High blood pressure & anemia drive racial birth complication gap

Stanford Medicine reveals role of hypertension and anemia in non-white birth complication rates.


A recent pair of studies from Stanford School of Medicine, of Stanford University set to be published on September 7 in Obstetrics and Gynecology, has revealed that two treatable medical conditions, high blood pressure (hypertension) and iron-deficiency anemia, play a significant role in causing differences in childbirth complications among racial and ethnic groups.

These studies found that pregnant individuals from black racial or ethnic backgrounds are more likely to experience high blood pressure and anemia, leading to higher rates of severe birth complications like preeclampsia and excessive bleeding.

This discovery is crucial because racial disparities in severe birth complications persist even in states like California, where efforts have been made to enhance the quality of care for birth complications.

Stephanie Leonard, Ph.D., an assistant professor of obstetrics and gynecology who led the study on hypertension, said, “Clearly, just focusing on the bigger picture of birth complications and maternal mortality is not enough. We must understand what drives the inequalities and tailor our interventions to them.” 

Minority women are at a higher risk during pregnancy, and this might be because they don’t get enough prenatal care. But, it could also be due to old rules on treating anemia and high blood pressure during pregnancy.

Before 2021, doctors had different rules for treating anemia depending on a person’s race. Black women had to have more severe anemia before they got treatment.

Dr. Irogue Igbinosa, who led the anemia study, said, “The old rules didn’t make much sense. They were based on how anemia was seen in different groups of people, especially Black women. But there wasn’t any good proof that it was because of race, not other health factors.”

Until 2022, doctors also had higher blood pressure limits for pregnant people because they worried that treating high blood pressure might harm the baby. However, recent research shows that treating high blood pressure earlier during pregnancy can help the mother without hurting the baby.

“The more we use solid evidence to set our standards for prenatal care, the better we can deal with and break down the effects of unintentional bias in healthcare,” said Igbinosa. 

Studying the connections between birth problems and high blood pressure or anemia is essential because we already have effective treatments. She added, “This is something we can do something about; we can take action.”

Preeclampsia, a severe condition during pregnancy, and kidney problems can be prevented.

When a woman is pregnant, her body goes through many changes to support the baby’s growth. These changes affect her blood pressure, making it drop at first and then return to normal levels by the third trimester. This means it’s easy to miss high blood pressure, especially if the patient’s medical records don’t have her blood pressure before pregnancy. 

Additionally, the amount of blood in a pregnant person’s body increases by 50%, which makes the blood thinner. When the blood becomes too thin, it’s called anemia.

The new research strongly suggests that doctors should monitor anemia and high blood pressure during pregnancy and treat them when necessary.

In the study on hypertension, the researchers looked at medical and birth records for almost 8 million pregnancies in different states from 2008 to 2020. They checked how often chronic hypertension, which is high blood pressure that lasts a long time, led to various birth problems like severe preeclampsia or eclampsia (a severe form of high blood pressure that can cause seizures), placental abruption (when the placenta comes off the womb wall too early), postpartum hemorrhage (heavy bleeding after giving birth), stroke, fluid buildup in the lungs (pulmonary edema), acute kidney failure, and all severe birth problems combined, for everyone in the study.

Of all the pregnancies studied, 2.1% had chronic hypertension, which is high blood pressure that lasts a long time. Pregnant people with chronic hypertension were likelier to have pregnancy and birth problems. For example, they were ten times more likely to have severe preeclampsia or eclampsia, nearly six times more likely to experience acute kidney failure, and almost five times more likely to develop lung fluid buildup (pulmonary edema). 

The researchers estimated that chronic hypertension explained about one-quarter of all severe preeclampsia and eclampsia cases, 13.6% of acute kidney failure cases, and 10.7% of pulmonary edema cases for all pregnancies.

The rates of hypertension varied among different racial and ethnic groups. Black women had the highest rate at 5.1%, followed by Native Hawaiian/Pacific Islander women at 2.9% and Indigenous peoples of America Native women at 2.5%. These rates were higher than the average for the whole population.

The impact of chronic hypertension on severe birth complications and kidney failure was most significant among Black and Native Hawaiian-Pacific Islander populations. However, according to the study, it had the most negligible impact on white people.

A study in California from 2011 to 2020, involving 4 million pregnancies and births, focused on iron-deficiency anemia in pregnant women, excluding inherited forms. They used universal guidelines for diagnosing anemia. Anemia rates varied by race: 21.6% in Black, 18.2% in Pacific Islander, 14.1% in American Indian/Alaska Native, 14% in multiracial, 12.6% in Hispanic, 10.6% in Asian, and 9.6% in white pregnant patients. 

Pregnant individuals with anemia were more likely to face severe birth complications, affecting 6.5% of Pacific Islander, 6.3% of American Indian/Alaska Native, 5.1% of Black, 4.6% of Hispanic, 4.2% of multiracial, 3.8% of Asian, and 3.4% of white patients with anemia. 

Anemia explained around 20% of severe birth complications, such as those requiring blood transfusions, particularly among multiracial, Black, Hispanic, Indigenous peoples of America Native, and Pacific Islander mothers. 

Researchers are interviewing Black women with anemia during pregnancy to understand their treatment experiences better and emphasize that speaking with disproportionately affected communities is vital because anemia is preventable and treatable.

These studies show that dealing with high blood pressure and anemia during pregnancy is essential, especially for women from different racial backgrounds. To make things fairer, doctors must use the same proven methods for all pregnant women and not let biases affect care.

Journal reference:

  1. Igbinosa, Irogue I. MD; Leonard, Stephanie A. Ph.D., et al., Racial and Ethnic Disparities in Anemia and Severe Maternal Morbidity. Obstetrics Gynecology. DOI: 10.1097/AOG.0000000000005325.
  2. Leonard, Stephanie A. PhD, MS; Formanowski et al., Chronic Hypertension in Pregnancy and Racial-Ethnic Disparities in Complications. Obstetrics Gynecology. DOI: 10.1097/AOG.0000000000005342.