Chronic Toxoplasma gondii, Diabetes, and Retinopathy in Pregnancy

We carried out a prospective study of 690 Hispanic pregnant women (158 T.gondii (TG) positive, 532 TG negative) enrolled at an initial early prenatal visit and then followed for adverse events across the course of their pregnancies. After the initial study visit data were collected from the electronic health record (EHR). From the EHR, pre-pregnancy type 2 diabetes (T2D), and the occurrences of gestational diabetes (GDM) were significantly higher in the T. gondii positive women. GDM was diagnosed in 20% of the T. gondii positive women (χ2=4.4,df=1, p=0.04). compared to 11% in the T. gondii negative women (χ2=7.3, df=1, p=0.007). The frequency of an abnormal insulin glucose tolerance test (IGTT) without diagnosis of GDM was the same in both groups (about 16%).

Additionally, from the initial enrollment, 285 women were recruited into a prospective study with 5 study visits in their prenatal clinics. There were 158 TG positive women who had a chronic, high avidity chronic infection and 127 T.gondii negative "controls". Blood samples, health exams and retinal scannings were done at the clinic study visits. Serial retinal scanning was done only in the T. gondii positive women, as the aim of this analysis was to explore lesions and scars characteristic of toxoplasma disease. Only one scar was found in the population. Retinal images were scanned and graded by an independent retinal scanning service. We found diabetic retinopathy, mostly mild, non-proliferative in type, in 55 of the 130 women who had retinal images done, with 30 of these women having either GDM, positive IGTT, or T2D. The remaining 25 had no other related pathology.

The relationship of chronic TG infection with retinopathy is unknown at this time. The increased prevalence of GDM and T2D in TG positive pregnant women may be important factors, as we have found differences in immune function in pregnant TG positive women (Prescott S, et al.,2023). Plasma levels of IFN- γ and IL-10 were significantly lower in GDM and IL-17 was lower in T2D. A comparison group of TG negative pregnant Hispanic women is necessary to determine this relationship.

Prescott et al., Am J Reprod Immunol. 2023 Sep;90(3):e1376.