 (70.7%) were admitted to a tertiary NICU. Sixty-six per cent of stillbirths were identified by both data collections, 16.5% by the MDC only and 17% by NICUS only. There was a high major congenital anomaly rate (18.5%) among the stillbirths. Two-thirds of the infants admitted to NICUs survived to 1 year. Information was available on at least one follow-up parameter for 89% (255/288) of the survivors to 12 months (corrected age). Of the 244 infants who had a neurological assessment by a paediatrician, 17% were diagnosed to have cerebral palsy. Eleven per cent of the 239 who had a formal Griffiths developmental assessment had a major intellectual disability. Five (2% of 255) of the 1-year-olds were blind, and 12 (4.7% of 255) had bilateral hearing aids. Seventy-one per cent of the infants examined at 1 year did not have a major disability. For accurate perinatal death data, collection from more than one source is recommended. Infants born at 20-27 weeks' gestation contribute 40% of all stillbirths in NSW, most of the costs of neonatal intensive care as well as the costs of long-term morbidity. In Australia in the early 1990s, the survival of infants born at less than 28 weeks' gestation was best from 26 weeks gestational age onwards. Long-term morbidity did not change from that of earlier cohorts. The most common major disability was cerebral palsy.

Trends in stillbirths and neonatal deaths for very pre-term infants (< 32 weeks' gestation) born in Victoria, 1986-1993

We have examined the trends in stillbirth rates and neonatal mortality rates of infants of 20-31 weeks' gestational born in Victoria during 1986-1993 (n = 6,462), using data from the Victorian Perinatal Data Collection Unit. Seventy four percent of all infants and 83% of all liveborn infants were born in level 3 hospitals. Both stillbirth and neonatal mortality rates were lower for infants of higher gestational ages, and those born in level 3 hospitals. During 1986-1993, annual stillbirth rates remained steady, with mean values of 61.2%, 40.2%, 24.7%, 16.0%, and 11% for infants of gestational ages 20-23, 24-25, 26-27, 28-29, and 30-31 weeks, respectively. The neonatal mortality rates decreased from 76.1 to 38.6%, 42.3 to 17.6%, 12.9 to 6.0%, and 8.4 to 3.7% for liveborn infants of gestational ages 24-25, 26-27, 28-29, and 30-31 weeks, respectively. The time-related falls in neonatal mortality were not due to changes in Caesarean section rates, intubation rates, or the proportions of infants born in, or transferred to, level 3 hospitals. They probably reflect continuing improvements in perinatal care.

Clomiphene citrate and pregnancy outcome

Data from Australia and elsewhere have shown consistently that adverse perinatal outcomes such as preterm birth and perinatal mortality are more common in pregnancies resulting from assisted conception with IVF and GIFT than normally conceived pregnancies. Factors that may contribute to the excess of poor outcomes include maternal factors, the assisted conception procedures themselves and possibly the influence of drugs used to induce superovulation. This review examines the medical literature describing pregnancies following ovulation induction with one of the drugs used to induce superovulation, clomiphene citrate, and compares their outcomes with Australian IVF and GIFT pregnancy outcomes. The review shows that whilst some studies have suggested higher rates of ectopic pregnancy, spontaneous abortion and congenital malformations in clomiphene citrate induced pregnancies, the findings are inconsistent and the data are flawed. There are only very poor data available on the incidence of preterm birth. Multiple pregnancy is a well-recognized adverse outcome of clomiphene citrate induced pregnancies. Attempts to improve perinatal outcomes of pregnancies following assisted conception will be helped by a better understanding of the relative contributions of maternal and treatment factors and further studies of pregnancy outcome after ovulation induction are needed.

Births after a period of infertility in Victorian women 1982-1990

Pregnancies following a period of infertility are often thought to be at increased risk of adverse outcomes. Between 1982-1990, 1465 births were reported to the Victorian Perinatal Data Collection Unit with a history of infertility. We present some characteristics of these births and compare them with all Victorian births in 1986 (n = 61,253) and Australian and New Zealand IVF and GIFT births 1979-1989 (n = 6,675). Women with a history of infertility were older than other Victorian women but younger than the IVF and GIFT group. Multiple births comprised 9% of the infertility group compared with 1.3% in the general Victorian population and 23.7% of IVF and GIFT births. The incidence of low birth-weight (18.6%) and very low birth-weight (4.2%) was higher than in other Victorian births (5.8% and 1.1% respectively) but lower than in IVF and GIFT births (34.6% and 8.9%). Perinatal mortality in the infertility group (33.4 per 1,000) was higher than in the general population (11.1 per 1,000) and similar to the IVF and GIFT group (34.9 per 1,000). The Caesarean section rate after infertility (41%) was more than double the rate in the rest of the Victorian population (16%), and showed a different pattern of indications. The relative risks of low and very low birth-weight, perinatal mortality and Caesarean delivery remained significantly increased for singletons after adjustment for maternal age and parity.

Cerebral palsy in four northern California counties, births 1983 through 1985

To examine the impact of demographic shifts and changes in perinatal medicine on the distribution of cerebral palsy (CP), we investigated characteristics of affected children in a large, recent population-based American cohort study. Children with moderate or severe congenital CP born in four northern California counties in 1983 through 1985 and surviving to age 3 years were identified through records of state service agencies and clinical examination or record review by a single physician. We compared information from birth certificates for 192 children with CP and 155,636 survivors without CP born in those counties in the same period. Children with birth weights < 2500 gm contributed 47.4% of the CP in this population; those < 1000 gm, who were 0.20% of survivors, contributed 7.8%. Children with birth weights of 4000 to 4500 gm were at lowest risk. Among singletons, prevalence of CP was lowest (0.92/1000) in infants born to women aged 25 to 34 years, and was significantly higher in children whose mothers were 40 years or older (3.3/1000), especially if they were high in parity (6.9/1000). Children of teenaged mothers or fathers were at somewhat increased risk of CP. Early gestational age at birth was also an important independent risk factor. Prevalence of CP was slightly higher in black children, apparently related to a greater tendency to be low in birth weight. The time during pregnancy when prenatal care began was similar for children with CP and for the general population. For the 95% of children born weighing > or = 2500 gm, birth in a hospital lacking a special care nursery was not associated with increased risk of CP. Almost 8% of CP occurred in children born weighing < 1000 gm, a group that produced few survivors in the past; 28.1% occurred in children born weighing < 1500 gm. Neither early initiation of prenatal care nor, for that large majority of neonates weighing > 1500 gm, delivery at a hospital with specialized facilities was associated with a lower risk of CP.

Changing two-year outcome of infants weighing 500 to 999 grams at birth: a hospital study

Survival and neurodevelopmental outcome to 2 years were determined for two cohorts of infants weighing 500 to 999 gm at birth, born in a tertiary maternity hospital. Live births increased over time from an annual average of 48.7 in the first era (January 1977 to March 1982) to 64.6 in the second era (January 1985 to December 1987), largely from referrals of additional mothers with pregnancy complications. In the first era, 33.6% (86/256) of infants survived to 2 years; the survival rate improved significantly to 45.9% (89/194) in era 2. After adjustment for birth weight, the odds ratio for survival in era 2 versus era 1 was 1.39 (95% confidence interval = 1.12, 1.73; p less than 0.01). One known survivor in each era was not seen at 2 years of age. In the first era, 59.3% (51/86) of 2-year-old children were free of disability compared with 68.5% (61/89) in era 2 (NS), but the Mental Development Index of the Bayley Scales improved significantly, from 90.0 in era 1 to 98.0 in era 2. For infants weighing less than 800 gm at birth, not only did the 2-year survival rate improve, adjusted for birth weight (odds ratio = 1.53; 95% confidence interval = 1.06, 2.20; p less than 0.05), but there was also a significant reduction in neurologic disabilities in survivors (p = 0.03). For infants weighing 800 to 999 gm at birth, there was a significant improvement in the survival rate, adjusted for birth weight (odds ratio = 1.37; 95% confidence interval = 1.04, 1.79; p less than 0.05), but the rate of neurologic disabilities was unchanged. Increased survival in our tertiary maternity center was achieved without increasing the annual number of severely disabled 2-year-old survivors.

Preventing and managing prematurity

In the past decade the prevention and management of prematurity have begun to be addressed with more appropriate designs. A few strategies--very few--can now be recommended. A few, some widely implemented, can be abandoned. The risks and benefits of most interventions still require clarification.

Methods of delivery and resuscitation of very-low-birthweight infants in Victoria: 1982-1985

This article describes the patterns of delivery and resuscitation for very-low-birthweight infants who were born in Victoria from 1982 to 1985. Caesarean delivery rates increased from 15% to 30% for infants of birthweights of 500-999 g, and from 39% to 52% for infants of birthweights of 1000-1499 g. In level-III hospitals, the proportion of live-born infants who did not receive active resuscitation fell from 32% to 18% for those who weighed 500-999 g, and from 28% to 15% for those who weighed 1000-1499 g. Time trends over the four years showed the management of very-low-birthweight infants to be in a state of rapid transition in all birth settings. At the same time there was a fall in the still-birth rate of infants of birthweights of 500-999 g. Still-births rates for infants of birthweights of 1000-1499 g remained unchanged, as did neonatal mortality rates in both weight groups.

Outcomes of extremely-low-birth-weight infants between 1982 and 1988

Infants with birth weights under 750 g are disproportionately represented in perinatal mortality and morbidity rates. We reviewed the outcomes of 98 infants delivered at our perinatal center between July 1982 and June 1985 (period 1) whose lengths of gestation were 20 or more weeks and whose birth weights were under 750 g, and compared them with the outcomes of 129 such infants born between July 1985 and June 1988 (period 2). The frequency of cesarean section increased from 12 to 19 percent between the two periods. During the entire six-year period, 12 percent of the infants with birth weights under 500 g were intubated, as compared with 28 percent of those between 500 and 599 g, 60 percent of those between 600 and 699 g, and 90 percent of those between 700 and 749 g. The frequency of endotracheal intubation increased between the two periods only for infants with birth weights above 500 g (P less than 0.02). Despite more aggressive treatment, survival did not change, although the mean time to death among infants transferred to the neonatal intensive care unit increased from 73 to 880 hours. Among all live-born infants with birth weights under 750 g, the rate of survival was 20 percent during period 1 and 18 percent during period 2, but 48 and 43 percent of those transferred to the neonatal intensive care unit survived in the two periods reviewed. Neonatal morbidity also did not change. Among survivors at a corrected age of 20 months, 4 of 18 born during period 1 and 7 of 14 born during period 2 had moderate-to-severe neurodevelopmental impairment. When all live-born infants of less than 28 weeks' gestation were considered, only 8 percent of those born at 23 weeks survived, as compared with 16 percent of those born at 24 weeks, and 53, 63, and 72 percent of those born at 25, 26, 27 weeks, respectively. Thus, despite a tendency to perform more cesarean sections and active resuscitations, no improvement in the survival of babies with lengths of gestation below 25 weeks or birth weights under 750 g was observed. The probability of survival is very poor if the length of gestation is less than 24 weeks or the birth weight less than 600 g.