Don’t change your withholding status on your W-4 to “Married,” if both you and your spouse work. There is a third box that allows you to select “Married” but to withhold at the higher Single rate.
The Married option is intended for single-income households. A smaller portion of your paycheck will be withheld, but you’ll end up with a large tax bill in April.
I’m not a CPA, so don’t take my word for it! (You probably shouldn’t take unsolicited tax advice as a general rule. . .) However, here’s the IRS’s explanation of the different withholding options.