Having Twins Ups the Risk of CVD Over the Next Year

Women who give birth to twins, regardless of whether they have hypertensive disorders of pregnancy (HDP), are more likely to be readmitted to the hospital with CVD complications within 1 year than those who give birth to just one baby, according to nationwide US data spanning 2010 to 2020.

Without HDP, the risk of readmission after twins doubled—with HPD, however, that risk spiked by eightfold. All-cause mortality also was higher after twin versus singleton pregnancies.

The researchers were “astounded” by the degree to which readmissions were elevated for mothers of twins, said senior author Cande V. Ananth, PhD, MPH (Rutgers University, New Brunswick, NJ). “These risks are pretty much off the charts.”

While it’s known that preeclampsia and other adverse pregnancy outcomes can put women at risk for developing cardiovascular disease decades later, an “unanswered question is what happens to the obstetrical complications in terms of cardiovascular health in the immediate postpartum period,” said Ananth.

Events that occur in the year after pregnancy are often overlooked, he told TCTMD. “It’s an extremely crucial window. Typically women deliver and they come back for a postpartum visit at about 6 weeks,” then may not return for care until they get pregnant again.

The issue is of particular relevance given the rise in use of assistive reproductive technology, such as in vitro fertilization (IVF), known to disproportionally result in multiple gestation pregnancies, Ananth added. Even without multiples, IVF has been linked to higher risk of CV complications.

For clinicians, the new findings present multiple opportunities along the care continuum, not just for twin pregnancies but also for singletons, an editorial notes.

Alexandria F. Williams, MD, MPH, Anne Marie Valente, MD, and Katherine E. Economy, MD (Brigham and Women’s Hospital, Boston, MA), point out that the highest risk of all-cause mortality in this study was seen among patients with HDP who had just one baby. “This stresses the importance of implementing further interventions to reduce maternal and pregnancy-related mortality and morbidity among all birthing people,” they write.

These risks are pretty much off the charts. Cande V. Ananth

Through team-based collaboration among specialists, “we must embrace the fourth trimester (12 weeks after delivery) as a critical time period to make impactful changes that will influence long-term cardiovascular health,” they urge.

Led by Ruby Lin, MD (Rutgers University), the paper was published online recently in the European Heart Journal.

Hypertensive Disorders Pose Extra Risk

For the study, Lin, Ananth, and colleagues turned to the Nationwide Readmissions Database of US hospitals to collect rates of CVD readmission from 2010 to 2020 for four groups: women with or without HDP (gestational hypertension, preeclampsia, eclampsia, or superimposed preeclampsia) who delivered twins or singletons.

Out of 36 million deliveries, 1.8% were twin births. Nearly a quarter (23.1%) of the pregnancies resulting in twins were affected by HDP, as compared with 10.4% of singleton pregnancies, and the prevalence of HDP rose over the 11-year study period. Overall, the mothers of twins with HDP tended to be older and have pregnancies that involved treatment for infertility.

In the year after giving birth, the rates of CVD readmission were 1,105.5 per 100,000 in patients who had twins and 734.1 per 100,000 in those who had singletons. Risks of readmission were higher after twin pregnancies with and without HDP, and in singleton pregnancies with HDP, than after singleton pregnancies unaffected by HDP. The added risk was seen mainly within the 30 days after delivery and then decreased progressively up to 1 year.

CVD Readmission Risk ≤ 1 Year After Delivery for Patients With vs Without HPD

For twin pregnancies with HDP, adjusted risks of readmission were particularly elevated for hypertensive heart disease (HR 32.39), heart failure (HR 18.52), and cardiomyopathy (HR 12.19) in comparison to singleton pregnancies without HDP. Additionally, both twin and singleton pregnancies that involved HDP were more likely to result in readmission for stroke than singleton pregnancies without the disorders (HR 5.37 and 6.27, respectively), as were—to a lesser but still significant degree—twin pregnancies without HDP (HR 1.38).

The risk of all-cause death in the year postpartum, when compared with singleton pregnancies without HDP, was highest after singleton pregnancies with HDP but also elevated after twin pregnancies with the disorders (HR 2.38 and 1.94).

While this population-based study doesn’t address the mechanism driving the added risk with twins, the literature does hint at possibilities, the researchers say.

“First, the underlying cause of preeclampsia in patients with multifetal pregnancy could be more specific to pregnancy itself, such as higher demand on the cardiovascular system from increased stress from larger placenta burden, rather than the preexisting CVD risk factors that predispose a patient to preeclampsia and future CVD complications,” they write. “Second, multifetal pregnancies that result in live births may tend to occur in patients who, at baseline, are healthy or have access to medical care.”

To get to the bottom of this, though, would require mechanistic studies of “what is happening at the cellular level, molecular level, and the genetic basis for these associations,” Ananth noted, adding that possible explanations for the relationship between twin pregnancies and CV risk include the underlying burdens posed by comorbidities (hypertension, obesity, diabetes, and thyroid dysfunction) and stress.

Ananth told TCTMD that their research is ongoing. Future work will look more deeply into HDP’s impact on singleton pregnancies, the varying risks posed by the individual conditions that fall under the umbrella of HDP, as well as the trajectory of CV complications and mortality in the first 5 years after delivery.

As for clinical takeaways, Anath emphasized that preconception counseling is helpful for patients with existing CV risk factors who are undergoing infertility treatment.

During pregnancy, the editorialists note, the American College of Obstetricians and Gynecologists “recommends that twin and higher order gestations have increased maternal and fetal surveillance including close monitoring of blood pressure, maternal weight gain, maternal nutrition, and fetal well-being.”

Then, after delivery, opportunities to improve care include postpartum BP monitoring, use of telehealth and other technologies for remote care, and expanded insurance coverage to enable better follow-up, they suggest.