During pregnancy, a woman’s body makes more blood for the growing baby. Her body adjusts; the heart gets bigger and pumps faster and harder. In women with congenital heart defects, pregnancy may strain the heart and cause it not to function as well.
As the mother’s heart gets ready for delivery, additional hormones are released that make the heart pump stronger. These hormones can also make the heart have irregular or fast heartbeats.
Also, the mother’s body prepares for delivery by making it easier for their blood to clot. Some women with congenital heart disease develop blood clots in the circulation more easily than others. Medications can help manage this.