13.1.1 General Considerations. Although glaucoma is infrequently diagnosed in pregnant patients, occasionally patients with preexisting glaucoma become pregnant. Whenever medications are prescribed for glaucoma, the clinician considers the potential for systemic effects on the patient. In pregnant women, this concern extends to the developing child, as well. One major advantage to the use of topical medications for glaucoma is the reduced systemic absorption and coincident decrease in systemic symptoms. There is little literature demonstrating adverse events of topical medications during pregnancy.1,2
13.1.2 Natural History of Intraocular Pressure During Pregnancy. Metabolic and physiologic changes during pregnancy cause a mild decrease in the intraocular pressure (IOP) compared to the pressure before pregnancy. This has been proposed to occur by several mechanisms. The episcleral venous pressure decreases due to changes in the mother's hemodynamics. A metabolic acidosis occurs, which affects aqueous production and decreases IOP. Comparisons of prepregnancy and pregnancy IOP show an average decrease of 1.5mmHg during pregnancy.3-5 In one study, the majority of eyes required treatment with glaucoma medications and maintained stable visual fields.6 However, the course of glaucoma was variable, with 18% developing visual field loss and another 18% developing increased IOP without visual field loss.6
13.1.3 Teratogenicity. There are no direct studies that show teratogenicity of glaucoma medicines, and few human studies have addressed topical medications. Most data are extrapolated from similar studies of the class of medications. In one study of systemic anticholinergic medications, there were no reported gestational or congenital anomalies.7 Adrenergic compounds interfere with contractions of the uterus (by interfering with the oxytocin pathway), and so may delay labor and cause uterine hypotony (which can prolong postpartum bleeding).7 Prostaglandin analogs for ophthalmic use are in the same class of prostaglandins that may cause abortion when administered as a periuterine injection. The dosage used to stimulate abortion is the equivalent of 400 cc of latanoprost as formulated for ocular use;8 however, caution is advised for use in pregnancy.
13.1.4 FDA Safety Categories. The Food and Drug Administration classifies drugs into several categories of safety levels for use in pregnancy. Class A drugs have an established safety record, with human testing data proving safety. Class B drugs have animal safety data but no human data to confirm. Class C drugs have either animal studies with adverse effects or no human or animal data. Class D drugs have clear risks, although use can be justified under certain conditions. Class X drugs are known to cause birth defects and should never be used during pregnancy. FDA category classifications for glaucoma medications are shown in table 13.1.
Despite the extensive classification of mediations, and high awareness among physicians regarding the importance of the cautious use of medications in women of reproductive age, a retrospective study of 152,531 deliveries from 1996 through 2000 showed that almost half of them received a drug from FDA safety category B, C, D, or X.9
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