The standard medical advice given to pregnant women is to call their doctor if something doesn’t seem “normal.” The problem is, when you’re pregnant, distinguishing normal from abnormal may not be so simple. “Pregnancy comes with a lot of symptoms,” notes Dr. Ami B. Bhatt, Medical Director of the MGH Adult Congenital Heart Disease Program. “It’s very easy to get so worried about these symptoms that you don’t enjoy your pregnancy. The first thing to acknowledge that these body changes are the cause of the symptoms, and most of the time, they’re perfectly normal.”

Some of the greatest changes during pregnancy are occurring in your cardiovascular system. The mother-to-be’s blood volume — the fluid portion of her blood — increases up to 50%. Her heart rate also increases. As the belly gets bigger, the uterus can push up her diaphragm, preventing the lungs from expanding as they normally would. The result is shortness of breath especially when she’s lying down and her belly is close to her chest. As Dr. Bhatt explains, “Interestingly, if this happened in an older person, we might immediately think that it was heart failure, but in pregnancy, it may all be explainable and normal.”

Dr. Bhatt adds that although blood volume increases, the number of iron-carrying red blood cells do not increase as much, which can lead to iron deficiency anemia. Symptoms may include excess fatigue, shortness of breath, an even more rapid heart rate than typically seen in pregnancy, lightheadedness and pallor. The diagnosis can be confirmed by a simple blood test. An additional iron supplement may be prescribed to treat the anemia.

Although we tend to think of high blood pressure as a problem of older people, some women develop it early in life. If you have high blood pressure, it’s important to know that some blood pressure lowering medications — one example is an ACE inhibitor — may be teratogenic, which means they can be harmful to the developing baby. Dr. Bhatt cautions, “Women should be off these medications before conception and put on a medication that is not harmful to the fetus, of which there are several options.”

Dr. Bhatt advises all women who are even considering becoming pregnant to check with their doctors beforehand to make sure that they’re not taking any medication that could harm the fetus. “The only safe medications during pregnancy are prenatal vitamins and drugs that are approved by your physician and known to not cause problems in the first trimester,” she explains.

If you’re being treated for high blood pressure prior to pregnancy, it’s vital to continue treatment during pregnancy. Untreated high blood pressure can increase the risk for a potentially serious condition called preeclampsia, which can lead to seizures, strokes and other complications for mother and baby. Some women who never had high blood pressure before may develop it during pregnancy and require treatment. Although pregnancy-induced high blood pressure may disappear after delivery, it increases the risk for developing high blood pressure later in life. Women with this condition should be aware, however, that it’s possible for high blood pressure to persist even after pregnancy. Whatever the cause, high blood pressure should not be ignored.

Dr. Bhatt adds, if you have a history of high blood pressure or develop it during pregnancy, it’s a good idea to keep an eye on your BP by using an at-home blood pressure tracker.

Fatigue, breathlessness and even anxiety may be normal in pregnancy, but there are some symptoms that shouldn’t be ignored. As Dr. Bhatt explains, “If it’s something that is persistent, or something that prevents you from getting around and doing your daily business, those are generally the symptoms for which we say, pick up the phone.”