NEW YORK, Oct 5 (Reuters) A Swedish study indicates that the fertility of women with type 1 diabetes was reduced prior to 1985, but since then is its begun to normalize, if diabetic complications were avoided.
''Stricter metabolic control exercised in the past 20 years may have helped prevent subfertility,'' the researchers speculate in the September issue of Diabetes Care.
Dr Junmei Miaof Jonasson and colleagues from the Karolinska Institute, Stockholm, identified all 5,978 women who had been hospitalized for type 1 diabetes when they were16 years of age or younger. These subjects were followed until the end of 2004 through linkage to nationwide registers.
The investigators used a standardized fertility ratio, the ratio of observed to expected number of live births, to express the relative fertility rate. They also compared the proportion of newborns with congenital malformations with that of the general population.
A total of 4013 live births were recorded among the diabetic women during follow-up. The team reports that the standardized fertility ratio was smaller than expected (0.80). For women with retinopathy, nephropathy, neuropathy, or cardiovascular complications, the respective fertility ratios were 0.63, 0.54, 0.50, and 0.34.
Stratification by year of first hospitalization showed that the reduced fertility was confined to women hospitalized before 1985.
However, those with diabetic complications also had lower fertility rates in all calendar years.
There was also a decrease in the proportion of infants with congenital malformations born to women with type 1 diabetes, from 11.7 percent during 1973-1984 to 6.9 percent during 1995-2004.
However, the proportion of congenital malformations was consistently higher than that for the general population.
''Our results suggest that the new strategy with more rigorous metabolic control instituted in the mid- or late-1980s has been successful also with regard to fertility,'' Jonasson said in an interview with Reuters Health.
''However, the risk of congenital malformations in live newborns of mothers with type 1 diabetes is higher than that of mothers in the general Swedish population although a decreasing trend has been observed in the last 30 years,'' she noted.
''Thus,'' Jonasson said, ''we tell women that when they plan to have a baby the metabolic control must be normal or near-normal,'' before and after conception and in early pregnancy.
Because the study is based on the Swedish population, Jonasson cautioned. ''The results might not be generalized to other populations due to the difference in the quality of health care and strategies'' used to control diabetes.
Reuters SYU DB0911