Clinical signs of normal plasma volume expansion during pregnancy

Classification of longitudinal profiles using semi-parametric nonlinear mixed models with P-Splines and the SAEM algorithm

In this work, we propose an extension of a semiparametric nonlinear mixed-effects model for longitudinal data that incorporates more flexibility with penalized splines (P-splines) as smooth terms. The novelty of the proposed approach consists of the formulation of the model within the stochastic approximation version of the EM algorithm for maximum likelihood, the so-called SAEM algorithm. The proposed approach takes advantage of the formulation of a P-spline as a mixed-effects model and the use of the computational advantages of the existing software for the SAEM algorithm for the estimation of the random effects and the variance components. Additionally, we developed a supervised classification method for these non-linear mixed models using an adaptive importance sampling scheme. To illustrate our proposal, we consider two studies on pregnant women where two biomarkers are used as indicators of changes during pregnancy. In both studies, information about the women's pregnancy outcomes is known. Our proposal provides a unified framework for the classification of longitudinal profiles that may have important implications for the early detection and monitoring of pregnancy-related changes and contribute to improved maternal and fetal health outcomes. We show that the proposed models improve the analysis of this type of data compared to previous studies. These improvements are reflected both in the fit of the models and in the classification of the groups.

Association of the maternal serum albumin level with fetal growth and fetal growth restriction in term-born singletons: a prospective cohort study

OBJECTIVE

To investigate the association of the maternal serum albumin (MAlb) level with fetal growth and fetal growth restriction (FGR) risk in term-born singletons.

DESIGN

Prospective cohort study.

SETTING

Four hospital maternity units of the Tongji Maternal and Child Health Cohort study initiated from September 2013 to April 2016 at Wuhan City, in central China.

PATIENT(S)

A total of 3,065 mother-offspring pairs.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Fetal growth was evaluated by birth weight (BW) and birth length. Fetal growth restriction was defined as BW below the 10th percentile.

RESULT(S)

All MAlb levels were within the upper limit of normal. After adjustment for liver function parameters, inflammatory indicators, and others, a reverse U-shaped relationship between MAlb and fetal growth was observed. Specifically, BW increased significantly with an increasing MAlb level when the MAlb level was <36.1 g/L (per g/L: β = 36.8; 95% CI, 0.8, 72.7) but decreased with increasing the MAlb level when the MAlb level was >36.1 g/L (per g/L: β = -15.1; 95% CI, -21.2, -8.9). There was a similar association between MAlb and birth length. Furthermore, the adjusted odd ratios of FGR across increasing tertiles of the MAlb levels were 1.0 (reference), 1.1 (0.7, 1.8), and 1.7 (1.0, 2.6).

CONCLUSION(S)

There was a reverse U-shaped association between MAlb and fetal growth. A higher MAlb level was associated with an increased risk of FGR.

CLINICAL TRIAL REGISTRATION NUMBER

NCT03099837.

Emerging understanding and measurement of plasma volume expansion in pregnancy

Plasma volume expansion is an important component of a successful pregnancy. The failure of maternal plasma volume expansion has been implicated in adverse obstetric outcomes such as pre-eclampsia, fetal growth restriction, and preterm birth. Altered iron homeostasis and elevated maternal hemoglobin concentrations have also been associated with adverse pregnancy outcomes; limited data have suggested that these effects may be mediated by inadequate plasma volume expansion. In addition, it has been noted that pregnant, obese women, compared with lean subjects, have decreased plasma volume expansion along with impaired iron homeostasis and increased inflammation. Current estimates of plasma volume expansion are outdated and do not necessarily reflect contemporary obstetric populations. Moreover, the validation of clinically applicable methods of plasma volume determination as well as enhanced methodologies should be a priority. Further study is needed to characterize diminished plasma volume expansion during pregnancy and to understand the potential role of impaired iron homeostasis and inflammation in adverse obstetric outcomes, especially in obese women.

Maternal anemia in Benin: prevalence, risk factors, and association with low birth weight

We studied the prevalence of anemia during pregnancy and its relationship with low birth weight (LBW; birth weight < 2,500 g) in Benin. We analyzed 1,508 observations from a randomized controlled trial conducted from 2005 to 2008 showing equivalence on the risk of LBW between two drugs for Intermittent Preventive Treatment of malaria during pregnancy (IPTp). Despite IPTp, helminth prophylaxis, and iron and folic acid supplementations, the proportions of women with severe anemia (hemoglobin [Hb] concentration < 80 g/L) and anemia (Hb < 110 g/L) were high throughout pregnancy: 3.9% and 64.7% during the second and 3.7% and 64.1% during the third trimester, but 2.5% and 39.6% at the onset of labor, respectively. Compared with women without anemia (Hb ≥ 110 g/L) during the third trimester, women with severe anemia (Hb < 80 g/L) were at higher risk of LBW after adjustment for potential confounding factors (prevalence ratio [PR] = 2.8; 95% confidence interval [1.4-5.6]).

Maternal hemoglobin concentration and its association with birth weight in newborns of mothers with preeclampsia

OBJECTIVE

Maternal hemoglobin concentration is inversely related to newborn size presumably through plasma volume constriction. We sought to determine whether birth weight would show an inverse relationship to hemoglobin concentration in a group of infants whose mothers had preeclampsia, where plasma volume constriction is common.

METHODS

Electronic and paper chart review identified 142 nulliparous women with preeclampsia (excluding hemolysis, elevated liver enzymes, low platelets syndrome). Birth weight percentile was determined based on cross-sectional hybrid growth curves. Maximal third trimester maternal hemoglobin concentrations were obtained and standardised to z-scores based on gestational age matched normative data. Birth weight percentile was examined as a function of hemoglobin z-score using appropriate statistics.

RESULTS

Average gestational age at delivery was 35.9 +/- 1.9 weeks. Mean birth weight percentile for infants of preeclamptic mothers was 34 +/- 32. Mean hemoglobin z-score for mothers with preeclampsia was 0.3 +/- 1.5, significantly higher than a control population (p = 0.04). Maternal hemoglobin z-score was inversely associated with birth weight percentile (r = -0.18, p = 0.03).

CONCLUSION

Maternal hemoglobin concentrations are significantly elevated prior to delivery in women with preeclampsia. There is a statistically significant inverse correlation of maternal hemoglobin concentration to birth weight percentile.

Ontogeny of hematological cell and biochemical profiles in maternal and fetal baboons (Papio species)

The normal ranges of hematological cell profiles and biochemistry are documented in adult non-pregnant, pregnant, juvenile, and neonatal baboons. Despite the extensive use of the baboon as a model for the study of various aspects of pregnancy, there is no data from paired mothers and their fetuses at different stages of gestation. Hematologic and biochemical profile data were obtained from eight non-pregnant female baboons, 37 mothers and 38 fetal baboons at 30 +/- 2, 90 +/- 2, 125 +/- 2, and 175 +/- 2 days of gestation (mean +/- range; dGA; term, 180 dGA). Changes observed in fetal and maternal blood during normal baboon pregnancy were similar to those reported in human pregnancy. The level of alkaline phosphatase was two times higher in fetal blood circulation than that reported in human pregnancy.

Anemia during pregnancy in a Chinese population

OBJECTIVES

To study prevalence, risk factors, and birth outcomes of women with anemia during pregnancy in a Chinese population.

METHODS

A retrospective cohort study was performed based on 16936 pregnancies delivered between January 1989 and December 1990 in Suzhou, China. Anemia was defined as hemoglobin less than 10 g/dl. Multivariate logistic regression was used to estimate odds ratio, 95% confidence interval, and to control for confounding variables.

RESULTS

The prevalence of anemia was 10.3% at the first trimester, 18.9% at the third trimester. Overall, 26.2% pregnant women experienced anemia in pregnancy. Anemia during early pregnancy was not associated with increased risk of adverse perinatal outcomes. However, anemia in later pregnancy was inversely associated with preterm birth and low birth weight.

CONCLUSIONS

Anemia during pregnancy does not increase the risk of poor birth outcomes.

Hemoglobin concentrations influence birth outcomes in pregnant African-American adolescents

Relationships between hemoglobin concentrations and birth outcomes have not been well characterized in African-American adolescents despite the fact that this group is at a higher risk of early childbearing. To address this issue, we characterized the prevalence of anemia and maternal factors associated with anemia in pregnant African-American adolescents. A retrospective medical chart review was undertaken of 918 adolescents who had received prenatal care at an inner-city maternity clinic between 1990 and 2000. Multiple log-linear regression analyses were used to address relationships between hemoglobin and adverse birth outcomes. The prevalence of anemia during the third trimester averaged 57-66% and was substantially higher than typically reported in adolescent and adult women. Multiparity, inadequate prenatal care, low prepregnancy BMI, history of self-reported cigarette use and infection with sexually transmitted diseases were significantly associated with lower hemoglobin during pregnancy. Adolescents with pre-eclampsia had higher hemoglobin (P < 0.01). Compared with the reference group (106-120 g/L), high hemoglobin (>120 g/L) during the second and third trimester significantly increased the risk of low birth weight (risk ratio (RR) = 3.11; [CI] 1.35, 7.13), and in the second-trimester cohort only, high hemoglobin concentrations increased the risk of preterm delivery (RR = 2.33; [CI] 1.07, 5.05). A U-shaped distribution between hemoglobin concentration and adverse birth outcomes was found in the third-trimester cohort when the reference range was decreased to 96-105 g/L to adjust for potentially lower hemoglobin concentrations among the African-American population. Our results suggest that additional medical attention may be warranted in pregnant African-American adolescents with hemoglobin concentrations of <or=95 g/L or >120 g/L.

Effect of maternal oral hydration on amniotic fluid index in women with pregnancy-induced hypertension

OBJECTIVE

To evaluate the effect of maternal oral hydration on amniotic fluid index (AFI) in women with pregnancy-induced hypertension.

METHODS

Five women with pregnancy-induced hypertension and five normotensive gravidae at 32-37 weeks gestation with normal AFI (8-18cm) were hydrated by oral intake of 2L of water over 1 h. Both groups were similar in age, parity and gestation. Repeat AFI was measured in all women after 3 h. The differences between pre- and post-hydration AFI in the two groups were analyzed with Student's t-test for statistical significance.

RESULTS

Maternal oral hydration resulted in a significant increase in AFI in both hypertensive and normotensive gravidae (1.7cm and 3.48cm, respectively). However, the extent of increase was significantly lower in the hypertensive group (P = 0.03).

CONCLUSION

Pregnancy-induced hypertension adversely affects the increase in amniotic fluid volume with maternal hydration. This observation is of clinical relevance in the management of oligohydramnios associated with pregnancy-induced hypertension.

Individual longitudinal patterns in biochemical and hematological markers for the early prediction of pre-eclampsia

OBJECTIVE

To analyze the individual longitudinal patterns of maternal biochemical and hematological tests performed throughout gestation in order to predict at the 20th week of pregnancy the later development of pre-eclampsia.

STUDY DESIGN

A longitudinal study was conducted on 187 white normotensive pregnant women all with a history of pre-eclampsia. Blood samples were performed at the 8th week of gestation and then every 4 weeks until the 36th week. The longitudinal patterns of urea, creatinine, uric acid, total proteins, hematocrit, red blood cells, hemoglobin, mean red cell volume, ferritin and iron were derived. By means of regression analysis, for each woman and each significant marker, a 'theoretical physiological pattern', from the 8th to the 20th week, was constructed. By comparing the observed values of each marker for each woman with her 'theoretical physiological pattern', variables indicating the match or mismatch to it were derived. Such variables were used, together with other maternal characteristics, in a logit regression for the probability of developing pre-eclampsia later in pregnancy.

RESULTS

In 140 cases, pregnancies followed a physiological course, while 47 women developed pre-eclampsia during the third trimester. In the physiological gestations, the weekly mean values of creatinine, hematocrit, total proteins, uric acid and urea showed patterns that were significantly different from those of the pathological group. The logit model was able to classify correctly 96% of the physiological and 87% of the pathological pregnancies, with a negative predictive value of 96% and a positive predictive value of 89% (area under the receiver operator characteristics (ROC) curve 0.98). The ability of the model to predict later complications at the 20th week was confirmed by a validation procedure.

CONCLUSION

The simultaneous use of individual longitudinal patterns of parameters, achieved non-invasively as part of the standard methods of antenatal care that provide a global evaluation of plasma volume expansion, showed a high ability to predict, early in pregnancy, the later development of pre-eclampsia.

Prediction of the development of pregnancy-induced hypertensive disorders in high-risk pregnant women by artificial neural networks

Pregnancy-induced hypertensive disorders (PIHD) are common complications of pregnancy and are associated with increased maternal and fetal morbidity. In this study, artificial neural networks (aNN) and multivariate logistic regression (MLR) were applied to a set of clinical and laboratory data (urea, creatinine, uric acid, total proteins, hematocrit, iron and ferritin) collected at 16 and 20 weeks of gestation. The efficacy of the two approaches in predicting the development of PIHD in 303 consecutive normotensive pregnant women at high risk of pre-eclampsia and intrauterine fetal growth retardation was then compared. The aNN were trained with a randomly selected set of 187 patient records and evaluated on the remainder (n=116). MLR analysis was done with the same 116 patients. The performance of each model was assessed using receiver operator characteristic (ROC) curves. Pregnancies had a normal physiological course in 227 cases, whereas 76 (25.1%) women developed PIHD during the third trimester. The best aNN at 20 weeks yielded an area under the ROC curve of 0.952, the sensitivity of 86.2%, the specificity of 95.4%, the positive predictive value of 86.2% and the negative predictive value of 95.5% for PIHD. The corresponding values for the MLR at 20 weeks were 0.962, 79.3%, 97.7%, 92% and 93.4%, respectively. The computer-aided integrated use of these conventional tests seems to provide a useful means for and early prediction of PIHD development.

Anemia in pregnancy

Anemia is one of the most frequent complications related to pregnancy. Normal physiologic changes in pregnancy affect the hemoglobin (Hb), and there is a relative or absolute reduction in Hb concentration. The most common true anemias during pregnancy are iron deficiency anemia (approximately 75%) and folate deficiency megaloblastic anemia, which are more common in women who have inadequate diets and who are not receiving prenatal iron and folate supplements. Severe anemia may have adverse effects on the mother and the fetus. Anemia with hemoglobin levels less than 6 gr/dl is associated with poor pregnancy outcome. Prematurity, spontaneous abortions, low birth weight, and fetal deaths are complications of severe maternal anemia. Nevertheless, a mild to moderate iron deficiency does not appear to cause a significant effect on fetal hemoglobin concentration. An Hb level of 11 gr/dl in the late first trimester and also of 10 gr/dl in the second and third trimesters are suggested as lower limits for Hb concentration. In an iron-deficient state, iron supplementation must be given and follow-up is indicated to diagnose iron-unresponsive anemias.

Fetal diuretic responses to maternal hyponatremia: contribution of placental sodium gradient

Maternal hyponatremia induces fetal hyponatremia and increased fetal urine flow. We sought to examine the relative contributions of the placental Na(+) gradient vs. the absolute decrease in fetal plasma Na(+) in the fetal diuretic response to hyponatremia. Seven ewes with singleton fetuses (130 +/- 2 days) were prepared. Ewes received intravenous 1-desamino-8-D-arginine vasopressin (20 microg) and warm tap water (2 liters). Maternal plasma Na(+) was decreased to achieve two levels of maternal hyponatremia. Maternal and fetal blood volume were measured with radiolabeled red blood cells. In response to the first decrease in maternal plasma Na(+), fetal plasma Na(+) did not change initially. Subsequently, fetal plasma Na(+) decreased, normalizing the gradient. The second decrease in maternal plasma Na(+) similarly induced a reduced and normalized placental gradient at lower fetal plasma Na(+) values. Fetal urine flow increased in direct proportion to the degree of fetal hyponatremia (13, 38, 63, 100%, respectively). Maternal, although not fetal, blood volume significantly increased in response to hyponatremia. These results suggest that chronic fetal hyponatremia will result in a persistent diuresis, despite placental equilibration.

Maternal 1-deamino-8-D-arginine-vasopressin-induced sequential decreases in plasma sodium concentration: ovine fetal renal responses

OBJECTIVE

Acute maternal plasma hypotonicity induces a reduced placental osmotic gradient that contributes to augmented maternal-to-fetal water flow. Subsequently, maternal plasma hyponatremia results in fetal plasma hyponatremia, increased fetal urinary flow, and ultimately increased amniotic fluid volume. We hypothesized that both the degree of reduction in the placental osmotic gradient and the degree of fetal plasma hyponatremia influence fetal urinary diuretic responses. To differentiate the roles of these factors, we determined fetal urinary responses to graded levels of plasma hyponatremia during a constant placental osmotic gradient. Furthermore, we sought to establish the minimum level of plasma hyponatremia necessary to facilitate an increase in fetal urine production.

STUDY DESIGN

Seven pregnant ewes (130 +/- 2 days) were prepared with maternal and fetal vascular catheters and a fetal bladder catheter. After 6 days of recovery, fetal urinary flow and urine and plasma compositions were measured during a 2-hour control period. At 2 hours, tap water (2 L, 38 degreesC) with a 20-g bolus of 1-deamino-8-d-arginine-vasopressin was administered to the ewe. Maternal plasma sodium concentration was decreased from control by 5 to 7, 10 to 12, and 15 to 17 mEq/L, and held at each level (levels 1, 2, and 3) for 60 minutes.

RESULTS

1-Deamino-8-d-arginine-vasopressin administration induced sequential decreases in maternal and fetal plasma sodium concentrations (control 146.9 +/- 0.5 mEq/L and 141.0 +/- 0.5 mEq/L, respectively) at level 1 (140.1 +/- 0.6 mEq/L and 136.7 +/- 0.7 mEq/L, respectively), level 2 (132.5 +/- 0.7 mEq/L and 130.6 +/- 1.1 mEq/L, respectively), and level 3 (125.4 +/- 1.2 mEq/L and 123.0 +/- 1.5 mEq/L, respectively). The maternal-fetal placental osmolality and sodium gradients were constant at each hypotonicity level. Fetal urinary flow significantly increased in association with the degree of hyponatremia (from 0.17 +/- 0.03 mL/kg/min to 0. 26 +/- 0.04 mL/kg/min, 0.33 +/- 0.05 mL/kg/min, and 0.38 +/- 00.5 mL/kg/min at levels 1, 2, and 3, respectively).

CONCLUSIONS

These results indicate the following: (1) Sequential decreases in maternal plasma tonicity result in parallel decreases in fetal plasma tonicity. (2) The fetal urinary diuretic response is highly correlated with the degree of fetal plasma hypotonicity, despite a constant placental osmotic gradient. A fetal therapeutic response (53% increase in fetal urine production) may be induced by a maternal plasma sodium concentration decrease of only 5 to 7 mEq/L.

Preanalytical and analytical factors affecting laboratory results

The results of laboratory tests have a substantial role in the diagnostics of diseases. However, laboratory results do not always correspond with the patient's clinical status. They may be unexpected and surprising. On the other hand, an abnormal laboratory result may be accepted as such and interpreted as a sign of a disease. However, an abnormal result may result from several factors other than disease. Conventionally, these interfering factors have been divided into preanalytical and analytical factors and furthermore into factors acting in vivo and in vitro. The list of these factors is long and laborious to bear in mind. In this review we focus on the factors which, in practice, most often affect laboratory results in healthy individuals and which explain an unexpected result.

Anaemia in pregnancy--is the current definition meaningful?

OBJECTIVE

To determine if the current definition of antenatal anaemia (haemoglobin < 10 g/dl) has any clinical significance.

STUDY DESIGN

A retrospective study on all singleton deliveries over a 3-year period in two teaching hospitals under one university department was conducted by the extraction of data from a computer database. The major pregnancy complications and perinatal outcome were compared between mothers with and without anaemia and adjusted for parity.

RESULTS

The incidence of multiparity was significantly higher in the 817 anaemia patients compared to the 10125 non-anaemia patients, but there was no difference in the incidence of other major antenatal complications, type of labour or mode of delivery, incidence of preterm delivery, or perinatal mortality or morbidity, after adjusting for parity. Among the anaemia patients, those with thalassaemia trait (54.8%) had a significantly higher incidence of gestational glucose intolerance but the incidences of other complications and the perinatal outcome were similar to the iron deficiency patients.

CONCLUSION

Antenatal anaemia, defined as a maternal haemoglobin of < 10 g/dl, does not adversely affect pregnancy outcome. This raises the question of whether the diagnosis of anaemia should be redefined.

Treatment of oligohydramnios with maternal 1-deamino-[8-D-arginine] vasopressin-induced plasma hypoosmolality

OBJECTIVE

Maternal 1-deamino-[8-D-arginine] vasopressin (a selective antidiuretic agonist) and oral water loading decrease maternal and fetal plasma osmolality and markedly increase fetal urine flow in sheep. We hypothesized that a titrated reduction in maternal plasma osmolality would increase human amniotic fluid volume.

STUDY DESIGN

Pregnant women (n = 5) with oligohydramnios at term were administered oral water loading (20 ml/kg) and intravenous 1-deamino-[8-D-arginine] vasopressin (2 micrograms) to induce antidiuresis. Maternal plasma and urine osmolality and urine production were measured hourly, and water replacement was titrated for 8 hours to reduce plasma osmolality by 15 to 20 mOsm/kg. The amniotic fluid index determined by ultrasonography was measured at baseline, 8 hours, and 24 hours. A control group of pregnant women (n = 5) with oligohydramnios at term was observed for 8 hours with maintenance intravenous hydration.

RESULTS

In 1-deamino-[8-D-arginine] vasopressin-treated women, maternal urine flow increased with oral water loading, decreased with 1-deamino-[8-D-arginine] vasopressin administration, and remained reduced for 8 hours. Maternal plasma osmolality significantly decreased (285 +/- 4 to 265 +/- 4 mOsm/kg) and the amniotic fluid index significantly increased (4.1 +/- 0.6 to 8.2 +/- 1.5 cm) at 8 hours. Although maternal urine osmolality returned to basal values at 24 hours, plasma osmolality was reduced and the amniotic fluid index remained significantly increased (8.2 +/- 1.3 cm). There was no change in the amniotic fluid index (4.3 +/- 0.4 to 4.7 +/- 0.7 cm) in control patients observed with maintenance intravenous hydration.

CONCLUSIONS

Maternal 1-deamino-[8-D-arginine] vasopressin and oral water administration can reduce and stabilize plasma osmolality and increase amniotic fluid volume. 1-Deamino-[8-D-arginine] vasopressin therapy has potential for the prevention and treatment of oligohydramnios.

Volume homeostasis in normal pregnancy and pre-eclampsia: physiology and clinical implications

The pieces of the jigsaw puzzle of volume homeostasis in human pregnancy are being put together gradually. This chapter has focused on recent advances in our understanding of factors controlling extracellular fluid volume in normal pregnancy and their disturbance in women who develop pre-eclampsia. We have explored the clinical implications of these guidelines for management of patients with pre-eclampsia. Clearly there is still much to be learned. Studies of the cellular and subcellular handling of sodium are still in their infancy and will add much to our understanding of the physiology of volume homeostasis in normal pregnancy and its disturbance in pre-eclampsia and other causes of hypertension in pregnancy.

Anemia in pregnancy

In evaluating pregnant women with anemia, it is essential to do a complete history and physical examination, as well as a complete blood count with indices and a blood smear examination. Based on these findings, other tests such as ferritin and serum or red cell folate may be ordered. Because of the normal physiologic changes in pregnancy that affect the hematocrit, indices, and some other parameters, diagnosing true anemia, as well as the etiology of anemia, is challenging. Because of the increased nutritional requirements of the mother and fetus, the most common anemias are iron deficiency anemia and folate deficiency megaloblastic anemia. These anemias are more common in women who have inadequate diets and who are not receiving prenatal iron and folate supplements. Other less common causes of acquired anemia in pregnancy are aplastic anemia and hemolytic anemia associated with preeclampsia. In addition, congenital anemias such as sickle cell disease can impact on the health of the mother and fetus. Obviously, severe anemia has adverse effects on the mother and the fetus. There is also evidence that less severe anemia is associated with poor pregnancy outcome. The cause of this association has yet to be elucidated. It is important, however, to diagnose and treat anemia in pregnancy to provide for optimal health of the mother and infant.

First antenatal visit haematocrit and pregnancy induced hypertension

First antenatal visit haematocrit values during the first and second trimesters were retrospectively collected from 546 nulliparas with singleton pregnancies. The results were analysed for correlation with development of pregnancy induced hypertension (PIH) later in pregnancy. It was found that women with higher haematocrit values, especially over 0.40, had an increased risk of developing PIH. However, there appeared to be no absolute level of haematocrit which had sufficient discriminative value to be useful in clinical practice.

Anemia and spontaneous preterm birth

The association between anemia during pregnancy and spontaneous preterm birth was studied with a two-stage case-control design in a large, multiethnic cohort. Results of all hematologic measurements were abstracted from the prenatal and delivery records of 1706 of the 26,901 women in the cohort. Among women delivered of infants at term, mean hematocrit value was low during the early phase of the second trimester, stable until near term, then reached a maximum at 40 weeks' gestation. The mean hematocrit value of black women was consistently lower than that of Asian, Mexican, and white women. Anemia (hematocrit value less than the tenth percentile for ethnic group and duration of pregnancy) at any time during the second trimester was positively associated with subsequent spontaneous preterm birth (odds ratio, 1.9; 95% confidence interval, 1.3 to 2.8). Compared with white women, the odds ratios for preterm birth were 2.0 (95% confidence interval, 1.6 to 2.4) for black, 1.2 (95% confidence interval, 0.9 to 1.6) for Asian, and 1.2 (95% confidence interval, 1.0 to 1.5) for Mexican women. Adjustment for second-trimester anemia had minimal influence on the odds ratios. We conclude that anemia during the second trimester was associated with preterm birth. However, it does not account for the large ethnic differences in preterm birth.

Haematologic parameters and pregnancy outcome. A prospective cohort study in the third trimester

The relationship between haematologic parameters and pregnancy outcome was investigated in a prospective study, taking important covariates into consideration. A questionnaire asking information about smoking, alcohol consumption and iron intake was completed by a consecutive series of 796 ambulatory singleton pregnant women at 31-32 weeks of gestation. Subsequently, haematologic parameters were measured. After delivery, birth weight, gestation length and blood pressure values during pregnancy were abstracted from the obstetricians' records. Low birth weight (less than 2.500 g) and preterm birth (less than 37 weeks), were significantly more frequently seen in women with high haemoglobin (greater than or equal to 8.0 mmol/l) or high haematocrit (greater than 38%) values, with Mantel-Haenszel odds ratios varying from 2.4 to 4.2. Also a high erythrocyte count (greater than or equal to 4.5/pl) was correlated with low birth weight, while for mean corpuscular volume (MCV) no such relationships were found. Pregnancy induced hypertension was positively associated with haemoglobin, haematocrit and erythrocyte count, but could not fully explain the relationships between these parameters and adverse outcomes. Using multiple logistic regression with low birth weight and or preterm birth as the dependent variable, the effect of haematocrit still was demonstrable after controlling for smoking, hypertension, parity, alcohol consumption and iron intake. These results are in agreement with the hypothesis that a higher blood viscosity is a risk factor for suboptimal placenta-perfusion.

Recording maternal vaginal apex pulse

A photoelectric plethysmographic probe, which emits and receives a low-voltage infrared light was placed in the vaginal apex of 122 high-risk pregnant women. The normal pulse form of the upper vagina does not have a diastolic notch. A study was undertaken to determine whether the vaginal apex pulse recording equals the accuracy, sensitivity, and specificity of the uterine artery Doppler velocimetry, and whether abnormal uterine artery wave forms are fixed. The vaginal apex recordings had greater sensitivity to abnormal outcome than did the uterine artery Doppler technique. The vaginal apex pulse height decreased significantly in a majority of the women undergoing elective cesarean section and during uterine contractions. In patients with abnormal wave forms (diastolic notches) and treated with either terbutaline sulfate or magnesium sulfate, the diastolic notch disappeared in eight out of 14 cases.

Volume homeostasis in normal and hypertensive human pregnancy

In this chapter are outlined the many factors involved in the regulation of sodium and volume homeostasis in normal human pregnancy and their interrelationships. New developments concerning the role of sodium/potassium ATPase, atrial natriuretic peptide, arginine vasopressin and angiotensin II as regulatory forces are outlined, together with a review of earlier work. Abnormalities found in women with, or destined for, PAH are described and their significance is discussed.

The origin of increased serum iron in pregnancy-induced hypertension

Serum iron was measured in 30 patients with pregnancy-induced hypertension and 24 normal pregnant women. The mean iron concentration was significantly higher in the group with pregnancy-induced hypertension (111 +/- 26 micrograms/ml) than in the controls (69 +/- 17 micrograms/ml) (p less than 0.0001). Readily available laboratory variables were used to determine whether the increased serum iron was the result of (1) hemolysis, (2) hepatocellular injury, or (3) intravascular volume contraction leading to hemoconcentration. It appears that a clinically silent, ongoing hemolytic reaction is responsible for the increase in serum iron seen in patients with pregnancy-induced hypertension.

Blood rheology and pregnancy

Pregnancy is a hypervolaemic situation with early expanded plasma volume, a high cardiac output and a decrease in the vascular and rheological resistance. The increase in plasma volume correlates better with fetal size than maternal size. The hypervolaemic and vasodilated state that accompanies normal pregnancy results in a high flow in the uterine arteries. In contrast, patients with PIH (pregnancy-induced hypertension) or placental insufficiency may have a contracted plasma volume secondary to diffuse vasoconstriction. In spite of the intense vasospasm and hypovolaemia, pre-eclampsia has generally a cardiac output which may be equal, higher or lower compared with non-eclamptic pregnancy. Hypovolaemia is reflected in a higher haematocrit than normal. In the case of a hypovolaemic state, haemoconcentration is associated with high red cell aggregation. In fetal distress and severe PIH, the rheological status (haemoconcentration and elevated red cell aggregation) has a high predictive value for perinatal complications. In patients with severe PIH, erythrocyte filtration is impaired. The increased leukocyte count in patients with PIH may occlude small vessels and could be a factor impairing intervillous blood flow. The increased erythrocyte rigidity may result from a re-distribution of cellular calcium metabolism (Blaustein concept). We conclude that there is an optimal haematocrit during pregnancy between 30% and 38%. The presence of a high haematocrit and in addition elevated red cell aggregation should alert the physician to an increased risk of fetal compromise.

Differing effects of fetal sex on pregnancy and its outcome

An analysis of 52,198 pregnancies was undertaken to determine if male and female fetuses had differing environmental effects on their mothers. Early gestational blood pressure and weight gain were significantly higher in preeclamptic women with male than with female fetuses. Preeclamptic women had lower third trimester hemoglobin values and less frequent proteinuria with male than with female fetuses. Excessive syncytial knots, a characteristic placental consequence of low uteroplacental blood flow, were seen less frequently with male than with female fetuses. These findings are hypothesized to be due to a greater maternal blood plasma volume expansion with male than with female fetuses in preeclamptic pregnancies.

Relation of haemoglobin levels in first and second trimesters to outcome of pregnancy

The relation between haemoglobin (Hb) concentrations at antenatal booking and subsequent outcome was examined in 54 382 singleton pregnancies. Both high (greater than 13.2 g/dl) and low (less than 10.4 g/dl) Hb values were associated with an adverse outcome. Mothers with a booking Hb in the intermediate range (10.4-13.2 g/dl) fared best. Significant differences emerged in perinatal mortality between those with high and those with intermediate Hb levels at 13-19 weeks' gestation. The frequencies of perinatal death, low birthweight, and preterm delivery were greater with high than with intermediate Hb. There was a striking relation between booking Hb values and the subsequent frequency of hypertension (p less than 0.001). In primiparas, the frequency of subsequent hypertension ranged from 7% at Hb values under 10.5 g/dl to 42% at Hb concentrations over 14.5 g/dl.

Simultaneous investigations of maternal cardiac output and fetal blood flow during hypervolemic hemodilution in preeclampsia--preliminary observations

In pre-eclampsia hemodynamic alterations are characterized by a lack of plasma volume expansion and a raised peripheral vascular resistance. For the compensation of plasma volume deficit and to restitute blood fluidity the therapeutic use of plasma volume expanders (f.e. low molecular dextran) is recommended. Several groups (Goodlin et al., Cloeren et al., Heilmann et al., Seghal et al., Schröck) have demonstrated benefitial effects on fetal status and development in the course of hypervolemic hemodilution in preeclampsia. This therapeutic procedure presumes the continuous surveillance of maternal hemodynamics to early recognize heart insufficiency or fluid overload in the lungs. We use the noninvasive thoracic impedance cardiography for continuous monitoring of maternal heart performance. The effect of hypervolemic hemodilution on fetal circulation has not been quantitatively investigated yet. Meanwhile pulsed doppler ultrasonography offers the possibility of estimating quantitative changes on fetal blood flow. We used both noninvasive techniques--thoracic impedance cardiography and pulsed doppler imaging system--for the simultaneous evaluation of maternal and fetal hemodynamic parameters during hypervolemic hemodilution. This preliminary report summarizes the investigations in 5 patients with pre-eclampsia (mean arterial blood pressure greater than or equal to 103.3 mm Hg, hemoconcentration with elevated hematocrit levels greater than or equal to 38%). The patients received an infusion of 500 ml dextran 40 over a period of exactly 60 minutes. The simultaneous measurements of maternal and fetal cardiovascular parameters were performed in 15-minutes intervals during dextran application and 15 minutes (p 15), 30 minutes (p 30) and 60 minutes (p 60) after the end of infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated static pressure and pregnancy well-being

Static pressure is defined as the pressure existing at all points in the circulation when the heart is stopped and is a determinant of cardiac output and blood pressure. By using the proposed relationship that static pressure = cardiac output X "resistance to venous return," estimates were made of peripheral static pressure in pregnant women. Measurements of cardiac output and venous resistance were accomplished with indirect plethysmographic techniques. Approximately 65% of pregnant women with complications had elevated values for their estimated peripheral static pressure. It is proposed that estimation of peripheral static pressure has both diagnostic and therapeutic applications in women with complications of pregnancy.

Plasma volume determination in normal and preeclamptic pregnancies

To determine the clinical usefulness of plasma volume determinations, we measured plasma volume serially throughout pregnancy with the use of the Evans blue dye-dilution technique in 20 subjects with normal pregnancies. In comparison, four preeclamptic subjects were studied. In preeclamptic subjects compared to normal subjects, plasma volume was reduced (1763 +/- 216 versus 2345 +/- 198 ml/m2, p less than 0.001). Two normotensive subjects who subsequently developed preeclampsia had reduced plasma volumes prior to the onset of hypertension as compared to volumes in those who remained normotensive (1918 +/- 86 versus 2345 +/- 198 ml/m2, p less than 0.01). Those subjects who were delivered of infants who were small for gestational age had significantly reduced plasma volumes compared to volumes of those who were delivered of infants who were appropriate for gestational age (1950 +/- 333 versus 2237 +/- 259 ml/m2, p less than 0.05), but this was true only among gravid women with pregnancies complicated by preeclampsia. We conclude that failure of plasma volume expansion is associated with the development of preeclampsia and also intrauterine fetal growth retardation in preeclamptic subjects.