Hypertensive disease in twin pregnancies: a review.

Reports over the past seventy years show that twin gestations lead to an increased risk of hypertensive disorders. Numerous studies discuss the incidence of hypertensive disease in twin versus singleton gestations, as well as effects of parity, race, age, income level, smoking, zygosity and heritability on this condition. The range of relative risk of gestational hypertension, preeclampsia and eclampsia for twin compared to singleton gestations is 1.2 to 2.7, 2.8 to 4.4 and 3.4 to 5.1 respectively. Parity, African-American ethnicity, and young maternal age are all factors that increase the relative risk of acquiring hypertensive disease to 4.0, 1.8 and 1.5 in mothers of twin gestations. Factors such as maternal smoking, income level and zygosity have a negligible effect on the relative risk of acquiring hypertensive disease in twin gestations. In addition to twin mothers exhibiting a higher incidence of hypertensive disease compared to their singleton counterparts, they also exhibit an earlier onset of hypertensive disease at both 35 and 37 weeks of gestation comparatively. Uric acid levels measured at 30-31 weeks of gestation in twin mothers predicted the onset of preeclampsia with a sensitivity of 73% and a specificity of 74%. The range of risks presented in the literature is wide and the therapies avocated are diverse. We therefore decided to summarize the risks in a comparative fashion and to review current therapeutic strategies for the convenience of clinicians who confront increasing numbers of multiple pregnancies. The tables bring all recent published risks together in the first comparative analysis in which the data has been converted to relative risks and confidence intervals. Because the literature is relatively silent on specific management of hypertensive disease in twin pregnancies, general management recommendations for singleton gestations should be used by practitioners caring over twin gestations.     

孕中期双胎妊娠与单胎妊娠孕妇血清AFP与F-β-Hcg水平的比较

目的：检测双胎妊娠孕中期孕妇血清甲胎蛋白（AFP）和人绒毛膜促性腺激素游离B亚基（F-β-hCG）的水平,探索双胎妊娠时孕妇血清学筛查用于Down＇s胎儿高风险评估的AFP、F-β-hCG界定值。方法：收集双胎妊娠129例,孕中期（15～2l周）采集孕妇静脉血,用时间分辨荧光免疫分析技术测定血清AFP和F-β-hCG的浓度,并于分娩后随访,确定胎儿有无异常。另选2603例胎儿无异常的单胎妊娠作对照组。结果：129例双胎妊娠孕妇血清AFP浓度的中位教为98.98ng／ml,F-β-hCG浓度的中位数为32.20ng／mt;2603例单胎妊娠孕妇血清AFP和F-β-hCG浓度的中位数分别为52.15ng／ml和13.00ng／mt。双胎妊娠孕妇血清AFP和F-β-hCG的水平均明显高于对照组（P均〈0.01）。结论：鉴于双胎妊娠孕妇血清AFP和F-β-hCG水平明显升高,双胎妊娠的产前唐氏筛查风险评估时应引入正常双胎妊娠的AFP、F-β-hCG值。     

Uncertainties in age- and gender-based health risk assessment for recreational bathing: Arsenic in Del Azul stream,Argentina

The aim of this study was to assess the risk associated with recreational bathing at Del Azul stream, Argentina, a water course naturally containing Arsenic. It represents a case study on the carcinogenic risk for bathers and on how the risk varies among age groups and genders, analyzing the uncertainties of the model input variables and the risk quantification technique. The risk was probabilistically estimated with the 2D Monte Carlo method considering four age groups (5, 10, 15, and 20 years old) and separate exposure routes: accidental water intake, skin contact, and the two combined. Although in all the studied groups the risk levels were within safety limits, differences in risk values were observed among age groups and genders. Accidental water intake during bathing was the most risky exposure route. The risk decreased with age and it was higher in males than in females, with larger differences between the two older age groups. This could be attributed to the difference in the accidental water intake rate associated with the daily duration of the bathing event, which varied according to age and gender.     

Impact of periconceptional nutrition on maternal and fetal leptin and fetal adiposity in singleton and twin pregnancies

It has been proposed that maternal nutrient restriction may alter the functional development of the adipocyte and the synthesis and secretion of the adipocyte-derived hormone, leptin, before birth. We have investigated the effects of restricted periconceptional undernutrition and/or restricted gestational nutrition on fetal plasma leptin concentrations and fetal adiposity in late gestation. There was no effect of either restricted periconceptional or gestational nutrition on maternal or fetal plasma leptin concentrations in singleton or twin pregnancies during late gestation. In ewes carrying twins, but not singletons, maternal plasma leptin concentrations in late gestation were directly related to the change in ewe weight that occurred during the 60 days before mating [maternal leptin = 0.9 (change in ewe weight) + 7.8; r = 0.6, P < 0.05]. In twin, but not singleton, pregnancies, there was also a significant relationship between maternal and fetal leptin concentrations (maternal leptin = 0.5 fetal leptin + 4.2, r = 0.63, P < 0.005). The relative mass of perirenal fat was also significantly increased in twin fetal sheep in the control-restricted group (6.0 +/- 0.5) compared with the other nutritional groups (control-control: 4.1 +/- 0.4; restricted-restricted: 4.4 +/- 0.4; restricted-control: 4.3 +/- 0.3). In conclusion, the impact of maternal undernutrition on maternal plasma leptin concentrations during late gestation is dependent on fetal number. Furthermore, we have found that there is an increased fetal adiposity in the twins of ewes that experienced restricted nutrition throughout gestation, and this may be important in the programming of postnatal adiposity.     

Echocardiographic and Doppler assessment of maternal cardiovascular function in normal and abnormal canine pregnancies

The objective was to verify maternal hemodynamic differences between normal and abnormal pregnancies in dogs. Brucella-negative pregnant bitches (n = 31) were retrospectively classified into abnormal (which had either their pregnancy interrupted between Days 52 and 60 or perinatal death of more than 50% of the litter; n = 14) and normal (which had delivered healthy puppies at term; n = 17). These dogs were evaluated with echocardiography every 10 days from Days 0 to 60 of gestation (Day 0 = estimated day of LH peak). Systolic blood pressure was also assessed. At Day 50 of gestation, left ventricular free wall in systole increased in the normal but not in the abnormal group (P < 0.01). In contrast, end systolic stress (P < 0.01) and systolic blood pressure (P < 0.01) diminished only in normal animals. We concluded that signs of altered maternal cardiovascular adaptation to pregnancy may be predictors of obstetrical complications in dogs.     

The effect of maternal hypothyroidism on maternal and fetal tissue glucose-1-14C incorporation in rats.

These experiments were conducted to help elucidate the mechanism for the impaired fetal development occurring during maternal hypothyroidism. The disposition of glucose was measured using glucose-1-14C. Maternal hypothyroidism depressed glucose utilization in thematernal-fetal system. Maternal net glycogen synthesis from the labeled glucose was impaired. However, while the fetal glycogen storage system may be capable of at least relatively normal glycogen synthesis, abnormally low levels of glycogen were measured. If, as the data suggest, enzymatic deficiencies do not exist, the low liver glycogen might be a result of the inability of the maternal-placental system to provide adequate substrate to the fetus.     

Thoughts of a travelling ecologist 14. Structure-function conflation in environmental risk assessment and monitoring

正Recently,I attended a conference organised by the European Food Safety Authority in the beautiful and prosperous Italian city of Parma.The overall topic of the conference was risk assessment,and the program included a section on aspects of environmental risk assessment.In various areas,including the evalution of the effects of pesticide applications,invasive     

Factors affecting pregnancy loss for single and twin pregnancies in a high-producing dairy herd

Our objective was to determine the magnitude of, and factors affecting, pregnancy loss for lactating Holstein cows on a commercial dairy farm when diagnosed with twin (n = 98) or single (n = 518) pregnancies using transrectal ultrasonography. Pregnancy losses were assessed with records of non-viable embryos at first pregnancy examination and embryo losses between the first (25-40 d after AI) and second (48 and 82 d after AI) post-breeding pregnancy examinations. Among cows diagnosed with single pregnancies, 3.7% were diagnosed with a non-viable embryo at first pregnancy examination, and 4.6% of those diagnosed with a viable embryo underwent pregnancy loss by the second examination. A total of 11.2% of cows diagnosed with twins experienced a single embryo reduction, whereas 13.3% lost both embryos. Overall, the total proportion of cows experiencing pregnancy loss or experiencing embryo reduction was greater for cows diagnosed with twin than single pregnancies (odds ratio; OR = 3.6), resulting in an embryo survival rate of 91.9% for cows diagnosed with single compared to 75.5% for cows diagnosed with twin pregnancies. Season of breeding and milk production were associated with pregnancy loss for single pregnancies, whereas CL number was associated negatively with embryo reduction and pregnancy loss for twin pregnancies. The risk of twinning and double ovulation among pregnant cows increased with days in milk (DIM), and the risk of double ovulation was greater for cows diagnosed with ovarian cysts and lacking a CL at initiation of an Ovsynch protocol. We concluded that in this herd, embryo reduction and pregnancy loss during early gestation was greater for lactating Holstein cows diagnosed with twin compared to single pregnancies. In addition, cows diagnosed with ovarian cysts and lacking a CL had an increased risk for double ovulation.     

Measuring exposure to injury risk in schoolchildren aged 11-14.

OBJECTIVE--To apply a measure of exposure to injury risk for schoolchildren aged 11-14 across a population and to examine how risk factors vary with sex, age, and affluence. DESIGN--Self completion questionnaire survey administered in schools in May 1990. SETTING--24 schools in Newcastle upon Tyne. SUBJECTS--5334 pupils aged 11-14, of whom 4637 (87%) completed the questionnaire. RESULTS--Boys were exposed to greater risk than girls in journeys to places to play outdoors; they took longer trips and were more likely to ride bicycles (relative risk 5.30 (95% confidence interval 4.23 to 6.64)) and less likely to travel by public transport or car. Younger pupils (aged 11-12) were less exposed to traffic during journeys to and from school: their journeys were shorter, they were less likely to walk (trip to school, relative risk 0.88 (0.83 to 0.94)), and they were more likely to travel by car (trip to school, relative risk 1.33 (1.13 to 1.56)) or school bus (1.33 (1.10 to 1.62)). Poorer children were exposed to greater risk than affluent children (from families that owned a car and a telephone): they were less likely to travel to school by car (relative risk 0.26 (0.20 to 0.33)) or to be accompanied by an adult (0.39 (0.32 to 0.48)). CONCLUSION--Injury risk data can provide useful information on child injury prevention and can be used to identify priorities and target resources for injury prevention on a citywide scale or for an individual school.     

Sexual immaturity and maternal age: incidence of aneuploidy and polyploidy in first-cleavage mouse embryos

The influence of maternal age on the incidence of aneuploidy and polyploidy was studied, using C57Bl/6J X CBA/Ca hybrid mice, including immature females, as gamete donors. The age of the females ranged from 3.5-4 wk (immature or prepubertal), to 10-12 wk (young adults), to 24-28 wk (aged females). Ovulation was induced with gonadotrophins, and the differential condensation of paternal and maternal chromosomes was used to elucidate the origin of chromosome abnormalities in first-division metaphase plates. The results indicated a high incidence of aneuploid oocytes in immature and older female mice, as compared to young adult females. Eggs of immature female mice underwent polyspermic fertilization more often than those of young adults and older females, and the production of diploid oocytes was more frequent in immature females than in the other age groups.     

PCR quantitation of fetal cells in maternal blood in normal and aneuploid pregnancies.

Fetal cells in maternal blood are a noninvasive source of fetal genetic material for prenatal diagnosis. We determined the number of fetal-cell DNA equivalents present in maternal whole-blood samples to deduce whether this number is affected by fetal karyotype. Peripheral blood samples were obtained from 199 women carrying chromosomally normal fetuses and from 31 women with male aneuploid fetuses. Male fetal-cell DNA-equivalent quantitation was determined by PCR amplification of a Y chromosome-specific sequence and was compared with PCR product amplified from known concentrations of male DNA run simultaneously. The mean number of male fetal-cell DNA equivalents detected in 16-ml blood samples from 90 women bearing a 46,XY fetus was 19 (range 0-91). The mean number of male fetal-cell DNA equivalents detected in 109 women bearing a 46,XX fetus was 2 (range 0-24). The mean number of male fetal-cell DNA equivalents detected when the fetus was male compared with when the fetus was female was highly significant (P = .0001). More fetal cells were detected in maternal blood when the fetus was aneuploid. The mean number of male fetal-cell DNA equivalents detected when the fetal karyotype was 47,XY,+21 was 110 (range 0.1-650), which was significantly higher than the number of male fetal-cell DNA equivalents detected in 46,XY fetuses (P = .0001). Feto-maternal transfusion of nucleated cells appears to be influenced by fetal karyotype. The sixfold elevation of fetal cells observed in maternal blood when the fetus had trisomy 21 indicates that noninvasive cytogenetic diagnosis of trisomy 21 should be feasible.     

The rate of preterm twin births (22-27 weeks) as a criterion for measuring the quality of prenatal care.

While the true figures are not well established, outcomes of twin pregnancies are directly dependent on a small number of preterm births between 22 and 27 weeks. Observation of perinatal outcomes in twin pregnancies yields two contradictory results. Firstly, it shows an improvement in perinatal mortality figures. Secondly, it reveals an increase in the rates of preterm deliveries. These findings result from the observation of 783 twin pregnancies followed and delivered in a level 3 perinatal centre in Paris between 1993 and 1998. Women followed since the beginning of pregnancy through the outpatient clinic of the institution are included in this number, as are women who were referred or transferred to the centre at a later date due to complications, This analysis reflects the influence of two contrasting policies. The first, and less recent policy is devoted to the prevention of preterm births, and is reflected by the low number of extremely preterm deliveries at 22-32 weeks. The second is the effect of our new approach to the prevention of foetal deaths in relation to foetal growth retardation in twins which has resulted in increased medical intervention such as the induction of labour or scheduled Caesarean birth. This has resulted in an increase in twin preterm births from 33 to 36 weeks, with the expected result of fewer foetal deaths.     

Interaction between maternal smoking and malnutrition in infant risk of gastroschisis

BACKGROUND: Gastroschisis is a severe birth defect characterized by a tear in the infant's abdominal wall. Young mothers have the highest risk of having an infant with gastroschisis. In an animal model, the defect resulted from exposure of pregnant mice to carbon monoxide (CO) in combination with a low protein and low zinc diet. METHODS: We evaluated this model in a study of 55 infants with gastroschisis and 94 age-matched controls that included maternal interview with a food frequency questionnaire. Smoking cigarettes (> or = 1 pack/day) or marijuana (more than once) 3 months prior to pregnancy indicated CO exposure. Low protein or zinc intake and a low body mass index (BMI) indicated maternal malnutrition. RESULTS: When assessed separately, high CO, low protein, low zinc, and low BMI were each significantly associated with an increased risk of gastroschisis. Although we observed significant CO-BMI and CO-zinc interactions after adjusting for income, only a combination of high CO exposure and low BMI yielded a synergistic adverse effect. Compared to the low risk of having an infant with gastroschisis for mothers who did not have low BMI and did not smoke, the risk of having an infant with gastroschisis was 16.3 times (95% CI, 2.49-113.4) higher for mothers who did not have low BMI but smoked, and 19.7 times (95% CI, 4.33-89.6) higher for mothers who did not smoke but had low BMI. However, the risk was 26.5 times (95% CI, 7.85-89.4) higher for mothers who had low BMI and smoked. CONCLUSIONS: Our results suggest that young mothers are at increased risk of having an infant with gastroschisis if they smoke and are also malnourished.     

Maternal and neonatal outcome in pregnancies with no risk factors.

Between November 1979 and April 1984, 790 consecutive pregnant women who considered themselves as having a "normal" pregnancy were followed in private practice from 9 weeks'' gestation until 6 weeks post partum. The women had no pre-existing disease or problem classified as a risk to the pregnancy at the time of their first visit, had a singleton pregnancy and gave birth at Notre-Dame Hospital, Montreal. Maternal complications occurred during the course of pregnancy in 181 women (23%). Complications were mostly related to obstetric conditions (10%), such as preterm labour, intrauterine growth retardation (IUGR) and antepartum hemorrhage, or to medical conditions (12%), the most prevalent of which was hypertension (77% of medical conditions). Neonatal complications occurred in 183 infants (23%). The corrected perinatal death rate was 2.5 per 1000. Prematurity, IUGR and dysmaturity/postmaturity accounted for nearly half of the complications. Hyperbilirubinemia occurred in 7% of the cases. Among women without any maternal complications during pregnancy, the frequency rate of neonatal complications was 19%, compared with 23% among the entire group of 790 women. Our results suggest that the absence of maternal complications does not protect the infant from a neonatal complication. Further refinement is needed to identify markers of obstetric, medical and neonatal complications in pregnancies with no risk factors.