Annabelle Chan

Maternal and perinatal health outcomes by body mass index category

Aims:  To determine the effect of increasing maternal body mass index (BMI) during pregnancy on maternal and infant health outcomes.

Surgically obtained sperm, and risk of gestational hypertension and pre-eclampsia

The cause of pre-eclampsia is unknown, although a partner-specific immune maladaptation might be involved. We compared rates of pre-eclampsia and gestational hypertension in women whose genital tracts had and had not been exposed to their partners sperm cells. Our aim was to ascertain whether or not protective partner-specific immune-tolerance is conveyed by sperm cells, rather than seminal fluid. Our findings indicate that, compared with women exposed to their partners sperm cells and seminal fluid--ie, those treated with in-vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) with ejaculated sperm--the risk of hypertension was doubled and the risk of pre-eclampsia tripled in those never exposed to their partners sperm--ie, those treated with ICSI done with surgically obtained sperm.

Perinatal risk factors for developmental dysplasia of the hip

AIMS To identify perinatal risk factors for developmental dysplasia of the hip (DDH) and define the risk for each factor. METHODS In this case control study, using logistic regression analysis, all 1127 cases of isolated DDH live born in South Australia in 1986-93 and notified to the South Australian Birth Defects Register were included; controls comprised 150 130 live births in South Australia during the same period without any notified congenital abnormalities. RESULTS Breech presentation, oligohydramnios, female sex and primiparity were confirmed as risk factors for DDH. Significant findings were an increased risk for vaginal delivery over caesarean section for breech presentation (as well as an increased risk for emergency section over elective section), high birthweight (⩾4000 g), postmaturity and older maternal age; multiple births and preterm births had a reduced risk. There was no increased risk for caesarean section in the absence of breech presentation. For breech presentation, the risk of DDH was estimated to be at least 2.7% for girls and 0.8% for boys; a combination of factors increased the risk. CONCLUSIONS It is suggested that the risk factors identified be used as indications for repeat screening at 6 weeks of age and whenever possible in infancy. Other indications are family history and associated abnormalities.

Risks of adverse outcomes in the next birth after a first cesarean delivery.

OBJECTIVE: To estimate the risks of cesarean first birth, compared with vaginal first birth, for adverse obstetric and perinatal outcomes in the second birth. METHODS: Population-based retrospective cohort study of all singleton, second births in the South Australian perinatal data collection 1998 to 2003 comparing outcomes for 8,725 women who underwent a cesarean delivery for their first birth with 27,313 women who underwent a vaginal first birth. Predictor variables include age, indigenous status, smoking, pregnancy interval, medical and obstetric complications, gestation, patient type, hospital category, and history of ectopic pregnancy, miscarriage, stillbirth or termination of pregnancy. RESULTS: The cesarean delivery cohort had increased risks for malpresentation (odds ratio [OR] 1.84, 95% confidence interval [CI] 1.65–2.06), placenta previa (OR 1.66, 95% CI 1.30–2.11), antepartum hemorrhage (OR 1.23, 95% CI 1.08–1.41), placenta accreta (OR 18.79, 95% CI 2.28–864.6), prolonged labor (OR 5.89, 95% CI 3.91–8.89), emergency cesarean (relative risk 9.37, 95% CI 8.98–9.76) and uterine rupture (OR 84.42, 95% CI 14.64-infinity), preterm birth (OR 1.17, 95% CI 1.04–1.31), low birth weight (OR 1.30, 95% CI 1.14–1.48), small for gestational age (OR 1.12, 95% CI 1.02–1.23), stillbirth (OR 1.56, 95% CI 1.04–2.32), and unexplained stillbirth (OR 2.34, 95% CI 1.26–4.37). The range of the number of primary cesarean deliveries needed to harm included 134 for one additional preterm birth, up to 1,536 for one additional placenta accreta. CONCLUSION: Cesarean delivery is associated with increased risks for adverse obstetric and perinatal outcomes in the subsequent birth. However, some risks may be due to confounding factors related to the indication for the first cesarean. LEVEL OF EVIDENCE: II

Substance use during pregnancy: risk factors and obstetric and perinatal outcomes in South Australia.

Objective: To determine the prevalence of self‐reported substance use during pregnancy in South Australia, the characteristics of substance users, their obstetric outcomes and the perinatal outcomes of their babies.

Subsequent birth outcomes after an unexplained stillbirth: preliminary population‐based retrospective cohort study

The objective of this study was to determine whether women who have experienced an unexplained stillbirth have a higher risk of adverse perinatal outcomes in subsequent births. We compared 316 subsequent births to women with a previous unexplained stillbirth, with 3160 births to women with no previous history of stillbirth, matched by year of birth, in the period 1987–1997, from the South Australian perinatal database, using logistic regression analysis. There was no increase in the rate of stillbirth and no statistically significant increase in the rate of perinatal death (OR 1.62 [95% CI 0.63^4.20]) or neonatal death, although larger studies are needed to confirm this. However, after adjusting for age, parity, and hospital category of birth, women who had a previous stillbirth had increased incidences in subsequent births of abnormal glucose tolerance or gestational diabetes (a fourfold increase); induction of labour and elective Caesarean section; fetal distress and postpartum haemorrhage; and forceps and emergency Caesarean delivery and preterm birth, which were independent of Induction of labour. Gestational age at birth and birthweight were also significantly reduced, suggesting a need for close monitoring of their future pregnancies.

Late diagnosis of congenital dislocation of the hip and presence of a screening programme: South Australian population-based study

BACKGROUND The Medical Research Council Working Party on Congenital Dislocation of the Hip have reported an ascertainment-adjusted incidence of a first operative procedure for congenital dislocation of the hip (CDH) of 0.78 per 1000 livebirths, which is similar to the incidence of CDH before the start of the UK screening programme. The report showed that CDH had not been detected by routine screening before age 3 months in 70% of children reported to the national orthopaedic surveillance scheme. This report raised concerns about the merit of screening at birth for CDH. We aimed to find out the incidence of an operative procedure for CDH in the first 5 years of life among children born in South Australia between 1988 and 1993, and the proportion of these patients that were detected at age 3 months or older. METHODS The states database for inpatient separations between January, 1988, and April, 1998 was searched. Case records were examined for the age and circumstances of diagnosis, and type of operative procedures. Prevalence rates of CDH were obtained from the South Australian Birth Defects Register, which receives notifications from a statutory perinatal data collection of birth defects detected at birth and subsequent voluntary notifications for children up to age 5 years. FINDINGS Of the 55 children born in South Australia between 1988 and 1993 identified as having non-teratological CDH and operative procedures, only 22 (40%) had been diagnosed at age 3 months or older. 18 had an open reduction of the hip joint or osteotomy, or both, and the remainder had arthrograms, closed reductions, and/or tenotomy. The prevalence of non-teratological CDH in children was 7.74 per 1000 livebirths. The incidence of surgery for CDH in the first 5 years of life was 0.46 per 1000 livebirths (95% CI 0.34-0.59) and only 0.19 per 1000 livebirths (0.11-0.26) for those diagnosed late (age 3 months or older). These children diagnosed late represented 2.4% of all known cases of CDH. INTERPRETATION Only 2.4% of known cases of CDH in children born in South Australia had been detected late and required surgery. These results show that a screening programme for CDH can be successful, contrary to the findings of the UK Medical Research Council Working Party.

Risk of uterine rupture in Australian women attempting vaginal birth after one prior caesarean section: a retrospective population-based cohort study

Please cite this paper as: Dekker G, Chan A, Luke C, Priest K, Riley M, Halliday J, King J, Gee V, O’Neill M, Snell M, Cull V, Cornes S. Risk of uterine rupture in Australian women attempting vaginal birth after one prior caesarean section: a retrospective population‐based cohort study. BJOG 2010;117:1358–1365.

Hypertension during pregnancy in South Australia, Part 1: Pregnancy outcomes

Background:  There have been conflicting reports about pregnancy outcome in the hypertensive disorders of pregnancy. The present study was undertaken to examine outcomes using a population database.

Differences in risk factors between early and late diagnosed developmental dysplasia of the hip.

Background: Developmental dysplasia of the hip (DDH) is common, affecting 7.3 per 1000 births in South Australia. Clinical screening programmes exist to identify the condition early to gain the maximum benefit from early treatment. Although these screening programmes are effective, there are still cases that are missed. Previous research has highlighted key risk factors in the development of DDH. Objective: To compare the risk factors of cases of DDH identified late with those that were diagnosed early. Methods: A total of 1281 children with DDH born in 1988–1996 were identified from the South Australian Birth Defects Register. Hospital records of those who had surgery for DDH within 5 years of life were examined for diagnosis details. Twenty seven (2.1%) had been diagnosed at or after 3 months of age and were considered the late DDH cases (a prevalence of 0.15 per 1000 live births). Various factors were compared with early diagnosed DDH cases. Results: Female sex, vertex presentation, normal delivery, rural birth, and discharge from hospital less than 4 days after birth all significantly increased the risk of late diagnosis of DDH. Conclusions: The results show differences in the risk factors for early and late diagnosed DDH. Some known risk factors for DDH are in fact protective for late diagnosis. These results highlight the need for broad newborn population screening and continued vigilance and training in screening programmes.