COSMOS logo thumbnail


standard maternity care
'one-to-one' midwifery support



In July 2012, findings from the COSMOS trial were published in the British Journal of Obstetrics and Gynaecology. In October 2015, the International Journal of Obstetrics and Gynaecology (BJOG) published the results (see press release).

COSMOS — 'COmparing Standard Maternity care with One to one midwifery Support' — was a trial of caseload midwifery, a model of maternity care recommended in Victoria and throughout Australia.

A number of hospitals have introduced caseload in recent years; however, the model had not been subjected to rigorous evaluation.

Funded by the National Health and Medical Research Council, the trial compared caseload midwifery care with standard options of care for women at low risk of medical complications at the Royal Women's Hospital in Melbourne. In caseload midwifery, women are cared for by a primary midwife throughout pregnancy, birth and the early postnatal period, and care is provided by one or two back-up midwives when needed.

The study is the first randomised controlled trial of caseload midwifery in Australia and only the third internationally. It is also the largest study of its kind in the world.


The COSMOS trial, which recruited over 2,300 women, found that women who were randomly allocated to receive caseload midwifery care (compared with women allocated to standard care)

  • were less likely to have a caesarean birth,
  • more likely to have a normal birth, and
  • less likely to have epidural pain relief during labour.
  • The study also found that babies of women who had caseload midwifery care were less likely to be admitted to the special care nursery or neonatal intensive care.
  • Women allocated to caseload midwifery were also more satisfied with their care during pregnancy, birth, and after the birth in hospital and at home.

The reduction in caesarean births and associated reduction in length of stay may also yield some cost savings. A full cost analysis and cost-effectiveness analysis will be completed based on these birth outcomes and data on service use and costs over the first six months after birth.

The results will assist policy-makers and maternity services in planning for future models of maternity care in Australia and internationally.


McLachlan HL, Forster DA, Davey MA, Lumley J, Farrell T, Oats J, Gold L, Waldenstrom U, Albers L, Biro MA. COSMOS: COmparing Standard Maternity care with one-to-one midwifery support: A randomised controlled trial. BMC Pregnancy Childbirth  2008; 8: 35. View this article online

Publication of results

McLachlan HL, Forster DA, Davey MA, Farrell T, Gold L, Biro MA, Albers L, Flood M, Oats J, Waldenström U. Effects of continuity of care by a primary midwife (caseload midwifery) on caesarean section rates in women of low obstetric risk: the COSMOS randomised controlled trial. BJOG 2012;119(12):1483–92. View this article online

Davey M-A, McLachlan H, Forster D, Flood M. Influence of timing of admission in labour and management of labour on method of birth: results from a randomised controlled trial of caseload midwifery (COSMOS trial). Midwifery 2013;29(12):1297–302. View this article online

McLachlan HL, Forster DA, Davey MA, Farrell T, Flood M, Shafiei T, Waldenström U. The effect of primary midwife-led care on women's experience of childbirth: results from the COSMOS randomised controlled trial. BJOG 2015 (in press). Epub 2015 Oct 26. View this article online

Related news articles

There has been a lot of media coverage since the findings were published on 25 July 2012. Here are some of the headlines:

more information

ACM-Hobart-2013-CosmosFor more information about the trial, please contact Professor Helen McLachlan on
(03) 9479 8800 or email