Academic journal article Australian Health Review

Multifetal Pregnancies: Preterm Admissions and Outcomes

Academic journal article Australian Health Review

Multifetal Pregnancies: Preterm Admissions and Outcomes

Article excerpt


Although multifetal pregnancies (twins, triplets and other higher order multiple pregnancies) affect only a small number of women in Australia (16.1 : 1000 mothers in 2008), they contribute significantly to the rates of preterm birth (21.6% of all preterm infants) and hence have a significant impact on health services.1 The rate of multifetal pregnancy increased in Australia from the 1970s until 2001, associated with increased use of assisted reproductive technologies (ART) and increasing maternal age.2,3 Despite increased use of ART, recent increased awareness of multifetal pregnancy complications and improvements in ART have led to a reduction in numbers of embryos transferred at in vitro fertilisation, and a subsequent reduction in multifetal pregnancy in Australia in 2009 compared with 2008.4,5 Triplet and higher order multifetal pregnancies have remained fairly stable with a rate of 0.3 to 0.4 per 1000 mothers since 1999, but dropped to a rate of 0.2 per 1000 mothers in 2008.1

Multifetal pregnancies increase the risk of pregnancy complications and adverse outcomes for mothers and babies and hence require a higher level of care than singleton pregnancies.3,6 Women with a multifetal pregnancy are at increased risk of hypertensive disorders, gestational diabetes, preterm birth, antepartum and postpartum haemorrhage, and are more likely to deliver by Caesarean section and to have serious maternal morbidity.3,6-8 Because maternal and fetal risks increase according to the number of fetuses, multifetal pregnancies should be assessed separately from singleton pregnancies. In practice, this has often meant that studies include only singleton pregnancies and are rarely repeated for multifetal pregnancies. Little health services research has specifically examined multifetal pregnancies.

We have previously reported rates of hospital admissions during weeks 20-36 for women with singleton pregnancies, and the outcomes of those admissions as discharge, transfer to higher care, or delivery of the infant.9 This study extends that work to multifetal pregnancies.


The study population comprised women with multifetal pregnancies who were admitted to hospital during weeks 20-36 and who delivered at gestations of 24 weeks or more in 2001-2008 in New South Wales (NSW).

Data were obtained from the NSW Perinatal (formerly Midwives) Data Collection (PDC) and linked to the NSW Admitted Patients Data Collection (APDC). Record linkage was conducted by the Centre for Health Record Linkage and was approved by the NSW Population and Health Services Research Ethics Committee. The PDC (birth record) is a population-based surveillance system covering all livebirths and stillbirths>20 weeks gestation or>400 g birthweight, and includes demographic, medical and obstetric information, and information on the condition of the infant. The APDC (hospital record) is a census of all inpatient admissions (public and private) in NSW. Diagnoses and procedures for each admission are coded according to the 10th revision of the International Classification of Diseases, Australian Modification (ICD-10-AM) and the Australian Classification of Health Interventions (ACHI). The validity of the probabilistic record linkage is extremely high with less than 1% of records having an incorrect match.10 Validation studies show that the PDC and APDC have low rates of missing data and generally high levels of agreement with information obtained directly from medical records. Only factors that are well and accurately reported were included in the analyses.11-14

Except for selecting multifetal pregnancies rather than singletons, record selection and extraction was as described for our earlier study of singleton pregnancies.9 Briefly, for each birth, records of all the mother's hospital admissions (including hospital-to-hospital transfers) where the admission occurred at 20-36 weeks gestation were retained. Gestational age (in weeks) at admission was estimated from the baby's date of birth and gestational age in the PDC, and the admission date in the APDC. …

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