
February 04, 2025
The heart of a mother carrying twins works harder than the heart of a mother carrying a singleton, putting moms of twins at higher risk of cardiovascular disease during the postpartum period, new research shows. The photo above is a file image of twins taken in Akron, Ohio in 2024.
Women who give birth to twins are twice as likely to be readmitted to the hospital for heart disease within a year compared to mothers who birth one infant, a new study shows.
The risk is even higher for mothers of twins who had high blood pressure during pregnancy. They're eight times more likely to be hospitalized for cardiovascular disease than mothers with hypertension who give birth to one baby, according to the study published Monday in European Heart Journal.
The majority of maternal deaths occur during the postpartum period – the first 365 days after giving birth. During the first week of this period, high blood pressure is the leading cause of death. But cardiomyopathy – a type of heart disease that makes it harder for the heart to pump blood, potentially leading to heart failure – is the primary cause later in the postpartum period, according to a 2022 report from the Commonwealth Fund.
Additionally, people pregnant with multiples are at an increased risk of complications and death. The rate of people carrying twins rose more than 75% in the decades after the first in vitro fertilization in 1978, because the procedure, commonly known as IVF, often involved transferring multiple embryos to the uterus to increase patients' chances of conceiving.
"Previous studies have shown no long-term increased risk of cardiovascular disease when following people with twin pregnancies for decades after delivery," researcher Cande Ananth said in a news release. "However, this is counterintuitive to what we observe clinically when caring for patients with twin pregnancies. Given the unacceptably high rate of maternal mortality in the first year after birth due to cardiovascular disease, we wanted to examine whether twin pregnancies increase this risk."
Ananth, a professor of obstetrics, gynecology and reproductive sciences at Rutgers University's Robert Wood Johnson Medical School, and his colleagues analyzed data about hospital readmission rates for more than 36 million hospital deliveries between 2010 and 2020. The readmission rate for any type of cardiovascular disease – including heart attack, heart failure or stroke – for mothers of twins was 1,105 per 100,000 deliveries. The readmission rate for mothers of singletons was 734 per 100,000 deliveries.
"The maternal heart works harder for twin pregnancies than for singleton pregnancies, and it takes weeks for the maternal heart to return to its pre-pregnancy state," said researcher Dr. Ruby Lin, a maternal-fetal medicine fellow at Robert Wood Johnson Medical School.
People pregnant with twins, especially those with cardiovascular risk factors or undergoing infertility treatment, should know about the higher chance of heart disease complications and be monitored for up to a year after giving birth, Lin said.
A seemingly contradictory study finding was that mothers of singletons who had high blood pressure conditions were more likely to die of any cause, including heart disease, compared to mothers of twins with high blood pressure.
"This suggests that the risk to mothers of twins decreases in the longer term, while the mothers of singletons may have other pre-existing cardiovascular risk factors," the researchers said.
Since 2014, twin pregnancies have been declining due to advances in IVF methods and some infertility specialists discouraging multiple embryo transfer.