As mentioned previously, diabetic retinopathy has a high regression rate in the end of pregnancy or in the postpartum period. The DCCT’s ancillary study was able to assess for any long-term effects of pregnancy on diabetic retinopathy [9]. In this study, the progression of diabetic retinopathy in pregnant women often continued into the first year postpartum. However, the end-of-study analysis demonstrated that this worsening of retinopathy during pregnancy had no long-term consequences. Women who did or did not have pregnancies during the DCCT had similar retinopathy levels at the study’s end (average of 6.5 years of follow-up).

Pathophysiology of Progression
The pathogenesis for the progression of diabetic retinopathy during pregnancy is unclear.  Several researchers have studied retinal circulatory changes in diabetic and control subjects during pregnancy.  Schocket et al.  [21] demonstrated a decrease in retinal venous diameter and volumetric blood flow in diabetic patients during pregnancy.  They hypothesized that the decrease in retinal blood flow may exacerbate retinal ischemia and hypoxia, leading to progression of diabetic retinopathy [22]. Larsen et al. [22] noted a decrease in the retinal arteriolar diameter from the first to the third trimester of pregnancy in diabetic women. However, the change in arteriolar diameter did not correlate with the increase in diabetic retinopathy levels noted from the first to the third trimester.

In contrast, several studies have reported an increase in retinal blood flow during pregnancy in diabetic patients.  Chen et al.  [23]  observed an increase in the retinal blood flow during pregnancy. They suggested that this hyperperfusion of the retina causes an added stress to an already compromised retinal circulation, leading to retinopathy progression.  In addition,  Loukovaara et al. [24]  demonstrated that the retinal capillary blood flow was higher in diabetic women during pregnancy compared with nondiabetic pregnant women.

Management
Diabetic women in their childbearing years should be counseled on the risk of development and progression of diabetic retinopathy,  as well as the importance of ocular examination before and during pregnancy.  Because patients with severe NPDR or proliferative retinopathy are at greatest risk of progression during pregnancy, postponement of conception should be considered until their ocular disease is treated and stabilized.  Also,  because the risk of retinopathy progression during pregnancy is higher in patients with inadequate glycemic control,  tight glycemic control should be attained before conception [16]. In addition,  diabetic patients in their childbearing years should consider planning their pregnancies early (because the risk of progression of diabetic retinopathy is greater in women who have had diabetes for a longer time) [14,15,20].

Treating proliferative diabetic retinopathy during pregnancy is based on the same criteria—as defined by the Diabetic Retinopathy Study and many subsequent rigorous clinical studies—as in nonpregnant patients [25].  The effect of panretinal photocoagulation for proliferative disease appears to be the same in pregnant women as it is in nonpregnant women;  however,  one should monitor retinopathy levels closely and initiate treatment early once indicated because retinopathy can progress rapidly during pregnancy.  Diabetic macular edema that is not threatening the center of vision is often observed without treatment because of its high rate of spontaneous regression in the postpartum period [11].

The American Academy of Ophthalmology offers guidelines for monitoring pregnant diabetic patients in the Preferred Practice Patterns for diabetic retinopathy [26].  Ideally,  pregnant women should receive an ophthalmologic examination before conception and then again in the first trimester.  Subsequent examinations should be based on the retinopathy level found. Women with gestational diabetes are not at an increased risk of diabetic retinopathy and thus do not need to be examined under these guidelines.

Conclusions
Diabetic retinopathy can be adversely affected by pregnancy. Diabetic women in their childbearing years should be counseled regarding the risk of development and progression of diabetic retinopathy during pregnancy.  Also, the importance of glycemic control and ophthalmic evaluations before conception and during pregnancy should be emphasized.  Ophthalmic evaluation should ideally occur before conception and then again in the first trimester of pregnancy.  Careful follow-up thereafter will be based on retinal findings. The practitioner can better manage these patients by understanding the various factors that influence the progression of diabetic retinopathy in pregnancy.

Disclosure
This work is supported in part by an unrestricted grant from the Research to Prevent Blindness, New York, NY.

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Provides American Academy of Opthalmology guidelines for monitoring acute changes in pregnant diabetic patients.

Corresponding author
Bhavna P. Sheth, MD
Eye Institute, Medical College of Wisconsin, 8701 Watertown Plank
Road, Milwaukee, WI 53226, USA.
E-mail: .(JavaScript must be enabled to view this email address)
Current Diabetes Reports 2008, 8:270–273
Current Medicine Group LLC ISSN 1534-4827

Bhavna P. Sheth, MD