The sentence in question: 少子化の影響などで婚姻件数そのものが減っているのに加え、結婚しても式や披露宴などを行わない、いわゆる「ナシ婚」が増えて、そのあおりでブライダルの市場規模が縮小傾向にあるのです。
My attempt at translation: "Even though the decling birthrates effect and the number of marriages itself shrinks, it increases and though people do marriage, they don't do ceremony and celebration and what is called "nankon" increases and with this ???gust (of wind)??? the wedding planning marketscale is in declining trend."
After I had googled ナシ婚 I could somehow figure out what this sentence is about, but obviously I'm still confused by the grammar. Especially 少子化の影響などで婚姻件数そのものが減っているのに加え really throws me off. I can't find any explicitely articulated reference point for 加え in the sentence and I don't know what to extrapolate from the context. Then, it is directly followed by 結婚しても which I find hard to integrate in this grammatical context which already makes it hard for me to find out what is being said precisely here.^^