Outcomes of pregnancy in insulin dependent diabetic women: results of a five year population cohort study

Objective: To monitor pregnancies in women with pre-existent insulin dependent diabetes for pregnancy loss, congenital malformations, and fetal growth in a geographically defined area of north west England. Design: Population cohort study. Setting: 10 maternity units in Cheshire, Lancashire, and Merseyside which had no regional guidelines for the management of pregnancy in diabetic women. Subjects: 462 pregnancies in 355 women with insulin dependent diabetes from the 10 centres over five years (1990-4 inclusive). Main outcome measures: Numbers and rates of miscarriages, stillbirths, and neonatal and postneonatal deaths; prevalence of congenital malformations; birth weight in relation to gestational age. Results: Among 462 pregnancies, 351 (76%) resulted in a liveborn infant, 78 (17%) aborted spontaneously, nine (2%) resulted in stillbirth, and 24 (5%) were terminated. Of the terminations, nine were for congenital malformation. The stillbirth rate was 25.0/1000 total births (95% confidence interval 8.9 to 41.1) compared with a population rate of 5.0/1000, and infant mortality was 19.9/1000 live births (5.3 to 34.6) compared with 6.8/1000. The prevalence of congenital malformations was 94.0/1000 live births (63.5 to 124.5) compared with 9.7/1000 in the general population. When corrected for gestational age, mean birth weight in the sample was 1.3 standard deviations greater than that of infants of non-diabetic mothers. Infants with congenital malformations weighed less than those without. Conclusion: In an unselected population the infants of women with pre-existent insulin dependent diabetes mellitus have a 10-fold greater risk of a congenital malformation and a fivefold greater risk of being stillborn than infants in the general population. Further improvements in the management of pregnancy in diabetic women are needed if target of die St Vincent declaration of 1989 is to be met.