Pregnancy Health, Mortality Link Particularly pronounced in black women

Pregnancy complications are linked to later mortality risks, and that relationship appears to be even stronger in black women, according to more than 50 years of follow-up data from the Collaborative Perinatal Project.

The results contribute to other research in which a decades of connection among conditions such as hypertensive disorders of pregnancy, preterm birth and adverse-effect gestational diabetes, but the study – launched in 1959 – goes a step further by highlighting deep-seated racial disparities that have not diminished in subsequent years.

“Our findings further add to and support the message that promoting healthy longevity must start early, starting with a healthy pregnancy,” said senior author Cuilin Zhang, MD, PhD (Yong Loo Lin School of Medicine, National University of Singapore), in an email to TCTMD. “This is especially true given additional data suggesting the intergenerational adverse health effects of common pregnancy complications.”

Natalie Bello, MD, MPH (Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA), who was not involved in the analysis, said “it confirms everything we know.”

Perhaps what is “most disturbing” is that even in the 1950s and 1960s, when the women participated in the study, “there were large racial disparities in maternal outcomes,” she told TCTMD. “If you look at the rates of hypertension in black women, even then chronic hypertension was twice as common in black women as in white women. It reinforces what we already knew and unfortunately we didn’t make much progress there.”

Over 50 years of data

For the study, published online last week ahead of print Circulation, Stefanie N. Hinkle, PhD (University of Pennsylvania, Philadelphia), Zhang and colleagues included 46,551 participants, 45% of whom were black, with a median duration of 52 years of data between pregnancy and death or censorship. The patients participated in the Collaborative Perinatal Project, which enrolled pregnant women from 12 U.S. centers between 1959 and 1966, and follow-up data was collected through 2016.

Overall, mortality was higher for black than white participants (41% vs. 37%), as was the incidence of preterm birth (20% vs. 10%).

All-cause mortality over time was associated with the following pregnancy complications after adjusting for age, pre-pregnancy body mass index, smoking, race and ethnicity, previous pregnancies, marital status, income, education, previous medical conditions, location and year:

• Premature spontaneous delivery: HR 1.07 (95% CI 1.03-1.1)
• Premature rupture of membranes: HR 1.23 (95% CI 1.05-1.44)
• Induced labour: HR 1.31 (95% CI 1.03-1.66)
• Pre-labor caesarean section versus full term: HR 2.09 (95% CI 1.75-2.48)
• Gestational hypertension: HR 1.09 (95% CI 0.97-1.22)
• Pre-eclampsia or eclampsia: HR 1.14 (95% CI 0.99-1.32)
• Superimposed pre-eclampsia or eclampsia: HR 1.32 (95% CI 1.20-1.46)
• Gestational diabetes/impaired glucose tolerance: HR 1.14 (95% CI 1.00-1.30)

There was an interaction between whether patients were black or white with regard to preterm birth (P = 0.009) as well as hypertensive pregnancy disorders (P = 0.05). Also, preterm birth was associated with a greater risk of death over time for black women (adjusted HR 1.64; 95% CI 1.10-2.46) compared to white women (adjusted HR 1.29; 95% CI 0.97-1.73).

‘We need to find out why’

The American Congress of Obstetricians and Gynecologists already supports a “warm transfer” of patients with pregnancy complications to cardiology or primary care, depending on the complexity of the case, Bello explains. But what often happens is that the patients get busy over time, don’t follow up and eventually get lost in the system. What can also complicate matters is that many patients who have a problem during pregnancy, such as gestational hypertension, see their symptoms disappear in the postpartum period and assume that the problem has also disappeared.

Bello cited another common situation where a patient never understood how serious a complication she was experiencing at the time. “They may have been told, but so much is happening at the time of delivery that it can sometimes get lost in the immediate concerns of ‘How’s me?’, ‘How’s my baby?’, pain and wound care ,” she said.

“It’s not just the collaboration between doctors, nurse specialists, the care team, but we also need to teach patients when they leave the hospital or during their postpartum visit that this is something that requires long-term follow-up and we can minimize your risk,” emphasized Bello.

However, that gets even more complicated when you consider the racial disparities seen in this study. “It is alarming that we have no influence on the differences [and] that they persist over time. . . . When we look at the black maternal mortality crisis in this country, it clearly has a long legacy and it’s not going to be solved overnight, but we really need to start working to reduce it. It’s not enough to just say, “Oh look, here’s where we found that black women have worse outcomes.” We need to find out why that is and fix them.”

In the future, she would like to see more studies look at the modification of risk factors after adverse pregnancy outcomes, especially with regard to more aggressive lipid lowering and what role antiplatelet or vascular modifying drugs may play for some. “We just don’t have the data,” Bello said.

Zhang also said more research is needed in “other race/ethnicity groups such as Asian and Hispanic, where limited data are available.”