Hypertension and anemia drive racial gaps in birth complications, Stanford Medicine-led studies find | News Center

“The more evidence we use to standardize our approach to prenatal care, the more we can address and dismantle the effects of implicit bias on health care delivery,” Igbinosa said. Studying the links between birth complications and high blood pressure or iron-deficiency anemia is especially important because good treatments already exist, she said, adding, “This is something we can intervene on; it’s actionable.”

Preventing severe preeclampsia, kidney failure

Biological changes that support fetal growth during pregnancy have a big impact on the mother’s circulatory system. Blood pressure initially drops, then rises to pre-pregnancy levels by the third trimester. This means that hypertension is easily missed, especially if a patient’s medical records lack a pre-pregnancy blood pressure measurement. Maternal blood volume also increases by 50%, meaning the pregnant person’s blood becomes more dilute. Each milliliter has less hemoglobin, the blood’s oxygen-carrying protein; beyond a certain threshold, this dilution is classified as anemia.

The new research findings strongly suggest that anemia and hypertension should be monitored and treated when necessary.

The hypertension study analyzed medical and birth records for almost 8 million pregnancies that occurred in California, Michigan, Oregon, Pennsylvania and South Carolina from 2008 to 2020. The researchers assessed rates of chronic hypertension for the entire group and among members of different racial and ethnic groups. They calculated how much chronic hypertension contributed, for everyone in the study, to the incidence of several birth complications thought to be connected to high blood pressure: severe preeclampsia or eclampsia (high blood pressure that can lead to seizures), placental abruption (early placental detachment from the uterine wall), postpartum hemorrhage, cerebrovascular accident (stroke), pulmonary edema (dangerous accumulation of fluid in the lungs), acute kidney failure and all severe birth complications measured together.

Of the pregnancies analyzed, 2.1% were affected by chronic hypertension. Patients with chronic hypertension were much more likely than those without it to have several pregnancy and birth complications. They were 10 times as likely to experience severe preeclampsia or eclampsia, nearly six times as likely to have acute kidney failure, and almost five times as likely to have pulmonary edema, for example. For all pregnancies, the researchers estimated that chronic hypertension explained nearly one-quarter of all cases of severe preeclampsia and eclampsia, 13.6% of cases of acute renal failure, and 10.7% of cases of pulmonary edema.

The prevalence of hypertension differed by racial and ethnic groups, with Black (5.1%), Native Hawaiian/Pacific Islander (2.9%) and American Indian-Alaska native (2.5%) populations all having more hypertension than the population average.

Chronic hypertension contributed most strongly to severe obstetric complications and acute renal failure among Black and Native Hawaiian-Pacific Islander populations and least among white populations, the study found.

Anemia rates rising for everyone

The anemia study examined about 4 million California pregnancies and births from 2011 to 2020. Pregnant patients with inherited forms of anemia (genetic diseases that affect the formation of red blood cells) were not included in the study because the researchers wanted to focus on iron-deficiency anemia, which can be treated by improving diet or taking iron supplements. The needs of the growing fetus often deplete the mother’s iron stores, making nutritional anemia a common problem for pregnant women around the world. Patients were classified as having anemia during pregnancy on the basis of current guidelines from the Centers for Disease Control and Prevention, which are the same for all races. The scientists looked at the links between anemia, race and a variety of birth complications.