Later life risks
The persistence of abnormalities of the metabolic syn- drome postpartum suggests that women who have had a hypertensive pregnancy may be at increased risk for cardio- vascular complications later in life. Assessment of later risks among women with a history of hypertensive pregnancy is limited by the long lag time between the age of child bearing and that when cardiovascular events become more likely. Remote diagnoses of new-onset hypertension in pregnancy cannot readily be confirmed by chart review, and a distinc- tion between de novo hypertension in pregnancy and under- lying essential hypertension may be impossible.
Although some earlier studies suggested no increase in future risk of hypertension among women who had pre- eclampsia or eclampsia (59, 60), the recognition that hyper- tensive pregnancy is associated with features of the insulin resistance syndrome has resulted in renewed interest in long- term sequelae of this condition. In a large study comparing women with severe preeclampsia or eclampsia to women with uncomplicated pregnancy, the risk for hypertension was increased almost 3-fold at 2–24 yr of follow-up; the mag- nitude of risk was correlated with the length of follow-up and was higher among women who had recurrent preeclampsia in their second pregnancy (61). Likewise, blood pressure was higher in women with preeclampsia on average 17 yr after pregnancy than among women who had uncomplicated pregnancy, despite similar body mass indexes in the two groups (55).
Similar to hypertension, the risk of other cardiovascular diseases may also be increased in women with prior pre- eclampsia, although studies of cardiovascular risk are like- wise limited by the difficulty in ruling out essential hyper- tension misdiagnosed as preeclampsia. In a study of Norwegian women (62), mortality due to cardiovascular causes was increased among women who had preeclampsia and preterm delivery (considered a proxy for severity of preeclampsia) compared with preeclamptic women who de- livered at term or women with preterm delivery alone. In another report, women who had a prior discharge diagnosis of preeclampsia were twice as likely as women with uncom- plicated pregnancy to be admitted to the hospital for or die from ischemic heart disease (63).
Clinical implications
Although available data do not prove a cause and effect relationship between the insulin resistance syndrome and
new-onset hypertension in pregnancy, the associations be- tween these conditions raise the possibility that interventions that improve insulin sensitivity may reduce the likelihood of this pregnancy complication. Because obesity is both a major contributor to insulin resistance and a recognized risk factor for preeclampsia, interventions geared to weight reduction before pregnancy and/or avoidance of excessive weight gain during pregnancy may have merit. Similarly, increased ex- ercise, which likewise improves insulin sensitivity, may also reduce risk. Given the well recognized adverse effects of obesity on many pregnancy outcomes, including gestational diabetes, these approaches make sense generally, but war- rant explicit study in women at high risk of hypertensive pregnancy. Studies of pharmacological interventions, such as the use of the insulin sensitizer metformin, may also war- rant study in women at high risk for preeclampsia.
Women who have had preeclampsia in one pregnancy are at increased risk in subsequent pregnancies. Thus, lifestyle interventions may be particularly relevant to reducing future preeclamptic pregnancy among these women, and studies are particularly warranted in this population.
Even beyond reproductive years, a history of hypertensive pregnancy may have important implications for medical care. The observations of increased prevalence of hyperten- sion and other cardiovascular disease many years after a pregnancy complicated by de novo hypertension suggests that this pregnancy complication might reasonably be viewed as another cardiovascular risk factor in women. In other words, the hormonal milieu of normal pregnancy may cause women with underlying insulin resistance to manifest transient hypertension, which would otherwise not be evi- dent until later in life (64).
Asking women about a history of hypertension in preg- nancy may be useful in stratifying future cardiovascular risk, although more data are needed to assess to what extent the risk associated with this condition is independent of obesity and other well established predictors of cardiovascular dis- ease. In women who have had hypertensive pregnancy, at- tention to cardiovascular risk factors and counseling regard- ing weight control, diet, and exercise may be particularly important.