Page 22 - RU Robert Wood Johnson Medicine • Summer 2020

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0.5 5
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0.01 0.1 15 20 25 30 35 40 45 50 1920 1930 1940 1950 1960 1920 1980 1990 2000 2010
Maternal Age (Years) Maternal Birth Cohort and PeriodTime-Scale
40 30
20 15
Above: Changes in rates of chronic hypertension during pregnancy among black and white women in relation to maternal age, year of delivery, and maternal year of birth in the United States, 1970-2010.
Defined as persistently high blood pressure, chronic hypertension (≥140 mm Hg systolic readings or ≥90 mm Hg diastolic or both) either
before pregnancy or up to the first 20 weeks of pregnancy complicates roughly 3 percent to
5 percent of pregnancies. It is associated with an increased risk of death of the fetus and, to a lesser extent, the mother. The potential consequences of chronic hypertension include preeclampsia, eclampsia, placental abruption, stroke, ischemic heart disease, myocardial infarction (a heart attack), congestive heart failure, cardiomyopathy, pulmonary edema, and renal failure.
“Many women have high blood pressure prior to pregnancy, so I wanted to see how elevated blood pressure early in pregnancy affects the mother and baby,” says Dr. Ananth. “When I went to look at the trends, the data didn’t exist. I was surprised that no one had looked at this yet.”
To study the issue, Dr. Ananth and his co- researchers culled the data of more than
151 million women with chronic hypertension who delivered babies in U.S. hospitals between 1970 and 2010. The data, from the National Hospital Discharge Survey, is believed to be representative of all pregnant women in the United States during that time. Maternal age, year of delivery (period), and maternal year of
birth (birth cohort) were examined as risk factors for chronic hypertension. Applying an age-time period-cohort (APC) analysis to the data enabled the team to examine all three variables independently. Trends in chronic hypertension also were examined separately among white and Black women.
What the Data Tell Us
The team’s research, which appeared in the October 2019 issue of Hypertension, revealed that rates of chronic hypertension among pregnant women increased 13-fold between 1970 and 2010. Surprisingly, while obesity and smoking are demonstrated risk factors for chronic hypertension, the growing prevalence of obesity and the declining prevalence of smoking during pregnancy had virtually no impact on the increase in national trends in chronic hypertension. Instead, advanced maternal age and year of delivery were strongly linked with an increased rate of chronic hypertension.
Specifically, the rate of chronic hypertension increased sharply with advancing maternal age and year of delivery, from 0.11 percent in 1970 to
1.52 percent in 2010. The rate of hypertension increased, on average, by 6 percent per year, 13 times what it was in 1970. Maternal birth cohort
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Rate (95% Confidence Interval) of Chronic Hypertension (%)
Rate Ratio (95% Confidence Interval) of Chronic Hypertension