Infant birthweight is correlated with cardiovascular disease (CVD) mortality risk in mothers with preterm birth and hypertensive disorders of pregnancy (HDPs), according to a recent study published in Pediatric and Perinatal Epidemiology.1
Previously, HDPs with increased risk to the infant have been assumed to also have increased maternal risk. However, this data indicated a potential negative correlation between CVD trends and infant birthweight among mothers with preterm HDP.
Key takeaways:
- Infant birthweight was linked to maternal cardiovascular disease (CVD) mortality risk among mothers with hypertensive disorders of pregnancy (HDP).
- Mothers with preterm HDP and larger-than-average infants had the highest CVD mortality risk, with a hazard ratio of 6.87.
- In contrast, higher infant birthweight was associated with lower CVD risk among mothers with term or normotensive preterm births.
- The findings suggest a potential subtype of preeclampsia in mothers with preterm HDP and large infants that may relate to diabetes.
- Experts emphasize collaboration between cardiologists and obstetricians to better identify and manage long-term cardiovascular risks in women.
“Mothers with term delivery or normotensive preterm in their first pregnancy had decreasing risk of CVD death with increasing infant size. The exception was mothers with preterm HDP, who instead had the highest risk with an above average size infant,” said Sage Wyatt, PhD candidate at the Faculty of Medicine, University of Bergen.
Hypertensive disorders and cardiovascular mortality
The study was conducted to evaluate CVD risk based on HDP, gestational age at delivery, and infant size for gestational age.2 Data was obtained from the Medical Birth Registry of Norway, a population-based database of still births, live births, and abortions in Norway. This data includes delivery information, infant outcomes, and maternal health.
Participants included women with a first birth between 1967 and 2013 with at least 7 years of follow-up information. Exclusion criteria included delivery before 20-weeks’ gestation and birthweight gestational age Z-scores above 5 or under -5.
HDP was reported as the primary outcome and included eclampsia, preeclampsia, gestational hypertension, and hemolysis, elevated liver enzymes, and low platelets syndrome. Additionally, HDP was stratified by preterm birth, defined as delivery before 27-weeks’ gestation.
Premature maternal death by CVD was reported as the primary outcome. Data about this outcome was obtained through linkage to the Norwegian Cause of Death Register. Mothers with a normotensive, term birth of an infant in the highest quartile of birthweight were considered controls.
Correlations between birthweight and CVD risk
There were 1,034,792 mothers included in the final analysis, 88.7% of whom had a term normotensive first birth. Term HDP was reported in 5.2% of mothers vs preterm HPD in 1%. For term infants, HDP was linked to an average population Z-Score of 0, vs a below average score of -0.96 for preterm birth infants whose mothers had HDP.
A negative correlation between infant weight and CVD mortality risk was reported in mothers with term delivery or normotensive preterm. However, CVD death risk was significantly associated with increasing infant birthweight in those with preterm HDP.
Mothers with preterm HDP and infants above average birthweight had the highest risk, with a hazard ratio (HR) of 6.87. In comparison, an HR of 3.06 was reported for mothers with preterm HDP and infants at or below the average birthweight, indicating a significant but less strong increase in risk.
Implications
Strong multiplicative interaction between HDP and birthweight was also reported for CVD mortality in preterm birth vs term births, with relative excess risk due to interactions of 1.99 and -0.27, respectively. Overall, the data indicated the highest CVD mortality risk in mothers with preterm HDP and a normal-to-large size infant.
“Our analysis shows that mothers with preterm HDP and large babies may have a clinically important subtype of preeclampsia that deserves further exploration, especially regarding the association with diabetes mellitus,” wrote investigators.
Women’s cardiovascular health
Sex-specific risk factors of CVD in female patients have been highlighted by Martha Gulati, MD, professor of cardiology at Cedars Sinai, in an interview with Contemporary OB/GYN.3These include age at menstruation onset, adverse pregnancy outcomes, and early menopause.
According to Gulati, collaboration between cardiologists and ob-gyns is vital to address these risks. Steps to managing cardiovascular health include screening measures such as blood pressure and cholesterol tests, alongside awareness of sex-specific risk factors.
“Understanding the consequences long-term and how we can be more proactive, and more preventative, and knowing you’re at risk… can really go to save women’s lives, which is ultimately all our goals,” said Gulati.
