The relationship of plasma volume, sympathetic tone, and proinflammatory cytokines in young healthy nonpregnant women

OBJECTIVE

Preeclampsia has been associated with elevated proinflammatory markers, increased sympathetic activity, and decreased plasma volume (PV). We hypothesized that these associations would be identified in women prior to a first pregnancy.

METHODS

We studied 76 healthy nulligravid participants measuring the proinflammatory markers C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-alpha). Plasma volume was measured in supine position and corrected for body mass index (BMI). We examined supine plasma levels of epinephrine and norepinephrine and blood pressure response to Valsalva maneuver to quantify sympathetic activation. We then examined the association of PV and sympathetic activity with proinflammatory cytokines with P < .05 accepted for significance.

RESULTS

CRP was significantly increased in participants with lowest PV/BMI quartile when compared to middle 2 quartiles and highest quartile (analysis of variance [ANOVA], P = .037). We found no significant association of PV/BMI with either IL-6 or TNF-alpha. Both plasma epinephrine concentration (r = .29, P = .02) and the late phase II (phase II_L) blood pressure response to Valsalva maneuver (r = .44, P < .0001) were associated with serum IL-6 concentrations.

CONCLUSIONS

Low PV is associated with increased CRP levels and increased sympathetic tone is linked to elevated IL-6 concentration in young nonpregnant women. These findings represent elements of a nonpregnancy phenotype that parallels the findings observed in preeclampsia and in women at risk for ischemic cardiovascular disease. This suggests that the relationships observed during preeclampsia, which have been associated with placental pathology, may predate pregnancy and be independent of placental activity.

Resistance artery adaptation to pregnancy counteracts the vasoconstricting influence of plasma from normal pregnant women

Using a rat model, we investigated the effects of circulating factors in pregnancy on cerebrovascular and systemic vascular function by comparing myogenic reactivity, tone, and endothelial vasodilator production of the posterior cerebral artery (PCA) and mesenteric artery (MA) of nonpregnant (NP) animals perfused with nonpregnant and pregnant human plasma. Arteries from late pregnant (LP) animals were then perfused similarly to evaluate a potential adaptive effect of pregnancy on vessel function. A 3-hour exposure to pregnant plasma caused increased myogenic reactivity and tone in vessels from NP animals and produced a decreased endothelium-derived hyperpolarizing factor response in NP PCAs, findings that were not seen with MAs. The increased reactivity and tone noted in NP vessels was abolished when pregnant plasma was perfused through LP arteries, suggesting these vessels adapt during pregnancy to the vasoconstricting influence of pregnant plasma.

Relationship between prepregnancy and early pregnancy uterine blood flow and resistance index

We evaluated the relationship between prepregnancy and early pregnancy uterine blood flow (UBF) and resistance index (RI). Nineteen nulliparous participants were studied during cycle day 8 + 4, and early pregnancy (13.4 + 1.6 weeks). Color Doppler ultrasound of both uterine arteries and maternal heart was performed to calculate uterine RI, volumetric UBF, and cardiac output (CO), respectively. We observed a strong negative association of uterine RI with prepregnancy UBF (r = -.82, P < .001) that weakened, but remained significant in early pregnancy (r =-.48, P = .04). Prepregnancy uterine index (UBF/CO) was significantly associated with early pregnancy uterine index; r = .48, P = .04). There was also a trend associating prepregnancy and early pregnancy volumetric UBF (r = .44, P = .068). Prepregnancy UBF may be a determinant of early pregnancy UBF and UBF may have independent value as a predictor of adverse pregnancy outcome.

Depressive symptoms predict smoking status among pregnant women

The current study assessed self-reported psychopathology in women who spontaneously quit or continued smoking after learning that they are pregnant and examined whether any potential differences remained after control for confounding variables. All participants (77 smokers and 50 spontaneous quitters) completed 3 assessments of psychological functioning prior to enrollment in either smoking cessation or relapse prevention studies. Assessments included the Brief Symptom Inventory (BSI); the Beck Depression Inventory (BDI); and the Adult Self-Report (ASR). Smokers and spontaneous quitters differed on sociodemographic and smoking characteristics. In terms of psychological functioning, smokers reported significantly more depression/anxiety symptoms and withdrawn behavior than spontaneous quitters on the BSI and the ASR. Higher depression scores on the BSI were associated with increased odds of continued smoking, even after controlling for sociodemographic and smoking variables in multivariate analyses. These results suggest that depressive symptoms may be an independent contributor to the problem of continued smoking during pregnancy, which may have implications for smoking-cessation interventions among pregnant women.

Proteomic profiling of urine identifies specific fragments of SERPINA1 and albumin as biomarkers of preeclampsia

OBJECTIVE

The cause of preeclampsia remains unknown and the diagnosis can be uncertain. We used proteomic-based analysis of urine to improve disease classification and extend the pathophysiologic understanding of preeclampsia.

STUDY DESIGN

Urine samples from 284 women were analyzed by surface-enhanced laser desorption/ionization. In the exploratory phase, 59 samples were used to extract the proteomic fingerprint characteristic of severe preeclampsia requiring mandated delivery and to develop a diagnostic algorithm. In the challenge phase, we sought to prospectively validate the algorithm in 225 women screened for a variety of high- and low-risk conditions, including preeclampsia. Of these, 19 women were followed longitudinally throughout pregnancy. The presence of biomarkers was interpreted relative to clinical classification, need for delivery, and other urine laboratory measures (ratios of protein to creatinine and soluble fms-like tyrosine kinase-1 to placental growth factor). In the translational phase, biomarker identification by tandem mass spectrometry and validation experiments in urine, serum, and placenta were used to identify, quantify, and localize the biomarkers or related proteins.

RESULTS

We report that women with preeclampsia appear to present a unique urine proteomic fingerprint that predicts preeclampsia in need of mandated delivery with highest accuracy. This characteristic proteomic profile also has the ability to distinguish preeclampsia from other hypertensive or proteinuric disorders in pregnancy. Pregnant women followed longitudinally who developed preeclampsia displayed abnormal urinary profiles more than 10 weeks before clinical manifestation. Tandem mass spectrometry and de novo sequencing identified the biomarkers as nonrandom cleavage products of SERPINA1 and albumin. Of these, the 21 amino acid C-terminus fragment of SERPINA1 was highly associated with severe forms of preeclampsia requiring early delivery. In preeclampsia, increased and aberrant SERPINA1 immunoreactivity was found in urine, serum, and placenta, in which it localized predominantly to placental villi and placental vascular spaces adherent to the endothelium. In addition, significant perivascular deposits of misfolded SERPINA1 aggregates were exclusively identified in preeclamptic placentae.

CONCLUSION

Proteomics-based characterization of urine in preeclampsia identified a proteomic fingerprint composed of SERPINA1 and albumin fragments, which can accurately diagnose preeclampsia and shows promise to discriminate it from other hypertensive proteinuric diseases. These findings provide insight into a novel pathophysiological mechanism of preeclampsia related to SERPINA1 misfolding, which may offer new therapeutic opportunities in the future.

Effects of voucher-based incentives on abstinence from cigarette smoking and fetal growth among pregnant women

AIMS

This study examined whether voucher-based reinforcement therapy (VBRT) contingent upon smoking abstinence during pregnancy is an effective method for decreasing maternal smoking during pregnancy and improving fetal growth.

DESIGN, SETTING AND PARTICIPANTS

A two-condition, parallel-groups, randomized controlled trial was conducted in a university-based research clinic. A total of 82 smokers entering prenatal care participated in the trial.

INTERVENTION

Participants were assigned randomly to either contingent or non-contingent voucher conditions. Vouchers exchangeable for retail items were available during pregnancy and for 12 weeks postpartum. In the contingent condition, vouchers were earned for biochemically verified smoking abstinence; in the non-contingent condition, vouchers were earned independent of smoking status.

MEASUREMENTS

Smoking outcomes were evaluated using urine-toxicology testing and self-report. Fetal growth outcomes were evaluated using serial ultrasound examinations performed during the third trimester.

FINDINGS

Contingent vouchers significantly increased point-prevalence abstinence at the end-of-pregnancy (41% versus 10%) and at the 12-week postpartum assessment (24% versus 3%). Serial ultrasound examinations indicated significantly greater growth in terms of estimated fetal weight, femur length and abdominal circumference in the contingent compared to the non-contingent conditions.

CONCLUSIONS

These results provide further evidence that VBRT has a substantive contribution to make to efforts to decrease maternal smoking during pregnancy and provide new evidence of positive effects on fetal health.

Optimal growth modeling

Abnormal fetal growth is associated with preterm birth, stillbirth, neonatal death, respiratory distress syndrome, and necrotizing enterocolitis. An optimal fetal growth standard would be one that most correctly identifies the fetus at risk for poor perinatal outcome. A growth standard that is created using population-specific data is more applicable than generalized growth curves since there is evidence that optimal neonatal outcome is achieved at different birth weights in different populations. The development of fetal growth standards based exclusively on neonatal birth weights is flawed as fetal growth restriction is associated with preterm delivery. Likewise, employing clinically derived ultrasound standards for term gestations would include a population that is more likely to have abnormal growth. Novel approaches to defining normal intrauterine growth combine birth weights at term and fetal growth patterns in-utero to create growth curves useful in defining the normal intrauterine growth experience. This review examines the performance of a variety of the growth characterizing standards that have been employed to define abnormal growth and examines their performance in the prediction of adverse perinatal outcome.

Derivation of lung epithelium from human cord blood-derived mesenchymal stem cells

RATIONALE

Recent studies have suggested that both embryonic stem cells and adult bone marrow stem cells can participate in the regeneration and repair of diseased adult organs, including the lungs. However, the extent of airway epithelial remodeling with adult marrow stem cells is low, and there are no available in vivo data with embryonic stem cells. Human umbilical cord blood contains both hematopoietic and nonhematopoietic stem cells, which have been used clinically as an alternative to bone marrow transplantation for hematologic malignancies and other diseases.

OBJECTIVES

We hypothesized that human umbilical cord blood stem cells might be an effective alternative to adult bone marrow and embryonic stem cells for regeneration and repair of injured airway epithelium.

METHODS

Human cord blood was obtained from normal deliveries at the University of Vermont. Cultured plastic adherent cells were characterized as mesenchymal stem cells (MSCs) by flow cytometry and differentiation assays. Cord blood-derived MSCs (CB-MSCs) were cultured in specialized airway growth media or with specific growth factors, including keratinocyte growth factor and retinoic acid. mRNA and protein expression were analyzed with PCR and immunofluorescent staining. CB-MSCs were systematically administered to immunotolerant, nonobese diabetic/severe combined immunodeficiency (NOD-SCID) mice. Lungs were analyzed for presence of human cells.

MEASUREMENTS AND MAIN RESULTS

When cultured in specialized airway growth media or with specific growth factors, CB-MSCs differentially expressed Clara cell secretory protein (CCSP), cystic fibrosis transmembrane conductance regulator (CFTR), surfactant protein C, and thyroid transcription factor-1 mRNA, and CCSP and CFTR protein. Furthermore, CB-MSCs were easily transduced with recombinant lentiviral vectors to express human CFTR. After systemic administration to immunotolerant, NOD-SCID, mice, rare cells were found in the airway epithelium that had acquired cytokeratin and human CFTR expression.

CONCLUSIONS

CB-MSCs appear to be comparable to MSCs obtained from adult bone marrow in ability to express phenotypic markers of airway epithelium and to participate in airway remodeling in vivo.

Predictors of postpartum relapse to smoking

Postpartum relapse is common among women who stop smoking during pregnancy. We examined predictors of postpartum relapse in 87 women who quit smoking during pregnancy, 48% of whom relapsed by 6 months postpartum. We also explored the circumstances surrounding their first postpartum cigarette. Multivariate analyses revealed that having more friends/family members who smoke, smoking more heavily pre-pregnancy, and having higher depression scores and less concern about weight at the end of pregnancy were associated with increased risk of relapse postpartum. Most women's first postpartum cigarettes were unplanned, in the presence of another smoker, and while experiencing negative affect. The findings suggest targets for interventions to reduce postpartum relapse.

Biochemical verification of smoking status in pregnant and recently postpartum women

The present study was conducted to examine several different methods and cutpoints for determining smoking status in pregnant and recently postpartum women. Self-reported smoking status, urine cotinine levels determined by gas chromatography (GC) and by enzyme immunoassay testing (EMIT), and breath carbon monoxide (CO) levels were assessed at 28 weeks antepartum and 12 and 24 weeks postpartum in 131 women enrolled in studies on smoking cessation and relapse prevention. Classifications based on urine-cotinine GC testing served as the standard in most analyses. Overall agreement between self-reported smoking status and classification based on urine-cotinine GC testing was excellent (> or =95%) at several cutpoints (50, 25, and 12.5 ng/ml) but highest at 25 ng/ml. Classifications based on EMIT urine cotinine levels were in nearly perfect (> or =98%) agreement with those made by GC when the cutpoint for the former was set at approximately 80 ng/ml (79-87 ng/ml). Classifications based on breath CO were in relatively poor agreement (< or =87%) with GC classifications at all cutpoints examined but best at 4 ppm. Overall, these results provide detailed information on several commonly used methods for classifying smoking in pregnant and recently postpartum women that should be practically useful to researchers and clinicians involved in efforts to eliminate smoking in this population.

Smoking status in the initial weeks of quitting as a predictor of smoking-cessation outcomes in pregnant women

OBJECTIVE

Any smoking during the initial 2 weeks of attempting to quit predicts poor short- and longer-term outcomes in the general population of cigarette smokers. The present study examined whether that rule applies to pregnant women.

METHODS

Data were obtained from 129 women participating in clinical trials on smoking-cessation examining the efficacy of voucher-based incentives delivered contingent on biochemically-verified abstinence or a control condition wherein incentives were given independent of smoking status. Smoking status was assessed in weeks 1 and 2 of the cessation effort and again at an end-of-pregnancy assessment scheduled at weeks 28-32 gestation using self-report and biochemical verification.

RESULTS

Smoking in weeks 1 or 2 predicted smoking at the end-of pregnancy assessment independent of treatment condition. There was a 79% and 92% chance that those who smoked in weeks 1 or 2 would be classified as smokers at end-of-pregnancy in the contingent-incentive and control conditions, respectively.

CONCLUSIONS

Clinicians assisting pregnant women trying to quit smoking may want to monitor progress in the initial weeks of the cessation effort and consider enhancing/changing the intervention when smoking is detected.

The relationship between menstrual cycle phase and anterior cruciate ligament injury: a case-control study of recreational alpine skiers

BACKGROUND

Female athletes suffer a greater incidence of anterior cruciate ligament tears compared with male athletes when participating in common sports; however, very little is known about the factors that explain this disparity.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

Female recreational alpine skiers with an anterior cruciate ligament rupture and age-matched control skiers provided a serum sample and self-reported menstrual history data immediately after injury. Both serum concentrations of progesterone and menstrual history were then used to group subjects into either preovulatory or postovulatory phases of the menstrual cycle.

RESULTS

Analysis of serum concentrations of progesterone revealed that alpine skiers in the preovulatory phase of the menstrual cycle were significantly more likely to tear their anterior cruciate ligaments than were skiers in the postovulatory phase (odds ratio, 3.22; 95% confidence interval, 1.09-9.52; P = .027). Analysis of menstrual history data found similar results, but the difference was not statistically significant (odds ratio, 2.38; 95% confidence interval, 0.86-6.54; P = .086).

CONCLUSION

The likelihood of sustaining an anterior cruciate ligament injury does not remain constant during the menstrual cycle; instead, the risk of suffering an anterior cruciate ligament disruption is significantly greater during the preovulatory phase of the menstrual cycle compared with the postovulatory phase.

CLINICAL RELEVANCE

Phase of menstrual cycle may be one of the risk factors that influence knee ligament injury among female alpine skiers. The findings from this study should be considered in subsequent studies designed to identify persons at risk for anterior cruciate ligament injury and to develop intervention strategies.

Characterizing nicotine withdrawal in pregnant cigarette smokers

Maternal smoking is a leading preventable cause of poor pregnancy outcomes and infant morbidity and mortality. Whereas pregnancy has been thought of as a "window of opportunity" when women are more motivated to change health behaviors such as smoking, only 20% of pregnant women quit smoking upon learning they are pregnant and remain abstinent at the end of the pregnancy. Greater understanding of possible obstacles to smoking during pregnancy, such as nicotine withdrawal, is needed. The symptoms of nicotine withdrawal have been well characterized in nonpregnant smokers, but there has been only 1 report conducted during pregnancy, and that was a retrospective study. The aim of the present study was to characterize nicotine withdrawal and craving in pregnant cigarette smokers. These data were collected as part of prospective clinical trials assessing the efficacy of voucher-based incentives to promote abstinence from cigarette smoking during pregnancy and postpartum. The authors examined results from the Minnesota Nicotine Withdrawal Scale (J. R. Hughes & D. K. Hatsukami, 1998) in 27 abstainers (reported no or very low levels of smoking, which was confirmed biochemically) and 21 smokers (smoked at >80% of their baseline smoking level) during the first 5 days of a cessation attempt. Abstainers reported more impatience, anger, and difficulty concentrating than did smokers. The results also suggest that pregnant smokers generally may have elevated baseline levels of withdrawal, which need to be considered in the design and analysis of future studies.

Psychological Symptoms Following Smoking Cessation in Pregnant Smokers

This study examined the relationship between smoking status and psychological symptoms in pregnant women across pregnancy. Participants were 45 women who quit smoking early in pregnancy (early quitters), 22 who quit later in pregnancy (later quitters), and 84 who smoked throughout pregnancy (never quitters). Assessments of smoking status and psychological symptoms (Brief Symptom Inventory and Beck Depression Inventory) occurred near first prenatal visit, second visit, and end of pregnancy. Results indicated that scores on the Global Severity Index of the Brief Symptom Inventory, several Brief Symptom Inventory subscales, and on the Beck Depression Inventory were highest among never quitters, lowest among early quitters, and intermediate for later quitters. Scores decreased across pregnancy, especially between first and second assessments. We found no evidence that quitting smoking increased psychological symptoms either in the immediate post-withdrawal period or later in pregnancy. These findings should temper concerns that quitting smoking may have detrimental psychological consequences during pregnancy.

Maternal Smoking and Its Association With Birth Weight

OBJECTIVE

Maternal smoking has been associated with a reduction in newborn birth weight. We sought to estimate how the pattern of maternal smoking throughout pregnancy influences newborn size.

METHODS

One hundred sixty pregnant smoking women were enrolled in a prospective study. We collected data on maternal age, education, prepregnancy body mass index, and parity, as well as alcohol and illicit drug use. Cigarette use was defined as self-reported consumption before pregnancy, at the time of study enrollment, and in the third trimester. Statistical analyses were performed based on bivariate correlations and multiple linear regression.

RESULTS

Of the smoking parameters examined, maternal third-trimester cigarette consumption was the strongest predictor of birth weight percentile (partial r = -0.23, P < .001). For each additional cigarette per day that a participant smoked in the third trimester, there was an estimated 27 g reduction in birth weight. Prepregnancy smoking volume was not significantly associated with birth weight percentile in bivariate (r = -0.06, P = .47) or multivariable analyses. Additional factors contributing to birth weight include gestational age (partial r = 0.69, P < .001), maternal body mass index (partial r = 0.23, P < .001), and parity (partial r = 0.16, P < .004). In total, these 4 variables explain 61% of the variance in newborn birth weight.

CONCLUSION

Maternal third-trimester cigarette consumption is a strong and independent predictor of birth weight percentile. This supports the hypothesis that reductions in maternal cigarette consumption during pregnancy will result in improved birth weight, regardless of the prepregnancy consumption levels.

LEVEL OF EVIDENCE

III.

The effect of estradiol and progesterone on knee and ankle joint laxity

BACKGROUND

Female athletes suffer a higher incidence of anterior cruciate ligament injuries compared to their male counterparts, and they appear to be at increased risk for these injuries when they have increased anterior-posterior knee laxity and at specific phases of the menstrual cycle. Although the mechanism by which these factors combine to increase injury risk is unclear, studies suggest that cyclic variations in joint laxity produced by hormone fluctuation during the menstrual cycle predispose an athlete to increased risk of ligamentous injury. Little is known about whether joint laxity varies cyclically during the menstrual cycle and if so, whether it is modulated by cyclic variations of estradiol (E2) and progesterone (P4).

HYPOTHESIS

Increased serum estradiol (E2) and progesterone (P4) levels are associated with increased ankle and knee joint laxity.

STUDY DESIGN

Cohort study. Level of evidence, 2.

METHODS

Ankle laxity, anterior-posterior knee laxity, and serum concentrations of estradiol (E2) and progesterone (P4) were measured during the menstrual cycle in women and at corresponding time intervals in men (controls). Ankle laxity was measured from stress radiographs and included anterior talar translation relative to the tibia and talar tilt relative to the tibia; anterior-posterior knee laxity was measured with the KT-1000 arthrometer.

RESULTS

Women had greater knee and ankle laxity values compared to men. There was, however, no change in knee and ankle laxity over the normal menstrual cycle in women and no change over time in men. There was no relationship between estradiol and progesterone fluctuation and ankle and knee joint laxity.

CONCLUSIONS

Knee and ankle joint laxities are greater for women compared to men; however, the cyclic estradiol and progesterone fluctuations that occur during the menstrual cycle do not produce cyclic fluctuations of joint laxity. Studies using joint laxity to identify a subject at risk for ligamentous injury need only consider making measurements at a specific point in time, such as during a preseason screening evaluation.

The Influence of Pregnancy on Arterial Compliance

OBJECTIVE

To examine the effect of pregnancy and the interval between pregnancies on arterial compliance as measured by mean arterial pressure (MAP) and pulse pressure.

METHODS

We conducted a 3-month chart review of deliveries at a tertiary care hospital (index pregnancies). Data collected included demographics, obstetric history, blood pressures, prepregnancy weight, weight gain, and neonatal outcome. If a subject's first delivery occurred at our institution, these records were reviewed in a similar fashion. Mean antepartum MAP and pulse pressure were calculated and compared for each trimester between index and first pregnancies. Statistical methods employed included repeated measures analysis of variance, repeated measures analysis of covariance, and correlation analysis.

RESULTS

Two hundred eighty-five charts were reviewed. Forty-seven women had complete data covering both index and first pregnancy. Mean arterial pressure was significantly higher in all trimesters of first compared with index pregnancies (first pregnancy-first trimester 82.0 +/- 8.1 mm Hg, index pregnancy-first trimester 79.4 +/- 7.6 mm Hg, P = .032; first-second trimester 81.6 +/- 6.7 mm Hg, index-second trimester 78.7 +/- 6.6 mm Hg, P = .016; first-third trimester 83.9 +/- 6.9 mm Hg, index-third trimester 81.6 +/- 6.9 mm Hg, P = .047). Repeated measures analysis of covariance confirmed that pregnancy order contributed independently to differences in MAP. The interval between pregnancies was found to be inversely related to the difference in MAP from first to index pregnancies by trimester (r = -0.41, P = .004) and the change in MAP within pregnancy from first to third trimester (r = -0.31, P = .046).

CONCLUSION

Mean arterial pressure is reduced in subsequent pregnancies compared with first pregnancies. This raises the possibility that pregnancy plays a role in modifying cardiovascular compliance. Consistent with this, the effect has temporal limitations in that the shorter the interval between pregnancies, the greater the reduction in MAP.

A pilot study on voucher‐based incentives to promote abstinence from cigarette smoking during pregnancy and postpartum

We report results from a pilot study examining the use of vouchers redeemable for retail items as incentives for smoking cessation during pregnancy and postpartum. Of 100 study-eligible women who were still smoking upon entering prenatal care, 58 were recruited from university-based and community obstetric practices to participate in a smoking cessation study. Participants were assigned to either contingent or noncontingent voucher conditions. Vouchers were available during pregnancy and for 12 weeks postpartum. In the contingent condition, vouchers were earned for biochemically verified smoking abstinence. In the noncontingent condition, vouchers were earned independent of smoking status. Abstinence monitoring and associated voucher delivery was conducted daily during the initial 5 days of the cessation effort, gradually decreased to every other week antepartum, increased to once weekly during the initial 4 weeks postpartum, and then decreased again to every other week for the remaining 8 weeks of the postpartum intervention period. Contingent vouchers increased 7-day point-prevalence abstinence at the end-of-pregnancy (37% vs. 9%) and 12-week postpartum (33% vs. 0%) assessments. That effect was sustained through the 24-week postpartum assessment (27% vs. 0%), which was 12 weeks after discontinuation of the voucher program. Total mean voucher earnings across antepartum and postpartum were 397 US dollars (SD=414 US dollars) and 313 US dollars (SD=142 dollars) in the contingent and noncontingent conditions, respectively. The magnitude of these treatment effects exceed levels typically observed with pregnant and recently postpartum smokers, and the maintenance of effects through 24 weeks postpartum extends the duration beyond those reported previously.

Seasonal Variation in Preeclampsia Based on Timing of Conception

OBJECTIVE

Studies have suggested that the incidence of preeclampsia may be partially dependent on the month or season of delivery. We sought to evaluate whether preeclampsia occurs seasonally in our population and whether the timing of conception or delivery is more strongly associated with risk.

METHODS

Between January 1995 and August 2003, we identified 142 primiparous women with singleton pregnancies who met the American College of Obstetricians and Gynecologists' definition for preeclampsia and compared them with 7,762 primiparous control deliveries. We analyzed rates of preeclampsia by individual month and 3-month seasonal blocks based on conception and delivery. Data were analyzed with the chi2 test, and logistic regression and odds ratios were calculated where appropriate.

RESULTS

Preeclampsia occurred in 1.8% of singleton primiparous gestations (142/7,904). Cases were younger than controls (26.5 +/- 5.6 versus 28.0 +/- 0 6.0 years, P < .003), of similar race (97% white versus 96% white, P = .69), and equally likely to have a female child (45% versus 48%, P = .41). We found no significant association of month (logistic regression P = .20) of delivery with the risk of preeclampsia. There was a significant association of month (P = .003) of conception with risk of preeclampsia. Conception during the summer months had the highest risk (incidence 2.3%; odds ratio 1.7; 95% confidence limits 1.06, 2.75) compared with spring (incidence 1.4%). Fall (1.7%) and winter (1.6%) conceptions were associated with intermediate rates of preeclampsia.

CONCLUSION

We identified a seasonal variation in preeclampsia that appears to be more strongly related to timing of conception than to the timing of delivery. The highest incidence of preeclampsia was associated with conception in the summer months.

LEVEL OF EVIDENCE

II-2.

Platelet Activation, Sympathetic Tone, and Plasma Volume in Nulligravid Women of Reproductive Age

OBJECTIVE

Preeclampsia is associated with increased platelet activation, increased sympathetic activity, and decreased plasma volume. We sought to estimate the relationship of plasma volume, sympathetic activity, or both to platelet activation in nonpregnant nulligravid women.

METHODS

We studied 37 healthy nulligravid subjects during the follicular phase of the menstrual cycle. After intravenous access was obtained, subjects rested in the supine position for 15 minutes. Blood was drawn without venous constriction for measurement of plasma catecholamines (epinephrine and norepinephrine) and complete blood count. Antigenic markers of platelet activation, CD63 and CD61-CD14 (platelet-monocyte aggregates), were measured with flow cytometry. Plasma volume was estimated in the supine position by using Evans blue dye and is expressed in milliliters and corrected for body mass index (BMI). We compared data from the lowest plasma volume/BMI quartile with the 2 middle quartiles combined and with the upper quartile. Data are expressed as mean +/- standard deviation. P <.05 was considered significant.

RESULTS

Subjects were aged 26.5 +/- 5.0 years, BMI was 24.0 +/- 3.0 kg/m(2), and plasma volume was 2,685 +/- 429 mL. We identified no significant relationship of platelet concentration to plasma volume/BMI between quartile groups (P =.944). However, there was a significant difference between quartiles for %CD63 expression (P =.013) and for CD61/CD14 expression (P =.018), with the lowest quartile demonstrating elevated platelet activation.

CONCLUSIONS

We found evidence that enhanced platelet activation is associated with reduced plasma volume, but not with plasma catecholamine concentrations. There was no association of platelet concentration with reduced plasma volume. We speculate that elements of the clinical syndrome of preeclampsia coexist as a subclinical phenotype before pregnancy.

Extended somatic support for pregnant women after brain death

OBJECTIVE

To review case reports of pregnant women who have been supported after brain death until successful delivery of their infants. From these reports and other literature about brain death, normal physiologic changes of pregnancy, and specific needs for fetal development, recommendations were made to assist in supporting pregnant women after brain death until delivery of a mature fetus who is likely to survive.

DATA SOURCES

Personal files and experiences, MEDLINE review of case reports and publications about physiologic changes present during normal pregnancy and after brain death, and the critical needs for fetal development were included.

DATA EXTRACTION

Eleven reports of ten patients comprise the accumulated clinical experience. Hypotension, requiring fluid administration and inotropic/vasopressor therapy, occurred in all the mothers, and in six cases, was the reason for urgent delivery. The longest period of support was 107 days, from 15 to 32 wks of gestation. Two mothers also became organ donors. Recurrent infections, thermolability, and other complications common to prolonged ICU care were encountered. All infants survived. One had congenital abnormalities caused by phenytoin use by the mother. When followed, all others developed within normal growth and mental variables. These cases plus literature citations noted above were used to develop recommendations for maternal/fetal care.

CONCLUSION

Preservation of uterine/placental blood flow is the most important priority during somatic support. Imprecise autoregulation of the uterine vasculature during maternal hypoxemia or hypotension makes this goal a significant challenge. Special considerations for nutrition; medication use; cardiovascular, respiratory, or endocrine therapy; fetal monitoring; hormone replacement; and ethical concerns are discussed.

Relationship of plasma volume to sympathetic tone in nulliparous women

OBJECTIVE

We sought to determine whether resting supine plasma volume is related to sympathetic tone in healthy young nulligravid normotensive women.

STUDY DESIGN

Forty women were examined in the midfollicular phase. Alpha-adrenergic tone was estimated by an examination of the late phase II blood pressure response to the Valsalva maneuver. Resting heart rate was examined to evaluate the balance of sympathetic and parasympathetic input. Plasma catecholamines were measured during supine rest. Plasma volume was estimated by Evans blue dilution.

RESULTS

Plasma volume corrected for body surface area was correlated inversely to late phase II blood pressure response to the Valsalva maneuver (r = -0.31, P <.05) and was correlated directly to the cardiac R-R interval (r = 0.41, P <.01). There was no relationship of plasma volume corrected for body surface area to mean arterial pressure (r = -0.13, P not significant). We found no significant relationship of plasma epinephrine concentration (r = -0.05, P =.76) or plasma norepinephrine (r = -0.09, P =.60) with plasma volume corrected for body surface area.

CONCLUSION

We conclude that plasma volume is related inversely to both an estimate of alpha-adrenergic activation and heart rate. These findings are consistent with an adaptive physiologic response that is aimed at the maintenance of blood pressure in the face of reduced plasma volume.

Comparison of fetal growth estimates based on birth weight and ultrasound references

OBJECTIVE

To compare three different methods for modeling fetal weight gain during the third trimester of pregnancy.

METHODS

Ultrasound and live birth weight data were used to construct three models for defining fetal growth during the third trimester: longitudinal ultrasound estimates of fetal weight obtained serially at 3-4 week intervals in 50 uncomplicated, well-dated pregnancies between 19 and 40 weeks' gestation; cross-sectional ultrasound estimates of fetal weight obtained from 2018 ultrasound examinations of singleton, non-anomalous fetuses between 24 and 39 weeks' gestation; and cross-sectional birth weight data obtained from 9553 live singleton, non-anomalous neonates between 24 and 43 completed weeks. Analysis was performed by pairwise partial f test to compare regression curves and zeta test for comparison of mean weekly weight gain. A value of p < 0.05 was accepted for significance.

RESULTS

Derived regression lines depicting fetal size across gestation were significantly different from each other (f tests, p < 0.05). Estimates of mean fetal weight were significantly different between the three different models at specific gestational ages. Significant weekly variations in fetal weight gain were observed within the raw cross-sectional data sets, both for ultrasound-estimated fetal weight (range 91-278 g/week) and birth weight (65-309 g/week).

CONCLUSIONS

Each of the methods used to model normal fetal weight gain in the third trimester defined a distinct pattern of fetal growth. Normal fetal growth, defined longitudinally, was most closely matched by a combination of cross-sectional ultrasound-derived estimated fetal weight in preterm gestation below 34 weeks' gestation and live birth weight at or beyond 34 weeks.

Uterine artery hemodynamic adaptations through the menstrual cycle into early pregnancy

OBJECTIVE

To estimate the time course of human uterine artery vascular adaptation through the menstrual cycle into early pregnancy.

METHODS

We prospectively measured the uterine artery pulsatility index, peak systolic velocity, and volumetric blood flow during the menstrual cycle and at 4, 6, and 12 weeks of pregnancy in women who conceived. Upper extremity radial artery hemodynamic changes were examined as a control vessel. Ten subjects conceived within 12 months of menstrual cycle studies. Analyses were performed using repeated measures analysis of variance with P <.05 accepted for significance.

RESULTS

In women who conceived, uterine artery peak systolic velocity demonstrated a significant increase during the period of observation, which began after cycle day 10 (0.36 x 0.02 meters per second) of the menstrual cycle and continued though 12 menstrual weeks (1.05 +/- 0.10 meters per second, P <.001). Uterine artery pulsatility index decreased significantly during the observation window from 3.0 +/- 0.2 in the follicular phase to 1.6 +/- 0.2 at 12 menstrual weeks (P <.001). Blood flow in the uterine artery increased significantly from cycle day 10 (22.2 +/- 1.8 mL per minute) to 12 menstrual weeks' gestation (150.2 +/- 40.3 mL per minute, P <.001). These patterns were significantly different from the patterns observed for the radial artery.

CONCLUSION

Uterine artery hemodynamic adaptation in early pregnancy follows a continuum established during the menstrual cycle. These adaptations result in decreased uterine artery impedance and increased blood flow. These changes differ from those observed in the upper extremity radial artery (control vessel) suggesting independence of regional pelvic and systemic hemodynamic adaptations.