We routinely use every means possible to overcome the complications of hypertensive disorders and related preterm births. Yet our best opportunity to reduce morbidity and mortality could be before preeclampsia develops.
Preemptive tactics can be effective in preventing or reducing severity of preeclampsia. The patient’s active cooperation is a must, but the effort to recruit her cooperation can mean a better outcome.
If a diabetic or hypertensive woman doesn’t take her medications properly or if an obese woman postpones weight loss until after preeclampsia develops, it is too late to reduce the level of risk.
At-risk patients can benefit from being informed of any other ways to reduce risk as well; for example, by controlling the number of fetuses transferred via assisted reproductive techniques.
Trends that are driving up the prevalence of risk factors will only increase the number of preconception and obstetric cases with high-risk potential:
- The increased proportion of births among nulliparous women and women older than 35 years.
- The increased proportion of multifetal gestation as a result of assisted reproductive therapy.
- The increased prevalence of obesity in women, which is likely to lead to greater frequency of gestational diabetes, insulin resistance, and chronic hypertension.
Step 1Start risk-reducing tactics as early as possible
Retrospective studies have identified factors that multiply the risk of preeclampsia. Some are identifiable—and modifiable—before conception or beginning at the first prenatal visit (TABLE 1).
- Identify risk factors and recruit the patient’s efforts to reduce risks—before conception whenever possible.
- Set up prenatal care to watch closely for signal findings and make a prompt diagnosis.
- Develop a delivery plan that balances maternal and fetal needs. Identify indications for delivery.
Preconception risk factors
Obesity carries a 10 to 15% risk for preeclampsia. Prevention or effective treatment can greatly reduce risk.
Hypertension.Women with uncontrolled hypertension should have their blood pressure controlled prior to conception and as early as possible in the first trimester. In these women, the risk of preeclampsia may be reduced to below the 10 to 40% rate, depending on severity.
Renal disease. Risk for an adverse pregnancy outcome depends on maternal renal function at time of conception. Women should be encouraged to conceive while serum creatinine is less than 1.2 mg/dl.
Pregestational diabetes mellitus. Risk for preeclampsia and adverse outcomes depends on duration of diabetes, as well as vascular complications and blood sugar control prior to conception and early in pregnancy. Encourage these women to complete childbearing as early as possible and before vascular complications develop, and to aggressively control their diabetes and hypertension (if present) at least a few months prior to conception and throughout pregnancy.
Maternal age older than 35 years increases risk depending on associated medical conditions, nulliparity, and need for assisted reproductive therapy. These women are more likely to be nulliparous, overweight, chronically hypertensive, and to require assisted reproductive therapy. ART may involve multifetal gestation and donor insemination or oocyte donation—both of which increase risk and severity of preeclampsia. Therefore, these patients need to be made aware of their risks and helped to take steps to minimize risks.
Preconception risk factors for preeclampsia
|20 to 30%||Previous preeclampsia|
|50%||Previous preeclampsia at 28 weeks|
|15 to 25%||Chronic hypertension|
|20%||Pregestational diabetes mellitus|
|10 to 15%||Class B/C diabetes|
|35%||Class F/R diabetes|
|10 to 40%||Thrombophilia|
|10 to 15%||Obesity/insulin resistance|
|10 to 20%||Age >35 years|
|10 to 15%||Family history of preeclampsia|
|6 to 7%||Nulliparity/primipaternity|
Pregnancy-related risk factors
Many risk factors may be identified for the first time during pregnancy (TABLE 2). It is important to realize that the magnitude of risk depends on number of risk factors.
Nulliparity and primipaternity. Over the past decade, several epidemiologic studies suggested that immune maladaptation plays an important pathogenetic role in development of preeclampsia.
Generally, preeclampsia is considered a disease of first pregnancy. Indeed, a previous miscarriage of a previous normotensive pregnancy with the same partner is has a lowered frequency of preeclampsia. This protective effect is lost, however, with change of partner, suggesting that primipaternity increases the rate of preeclampsia.