MJA: Moses et al., Box 3

3: An estimate of the excess perinatal mortality rate for women not tested for gestational diabetes mellitus in NSW*

Victorian data: Mercy Hospital for Women, Melbourne
At the Mercy Hospital, the overall perinatal mortality rate for women delivering at or after 36 weeks' gestation (who presumably would have had a test if that was the intention) was 0.32%.⁴ For women tested for gestational diabetes mellitus (GDM), the perinatal mortality rate was 0.24%, and for women who did not have a test it was 0.68% (odds ratio, 2.81).

NSW data: Midwives Data Collection (MDC)
The NSW MDC annual publications from 1992 to 1994 show the gestational age of delivery and the perinatal mortality rate for all births at 32-36 weeks' gestation and for those at or after 37 weeks' gestation. For direct comparison with the data of Beischer et al.,⁴ births and perinatal deaths in week 36 were estimated as one-fifth of the total of births and perinatal deaths, respectively, for the period 32-36 weeks' gestation and added to the data available for deliveries at or after 37 weeks' gestation.
For the period 1992-1994, there was an annual average of 83 362 births (94.5% of total births) and 256 perinatal deaths at or after 36 weeks' gestation in NSW. The perinatal mortality rate of women delivering at or after 36 weeks' gestation in NSW was 0.31%.

To estimate the number of perinatal deaths in NSW, the odds ratio of 2.81 between the perinatal mortality rate for women tested for GDM and the perinatal mortality rate for women not tested for GDM who delivered at or after 36 weeks' gestation was extrapolated from the Victorian data to the NSW data.

The perinatal mortality rate for women tested for GDM (i.e., women who were either glucose tolerant or were being treated for GDM) should be 0.16%, and the perinatal mortality rate for women not tested for GDM (which will include women with undiagnosed GDM) should be 0.46%. Therefore, the estimated excess perinatal mortality rate for women not tested for GDM in NSW who delivered at or after 36 weeks is 0.30%, suggesting that there may have been a number of possibly avoidable perinatal deaths.

* Perinatal mortality rate: the number of perinatal deaths (neonatal deaths and stillbirths) per 1000 births.