History of abnormal glucose challenge test as a predictor of abnormal results in subsequent pregnancy

Objective
Currently, history of having an abnormal 1-hour 50-gram glucose challenge test (GCT) is not an indication for a 100-gram glucose challenge test (OGTT) in future pregnancies. We aimed to evaluate repeated GCT results in consecutive pregnancies, in a large population-based cohort.

Study Design
This cohort included all pregnant women who underwent GCT between the years 2005 to 2018 at the Central District of the largest health maintenance organization in Israel. Data were collected from the computerized database. Abnormal GCT was defined as >140 mg/dl. Multivariable logistic model was used to study the association between abnormal GCT results and a history of a previous abnormal GCT result, while adjusting for maternal age and inter- pregnancy interval (IPI).

Results
A total of 66,860 women performed 117,435 GCT's and 32,677 women performed at least two GCT’s in consecutive pregnancies. Women with history of abnormal GCT were more likely to have an additional abnormal result (10.7% vs. 39.2%, among women with history of normal vs. abnormal results, respectively, odds ratio (OR)=5.38, 95%CI 5.0-5.8). While women younger than 35y at second pregnancy (n=26,937) had 11% (3056) pathological GCT at first pregnancy and 36% (1093) in the consecutive one, those older than 35y at second pregnancy (n=5740) had 39% (963) pathological GCT at first pregnancy and 50% (482) in the consecutive one. IPI of more than 5 years was also found to be a risk factor for consecutive abnormal GCT.(Figure). Among women with IPI greater than 5 years, incidence rates were 16.1% and 49.3%, for women with history of normal vs. abnormal results, respectively (OR=5.05, 95%CI 4.2-6.1). Adjustment for maternal age and IPI did not change the results (adjusted OR=5.15; 95%CI 4. 8-5.5).

Conclusion
Women with a history of abnormal GCT are at increased risk for abnormal GCT in consecutive pregnancies. The risk increases among women with inter-pregnancy intervals greater than 5 years. A 100gr OGTT should be considered in women with a history of abnormal GCT results, especially for older women with long inter-pregnancies interval.