From the drug information on diclofenac...

FDA pregnancy category C. This medication may be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment. Taking diclofenac during the last 3 months of pregnancy may harm the unborn baby. Do not take diclofenac during pregnancy unless your doctor has told you to. Diclofenac can pass into breast milk and may harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby. Do not give this medicine to a child without the advice of a doctor.
Being a category C drug, there's no way I'd risk taking it. Before you start trying for a baby, I'd suggest you really need to chat to your doctor and find some other alternative. It may mean prednisone - a steroid rather than an NSAID, but there are safer drug options during pregnancy.

BW