WHAT CAUSES IT?
In your second trimester, pregnancy hormones (the usual suspect) stimulate your brain to increase the frequency and depth of your breaths, allowing you to take in more oxygen for your growing baby-to-be. Those hormones also swell the capillaries in your respiratory tract and relax the muscles of the lungs and bronchial tubes, making you feel like you're sucking wind after nothing more strenuous than a trip to the fridge. In the third trimester around week 31, your expanding uterus and baby have compressed your lungs, limiting their ability to fully expand when you take a breath and causing you to feel like you've just run a marathon when you've only climbed a flight of stairs.
WHAT YOU NEED TO KNOW
As your pregnancy advances, your uterus is going to get ever more selfish about space, unceremoniously shoving many of your other organs — like your lungs — out of the way to make room for baby. Fortunately, while the resulting breathlessness you're experiencing may make feel very uncomfortable to you, your baby is blissfully unaware and kept well-stocked with oxygen through the placenta. Here's something to look forward to: You might feel significantly less short of breath during the end of your pregnancy, when your baby drops down into your pelvis, freeing up room for your lungs.
Sometimes breathlessness can be caused if your body is low on iron, so be sure to check in with your doctor about it. And severe shortness of breath during pregnancy is not normal — if your lips or fingertips seem to be turning bluish, if you have chest pain and a rapid pulse, or if you have a persistent cough, call your practitioner immediately. Also consult with your doctor if you are pregnant and have asthma.
WHAT TO DO IF YOU'RE SHORT OF BREATH DURING PREGNANCY
• Mind your mom and stand as straight as you can. Proper posture gives your lungs a little more room to breathe, literally.
• Sleep propped up on your left side.
• Though you can still go about your daily activities and even continue exercising during pregnancy, don't push yourself too hard. And whenever you can, take it easy (you deserve it!).
What to Expect Editorial Team. Shortness of Breath During Pregnancy
What to Expect Online. 2014; [cited 2014 May 6]; [1 screen]. Available at URL: http://www.whattoexpect.com/pregnancy/symptoms-and-solutions/short-breath.aspx