NephMadness 2015: Obstetric Nephrology Region

Joel Topf, MD; Matthew Sparks, MD; Phyllis August, MD, MPH

Disclosures

March 02, 2015

Editorial Collaboration

Medscape &

In This Article

ACOG BP Goal <160/110 vs Lower BP Goal in Preeclampsia

ACOG BP Goal <160/110 in Preeclampsia

Hypertension in pregnancy can be due to multiple etiologies:

Preexisting chronic hypertension

Preeclampsia

Gestational hypertension

Preeclampsia superimposed on chronic hypertension

The prevalence of chronic hypertension among pregnant women has increased by 50% from 1995 to 2008 (0.9% to 1.5%). Gestational hypertension has likewise increased 184% from 1987 to 2004. Regardless of the etiology, the therapeutic goals in the treatment of hypertension are to prevent maternal morbidity (stroke, cardiac complications) while maintaining placental circulation and limiting medication toxicity to both the fetus and mother.

The definition of hypertension in pregnancy is the same as in non-pregnant patients (see last year’s NephMadness winner, JNC 8). However, the American College of Obstetrics and Gynecology (ACOG) doesn’t recommend drug intervention until the blood pressure reaches or exceeds 160/110, and then recommends physicians to target SBP between 140 and 160 and DBP between 90 and 100.

They point to a case series by Martin et al in which 28 patients with either eclampsia or preeclampsia who sustained strokes were scrutinized in terms of blood pressure control. Martin et al showed that all strokes occurred at SBP >155 mm Hg, and all but one exceeded 160 mm Hg. Diastolic blood pressures and mean arterial pressures were not nearly as reliable at predicting stroke. Thus, the argument is that treatment is warranted only if the systolic is sustained over 160 mm Hg.

Doctors urging more aggressive blood pressure control, more in line with the rest of medicine, have been stymied repeatedly by the Cochrane review which has not been able to find any benefit to treating mild to moderate hypertension during pregnancy. This review includes the most recent RCT published this past January which randomized ~1000 pregnant women to either a target diastolic BP of 100 mm Hg (less tight control) or 85 mm Hg (tight control) and could not detect a difference in pregnancy loss or high-level neonatal care. There was also no difference in serious maternal complications or preeclampsia.

For now the weight of data rests on the side of decreased medical interventions and a "let it ride" mentality when it comes to mild to moderate hypertension in pregnancy. This will be a tough battle for first round supremacy for sure.

Lower Blood Pressure Goal in Preeclampsia

Obstetricians are more tolerant of hypertension than other fields in medicine. The reason behind this is three-fold:

  • The outcome of interest is delivery of a healthy baby, and after delivery most of the hypertension and all of the controversy melts away. Given the limited time exposure there are fewer maternal events to worry about.

  • There is legitimate concern regarding fetal exposure to antihypertensives: renin-angiotensin-aldosterone inhibitors are known teratogens and diuretics in the third trimester can induce premature delivery.

  • Lowering blood pressure could adversely affect uterine hemodynamics, leading to decreased fetal growth and poor fetal outcomes.

Let’s take a look at the fetal growth story first. In the absence of well done, adequately powered clinical trials, the alarmists point to this meta-analysis from 2000 which found a decrease in fetal weight of 145 grams for every 10-mm Hg decrement in blood pressure. However the R2 was only 0.15, meaning that other factors were much more important than blood pressure at determining fetal weight. In the most recent RCT published in NEJM, there was no difference in the proportion of babies born at less than the tenth or third percentile for weight.

In regard to exposure to teratogens, there are certainly drugs that should be avoided but there is a cohort of drugs including methyldopa, labetalol, nifedipine, hydralazine and thiazides that are commonly utilized in pregnancy and have a long safety record.

And the last reason doctors are tolerant of hypertension in pregnancy is the belief that since pregnancy is a time-limited medical condition, there is little maternal morbidity from mild to moderate hypertension. This is probably false as the Martins et al case series of 28 women who had hypertensive strokes shows hypertensive morbidity is real and likely avoidable with judicious treatment of hypertension. Additionally, more aggressive use of antihypertensives in moderate maternal hypertension was shown to reduce the progression to severe hypertension while helping to avoid thrombocytopenia and elevated liver enzymes.

People are endlessly worrying about the over medicalization of natural human processes, but hypertension in pregnancy is pathologic and we have the means to treat it and should to prevent serious maternal complications.

Comments

3090D553-9492-4563-8681-AD288FA52ACE
Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.

processing....