Lady Gaga is stepping into motherhood. The pop superstar and her fiancé, Michael Polansky, were spotted for the first time since Page Six confirmed they recently welcomed their first child. In photos exclusively obtained by Page Six, the singer, 40, was seen carrying the infant close to her chest as she took a stroll alongside the entrepreneur, 42, in Northern California. Reps did not respond to our request for comment. Gaga kept things casual for the outing, wearing loose white pants and an oversized coat while shielding her eyes behind dark sunglasses. Polansky walked beside his fiancée in shorts, a hoodie, baseball cap and flip-flops….