Preeclampsia: 3 preemptive tactics
A strategy to prevent preeclampsia or minimize severity—starting before conception if possible—is the best way to reduce adverse outcomes.
A systemic review of 27 studies, which included approximately 13,000 women, revealed that an abnormal uterine artery Doppler waveform increases the risk of preeclampsia by 4- to 6-fold, compared to normal Doppler results. The review concluded that uterine artery Doppler evaluation has a limited value as a screening test to predict preeclampsia.
What should the physician do when faced with an ultrasound report indicating an abnormal uterine artery Doppler finding?
Is low-dose aspirin helpful? Several randomized trials evaluated the potential role of low-dose aspirin in reducing the risk of preeclampsia in women with abnormal uterine artery Doppler indices. A meta-analysis suggested that low-dose aspirin significantly reduced the rate of preeclampsia (16% in placebo versus 10% with aspirin, odds ratio of 0.55). This analysis included a total of 498 subjects.
In contrast, a recent randomized trial in 560 women with abnormal uterine artery Doppler at 23 weeks’, who were assigned to aspirin 150 mg or placebo, found no differences in rates of preeclampsia (18% versus 19%) or in preeclampsia requiring delivery before 34 weeks’ (6% versus 8%). A similar randomized trial using 100 mg aspirin daily in 237 women with abnormal uterine artery Doppler at 22 to 24 weeks revealed no reduction in rate of preeclampsia compared to placebo.
Consequently, low-dose aspirin is not recommended for prevention of preeclamp-sia in these women.
Close surveillance is warranted. Although there is no available proven therapy to reduce the risk of preeclampsia in these women, they should be closely observed because of the increased rate of adverse outcomes, including preeclampsia.
TABLE 2
Pregnancy-related risk factors for preeclampsia
| Magnitude of risk depends on the number of factors | |
|---|---|
| 2-fold normal | Unexplained midtrimester elevations of serum AFP, HCG, inhibin-A |
| 10 to 30% | Abnormal uterine artery Doppler velocimetry |
| 0 to 30% | Hydrops/hydropic degeneration of placenta |
| 10 to 20% | Multifetal gestation (depends on number of fetuses and maternal age) |
| 10% | Partner who fathered preeclampsia in another woman |
| 8 to 10% | Gestational diabetes mellitus |
| 8 to 10% | Limited sperm exposure (teenage pregnancy) |
| 6 to 7% | Nulliparity/primipaternity |
| Limited data | Donor insemination, oocyte donation |
| Limited data | Unexplained persistent proteinuria or hematuria |
| Unknown | Unexplained fetal growth restriction |
Step 2Watch for signal findings, diagnose preeclampsia early
Signs and symptoms may call for close surveillance at any time. Early detection of preeclampsia is the best way to reduce adverse outcomes.
Prenatal care does not prevent preeclampsia, of course. All pregnant women are at risk, some more than others. Still, adequate and proper prenatal care is the best strategy to detect preeclampsia early.
We may need to modify the frequency and type of maternal and fetal surveillance at any time. Thus, patients with multiple risk factors or risk exceeding 10% should have more frequent visits, especially beyond 24 weeks. Maternal blood pressure (both systolic and diastolic), urine protein values, abrupt and excessive weight gain, maternal symptoms, and fetal growth warrant particular attention.
Diagnostic criteria vary with risk
The diagnosis of preeclampsia is different in patients with different risk factors. In healthy nulliparous women, the diagnosis requires persistent hypertension and proteinuria (new onset after 20 weeks’ gestation). However, in some patients the diagnosis should be made based on new onset hypertension and maternal symptoms or abnormal blood tests (low platelets or elevated liver enzymes).
Urine dipstick is a reliable screening test in women who remain normotensive.
24-hour urine measurement is the best test to confirm proteinuria if hypertension develops. Several studies found that urine dipstick values less than (1+) and random urine protein to creatinine ratio measurements are not accurate to predict proteinuria in women with gestational hypertension.
When is it gestational hypertension? The term applies only women with all of these findings:
- mild hypertension <160/<110 mm Hg
- proteinuria <300 mg/24-hour urine
- normal platelet count
- normal liver enzymes
- normal fetal growth
- no maternal symptoms
Once gestational hypertension is diagnosed, obtain blood tests and ultrasound evaluation to document fetal growth and amniotic fluid status.
Women with severe gestational hypertension and those with abnormal tests should be diagnosed as having preeclampsia and managed as such.
Women with gestational hypertension are at high risk for preeclampsia, and risk of progression depends on gestational age at time of diagnosis. Women who develop gestational hypertension at 24 to 35 weeks have a 46% chance of developing preeclampsia with a high rate of preterm delivery (32% <36 weeks and 12.5% <34 weeks) (FIGURE). These women require very close surveillance. In contrast, maternal and perinatal outcome is usually favorable when only mild gestational hypertension develops at or beyond 36 weeks.
When hypertension, proteinuria occur before 20 weeks
The traditional diagnostic criteria for preeclampsia in healthy women are not reliable in women who have either hypertension or proteinuria prior to 20 weeks’ gestation, particularly in those taking antihypertensive medications and in those who have class F diabetes mellitus. Because of the physiologic changes during pregnancy, women with diabetes and renal disease will have serial increases in blood pressure as well as protein excretion with advanced gestational age, particularly in the third trimester. Diagnostic criteria (TABLE 3) should be individualized based on medical conditions and current therapy. Antihypertensive drugs and preexisting proteinuria make it more difficult to classify preeclampsia as mild or severe.
