Victorian Perinatal Data Collection Unit Research Articles

Cerebral palsy and assisted reproductive technologies: a case–control study

To determine whether assisted reproductive technologies (ART) were more likely to be the method of conception in singletons with cerebral palsy (CP) than in those without CP. Singletons with CP born between 1991 and 2004 were selected from the Victorian Cerebral Palsy Register and matched for birth year to two singletons randomly selected from the Victorian Perinatal Data Collection Unit. Data from both sources were linked to records from three ART centres. Conditional logistic regression was used to assess the association between CP and aspects of conception using ART. Multivariate models were adjusted for parity, previous miscarriages, sex, gestational age, birthweight, and weight for gestational age. We identified 1241 singletons with CP (males n=721 [58%], females n=420 [42/100]; motor type: spastic [87%; unilateral 37%; bilateral 63%], ataxic n=60 [5/100], dyskinetic n=46 [4/100], hypotonic n=29 [2/100], unknown n=25 [2/100]. Gross Motor Function Classification System levels were I n=363 [29/100], II n=297 [24/100], III n=137 [11/100], IV n=160 [13/100], V n=192 [15/100], and unknown n=92 [7/100]). Sixteen (1.3/100) of the children with CP and 25 (1.0/100) of 2482 children without CP were conceived using ART. There was no significant increase in the odds of children with CP being conceived using ART (adjusted odds ratio 1.19, 95% confidence interval (CI) 0.63, 2.24) nor in the odds of them being conceived by a subfertile couple without ART (adjusted odds ratio 2.7, 95% CI 0.87, 8.36). Singleton conception using ART is not strongly associated with an increased risk of CP.

Outcomes after ART mainly occur with fresh not frozen embryo transfers: significance and implications

OBJECTIVE: The aim was to determine which factors affect adverse birth outcomes of singletons after ART including low birthweight (LBW<2.5kg), preterm birth (PTB<37weeks), and perinatal death (PND, stillbirth or neonatal death <28 days). DESIGN: A record linkage study of birth information in the Victorian Perinatal Data Collection Unit linked to all the Melbourne ART centers' patients between 1991-2004 who delivered singletons of 20 or more weeks gestation. MATERIALS AND METHODS: Data were compared for the first singleton births from IVF or ICSI fresh and frozen (FET) embryo transfers with those of two control groups: 1. women seen for infertility but who conceived without ART (non ART) and 2. fertile controls from the general population matched 3:1 by age and year of parturition. Analysis included logistic regression to adjust for covariates. RESULTS: LBW, PTB and PND were significantly more frequent with fresh embryo transfers than in the control general population (Table 1). The higher LBW and PTB rates with FET and non ART were not significant after covariates such as parity were adjusted for by regression analysis but the results with fresh transfers remained highly significant. CONCLUSIONS: These results suggest the adverse birth outcomes of ART are associated with fresh embryo transfers and therefore embryology laboratory procedures affecting the embryos are not the cause because they are not seen with FET. The adverse effects must operate via the woman. If these involve ovarian stimulation or anesthesia for oocyte collection they may be able to be modified to improve birth outcomes. The other implication is that FET should be more widely used.Table 1Frequencies (number and (%)) of low birthweight (LBW), preterm birth (PTB), and perinatal death (PND) in singleton births after fresh (IVF/ICSI) and frozen embryo transfers (FET), non ART conceptions in women seen for infertility (non ART), and natural conceptions in the general population (Control)GroupLBWPTBPNDTotalIVF/ICSI469 (11.0)a527 (12.3)a80 (1.87)a4279FET163 (6.5)b237 (9.4)b29 (1.16)b2510Non ART149 (6.9)b177 (8.2)b27 (1.24)b2169Control1260 (5.1)c1519 (6.2)c224 (0.81)b24646Percentages with different letters are significantly different (p<0.05). Open table in a new tab Percentages with different letters are significantly different (p<0.05).

Merilyn Riley: Senior Research Officer, Victorian Perinatal Data Collection Unit, Department of Human Services, Victoria

Merilyn Riley: Senior Research Officer, Victorian Perinatal Data Collection Unit, Department of Human Services, Victoria

Stillbirths and neonatal deaths in appropriate, small and large birthweight for gestational age fetuses

To compare the risk of stillbirth and neonatal death in small-for-gestational-age (SGA), appropriate-for-gestational-age (AGA) and large-for-gestational-age (LGA) fetuses and neonates. Retrospective analysis of 662 043 births and outcomes recorded in the Victorian Perinatal Data Collection Unit (1992-2002). Births in Victoria in 1992-2002. Multiple pregnancy and congenital birth defects. Births, stillbirths and neonatal deaths at each week of gestation after 23 weeks were stratified by birthweight into appropriate, small and large for gestational age. Stillbirth risk per 1000 ongoing pregnancies and neonatal death rate per 1000 live births were calculated. For the AGA group, the overall stillbirth risk was 2.88 per 1000 and neonatal death rate was 1.35 per 1000. In the LGA group, these were 2.62 and 1.83 per 1000, respectively. The slight increase in neonatal death rate among LGA fetuses was confined to those delivered after 28 weeks gestation. In the SGA group, the stillbirth risk and neonatal death rate were 15.1 and 3.99 per 1000, respectively. The risk of stillbirth per week of gestational age and neonatal death rates do not differ significantly between AGA and LGA fetuses and neonates. The SGA fetus is at significantly greater risk of both stillbirth and neonatal death, particularly with advancing gestational age.

Population‐based study of antenatal detection of congenital heart disease by ultrasound examination

Ultrasound-based screening is widely employed for the detection of congenital malformations in utero including congenital heart disease (CHD), but there is widespread variability in the efficacy of screening programs. We aimed to evaluate current antenatal detection rates of selected congenital heart defects in Victoria. Data were collected from the Victorian Perinatal Data Collection Unit and Birth Defects Registry. There were 631 209 births in Victoria (1993-2002), of which 4897 cases had CHD. Cases included live births, stillbirths and termination of pregnancies because of CHD. We reviewed all cases from 1999 to 2002 with atrioventricular septal defect, simple coarctation of the aorta, double-inlet or -outlet ventricle, hypoplastic left heart syndrome, simple transposition of the great arteries (TGA), tetralogy of Fallot and truncus arteriosus. Outcome measures were antenatal diagnosis, pregnancy outcome and associated malformations. The overall birth prevalence of CHD from 1993 to 2002 in Victoria was 7.8/1000. The antenatal detection rate for the seven selected defects from 1999 to 2002 was 52.8%. All but 4.8% of the cases had an ultrasound examination at > 13 weeks' gestation. Antenatal detection was highest for hypoplastic left heart syndrome (84.6%) and lowest for simple TGA (17.0%). This study shows wide variation in the antenatal detection rate of CHD in Victoria. The low antenatal detection rate of TGA, a defect that should be detected easily, demonstrates suboptimal routine obstetric anomaly scanning.

Validation of the Victorian Perinatal Morbidity Statistics form: new items, pre-coded text and free text.

This study assessed the quality of information on the form used by the Victorian Perinatal Data Collection Unit. Information relating to four new and one modified data items, and to pre-coded and free text regions relating to maternal morbidity, was compared with that in the medical record. The new data items were documented correctly on 95.5% of forms, as were 67% of pre-coded conditions. Between 53% and 75% of free text items were correctly recorded. The results highlight the need for information and education sessions for midwives and other staff in order to collect and maintain high quality data.

Preterm infants 30-36 weeks' gestation in Victoria--where should they be delivered?

There is little doubt that very preterm infants <30 weeks' gestation should be born in level-3 perinatal centres. For preterm infants 30-36 weeks' gestation, however, the optimum place of birth is not so clear-cut. The aims of this study of livebirths 30-36 weeks' gestational age born in Victoria were to determine: 1) the proportions delivered outside level-3 centres, and 2) for infants born outside level-3 centres, the proportions transferred after birth to a level-3 nursery in the first days after birth. Data on the number of livebirths 30-36 weeks' gestational age in Victoria in the 3 years 1994-1996, inclusive, were supplied by the Victorian Perinatal Data Collection Unit. Data were obtained from the Newborn Emergency Transport Service (NETS) on all transfers within the first 3 days after birth to a level-3 centre for infants born outside level-3 centres. For the 3 years 1994-1996 there were 11,375 livebirths 30-36 weeks' gestational age in Victoria. The proportion born outside a level-3 perinatal unit was 57.9% overall, and rose with increasing gestational age, from 10.9% at 30 weeks to 69.0% at 36 weeks. Of the 6,587 livebirths outside a level-3 centre, 808 (12.3%) were transferred within the first 3 days after birth by NETS to a level-3 centre, the proportions falling with increasing maturity, being 73.7%, 48.5%, 28.4%, 26.9%, 18.8%, 11.8%, and 7.0% at 30, 31, 32, 33, 34, 35, and 36 weeks, respectively. These data may help medical practitioners when determining the place of delivery for infants 30-36 weeks' gestation.

Congenital malformations in Victoria, Australia, 1983-95: an overview of infant characteristics.

To provide an overview of the characteristics of Victorian infants born between 1983 and 1995 who are affected by one or more of 27 sentinel birth defects. Using data on congenital malformations supplied to the Victorian Perinatal Data Collection Unit from multiple sources between 1983 and 1995, information was summarised for 25231 infants (born at 20 weeks or more) and 1566 terminations of pregnancy before 20 weeks' gestation. During the 13-year study period in Victoria, 3.2% of babies had at least one malformation. Congenital dislocation of the hip was the most common defect with a prevalence of 28.9 per 10000 pregnancies or 1/346. Increase in birth prevalence between 1983 and 1995 is greatest in obstructive defects of the renal pelvis, hypospadias and the trisomies 21,13 and 18. Nearly 50% of pregnancies affected by anencephaly were terminated before 20 weeks compared to 26% affected by spina bifida. The perinatal mortality of infants born at 20 weeks or more with congenital malformations is more than 10 times greater than that of infants without any malformations. Males are more at risk of being born with a malformation than females. Congenital malformations are more common in infants of multiple pregnancies and those of low birthweight. This large data collection is a valuable source of information for perinatal epidemiologists, for providers of prenatal diagnostic services and for the care of the disabled. In addition, the continued reporting and monitoring of birth defects will allow for targeted research that may lead to a better understanding of their aetiology.

Validating a statewide data collection: differences in information technology resources between hospitals.

The Victorian Perinatal Data Collection Unit (VPDCU) is a statewide data collection established to collect information on the health of mothers and their babies. A Perinatal Morbidity Statistics Form is required to be completed for every birth, then forwarded to the VPDCU. Many medical record departments are responsible for both forwarding the forms to the VPDCU and responding to queries on data accuracy. In 1996 we undertook to determine if we were receiving a perinatal form for every birth occurring at every hospital in the State with obstetric beds. Health information managers were requested to supply a listing of all babies born at their hospitals in 1995-129 hospitals responded. Overall 62,759 births were validated. The VPDCU had received a perinatal form for 99.6 per cent of these births, with 251 missing forms. Reasons why the VPDCU had not received the forms were investigated.

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.

Growth and Physical Outcome of Children Conceived by In Vitro Fertilization

To determine the growth and physical outcome at 2 years of age for children born after assisted reproductive techniques in the state of Victoria. Using a case-matched control study between January 1991 and July 1993, 314 children (196 singletons, 47 sets of twins, 8 sets of triplets) conceived after in vitro fertilization (IVF) and related techniques at the Monash IVF and Royal Women's Hospital Reproductive Biology Unit and 150 control children (113 singletons, 17 sets of twins, 1 set of triplets) randomly selected from the general population using the Victorian Perinatal Data Collection Unit records were enrolled to be examined for minor dysmorphic and major organ abnormalities. Singleton and twin cases were matched for plurality and gestation and date of birth. Triplets were not matched. IVF status was not a significant independent factor for physical outcomes, including malformation rates, nor for days of hospitalization postdischarge and operations. There was no significant interaction between IVF status and mean percentiles for weight and head circumference. The IVF group had a greater mean length percentile. Twins in both groups had significantly poorer physical outcomes than singletons on some measures. This study did not demonstrate an independent IVF effect on the growth and physical outcome of children at 2 years of age when matched for plurality and gestation. The poor outcomes where noted were related to the effects of multiple births. These findings must be viewed in context of the response rates and therefore representativeness of the data. The need for longitudinal studies is demonstrated.

Method for cohort and nested case-control studies: the prevalence, timing and effectiveness of obstetric ultrasound, Victoria 1991-1992.

The study was designed to assess the effectiveness of obstetric ultrasound in the diagnosis of congenital malformations and to establish its prevalence of use and timing. Statewide data were collected in 138 of the 141 obstetric hospitals in Victoria over a 12-month period during 1991-1992. Within the final cohort of 55,226 mothers providing responses, a nested case-control study group was formed. This group comprised 719 cases (infants born with one or more malformations potentially diagnosable at 16-20 weeks) and 703 controls (non-malformed infants). The cases for the group were extracted from the Victorian Congenital Malformations Register; controls were randomly selected from the Victorian Perinatal Data Collection Unit's database. Of the 1422 in the study group, 1328 medical records were validated in 100 hospitals. The design, method, procedure, sample and outcome are described for the cohort and nested case-control studies. At the conclusion of the study it was established that major variations between the cohort and missing data were confined to mothers less likely to have had a spontaneous vaginal delivery or to those with poor perinatal outcome. There was no significant selective loss of cases or controls in the nested case-control study group.

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.

Improvement of Outcome for Infants of Birth Weight Under 1000g

THE VICTORIAN INFANT COLLABORATIVE STUDY GROUP The Women's Royal Hospital, The Royal Children's Hospital, The Mercy Maternity Hospital, and Monash Medical Center, Melbourne; and Victorian Perinatal Data Collection Unit, and Newborn Emergency Transport Service, Victoria, Australia