Aspirin and Prevention of Preeclampsia

Summary: 1. A heterogeneous group of randomized trials have been conducted using low-dose aspirin to prevent preeclampsia. The results do not support widespread use of low-dose aspirin to prevent preeclampsia.
2. On the basis of existing literature, it is reasonable to use prophylactic low-dose aspirin from early pregnancy in the following groups:
(i) Women with prior fetal loss after the first trimester, with placental insufficiency (ii) Women with severe fetal growth retardation in a preceding pregnancy either
due to preeclampsia or unexplained
(iii) Women with severe early-onset preeclampsia in a previous pregnancy
necessitating delivery at or before 32 weeks' gestation.
3. On the basis of existing literature, it is recommended that aspirin not be used in the following groups:
(i) Healthy nulliparous women
(ii) Women with mild chronic hypertension
(iii) Women with established preeclampsia.
4. The data are sufficient to support further trials in more homogeneous select subgroups of women considered at risk of developing preeclampsia.     

Effects of aspirin on placenta and perinatal outcomes in patients with poor obstetric history

Objective: The aim of this study was to compare a low-dose aspirin treatment on placental and perinatal effects in the patients with poor obstetric history such as preeclampsia, intrauterine growth retardation (IUGR) in previous pregnancy. Study design: This retrospective study of 86 pregnant women was conducted between April 2002 and June 2005. In this study period 364 placentas were examined and the patients with poor obstetric history such as IUGR and preeclampsia were selected. Then the patients were assigned to three groups; group 1 (n = 30) was composed of women with no risk in previous pregnancy; group 2 (n = 27) was composed of patients with poor obstetric history (e.g., preeclampsia, IUGR) who were treated with aspirin and patients in group 3 (n = 29) had poor obstetric history without any treatment (patients who were started to follow-up after 14 weeks of gestation). Patients in group 2 were treated with a low-dose aspirin (80 mg/day) as soon as a urinary pregnancy test was positive. Treatment was usually stopped at 34 completed weeks of gestation. On histopathologic examination of the placenta, uteroplacental vascular pathologic features and secondary villous damage (such as fibrinoid necrosis of desidual vessels, villous infarct, severely increased villous fibrosis, severely increased syncytiotrophoblast knotting, obliteration of the vessel lumen, severely increased villous hypervascularity) and also lesions involving coagulation (such as excessive perivillous fibrin deposition, multiple occlusive thrombi in uteroplacental vessels, avascular villi ) were examined. Results: There were no significant differences between the groups with respect to maternal age, body mass index at the first trimester and delivery. Also there were no significant differences among groups with respect to placental weight, fetal height, weight, gestational week, umbilical artery pH, pO2, pCO2 and base excess status. The incidences of preeclampsia were 3.3, 7.4, 6.8% and the incidences of IUGR were 6.7, 11.1, 6.8% in the groups, respectively (P > 0.05 for both). Although the percentages of all pathologic findings were higher in groups 2 and 3, these differences were not statistically important. Conclusion: When low-dose aspirin is taken, starting at the beginning of pregnancy in patients with poor obstetric history, there are still high frequencies of uteroplacental vascular and related villous lesions persisted on placental bed. Also it has no beneficial effects on perinatal outcomes in these patients.     

Family History of Hypertension,Cardiovascular Disease,or Diabetes and Risk of Developing Preeclampsia: A Systematic Review

Preeclampsia is a severe pregnancy complication with high potential for adverse effects on maternal and fetal health during the perinatal period. It is also associated with an increased risk of maternal cardiovascular disease later in life. Development of preeclampsia can be decreased by prescribing low-dose aspirin to high-risk women. At present, maternal and pregnancy factors are used to assess the risk of preeclampsia. One additional factor that could add to the assessment of risk is a family history of hypertension, cardiovascular disease, or diabetes, especially for nulliparous women who do not have a pregnancy history to inform treatment decisions. Therefore, we conducted a systematic review to assess the association between family history of the aforementioned conditions and preeclampsia.Four databases including MEDLINE, EMBASE, the Cochrane Library, and CINAHL/pre-CINAHL were searched for observational studies that examined a family history of hypertension, cardiovascular disease, or diabetes in women with preeclampsia and in a control population. Studies were evaluated for quality using the Newcastle-Ottawa Scale. A total of 84 relevant studies were identified. A meta-analysis was not conducted due to suspected heterogeneity in the included studies.Most studies reported a positive association between a family history of hypertension or cardiovascular disease and the development of preeclampsia. The majority of studies examining family history of diabetes reported non-significant associations. Overall, family history of hypertension or cardiovascular disease is associated with a higher risk for developing preeclampsia and should be considered when assessing women in the first trimester for low-dose aspirin.     

Hypertensive disorders in twin versus singleton gestations. National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units

OBJECTIVE: This study was undertaken to compare rates and severity of gestational hypertension and preeclampsia, as well as perinatal outcomes when these complications develop, between women with twin gestations and those with singleton gestations. STUDY DESIGN: This was a secondary analysis of prospective data from women with twin (n = 684) and singleton (n = 2946) gestations enrolled in two separate multicenter trials of low-dose aspirin for prevention of preeclampsia. End points were rates of gestational hypertension, rates of preeclampsia, and perinatal outcomes among women with hypertensive disorders. RESULTS: Women with twin gestations had higher rates of gestational hypertension (relative risk, 2.04; 95% confidence interval, 1.60-2.59) and preeclampsia (relative risk, 2. 62; 95% confidence interval, 2.03-3.38). In addition, women with gestational hypertension during twin gestations had higher rates of preterm delivery at both <37 weeks' gestation (51.1% vs 5.9%; P <. 0001) and <35 weeks' gestation (18.2% vs 1.6%; P <.0001) and also had higher rates of small-for-gestational-age infants (14.8% vs 7. 0%; P =.04). Moreover, when outcomes associated with preeclampsia were compared, women with twin gestations had significantly higher rates of preterm delivery at <37 weeks' gestation (66.7% vs 19.6%; P <.0001), preterm delivery at <35 weeks' gestation (34.5% vs 6.3%; P <.0001), and abruptio placentae (4.7% vs 0.7%; P =.07). In contrast, among women with twin pregnancies, those who remained normotensive had more adverse neonatal outcomes than did those in whom hypertensive complications developed. CONCLUSIONS: Rates for both gestational hypertension and preeclampsia are significantly higher among women with twin gestations than among those with singleton gestations. Moreover, women with twin pregnancies and hypertensive complications have higher rates of adverse neonatal outcomes than do those with singleton pregnancies.     

小剂量阿司匹林对子痫前期早期干预和预防作用

子痫前期是母儿围产期死亡及医源性早产的重要原因,近年来越来越多研究表明妊娠期应用小剂量阿司匹林可改善子痫前期发病过程中前列环素(PGI2)/ 血栓素A2(TXA2)比例失衡所致的血液高凝状态,从而预防子痫前期的发生。建议有高危因素的孕妇,在妊娠早期结束后尽快开始口服小剂量阿司匹林,在有效预防子痫前期发病的同时并不增加胎儿及产妇的出血风险,从而获得良好的母儿结局。     

Chronic hypertension in pregnancy

Pregnant women with chronic hypertension are at risk for maternal and perinatal morbidity. Careful assessment and management of these patients during pregnancy are the keys to reducing maternal and fetal complications. Antihypertensive treatment should be used in women with high-risk chronic hypertension, whereas drug therapy does not improve pregnancy outcome in women at low risk. Prophylactic low-dose aspirin started early in pregnancy in women with chronic hypertension is not effective in reducing the frequency of superimposed preeclampsia and should be avoided.     

Screening for preeclampsia in twin pregnancies

Twin pregnancies are an important risk factor for preeclampsia, a hypertensive disorder of pregnancy that is associated with a significant risk of maternal and perinatal morbidity. Given the burden of preeclampsia, the identification of women at high risk in early pregnancy is essential to allow for preventive strategies and close monitoring. In singleton pregnancies, the risk factors for preeclampsia are well established, and a combined first-trimester prediction model has been shown to adequately predict preterm disease. Furthermore, intervention with low-dose aspirin at 150 mg/day in those identified as high-risk reduces the rate of preterm preeclampsia by 62%. In contrast, risk factors for preeclampsia in twin pregnancies are less established, the proposed screening models have shown poor performance with high false-positive rates, and the benefit of aspirin for the prevention of preeclampsia is not clearly demonstrated. In this review, we examine the literature assessing prediction and prevention of preeclampsia in twin pregnancies.     

Comparison of obstetric outcomes in recipients of donor oocytes vs. women of advanced maternal age with autologous oocytes

OBJECTIVE: To evaluate obstetric complications in women conceiving with donated oocytes as compared to controls of advanced maternal age. STUDY DESIGN: We compared the obstetric outcomes of a cohort of 69 women who conceived through oocyte donation to all women over 38 years old (n = 681) who delivered at the same hospital in the same period. We first compared obstetric complications and outcomes in the entire cohort. Additional comparisons were made while controlling for multiple covariates: maternal and fetal complications, mode of delivery, estimated gestational age and infant weight at delivery. RESULTS: Women who conceived with donor oocytes were older than controls. In the cohort, oocyte recipients were at increased risk for several obstetric complications. However, when controlling for age and multiple gestations, only preterm labor, preeclampsia and protracted labor were increased in oocyte recipients. CONCLUSION: Women who conceive with donor oocytes might be at increased risk of complications during pregnancy. When age and multiple gestations are accounted for, these patients remain at risk for preterm labor, preeclampsia and protracted labor requiring cesarean delivery.     

Soluble Endoglin for the Prediction of Preeclampsia in a High Risk Cohort

Objectives. To evaluate soluble endoglin (sEng) and the soluble fms-like tyrosine kinase 1 (sFlt1) to placental growth factor (PlGF) ratio for the prediction of preeclampsia in high-risk women, and to evaluate differences in sEng between women with high-risk singleton and multiple gestation pregnancies. Study Design. We collected serial serum specimens from 119 women at high preeclampsia risk. sEng, sFlt1 and PlGF were measured by ELISA. Results. Among subjects who did not develop preeclampsia, mean serum sEng was significantly higher in those with multiple gestation pregnancies vs. high-risk singletons. Among women with singleton gestations, mean serum sEng was higher in subjects who developed early-onset (<34 weeks) and late-onset (≥ 34 weeks) preeclampsia, as compared with subjects without preeclampsia, from 22 weeks and 28 weeks gestation onward, respectively. The within-woman rate of change of sEng was also higher in women who later developed preeclampsia. Conclusions. sEng is higher in women with multiple gestations vs. high-risk singleton pregnancies. In high-risk women, serum sEng is increased prior to preeclampsia onset.     

Risk factors, pregnancy complications, and prevention of hypertensive disorders in women with pregravid diabetes mellitus

OBJECTIVE: To review the rate, risk factors, and potential prevention of preeclampsia in women with pregravid diabetes mellitus. METHODS: Detailed review of recent English literature describing pregnancy outcome in women with pregravid insulin-dependent diabetes mellitus (Type 1 diabetes). The primary focus of the review is risk factors for preeclampsia and potential methods suggested for prevention of preeclampsia. In addition, pitfalls in diagnosis of preeclampsia will be emphasized. RESULTS: The reported rate of preeclampsia ranged from 9% to 66%. This rate increased with increased severity of diabetes by White's classification, with the highest rate reported in women with pregravid diabetic nephropathy. Risk factors identified for preeclampsia were nulliparity, chronic hypertension, microalbuminuria prior to pregnancy, nephropathy, and poor glycemic control early in pregnancy. There is lack of agreement among reports in the literature concerning criteria used to diagnose preeclampsia. There are two randomized trials that included women with Type 1 diabetes who were randomized to receive either low-dose aspirin or placebo. There was no reduction in the rate of preeclampsia with low-dose aspirin in either trial. CONCLUSIONS: In women with pregravid Type 1 diabetes, the rates of preeclampsia and adverse neonatal outcome increase with increased severity of diabetes. Low-dose aspirin does not reduce rate of preeclampsia in such women. Further studies should address the role of good glycemic control prior to 20 weeks gestation and prevention of microalbuminuria.     

What we have learned about preeclampsia

Preeclampsia is a multisystem disorder that complicates 6% to 8% of pregnancies, with higher rates in women with preexisting hypertension, diabetes mellitus, or previous history of preeclampsia. Recent large randomized trials, including two large trials conducted by members of the Maternal-Fetal Medicine Network, have not shown a benefit in reducing the rate of preeclampsia or perinatal outcome from the use of low-dose aspirin. Secondary analysis from these trials revealed that the onset of mild gestational hypertension or mild preeclampsia at or near term was associated with minimal to low neonatal and maternal morbidities. During review of the medical records we found considerable differences among the various centers regarding the definitions of both mild and severe preeclampsia. These differences were more prevalent in those women with pre-existing hypertension or diabetes mellitus. The majority of adverse pregnancy outcomes occurred in women who developed severe gestational hypertension-preeclampsia prior to 35 weeks' gestation and in those women with previous preeclampsia and/or pre-existing vascular disease. We also found that epidural anesthesia is safe in parturients receiving low-dose aspirin in pregnancy and in women with severe preeclampsia.     

Antiphospholipid syndrome: obstetric diagnosis,management, and controversies

Antiphospholipid syndrome, a condition characterized by one or more thrombotic or pregnancy-related clinical features in association with medium to high levels of antiphospholipid antibodies, has emerged as an important diagnostic consideration in several medical fields. Antiphospholipid syndrome is one of the few treatable causes of pregnancy loss, and successful pregnancy rates of 70% or more can be achieved with appropriate treatment. Heparin, usually combined with low-dose aspirin, is used in patients at risk for thrombosis. Pregnancy in these women is associated with increased rates of preeclampsia, placental insufficiency, and preterm delivery, so that attentive clinical care is required for best outcomes. Recent studies indicate that women at low risk for thrombosis may be treated with low-dose aspirin. However, remaining controversies and unanswered questions in the field of antiphospholipid syndrome are a source of clinical confusion. This review highlights the most important controversies, taking into account the results of recent obstetric treatment trials and our own clinical experience.     

Risk factors,pregnancy complications,and prevention of hypertensive disorders in women with pregravid diabetes mellitus

Objective: To review the rate, risk factors, and potential prevention of preeclampsia in women with pregravid diabetes mellitus.

Methods: Detailed review of recent English literature describing pregnancy outcome in women with pregravid insulin-dependent diabetes mellitus (Type 1 diabetes). The primary focus of the review is risk factors for preeclampsia and potential methods suggested for prevention of preeclampsia. In addition, pitfalls in diagnosis of preeclampsia will be emphasized.

Results: The reported rate of preeclampsia ranged from 9% to 66%. This rate increased with increased severity of diabetes by White's classification, with the highest rate reported in women with pregravid diabetic nephropathy. Risk factors identified for preeclampsia were nulliparity, chronic hypertension, microalbuminuria prior to pregnancy, nephropathy, and poor glycemic control early in pregnancy. There is lack of agreement among reports in the literature concerning criteria used to diagnose preeclampsia. There are two randomized trials that included women with Type 1 diabetes who were randomized to receive either low-dose aspirin or placebo. There was no reduction in the rate of preeclampsia with low-dose aspirin in either trial.

Conclusions: In women with pregravid Type I diabetes, the rates of preeclampsia and adverse neonatal outcome increase with increased severity of diabetes. Low-dose aspirin does not reduce rate of preeclampsia in such women. Further studies should address the role of good glycemic control prior to 20 weeks gestation and prevention of microalbuminuria.     

Fetal Growth in Women Using Low-Dose Aspirin for the Prevention of Preeclampsia: Effect of Maternal Size

We wanted to determine whether low-dose aspirin has an effect on birthweight in a low-risk population and to evaluate the interaction between aspirin and maternal risk factors in relationship to their effect on birthweight. We also wanted to determine the specific fetal ultrasound measurements affected by low-dose aspirin and the gestational age at which this effect becomes apparent.

The women studied were derived from a population of 606 nulliparous women who participated in a randomized trial of low dose aspirin to reduce the incidence of preeclampsia. This analysis included only women who remained normotensive and delivered live horn singletons at term. There were 254 women in the group randomized to 60 mg of aspirin daily from 24 weeks onward, and 248 who received a daily placebo.

The mean birthweight was 3,353 g in the aspirin versus 3,282 g in the control group, a difference of 71 g (P = 0.08). In a regression analysis controlling for race, height, weight, smoking, and infant sex, the use of aspirin was associated with an 88-g increase in birthweight (P = 0.04). The effect of aspirin on birthweight in black and white infants and male and female infants was not significantly different. However, when the study population was divided at the median by height and weight, virtually the entire increase in birthweight associated with low-dose aspirin was found in the short and thin women, with birthweight increases in these groups of approximately 140 g (P ≤ 0.02). Sequential fetal ultrasound measurements in thin women revealed significant changes in the abdominal circumference (P < 0.001) at 27 weeks and above associated with aspirin use, but no differences in femur length or head circumference.

Low-dose aspirin has a significant impact on birthweight in a low-risk nulliparous population, which is most marked in thin and/or short women. The effect is related predominantly to an increase in the fetal abdominal circumference. These results are compatible with current knowledge about the mechanism of action of low dose aspirin, and the etiology of decreased birthweight in thin women.     

Obstetric conditions and erythropoietin levels

OBJECTIVE: Our purpose was to evaluate and compare erythropoietin levels as related to obstetric conditions, including acute and chronic bleeding, preeclampsia, and multiple gestations.Study Design: During April 1999 all women in the labor and delivery unit with delivery expected to occur within 24 to 72 hours of admission had erythropoietin and hematocrit values obtained. First-trimester hematocrit values, obstetric problems, medications, and history of vaginal bleeding were obtained from patient interview, examination, and the prenatal record. Statistics were analyzed by the Student t test and chi(2). RESULTS: During a 1-month period, 302 consecutive women were divided into 5 groups on the basis of obstetric events. Group 1 consisted of women with normal, uncomplicated term singleton gestations (n = 230); group 2, women with acute vaginal bleeding (n = 10); group 3, women with chronic vaginal bleeding (n = 29); group 4, women with multiple gestations (n = 13); and group 5, women with preeclampsia (n = 16). The mean erythropoietin level in group 1 (20. 2 +/- 10.3 mU/mL) was significantly different from values in the other 4 groups (group 2, 74.2 +/- 29.2 mU/mL; group 3, 65.0 +/- 33.0 mU/mL; group 4, 34.8 +/- 16.8 mU/mL; group 5, 43.4 +/- 11.4 mU/mL; P <.001). The admission hematocrit for group 1 (0.369 +/- 0.029) was significantly greater than for groups 2 and 3 (group 2, 0.323 +/- 0. 024; group 3, 0.321 +/- 0.023; P <.001) and significantly lower than for group 5 (0.384 +/- 0.022; P <.05). CONCLUSION: The maternal serum erythropoietin level varies depending on the events occurring during gestation. Acute and chronic bleeding, multiple gestations, and preeclampsia are all associated with various serum erythropoietin levels.     

Prevention of Pre-eclampsia: Low-dose Aspirin,Calcium and Antioxidants

Pre-eclampsia is a leading cause of maternal and perinatal morbidity and mortality. Early deliver remains the only effective treatment for this condition. The purpose of this article is to review the role of low-dose aspirin and calcium supplements and to address the potential role of antioxidants in the prevention of pre-eclampsia.Early studies and meta-analysis suggested that low-dose aspirin reduced the incidence of pre-eclampsia. In more recent reports, large clinical trials studying health nulliparous women and women at higher risk for pre-eclampsia have shown that low-dose aspirin has little effect. Calcium supplements also ail to reduce the risk of developing pre-eclampsia in nulliparous women. Recent findings support the hypothesis that “oxidative stress” may be involved in the pathogenesis of pre-eclampsia. This has led to the suggestion that antioxidant therapy may be beneficial. The disappointing results of the large trials of aspirin and calcium suggest that better support for the role of oxidative stress should be available before such trials are undertaken.In summary, large clinical trials have not supported the encouraging results of smaller trials and meta-analysis. There is little evidence that low-dose aspirin or calcium is effective or the prevention of pre-eclampsia. Further advances in preventative therapy await a more thorough understanding of the pathophysiology of the disease process.     

Preeclampsia in multiple gestation: the role of assisted reproductive technologies

OBJECTIVE: To estimate the relationship of assisted reproductive technologies and ovulation-inducing drugs with preeclampsia in multiple gestations. METHODS: This historical cohort study was conducted on 528 multiple gestations from a Colorado health maintenance organization. Using univariate and logistic regression analysis, we determined if women who conceived a multiple gestation as a result of assisted conception were at a greater risk of preeclampsia than those who conceived spontaneously. RESULTS: Between January 1994 and November 2000, there were 330 unassisted and 198 assisted multiple gestations. Sixty-nine multiple gestations followed assisted reproductive technologies (in vitro fertilization and gamete intrafallopian transfer). Human menopausal gonadotropins and clomiphene citrate were associated with 38 and 91 of the multiple gestations, respectively. Compared with unassisted multiple gestations, the relative risk of mild or severe preeclampsia among mothers who received assisted reproductive technologies was 2.7 (95% confidence interval [CI] 1.7, 4.7) and 4.8 (CI 1.9, 11.6), respectively. Adjusted for maternal age and parity, women who received assisted reproductive technologies were two times more likely to develop preeclampsia (odds ratio 2.1, CI 1.1, 4.1) compared with those who conceived spontaneously. The adjusted odds ratios of nulliparity and maternal age for preeclampsia were 2.1 (CI 1.3, 3.4) and 1.1 (CI 1, 1.1), respectively. Although the incidence of preeclampsia was greater in mothers who received clomiphene citrate and human menopausal gonadotropins, this association did not reach statistical significance at the P <.05 level. CONCLUSION: Women who conceive multiple gestations through assisted reproductive technologies have a 2.1-fold higher risk of preeclampsia than those who conceive spontaneously.     

睡前口服小剂量阿司匹林预防高危孕妇子痫前期的发生

目的:探讨小剂量阿司匹林对高危孕妇子痫前期及妊娠诱发的高血压综合征的预防作用。方法:将242例存在子痫前期高危因素暴露的孕13~16周的妇女随机分成阿司匹林处理组(n=120,睡前口服75 mg阿司匹林至分娩)和对照组(n=122,安慰剂替代阿司匹林),随访至妊娠结束后2周,记录子痫及妊娠高血压综合征的发生率。结果:本研究中共失访5例,其中阿司匹林组2例,对照组3例。子痫前期的发生率,阿司匹林组低于对照组(18.6%vs 52.9%),其中轻度子痫前期、早发子痫前期、严重子痫前期的发生率阿司匹林组(11.0%、3.4%、4.2%)均低于对照组(26.9%、12.6%、13.4%)。妊娠诱发高血压的发生率(4.2%vs 16.0%)、宫内发育迟缓发生率(13.6%vs 30.3%)、出生孕周<34周的孕妇比例(4.2%vs 13.4%)、37周前分娩的孕妇比例(18.6%vs 40.3%)、流产比例(2.5%vs 10.1%),阿司匹林组均低于对照组。平均出生体质量(2 890±340 g vs 2 611±479 g)、平均出生孕周(36.8±2.0 vs 35.0±3.1),阿司匹林组大于对照组(P<0.05)。阿司匹林组与对照组在新生儿围产期内死亡率(0.8%vs 1.7%)、胎盘早剥率(6.8%vs 5.0%)、阴道分娩率(43.2%vs 40.3%)之间均无统计学差异(P>0.05)。结论:睡前口服小剂量阿司匹林能使子痫前期高危孕妇受益。     

Relationship of twin zygosity and risk of preeclampsia

OBJECTIVE: Twin gestations are known to be at higher risk for preeclampsia. One theory suggests that maternal recognition of fetal and trophoblastic tissues as foreign may be a factor. If that hypothesis is true, mothers carrying monozygous (MZ) gestations (ie a single fetal graft) might be predicted to have a lower rate of preeclampsia than those carrying dizygous (DZ) gestations. To evaluate this hypothesis, we compared the rate of preeclampsia in mothers with MZ and DZ twin gestations. STUDY DESIGN: Seven hundred sixty-eight twin deliveries from 1994 to 1999 were reviewed. Placental pathology reports were reviewed to determine the chorionic state of each placenta. Monochorionic placentas were assumed to be MZ. Dichorionic placentas were categorized as DZ if the neonates were of different sexes or different blood types. Maternal and fetal data were abstracted from the medical records. Preeclampsia was defined by standard criteria of the National Institutes of Health Working Group on High Blood Pressure. Our analysis was limited to women with pregnancies reaching at least 30 weeks of gestation where zygosity could be determined. RESULTS: Our analysis included 464 twin pregnancies, 154 MZ and 310 DZ. Among nulliparous women, the rate of preeclampsia was 15% (25/170) for DZ twins versus 20% (15/75) for MZ twins (P =.3). Among multiparous women, the rate was 8% (11/140) for DZ twins and 5% (4/79) for MZ twins (P =.4). In a logistic regression performed to control for confounding by maternal age, gestational age at delivery, assisted reproduction, and male sex, dizygotic state was associated with an odds ratio of 1.4 (95% CI = 0.5-3.9) for developing preeclampsia in nulliparous women and 1.2 in multiparous women (95% CI = 0.3-5.0). CONCLUSIONS:: These results do not support the hypothesis that zygosity affects the rate of preeclampsia in twin gestations, though the number of subjects in our study was too small to allow definitive conclusions. Larger studies are needed to evaluate this finding.     

Risk of cesarean delivery with elective induction of labor at term in nulliparous women.

OBJECTIVE: To quantify the risk of cesarean delivery associated with elective induction of labor in nulliparous women at term. METHODS: We performed a cohort study on a major urban obstetric service that serves predominantly private obstetric practices. All term, nulliparous women with vertex, singleton gestations who labored during an 8-month period (n = 1561) were divided into three groups: spontaneous labor, elective induction, and medical induction. The risk of cesarean delivery in the induction groups was determined using stepwise logistic regression to control for potential confounding factors. RESULTS: Women experiencing spontaneous labor had a 7.8% cesarean delivery rate, whereas women undergoing elective labor induction had a 17.5% cesarean delivery rate (adjusted odds ratio [OR] 1.89; 95% confidence interval [CI] 1.12, 3.18) and women undergoing medically indicated labor induction had a 17.7% cesarean delivery rate (OR 1.69; 95% CI 1.13, 2.54). Other variables that remained significant risk factors for cesarean delivery in the model included: epidural placement at less than 4 cm dilatation (OR 4.66; 95% CI 2.25, 9.66), epidural placement after 4 cm dilatation (OR 2.18; 95% CI 1.06, 4.48), chorioamnionitis (OR 4.61; 95% CI 2.89, 7.35), birth weight greater than 4000 g (OR 2.59; 95% CI 1.69, 3.97), maternal body mass index greater than 26 kg/m2 (OR 2.36; 95% CI 1.61, 3.47), Asian race (OR 2.35; 95% CI 1.04, 5.34), and magnesium sulfate use (OR 2.18; 95% CI 1.04, 4.55). CONCLUSION: Elective induction of labor is associated with a significantly increased risk of cesarean delivery in nulliparous women. Avoiding labor induction in settings of unproved benefit may aid efforts to reduce the primary cesarean delivery rate.