(Hypertension. 2000;35:668.)
© 2000 American Heart Association, Inc.
Scientific Contributions |
From the Endocrine Hypertension Division, Brigham and Womens Hospital, Harvard Medical School, Boston, Mass, and Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, Conn (R.P.L.).
Correspondence to Robert G. Dluhy, MD, Endocrine Hypertension Division, Brigham and Womens Hospital, 221 Longwood Ave, Boston, MA 02115.
| Abstract |
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Key Words: hypertension, chronic pregnancy blood pressure hyperaldosteronism renin-angiotensin system glucocorticoids
| Introduction |
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| Methods |
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Analysis of Maternal BP Outcomes in All 35
Pregnancies
We used the classification scheme for hypertension during
pregnancy developed by the Joint National Commission (JNC) on
Hypertension.6 Categories are as follows.
1. Normal BP (<140/90 mm Hg)
2. Transient hypertension (BP<140/90 mm Hg before pregnancy
and a
30 mm Hg increase in systolic BP [SBP] or a
15 mm Hg increase in diastolic BP [DBP] during
pregnancy)
3. Chronic hypertension (BP
140/90 mm Hg or mother
requiring antihypertensive medication before pregnancy)
4. Chronic hypertension with superimposed preeclampsia
(BP
140/90 mm Hg before pregnancy and an increase of
30
mm Hg in SBP or
15 mm Hg in DBP and a grade of
2+ in
proteinuria during pregnancy)
5. Preeclampsia (BP<140/90 mm Hg before pregnancy and an
increase of
30 mm Hg in SBP or
15 mm Hg in DBP and a
grade of
2+ in proteinuria during pregnancy)
One limitation of the JNC criteria is the failure to
distinguish between women with chronic hypertension who have an
exacerbation of their hypertension during pregnancy and those whose
hypertension remains controlled or even improves during pregnancy.
Therefore, we added the diagnosis of (6) pregnancy-aggravated
hypertension (PAH) to our criteria. PAH is defined as a
30
mm Hg increase in SBP or a
15 mm Hg increase in DBP from a
baseline BP
140/90 mm Hg before pregnancy.
Summary statistics are presented as means±SD. Maternal outcomes were compared between groups within this study population on the basis of infant genotype and gender using Students t test or Fishers exact test, where appropriate. All statistics were performed using the SAS software package.7
Analysis of Maternal BP Patterns During Pregnancy in a
Subset of 14 Pregnancies
We used a subset of 14 pregnancies, which were defined as each
womans first pregnancy for which
3 recorded BP measurements
during pregnancy were available, for the analysis of BP
patterns. This analysis addressed the longitudinal effect of
pregnancy on the BP of women with GRA. Mixed models analyses
allowed a general specification of the covariance matrix in
this repeated measures growth curve design in which BPs were observed
at different times for different patients.7 8 Polynomial
mixed models analyses were conducted to allow for nonlinearity
in the trajectory of the BPs through the study period.
To characterize the time course of BP in pregnancy for all subjects,
the duration of gestation was standardized to 9 months. The month
during the pregnancy in which the BP was obtained was calculated as
follows: 9.0x(examination date-conception date)/(delivery
date-conception date). Conception date was assumed to be 14
days after the first day of the last menstrual period and 266 days
before the estimated date of confinement reported by the obstetrician.
In the 1 case in which a discrepancy between these 2 dates existed, the
estimated date of confinement was used to calculate the conception
date. For each subject, the nonpregnant baseline BP was calculated by
averaging the subject-specific BPs before conception and those
2
weeks after delivery. The analysis was repeated without the
baseline data to assess the pattern of observed BP during
pregnancy.
Analysis of Fetal Outcomes for All 38 Infants
For the analyses of fetal outcomes, all 38 infants were
included. Fetal outcomes were compared between groups within this study
population on the basis of maternal hypertension and infant
genotype using Students t test or Fishers exact
test, where appropriate.
| Results |
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BP Outcomes in All 35 Pregnancies
Hypertension was present in 26 of the 35 pregnancies (74%).
Of these pregnant subjects, 23 (66%) were classified as chronic
hypertension, 1 (3%) as transient hypertension, and 2 (6%) as chronic
hypertension with superimposed preeclampsia. None of the mothers
who were normotensive before pregnancy developed preeclampsia. When
only the GRA+ women who were hypertensive before pregnancy were
included, the rate of preeclampsia was 8%. Of the 23 pregnancies in
women with chronic hypertension, 39% demonstrated a
30 mm Hg
increase in SBP or a
15 mm Hg increase in DBP during pregnancy
(PAH), without preeclampsia. Four of the 23 pregnancies (17%)
complicated by chronic hypertension had a resolution of the
hypertension during the pregnancy. No cases of eclampsia or the
syndrome of hemolysis, elevated liver function tests, and low
platelets (HELLP) were reported.
Eight pregnancies (23%) required
1 antihypertensive medications. All
of the women who required medication during pregnancy were hypertensive
before pregnancy, and 6 of these women were on medication from the
onset of pregnancy. Antihypertensive medications used included
methyldopa (2 cases), potassium-sparing diuretics (3 cases),
ß-blockers (2 cases), and thiazide diuretics (5 cases).
Risk Factors and Impact of Infant Gender and GRA Status on
Maternal BP
The mean age (24.7±6.2 years) and weight (68.6±10.9 kg) of the
women who developed PAH were not significantly different from the mean
age (24.1±5.0 years) and weight (64.1±13.6 kg) of the women who did
not develop PAH (P=0.45 and P=0.61,
respectively).
Infant gender predicted PAH. A total of 64% of the pregnancies in mothers with chronic hypertension who were carrying male infants were complicated by PAH compared with only 17% of the pregnancies in mothers who were carrying female infants (P=0.036). Infant GRA genotype status was not predictive of maternal PAH (P=0.97).
Maternal BP Patterns in the Subset of 14 Pregnancies
The predicted quadratic curves resulted from fitting the data in
the polynomial mixed models analysis
(Figure). The relationship for both SBP
and DBP as a function of pregnancy had a significant quadratic trend
(P=0.0001). SBP could be characterized by the following
equation: SBP=139.5-8.0xmonth+0.86x month2.
Similarly, DBP could be characterized by the following equation:
DBP=90.2-7.5xmonth+0.78x month2. To avoid
bias, the analysis was repeated without delivery or baseline
observations. The equations that characterize "pregnancy-only" BP
are similar and the linear and quadratic trends remained significant
(SBP, P<0.01; DBP, P<0.05). Five of the
pregnancies included in this subset were complicated by PAH. The
pattern of BP during pregnancy in these patients also seemed to follow
a roughly quadratic curve, but the group was too small to allow
meaningful statistical analysis. Similar curves have been
described in the pregnancies of both normal and hypertensive
women.9 10 11 12
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Other Maternal Outcomes
A total of 43% of these 35 pregnancies were delivered by cesarean
section; 9 were primary cesarean sections and 6 were repeat cesarean
sections. The primary cesarean section rate was 32% (9 of 28
pregnancies, excluding repeat cesarean sections). Hypertension
did not seem to play a major role in the high cesarean rate. The
cesarean section rate was similar in hypertensive (45%) and
normotensive (48%) mothers. Indications for the 9 primary cesarean
sections included the following (some cases had >1 complication): 4
cases of fetal distress; 3 cases of failure of labor to progress; 2
cases each of severe hypertension, breech presentation,
fever, and partial placenta previa; and 1 case each of prolapsed cord,
nuchal cord, twin pregnancy, and head entrapment. Indications for the
remaining 6 cesarean sections were the following: 5 cases of repeat
cesarean section and 1 case each of twin pregnancy and fetal
distress. No cases of gestational diabetes occurred. Maternal
complications included 1 case of chorioamnionitis, 1 failure of
placental separation, and 2 women who lost >500 cc of blood during
delivery.
Fetal Outcomes
Fetal outcome measurements are summarized in Table 2. The mean gestational age at delivery
was 38.9±2.4 weeks, including twin pregnancies. Four pregnancies
(11.4%) were delivered before 37 weeks. The 4 premature deliveries in
the GRA+ women included 2 spontaneous vaginal deliveries, 1 scheduled
cesarean section for a twin pregnancy, and 1 emergent cesarean section
for hypertension and fetal distress. The average birth weight,
including the 3 sets of twins, was 3124±619 g. When twins were
excluded, the mean birth weight was 3219±586 g. The Apgar scores were
>7 at 1 minute and >9 at 5 minutes for 95% of the 38 infants. No
fetal malformations, prolonged neonatal hospitalizations, or neonatal
deaths were reported.
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Effect of Maternal Hypertension on Fetal Outcomes
The mean gestational age of infants whose chronically hypertensive
mothers had PAH during pregnancy was 39.6±1.5 weeks, which was similar
to the age of 39.1±1.6 weeks for infants whose mothers did not have
PAH (P=0.99). However, the mean birth weight of infants
whose chronically hypertensive mothers had PAH (3019±659 g) tended to
be lower (P=0.08) than those infants whose chronically
hypertensive mothers did not have PAH (3385±374 g).
Effect of Infant Characteristics on Fetal Outcomes
The effect of fetal GRA status on fetal outcome was
analyzed in the 29 nontwin pregnancies in which the infants
genotype was known. GRA+ infants had a mean gestational age at
delivery of 39.0 weeks and a mean birth weight of 3138 g. GRA-
infants had a mean gestational age of 39.7 weeks and a mean birth
weight of 3361 g. Mothers carrying GRA+ infants had a cesarean
section rate of 33%, compared with a rate of 25% in those carrying
GRA- infants. No significant difference existed between GRA+ and GRA-
infants in any outcome measurement (Apgar at 1 minute,
P=0.53; Apgar at 5 minutes, P=0.29; birth weight,
P=0.25; gestational age, P=0.3; and maternal
cesarean section rate, P=0.72).
| Discussion |
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Several factors limit the conclusions drawn in this study. First, studies of preeclampsia are complicated by the wide variability of the definition of preeclampsia in the literature.4 14 A second potential confounder is the number of twin pregnancies, because twin pregnancy itself is a risk factor for preeclampsia.3 The 6% incidence of preeclampsia in GRA+ women did not exclude twin pregnancies. When twin pregnancies were excluded, the incidence of preeclampsia dropped to only 3%. Finally, our sample size is small and the study is largely descriptive, which limits the extent to which statistical conclusions can be drawn.
In addition to preeclampsia, a lack of consensus exists on the definitions of other hypertensive syndromes during pregnancy. For example, the JNC criteria for hypertensive disorders of pregnancy do not include the possibility that pregnancy may improve or aggravate chronic hypertension.3 We evaluated the prevalence of PAH in GRA+ mothers; our definition of PAH was an increase of 30 mm Hg in SBP or of 15 mm Hg in DBP in women with known chronic hypertension. A total of 39% of the GRA+ women with chronic hypertension in this study had PAH. Sibai et al4 reported a 17% incidence of a worsening of BP control in their chronically hypertensive population during pregnancy. However, in contrast to the present study, PAH in Sibai et als study4 was defined as an exacerbation of mean arterial pressures and the need to begin BP medication. Thus, the 2 studies are not strictly comparable. Nevertheless, the fact that GRA+ women with chronic hypertension seem to be at risk for an exacerbation of their hypertension during pregnancy is important for 2 reasons. First, it lends support to the hypothesis that the some of the mechanisms underlying chronic hypertension predispose a woman to pregnancy-aggravated hypertension but that others do not. Second, it is clinically relevant in light of the tendency toward lower birth weights observed in the infants of the GRA+ mothers with PAH. This association of hypertension during pregnancy with lower birth weights is well known, both in women with chronic hypertension and with preeclampsia. It is unclear whether the treatment of maternal hypertension improves fetal outcomes.4 15 16 17
Infant gender predicted which mothers developed PAH, with the mothers of male infants more likely to develop PAH than the mothers of female infants. Some studies examining the relationship between infant gender and maternal BP have found a similar association, but it has not been consistent.18 19 20 21 Infant GRA status did not impact maternal BP. Other risk factors for the development of preeclampsia and PAH include primigravida, age, and obesity. A significant association was not demonstrated between any of these factors and the development of PAH in the present study. However, because of the small sample size, such factors may have not achieved statistical significance.
Evaluation of maternal BP during the time course of 14 pregnancies in GRA+ women revealed a pattern similar to that reported for normal pregnancies.10 12 In normal pregnancy, a decrease in maternal BP is noted during the first trimester, and the second trimester is characterized by BPs lower than those before pregnancy. Finally, during the third trimester, most women experience an increase in BP back to the levels seen before pregnancy.
One interesting finding of the present study was the high rate of cesarean sections: 43% compared with 15.2% for the general obstetric population14 or 21% for the chronically hypertensive population.4 Because women with prior cesarean sections are more likely to have repeat cesarean sections, the use of a total cesarean section rate is biased. Thus, the primary cesarean section rate is a more appropriate indicator. The primary cesarean section rate was 32% in this study, in contrast to the 13.1% reported in Sibai et als study of chronic hypertensives.4 However, the cesarean section rate is highly variable over decades, institutions, and individual practices. No obvious explanation for the high rates in GRA+ mothers was evident.
Overall, the mean birth weight and gestational age of infants of GRA+ mothers were comparable to those published for general obstetric populations.14 15 However, when we divided the GRA+ women into 2 groups: mothers with PAH during pregnancy and those without, the infants of the mothers with PAH demonstrated a trend toward a lower birth weight. Although no neonatal mortality was reported, our study was not designed to assess rates of fetal loss before 20 weeks of gestation.
The role of the RAAS in BP regulation during pregnancy and in the pathogenesis of preeclampsia is unclear. The BP outcomes and the pattern of BP during pregnancy in our GRA+ women question the hypothesis that the RAAS is a major regulator of BP during pregnancy. Because the RAAS was not assessed in these GRA+ mothers, it would be of interest to prospectively study the RAAS during pregnancy in GRA+ mothers and correlate hormonal changes with BP. Levels of aldosterone secretion during pregnancy would also be of particular interest in GRA mothers because the elevation of ACTH seen in normal pregnancy would be predicted to exacerbate this ACTH-regulated aldosterone excess state.
The present study was not designed to address the optimum treatment of the pregnant woman with GRA. Management of hypertension must be individualized for each patient. However, because GRA+ individuals, as a group, have an increased risk of hemorrhagic stroke secondary to intracranial aneurysm,22 we recommend periodically screening GRA+ women during their adult lives and before pregnancy with magnetic resonance imaging angiography to exclude the presence of intracranial aneurysm. One further recommendation is to screen infants born to GRA+ mothers for GRA, because these children can develop clinically significant hypertension in childhood.
In conclusion, GRA+ women did not seem to have an increased risk of preeclampsia. However, GRA+ women with chronic hypertension do seem to be at risk for an exacerbation of their hypertension during pregnancy. Maternal BP during pregnancy follows patterns similar to those found in normal pregnancy, with the exception of higher baseline pressures. The mean gestational age and mean birth weights of infants born to GRA+ mothers were not remarkable, but a tendency toward low birth weights was noted in infants of mothers with PAH. A high primary cesarean section rate was noted. Careful assessment of BP in pregnant women with GRA is necessary.
Received August 30, 1999; first decision September 30, 1999; accepted October 8, 1999.
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