Evidence of placental haemorrhage and preterm delivery

OBJECTIVE

To evaluate evidence of placental haemorrhage (PH) obtained through maternal interviews, patient charts and placental pathology examinations as potential indicators of a 'bleeding pathway' to preterm delivery (PTD).

DESIGN

Prospective cohort.

SETTING

Fifty-two clinics in five communities in Michigan, USA (1998-2004).

POPULATION

A subset (n = 996) of cohort participants with complete placental pathology data.

METHODS

First-trimester bleeding and placental abruption were ascertained by mid-trimester interviews and chart review, respectively. Disc-impacting blood clot was defined as a gross placental examination finding of a blood clot impacting adjacent tissue. Microscopic haemorrhage was defined as 'high' (top quintile) scores on an aggregate measure of placental pathology findings suggestive of atypical maternal vessel haemorrhage. These four PH indicators were compared with one another and with risk of PTD assessed by logistic regression analyses.

MAIN OUTCOME MEASURES

Preterm delivery and PTD subtypes (i.e. <35 weeks, 35-36 weeks; spontaneous, medically indicated) compared with term deliveries.

RESULTS

Placental abruption cases had 2.3-fold to 5.5-fold increased odds of the other three PH indicators. Disc-impacting blood clots and microscopic haemorrhage were associated with one another (odds ratio [OR] = 4.6), but not with first-trimester bleeding. In a multivariable model that included all four PH indicators and confounders, risk of PTD < 35 weeks was elevated with first-trimester bleeding (OR = 1.9 [1.0, 3.4]), placental abruption (OR = 5.2 [1.7, 16.2]), disc-impacting blood clots (OR = 2.3 [1.0, 5.0]) and microscopic haemorrhage (OR = 2.4 [1.4, 4.2]).

CONCLUSIONS

Multiple clinical and subclinical PH indicators are associated with PTD, particularly early PTD.

Smoking, alcohol and caffeine in relation to ovarian age during the reproductive years

BACKGROUND

We sought to determine whether smoking, alcohol and caffeine are related to four indicators of ovarian age: antral follicle count (AFC), follicle stimulating hormone (FSH), inhibin B and estradiol.

METHODS

Analyses drew on ultrasound scans and sera from 188 women, aged 22-49. We used least squares regression to estimate differences in AFC and hormone levels for women who smoke cigarettes or who drink alcohol or caffeine.

RESULTS

Current smoking is related to elevated FSH (beta for ln(FSH) = 0.21, 95% CI 0.04, 0.39), but not to AFC, inhibin B or estradiol. Neither alcohol nor caffeine is related to any ovarian age indicator. Exploratory analyses suggest that the association of current smoking with FSH varies with age: comparing current with never smokers, at ages 30, 35, 40 and 45, estimated differences in mean FSH are 0.3, 1.3, 3.2 and 6.9 mIU/ml.

CONCLUSIONS

The association of current smoking with FSH may reflect accelerated oocyte atresia, impaired follicle quality or dysregulation of the hypothalamic-pituitary-ovarian axis. Identification of the causal mechanism has implications for prevention or treatment of conception delay, infertility and morbidity associated with early menopause.

Predictors of antral follicle count during the reproductive years

BACKGROUND

We sought to identify indicators of antral follicle count which would be serviceable to clinicians seeking to estimate the number of ovarian follicles without relying on sonographic counts.

METHODS

We examined the relations of chronological age and four potential indicators of ovarian age-ovarian volume, FSH, dimeric inhibin B and estradiol-to antral follicle count in 176 recently pregnant women. We identified the regression models which best predict low antral follicle count (< or =10 follicles).

RESULTS

Chronological age, ovarian volume, FSH and inhibin B were each significantly associated with antral follicle count. Fifty-three (30.1%) women had < or =10 antral follicles. In the total sample, at the cutpoint corresponding to 80% sensitivity, the positive predictive value for a regression model with all four variables was 60%. All regression models performed less well in women <35 years (13.9% with low count) than in women > or =35 years (52.0% with low count). In older women, the positive predictive value for the model with all four variables was 79%, compared with 60% for a model with chronological age alone.

CONCLUSIONS

Our models provide a basis for advising women aged > or =35 years who are either trying to conceive or wish to learn whether they may postpone childbearing.

Trisomic pregnancy and the oocyte pool

BACKGROUND

We tested the hypothesis that trisomy risk is increased for women with fewer oocytes (older ovarian age) than other women of the same chronological age.

METHODS

Our study compared three indicators of ovarian age-number of antral follicles, level of dimeric inhibin B, level of FSH-among women who had trisomic pregnancy losses (n = 54) with those among women who had other losses (24 with other chromosomally abnormal loses, 21 with chromosomally normal losses) or who had chromosomally normal births (n = 65).

RESULTS

Ovarian age indicators did not differ between women with trisomic spontaneous abortions and the three comparison groups. Compared with live birth controls, adjusting for chronological age, we estimate that, on average, among trisomy cases the geometric means of 1 + follicle count, inhibin B and FSH are about 7.5% higher, 16.6% higher and 5.5% lower, respectively, with all 95% confidence intervals including zero. The sample size was sufficient to detect moderate differences (0.52 standard errors of regression) between trisomy cases and live birth controls.

CONCLUSIONS

Although our data do not support our hypothesis, they leave open the possibility that changes in follicular development unrelated to the size of the oocyte pool influence abnormal chromosome segregation.

Maternal infection, fetal inflammatory response, and brain damage in very low birth weight infants. Developmental Epidemiology Network Investigators

Echolucent images (EL) of cerebral white matter, seen on cranial ultrasonographic scans of very low birth weight newborns, predict motor and cognitive limitations. We tested the hypothesis that markers of maternal and feto-placental infection were associated with risks of both early (diagnosed at a median age of 7 d) and late (median age = 21 d) EL in a multi-center cohort of 1078 infants <1500 x g. Maternal infection was indicated by fever, leukocytosis, and receipt of antibiotic; fetoplacental inflammation was indicated by the presence of fetal vasculitis (i.e. of the placental chorionic plate or the umbilical cord). The effect of membrane inflammation was also assessed. All analyses were performed separately in infants born within 1 h of membrane rupture (n = 537), or after a longer interval (n = 541), to determine whether infection markers have different effects in infants who are unlikely to have experienced ascending amniotic sac infection as a consequence of membrane rupture. Placental membrane inflammation by itself was not associated with risk of EL at any time. The risks of both early and late EL were substantially increased in infants with fetal vasculitis, but the association with early EL was found only in infants born > or =1 after membrane rupture and who had membrane inflammation (adjusted OR not calculable), whereas the association of fetal vasculitis with late EL was seen only in infants born <1 h after membrane rupture (OR = 10.8; p = 0.05). Maternal receipt of antibiotic in the 24 h just before delivery was associated with late EL only if delivery occurred <1 h after membrane rupture (OR = 6.9; p = 0.01). Indicators of maternal infection and of a fetal inflammatory response are strongly and independently associated with EL, particularly late EL.

Antenatal corticosteroids and cranial ultrasonographic abnormalities

OBJECTIVE

This study was undertaken to determine whether very-low-birth-weight infants whose mothers received a course of antenatal corticosteroids were at decreased risk for 3 cranial ultrasonographic entities that predict neurodevelopmental dysfunction.

STUDY DESIGN

This retrospective cohort study evaluated 1604 infants weighing 500 to 1500 g who underwent >/=1 of 3 cranial ultrasonographic scans required by design at specified postnatal intervals and whose own and mother's hospital charts were reviewed. Infants were classified according to mother's course of antenatal corticosteroids (none, partial, or complete).

RESULTS

In the total sample the risks of intraventricular hemorrhage and of an echolucent image in the cerebral white matter were only modestly (and not statistically significantly) reduced after a full course of antenatal corticosteroids, whereas antenatal corticosteroids appeared to significantly reduce the risk of ventriculomegaly after even a partial course. Antenatal corticosteroids appeared to halve the risk of ventriculomegaly and echolucent image among the gestationally youngest infants and those with intraventricular hemorrhage, hypothyroxinemia, or vasculitis of the umbilical cord or chorionic plate of the placenta.

CONCLUSION

These observations are consistent with the hypothesis that antenatal corticosteroids protect very-low-birth-weight infants, especially those who are most vulnerable, against the risk of cranial ultrasonographic abnormalities.

Hypothyroxinemia of prematurity and the risk of cerebral white matter damage

OBJECTIVE

Infants with hypothyroxinemia of prematurity (HOP) are at increased risk for neurodevelopmental dysfunction. Infants born near the end of the middle trimester are also at increased risk for an echolucency (EL) in the cerebral white matter, which reflects white matter damage and is the cranial ultrasound abnormality that best predicts neurodevelopmental dysfunction. We postulated that some of the increased risk of neurodevelopmental problems associated with HOP reflects an increased risk of EL.

STUDY DESIGN

We studied 1414 infants weighing 500 to 1500 g who were born at 4 medical centers between 1991 and 1993. The infants had thyroxine blood levels measured during the first weeks of life, at least 1 of 3 cranial ultrasound scans performed at specified postnatal intervals, and their own and their mother's hospital charts reviewed. Infants were classified by whether or not their first thyroxine level placed them in the lowest quartile among all infants in this sample (ie, <67.8 nmol/L, our definition of HOP, equivalent to <5.3 micrograms/dL).

RESULTS

After adjusting for such potential confounders as low gestational age and measures of illness severity, infants with HOP had twice the risk of EL as their peers with higher thyroxine levels.

CONCLUSION

Our findings are consistent with the hypothesis that a "normal" blood thyroxine level protects infants born near the end of the middle trimester against the risk of cerebral white matter damage.

Association of maternal, antenatal and perinatal complications with suicide in adolescence and young adulthood

The aim of the present study was to investigate whether maternal, antenatal and perinatal complications are associated with adolescent or young adulthood suicide in offspring. Cases consisted of individuals, aged 15-22 years, born in New York City and committing suicide in New York City between 1985 and 1991 (n = 189). Two controls were selected for each case, constituting the hospital birth immediately preceding and following that of the case, matched with the case with regard to sex and ethnicity. Cases were compared with controls using an index that summed a range of maternal, antenatal and perinatal complications and also with regard to the frequency of individual complications. In the total sample, cases and controls did not differ either in the mean number of all complications combined or in the proportions with specific complications. This lack of association between complications and outcome also obtained in separate analyses by sex, ethnicity, socio-economic status and age at suicide. These results fail to replicate the findings of two previous reports implicating maternal, antenatal and perinatal complications in risk of youth suicide. At present, epidemiological evidence that adverse reproductive events increase the risk for suicide in offspring remains inconclusive.

Variation in use of corticosteroids among infants < or = 1,500 grams across hospitals in three states

We identified factors associated with no antenatal corticosteroid treatment among 1,369 women who delivered infants < or = 1,500 g and < 34 weeks gestation, 1991-1993. At four hospitals, infants weighing 500-1,500 g were enrolled. Information regarding corticosteroid use, maternal characteristics, and perinatal events were obtained. Factors associated with no corticosteroid treatment were examined in unadjusted and adjusted logistic regression models. Overall, 693 (50.6%) women did not receive corticosteroids. Two hospitals had higher rates of no corticosteroid usage (89% and 75%) as compared with the other two (32% and 50%). Black, Hispanic, and poor women were more likely to receive care at the hospitals where the rates of corticosteroid utilization were lower. Factors in the multivariate model included: < 1 or 1 day of hospitalization, vs. delivery on > or = 2 days of hospitalization (21.4: 14.5, 97.2; 4.7: 3.2, 6.9); gestational age < 26 weeks (2.7: 1.8, 4.1) or > 28 weeks (1.8: 1.3, 2.6) vs. 26-28 weeks; < 12 hours of labor vs. > 12 hours (1.7: 1.2, 2.4); delivering at hospital 2, 3, 4 vs. hospital 1 (1.6: 1.1, 2.5; 24.3: 13.6, 43.4; 10.2: 6.8, 15.3). We conclude that variations in hospital practice limit widespread use of this important antenatal treatment.

Thyroxine values from newborn screening of 919 infants born before 29 weeks' gestation

OBJECTIVES

Severe transient hypothyroxinemia in premature infants is associated with cerebral palsy and mental retardation: this study assessed its prevalence in very premature infants.

METHODS

Congenital hypothyroidism screening programs in three states provided thyroxine values for 919 newborn infants younger than 29 weeks who were enrolled in a multicenter study.

RESULTS

Thyroxine values were lower than 4.0 micrograms/dL in 21% of survivors and increased each week by 0.6 microgram/dL (95% confidence interval [CI] = 0.4, 0.7). At tests done 1 to 2 days after birth, levels were 2.5 micrograms/dL higher (95% CI = 1.8, 3.3) than at tests done at 8 to 14 days. In New York, levels were 1.0 microgram/dL higher (95% CI = 0.3, 1.6) than elsewhere. The levels of infants who died were 1.3 micrograms/dL lower (95% CI = 0.6, 2.0) than those of survivors.

CONCLUSIONS

Severe transient hypothyroxinemia is common in very premature infants and deserves further study.

Maternal receipt of magnesium sulfate does not seem to reduce the risk of neonatal white matter damage

OBJECTIVE

To investigate whether in utero exposure to magnesium sulfate is associated with a lower incidence of cranial ultrasonographic abnormalities that predict cerebral palsy in infants who weigh less than 1501 g at birth.

DESIGN

For a prospective study of the antecedents of cranial ultrasonographic abnormalities, we enrolled infants who weighed 500 to 1500 g when born at five institutions. Data were collected by interview of the mothers and review of medical records. Protocol cranial ultrasonograms were obtained as close as possible to postnatal days 1, 7, and 21. Abnormality on cranial ultrasound scans was determined by a consensus committee of three sonologists.

RESULTS

Of the 1518 infants for whom we knew whether the mothers received magnesium sulfate, the first protocol cranial ultrasound scan was available for 1409 infants, the second for 1274 infants, and the third for 1050 infants. Forty-five percent of infants were exposed to magnesium sulfate before delivery. The major correlates of magnesium sulfate exposure were receipt of antenatal corticosteroids and a diagnosis of preeclampsia and/or pregnancy-induced hypertension. Maternal magnesium receipt was not associated with a reduced incidence of hypoechoic or hyperechoic images of white matter parenchyma, intraventricular hemorrhage, or ventriculomegaly, even when the sample was stratified by each of six potential confounders. When adjustment was made for gestational age, a measure of birth weight for gestational age, antenatal corticosteroid exposure, preeclampsia and pregnancy-induced hypertension, route of delivery, and the occurrence of any labor, the risk ratios for each cranial ultrasonographic abnormality associated with magnesium sulfate exposure hovered close to 1.

CONCLUSION

Maternal receipt of magnesium sulfate does not seem to be associated with an appreciably reduced risk of cranial ultrasonographically defined neonatal white matter damage, intraventricular hemorrhage, or ventriculomegaly.

Correlates of low thyroxine values at newborn screening among infants born before 32 weeks gestation

We assessed the relation of perinatal factors to severe hypothyroxinemia of prematurity, defined as thyroxine value more than 2.6 standard deviations below the mean for newborns. The 365 survivors of birth before 32 weeks gestation were enrolled in a population-based study of the correlates of neonatal brain injury. In this historical cohort study, mothers were interviewed; perinatal data were abstracted from medical records and neonatal data were collected prospectively. Neonatal thyroxine screening values were retrieved from the New Jersey State Department of Health. Associated with severe hypothyroxinemia were: gestational age 23-27 weeks vs. 31 weeks (OR = 5.1, 95% CI 1.7, 15.2), later age at thyroxine test (OR = 1.6 per day, 95% CI 1.2, 2.1), fraction inspired oxygen at age 24 h > 40% (OR = 3.2, 95% CI 1.1, 8.8), mechanical ventilation (OR = 5.1, 95% CI 1.3, 19.4), diastolic blood pressure < 20 mmHg (OR = 2.3, 95% CI 1.2, 4.3), and > 12 years of maternal education (OR = 0.4, 95% CI 0.22, 1.0). Infants with severe hypothyroxinemia had higher mortality, more days of oxygen supplementation, ventilation and hospitalization and were 11 times more likely to require oxygen supplementation at the postnatal age equivalent to 36 weeks gestational age (odds ratio 10.6, 95% CI 2.3, 48.8). In preterm infants, neonatal thyroxine levels obtained at newborn screening in the first week of life may convey important prognostic information about mortality, morbidity, and the risk for bronchopulmonary dysplasia.

Transvaginal ultrasonography in gynecologic office practice: assessment in 663 premenopausal women

OBJECTIVES

We describe transvaginal ultrasonographic evaluation of 663 premenopausal women with signs or symptoms of gynecologic problems and compare the findings of transvaginal ultrasonography with those of antecedent bimanual examination.

STUDY DESIGN

In this retrospective descriptive study, data on age, menstrual history, results of bimanual examination, and subsequent surgical and pathologic findings were abstracted from the medical record and linked to indications and results on transvaginal ultrasonography reports from May 1991 through October 1993.

RESULTS

The result of bimanual examination of the uterus was normal in 125 of 347 women with transvaginal ultrasonography-diagnosed fibroids (36.0%). Findings were normal at bimanual examination of the corresponding adnexa in 134 of the 190 adnexa with transvaginal ultrasonography findings (70.5%). Among the subjects with normal results of bimanual examination of the adnexa, surgical procedures documented 12 endometriomas, 2 adnexal abscesses, and 5 benign and 1 malignant neoplasm.

CONCLUSION

Given the apparent considerable limitations of the bimanual examination, the utility of routine in-office transvaginal ultrasonography screening of both women with and women without symptoms should be prospectively investigated.

The relation of transient hypothyroxinemia in preterm infants to neurologic development at two years of age

BACKGROUND

Transient hypothyroxinemia, a common finding in premature infants, is not thought to have long-term sequelae or to require treatment. We investigated whether hypothyroxinemia in premature infants is a cause of subsequent motor and cognitive abnormalities.

METHODS

In this historical cohort study, we retrieved blood thyroxine values, obtained on routine screening in the first week of life, from state screening records on children who weighted 2000 g or less at birth, who were born at 33 weeks' gestation or earlier, and who were enrolled in a population-based study of the late sequelae of neonatal brain hemorrhage. We investigated the relation of these values to the odds for disabling cerebral palsy among 463 subjects for whom data were available and to the mental-development score on the Bayley Scales of Infant Development or the Stanford-Binet Intelligence Scales for Children at the age of two years in 400 subjects. The effects of severe hypothyroxinemia, defined as a blood thyroxine value more than 2.6 SD below the mean for New Jersey newborns, were assessed before and after adjustment for gestational age and potentially confounding variables.

RESULTS

In analyses adjusted for gestational age, infants with severe hypothyroxinemia had a risk of disabling cerebral palsy that was nearly 11 times that of infants without hypothyroxinemia (odds ratio, 10.8; 95 percent confidence interval, 3.0 to 39.3) and a mean mental-development score at the age of two that was 15.4 points lower (95 percent confidence interval, 8.1 to 22.6 points) than the mean score of children with normal neonatal blood thyroxine concentrations. After adjustment for gestational age and multiple prenatal, perinatal, and early and last neonatal variables, severe hypothyroxinemia was still associated with an increased risk of disabling cerebral palsy (odds ratio, 4.4; 95 percent confidence interval, 1.0 to 18.6) and a reduction of nearly 7 points (95 percent confidence interval, 0.3 to 13.2 points) in the mental-development score.

CONCLUSIONS

Severe hypothyroxinemia in preterm infants may be an important cause of problems in neurologic and mental development detected at the age of two years.

Efficiency of sampling: birthweight and gestational age distributions in two cohorts, < 31 weeks and 500-1499 grams

We studied the efficiency of two common sampling strategies used to assemble cohorts to study the long-term problems of preterm infants: infants with birthweights of 500-1499 g, and infants with gestational ages (GA) of < 31 weeks. Birthweight, GA and 2-year outcome data from a population based study of infants < 2001 g, the Central New Jersey Brain Hemorrhage Study (NBH), were used to define the birthweight and GA distributions, at enrollment and at the age of 2 years, of overlapping subsets: infants 500-1499 g (n = 599) and infants < 31 weeks of age (n = 522). Using frequencies from the NBH study, we estimated that 1000 infants of 500-1499 g enrolled at birth would produce 712 infants at the age of 2 years, 498 below 31 weeks and 214 above. Enrolling 1000 infants < 31 weeks would produce a cohort of 697 infants at the age of 2, all of whom were < 31 weeks. Neither sampling strategy maximised the statistical power to investigate the pathophysiological determinants of long-term outcomes associated with short GA. Both methods oversampled older GAs. A stratified sampling technique based on GA, designed to produce equal numbers of subjects at each week of GA, would improve statistical power to study long-term outcomes. As we move from descriptive to analytical studies of preterm infants, we need to devise efficient, GA-based, sampling strategies that maximise statistical power to test pathophysiological hypotheses.

Early ultrasound dating of pregnancy: selection and measurement biases

Can using early ultrasound examinations to date pregnancy introduce information bias in perinatal research? Our purpose was to identify determinants of early ultrasound examinations and to compare early ultrasound to menstrual history dating. Between January 1987 and June 1989, 1159 white, largely middle class, prenatal patients were contacted for a prospective observational study. 876 (76%) agreed to participate. Of these 764 (87%) met the eligibility criteria for this analysis, namely singleton pregnancy, delivered after 20 weeks (spontaneous or induced, vaginal or c-section), with prenatal chart abstracted. Selection factors for early ultrasound identified in multivariate analysis were: bleeding in early pregnancy, OR = 1.9 (1.0, 3.5), attendance at health maintenance organization OR = 7.2 (3.4, 15), no insurance or Medicaid only OR = 0.3 (0.1, 0.6), and increasing time from last menstrual period to first prenatal visit in weeks OR = 0.89 (0.85, 0.93). In conformity with previous results, ultrasound dating of pregnancy led to a higher estimate of preterm delivery (10 vs 7.6%), a higher estimate of term delivery (87.2 vs 82.7%) and a lower estimate of postterm delivery (2.8 vs 9.7%) than dating by menstrual history, p < 0.001. Selection factors and measurement issues, such as those described here, could introduce bias and should be carefully considered in the design, analysis and interpretation of perinatal research.

Obstetrical judgments of viability and perinatal survival of extremely low birthweight infants

OBJECTIVES

The purpose of the study was to determine whether the obstetrical judgment of viability makes a difference to fetal and neonatal survival of extremely low birthweight infants (500-749 g).

METHODS

We assessed the effect of the antenatal judgment of viability in a group of 66 infants born weighing from 500 to 749 g. These infants were alive at maternal hospital admission and were subsequently live-born or stillborn between January 1, 1984, and December 31, 1985. We related the antepartum assessment of viability and other factors recorded in the medical record to fetal survival and to postneonatal survival to hospital discharge.

RESULTS

The obstetrical judgement of viability was strongly associated with outcome. After birthweight and gestational age were controlled, fetuses considered viable were 18 times more likely to survive (95% confidence interval = 2, 175) than those considered nonviable.

CONCLUSIONS

The effects of obstetrical practices on perinatal mortality must be taken into consideration in estimating the survival potential of very small fetuses and in evaluating the relationship between survival and disability.

Emergency room use of transvaginal ultrasonography by obstetrics and gynecology residents

OBJECTIVE

The objective of this study was to evaluate the feasibility and diagnostic value of the emergency room use of transvaginal ultrasonography operated by the obstetrics and gynecology residents.

STUDY DESIGN

One hundred sixty-eight patients scanned in the emergency room constituted the study group and were compared with 61 patients for whom emergency room scanning was not available. Scanning and no-scanning days alternated for a 6-month period. The Student t test was used in the analysis.

RESULTS

By comparing the two patient groups a statistically significant (p less than 0.0001) difference was seen in the time spent by the group of patients scanned in the emergency room (40 minutes) when compared with that of the patients for whom no emergency room scanning was available (215 minutes). The residents expressed high confidence in the scanning procedure. There were six misdiagnosed cases, three of them nonruptured ectopic gestations. However, none of these patients was discharged without adequate treatment.

CONCLUSION

The study confirmed our hypothesis that obstetrics and gynecology residents can operate and should have available ultrasonography machines in the emergency departments to render quicker and better patient care.

Imaging the fetal brain in the second and third trimesters using transvaginal sonography

High-frequency transvaginal probes were used at 20-40 weeks' gestation to develop a systematic examination of the fetal brain. Modeling the procedure after the standard neonatal neurosonographic examination, we attempted to obtain three coronal sections (anterior, midline, posterior) and two sagittal sections (midsagittal, right or left parasagittal). In 70 normal patients, all planes were imaged with a similar frequency (74-76%) except for the posterior coronal plane, which was imaged 59% of the time. Among the first 35 cases, 17% had a complete study, compared with 71% of the second 35 cases. Transvaginal sonography established or changed the diagnosis in five of the 13 cases with central nervous system or other abnormalities. We recommend that a complete fetal neurosonographic examination include transvaginal sonography to complement and enhance the transabdominal examination, especially for cases in which a fetal abnormality is suspected.

Phasic blood flow patterns in the superior and inferior venae cavae and umbilical vein of fetal sheep

Measurements of phasic blood flow in the inferior and superior venae cavae and umbilical vein of fetal sheep (gestational age, 121 to 140 days) were made with chronically implanted electromagnetic flow transducers. In the venae cavae blood flow was inversely related to phasic changes in venous and/or intrathoracic pressure. During fetal apnea a forward surge of flow occurred during ventricular systole (systolic surge) and ventricular diastole (diastolic surge). Slower fetal heart rates were associated with a more prominent diastolic surge. Reductions in afterload caused by acetylcholine administration augmented the peak diastolic venous flow. In contrast, increased afterload caused by hypoxia and norepinephrine administration was associated with increased peak systolic flow. During regular fetal breathing movements the phasic flow pattern was determined largely by the respiratory cycle with the effect of the cardiac cycle superimposed. There was minimal venous pulsation in the intra-abdominal umbilical vein, compared with that of the intrathoracic venae cavae of the apneic fetus. Our findings demonstrate that fetal systemic vascular resistance profoundly influences right atrioventricular filling patterns.

Hemodynamic effects of alpha-adrenergic blockade during hypoxia in fetal sheep

During hypoxemia there is a redistribution of cardiac output in the sheep fetus associated with increased vascular resistance in some fetal organs. The role of the alpha-adrenergic blocking drug to eight chronically instrumented hypoxemic sheep fetuses. We measured arterial blood pressure and heart rate, determined cardiac output and organ blood flows by means of radionuclide-labeled microspheres, and calculated vascular resistances in fetuses before and during hypoxia, and after injection of phenoxybenzamine 15 mg into the inferior vena cava of the hypoxemic fetus. Hypoxemia resulted in an increased vascular resistance in certain vascular beds. Alpha-adrenergic blockade during hypoxia abolished the increase in vascular resistance of the fetal body and caused an increase in the blood flow to some tissues which had a hypoxia-induced vasoconstriction. After alpha-adrenergic blockade during hypoxia, mean arterial blood pressure decreased from 48 +/- 6 to 42 +/- 6 mm Hg (p less than 0.05) and heart rate increased from 128 +/- 19 to 235 +/- 51 beats per minute (p less than 0.001). Cardiac output increased 23% and blood flow to the brain was maintained. We conclude that the alpha-adrenergic system is important in maintaining the redistribution of cardiac output that occurs in hypoxic fetal sheep.

Selective distribution of microspheres injected into the umbilical veins and inferior venae cavae of fetal sheep

To investigate the extent of streaming of umbilical venous blood in the venous and arterial circulations of normal and hypoxic sheep fetuses and to experimentally determine its effect on determinations of blood flow by means of the microsphere method, we injected 15 mu microspheres labeled with different radionuclides into the umbilical veins (UVs) and distal inferior venae cavae (DIVC) of 21 chronically catheterized near-term sheep fetuses. We determined the ratio of the radioactive counts from the UV-injected microspheres to the radioactive counts from the DIVC-injected microspheres (UV/DIVC count ratio) in each fetal tissue in 40 experiments. In 75% of the normal fetuses and 58% of the hypoxic fetuses, UV-injected microspheres streamed preferentially through the foramen ovale to the left atrium and ventricle when compared with DIVC-injected microspheres. Fetal hypoxia was associated with a significant decrease in the extent of preferential streaming. In the arterial circulation, we found no evidence for preferential streaming of UV-injected and DIVC-injected microspheres.

Increased fetal heart rate variability with acute hypoxia in chronically instrumented sheep

Fetal heart rate (FHR) and oxygen consumption were determined in 45 studies in 20 chronically instrumented, normoxic sheep. FHR variability was measured by a template device to determine amplitude range, and oscillatory frequency was manually counted over 5-min periods. During 26 min of isocapnic hypoxia, fetal O2 consumption decreased 39% and FHR decreased 18%, and FHR variability increased, the changes being maintained over the treatment period. It is suggested that the maintenance of FHR variability during this profound hypoxia denotes adequate cardiorespiratory compensatory mechanisms during the short period; prolongation of the hypoxia would probably result in fetal cerebral or myocardial decompensation, and disappearance of FHR variability. The increased variability may be due to increased alpha-adrenergic activity.

Distribution and recirculation of umbilical and systemic venous blood flow in fetal lambs during hypoxia

The presence of vascular shunts in the fetal circulation results in mixture of oxygenated blood returning from the placenta with venous blood returning from the fetal body. In fetal sheep with chronically implanted vascular catheters we found during normal oxygenation that 22% of umbilical venous blood recirculated to the placenta without being presented to the fetal tissues (left-to-right shunt analogue) while about half of systemic venous blood recirculated to the fetal body and not to the placenta for oxygenation (right-to-left shunt analogue). These shunts comprised 34% of cardiac output and increase the workload on the fetal heart, as they are ineffective in terms of oxygen uptake and delivery. In normally-oxygenated fetuses, 11% of cardiac output was comprised of umbilical venous blood recirculating to the placenta (left-to-right shunt analogue) whereas 23% of cardiac output consisted of systemic venous blood circulating to the fetal body (right-to-left shunt analogue). During induced maternal-fetal hypoxia (10% O2 to ewe), although the percentage of ineffective cardiac output did not change (31%), the left-to-right shunt analogue increased to 19% and the right-to-left shunt analogues decreased to 12% of cardiac output. Hypoxia also resulted in an increase in the percentage of umbilical venous blood which bypassed the liver through the ductus venosus (control 57 +/- 12%; hypoxia 65 +/- 12%, P < 0.02), causing the proportion of umbilical venous blood contributing to the fetal cardiac output to increase from 27 +/- 10% during normoxia to 39 +/- 9% during hypoxia (P < 0.005). This factor, together with the redistribution of cardiac output during hypoxia, resulted in a 100% increase in oxygen delivery from umbilical venous blood to the myocardium and a maintenance of the umbilical vein derived oxygen supplied to the brain and placenta, despite a 40% reduction in total available oxygen in umbilical venous blood.