Mothers of Twins Have a Higher Risk of Heart Disease in the Year Following the Birth

The risk of being admitted to hospital with heart disease is twice as high for mothers of twins in the year after giving birth as for mothers of singletons, a study published in the European Heart Journal shows. The risk is even higher for mothers of twins who suffered from high blood pressure during pregnancy.

The study was led by Professor Cande Ananth from the Department of Obstetrics, Gynecology and Reproductive Sciences at Rutgers Robert Wood Johnson Medical School in New Jersey, USA. He said: “The rate of twin pregnancies has increased worldwide in recent decades due to fertility treatments and older maternal age. Previous studies have shown that there is no increased risk of cardiovascular disease in the long term when observing people with twin pregnancies for decades after delivery. However, this is contrary to what we observe clinically when caring for patients with twin pregnancies. “Given the unacceptably high rate of maternal mortality from cardiovascular disease in the first year after childbirth, we wanted to investigate whether twin pregnancies increase this risk.”

How Twin Births and Heart Disease are Linked

The researchers analyzed data on 36 million hospital births from the US Nationwide Readmissions Database from US hospitals between 2010 and 2020. They divided pregnant patients into four groups: those who had twins but had normal blood pressure during pregnancy, those who had twins and had hypertensive pregnancy disease (high blood pressure), those who had a single pregnancy with normal blood pressure, and women who had a single pregnancy with hypertensive pregnancy disease.

Gestational hypertensive disorders include pre-eclampsia, eclampsia, gestosis, and superimposed pre-eclampsia (pre-eclampsia that develops on the basis of chronic hypertension). For each group, the researchers calculated the proportion of patients who were readmitted to hospital with any type of cardiovascular disease, including heart attack, heart failure or stroke, within one year of delivery. The researchers found that the rate of cardiovascular re-admissions within one year of giving birth was higher overall for twin births (1,105.4 per 100,000 births) than for singleton pregnancies (734.1 per 100,000 births).

Compared to singleton pregnancies with normal blood pressure, women with twins and normal blood pressure were about twice as likely to be hospitalized for cardiovascular disease. For women with twins and high blood pressure during pregnancy, the risk is more than eight times higher. However, one year after giving birth, the mortality rate from any cause, including heart disease, was higher for singleton mothers with high blood pressure than for mothers of twins with high blood pressure. This suggests that the risk for mothers of twins decreases in the long term, while mothers of singletons may have other pre-existing cardiovascular risk factors. The researchers were unable to examine key risk factors for cardiovascular disease, such as race/ethnicity, smoking, obesity and drug use, because these were not consistently recorded in the database. Dr. Ruby Lin, a maternal-fetal medicine fellow at Rutgers Robert Wood Johnson Medical School and lead author of the study, said, “The mother’s heart works harder in twin pregnancies than in singleton pregnancies, and it takes weeks for the mother’s heart to return to its pre-pregnancy state.

Proper Follow-Up is Important for up to a Year After Delivery

Women who have had twin pregnancies should be aware of a short-term increase in complications of heart disease in the first year after childbirth, even if their pregnancy was not complicated by hypertension such as preeclampsia. Patients undergoing fertility treatment, especially those with other cardiovascular risk factors such as older age, obesity, diabetes, hypertension or heart disease, should be made aware that twinning pregnancies may cause a short-term increase in cardiovascular disease complications, according to the researchers.

Given these higher risks, healthcare providers should continue to offer follow-up for high-risk pregnancies such as twin pregnancies for up to a year after delivery. According to the researchers, the fourth trimester (12 weeks after delivery) should be recognized as a critical period for making effective changes that will have a long-term impact on cardiovascular health. Collaboration between obstetricians, cardiologists and other medical professionals is essential to overcome the crisis of maternal mortality and reduce postpartum complications.