The contribution of maternal stress to preterm birth: issues and considerations

Preterm birth represents the most significant problem in maternal-child health, with maternal stress identified as a variable of interest. The effects of maternal stress on risk of preterm birth may vary as a function of context. This article focuses on select key issues and questions highlighting the need to develop a better understanding of which particular subgroups of pregnant women may be especially vulnerable to the potentially detrimental effects of maternal stress, and under what circumstances and at which stages of gestation. Issues related to the characterization and assessment of maternal stress and candidate biologic mechanisms are addressed.     

Diabetes mellitus and the risk of preterm birth with regard to the risk of spontaneous preterm birth

Introduction.?It is internationally agreed that diabetes mellitus (DM) is associated with increased maternal and fetal morbidity and long-term complications. To avoid these complications, it is often necessary to induce birth before term. The impact of DM on spontaneous preterm birth (spontaneous labor, preterm premature rupture of membranes and/or cervical incompetence resulting in delivery before the completion of 37 gestation weeks) is still unexplained. Preterm birth accounts for the most neonatal deaths and infant morbidities, and therefore it still remains one of the biggest challenges in obstetrics.

Objective.?Our study determined if there is an increasing tendency towards spontaneous preterm birth in mothers with gestational and preexisting DM.

Methods.?In this retrospective cohort study, 187 pregnant women with gestational DM and preexisting DM were compared to a randomized control group consisting of 192 normoglycemic women concerning gestational age and perinatal outcome. Data were collected by the Medical University of Vienna. Multiple pregnancies and women with severe maternal diseases, such as preeclampsia, were excluded.

Results.?Women with DM tended significantly more often to preterm births (P?=?0.002). A significant difference in the incidence of spontaneous preterm birth was found (P?=?0.047).

Conclusion.?DM affects the length of gestation and incidence of spontaneous preterm birth.     

Nursing's contribution to the literature on preterm labor and birth

Although preterm labor and birth continues to plague us as an unsolved mystery in maternal/child health, much has actually been learned over the past few decades. Most reviews of the preterm labor literature examine the research in an interdisciplinary manner; this article instead looks at the active role that nurses have taken in the research concerning preterm labor and birth. This article will categorize research conducted by nurses over the past 30 years on preterm labor and birth, emphasizing some of the changes in nursing practice engendered by nursing's important research effort.     

双胎自发性早产预测及预防

随着辅助生殖技术的发展,双胎妊娠的发生率增加,早产的发生率也随之增加。有证据表明,超声检测宫颈长度和胎儿纤维蛋白测试可以预测双胎妊娠的自发性早产,但是到目前为止,没有任何有效的双胎妊娠的自发性早产的干预措施。本文对双胎自发性早产的预测和预防进行阐述。     

Inflammatory cytokine gene polymorphisms and spontaneous preterm birth

The objective was to search for an association between spontaneous preterm birth (sPTB) and single and/or combined polymorphisms in genes TNFA −308 G > A, IL10 −1082 G > A, IL10 −819 C > T, IL10 −592 C > A, IL6 −174 G > C, and IFNG +874 A > T. Genotyping was performed on 410 Brazilian ethnically matched women managed at two hospitals (two independent case–control sets). One set consisted of 122 cases and 101 controls, and the other set comprised 82 cases and 105 controls. We compared genotype and genotype-combination frequencies between cases and controls using Fisher's exact or the χ² tests and confirmed results using logistic regression. Among the six SNPs studied, we found no independent association between any single SNP and sPTB risk. The multi-locus analysis revealed a significant association between sPTB and the TNFA(GG)/IL6(GG)/IFNG(AA) genotype combination (p = 0.002), confirmed by logistic regression. Our data suggest that the combination of TNF-α, IFN-γ, and IL-6 maternal gene polymorphisms might contribute to susceptibility to sPTB. This finding could be investigated as a possible genetic marker for the risk of spontaneous preterm birth.     

The preterm prediction study: failure of midtrimester cervical sialidase level elevation to predict subsequent spontaneous preterm birth.

OBJECTIVE: Our objective was to determine any associations among midtrimester cervical fluid sialidase activity, bacterial vaginosis, and subsequent spontaneous preterm birth. STUDY DESIGN: In this nested case-control study all patients (n = 126) with spontaneous preterm birth at <35 weeks' gestation and selected control subjects delivered at >/=37 weeks' gestation (n = 126, matched for race, parity, and center) were derived from women enrolled in the multicenter National Institute of Child Health and Human Development Preterm Prediction Study. Sialidase activity and presence of bacterial vaginosis according to Gram stain were determined in cervical swabs and vaginal smears, respectively, obtained at 22 weeks' to 24 weeks 6 days' gestation. RESULTS: The mean +/- SD sialidase activities were similar in case patients and control subjects (0.64 +/- 1.60 vs 0.41 +/- 0.94 nmol. mL-1. min-1, P =.21). Neither sialidase activity above the 90th percentile (10.3% vs 9.5%, P =.8) nor sialidase activity above the 95th percentile (7.9% vs 4. 8%, P =.3) of control specimens (>1.43 and >2.23 nmol. mL-1. min-1, respectively) was associated with spontaneous preterm birth. The frequency of combinations of bacterial vaginosis and elevated sialidase activity was similar (P >/=.63 with either cutoff) in case patients and control subjects. Sialidase activity was significantly higher among women with bacterial vaginosis than among those without bacterial vaginosis (1.35 +/- 1.87 vs 0.03 +/- 0.14 nmol. mL-1. min-1, P <.0001). CONCLUSIONS: Elevated cervical fluid sialidase activity at 22 to 24 weeks' gestation did not distinguish women at increased risk for spontaneous preterm birth, nor did it discriminate a subgroup of patients who had bacterial vaginosis associated with spontaneous preterm birth.     

Risk of spontaneous preterm birth in IVF-conceived twin pregnancies

Objective: To compare the mean transvaginal ultrasound (TVU) cervical length (CL) at midtrimester in screening for preterm birth in in vitro (IVF)-conceived twin pregnancies versus spontaneously-conceived twin pregnancies.

Methods: This was a retrospective cohort study. Potential study subjects were identified at the time of a routine second trimester fetal ultrasound exam at 18 0/7 to 23 6/7-week gestation. All women with twin diamniotic pregnancies screened with a single TVU CL for this trial were included. Mean TVU CLs were compared between IVF-conceived twin pregnancies and spontaneously-conceived twin pregnancies. The relationship of TVU CL with gestational age at delivery was assessed. Incidence of short TVU CL, defined as TVU CL ≤30?mm, was also calculated in the two groups. The primary outcome was the mean of TVU CL. Distribution of CL was determined and normality was examined in both groups

Results: A total of 668 women with diamniotic twin pregnancies who underwent TVU CL screening between 18 0/6 and 23 6/7 weeks were included. 158 (23.7%) were IVF-conceived pregnancies, and 510 (76.3%) were spontaneously-conceived pregnancies. No women received progesterone, pessary, or cerclage for preterm birth prevention during pregnancy. The mean TVU CL was significantly lower in the IVF-conceived group (32.2?±?10.5?mm) compared to the spontaneously-conceived group (34.1?±?9.1?mm) (mean difference (MD)???1.90?mm, 95%CI ?3.72 to ?0.08). The incidence of TVU CL ≤30?mm was 30.4% in the IVF-conceived group and 21.6% in the spontaneously-conceived group (adjusted odds ratio (aOR) 1.59, 95%CI 1.06–2.37). IVF-conceived twins had a significantly higher risk of spontaneous preterm birth <34 weeks (32.9 versus 21.2%; aOR 1.83, 95% confidence interval (CI) 1.23–2.71) and higher rate of delivery due to spontaneous onset of labor (64.5 versus 54.9%; aOR 1.50, 95%CI 1.03–2.17). For any given TVU CL measured between 18 0–7 and 23 6/7 weeks, gestational age at delivery for IVF-conceived twins was earlier by about 1 week on average compared with spontaneously-conceived twins.

Conclusions: The higher rate of spontaneous preterm birth in IVF-conceived twin pregnancies is predicted by lower midtrimester TVU CL, as well as by the lower gestational age at birth per any given CL in the IVF-conceived compared to the spontaneously-conceived twin pregnancies.     

Weight gain and spontaneous preterm birth: the role of race or ethnicity and previous preterm birth

OBJECTIVE: To study how the relationship between gestational weight gain and spontaneous preterm birth interacts with maternal race or ethnicity and previous preterm birth status. METHODS: This was a retrospective cohort study of singleton births to women of normal or low prepregnancy body mass index. Gestational weight gain was measured as total weight gain divided by weeks of gestation at delivery, and weight gain was categorized as low (less than 0.27 kg/wk,), normal (0.27-0.52 kg/wk), or high (more than 0.52 kg/wk). Univariable and multivariable analyses were performed on the relationship between weight gain categories and spontaneous preterm birth, stratified by maternal race or ethnicity and history of previous preterm birth. RESULTS: Overall, low weight gain was associated with spontaneous preterm birth (adjusted odds ratio [AOR] 2.5, 95% confidence interval [CI] 2.0-3.1). Although low gain was consistently associated with increased spontaneous preterm birth, some differences were found in subgroup analysis. Among African Americans with a previous preterm birth, both low and high weight gain were associated with increased odds of spontaneous preterm birth (AOR for low weight gain 4.3, 95% CI 1.2-15.5; AOR for high weight gain 6.1, 95% CI 1.8-20.2). For all other groups, high weight gain was not associated with spontaneous preterm birth. Among Asians with a previous preterm birth, low weight gain was not statistically significantly associated with spontaneous preterm birth (AOR 1.9, 95% CI 0.5-7.7). Among Asians there was also a non-statistically significant inverse relationship between high weight gain and spontaneous preterm birth (AOR 0.5, 95% CI 0.3-1.1). CONCLUSION: These results confirm an association between low maternal weight gain and spontaneous preterm birth. The effect modification of maternal race or ethnicity and history of previous preterm birth on this association deserves further study. LEVEL OF EVIDENCE: II-2.     

Inflammatory biomarkers and spontaneous preterm birth among obese women

Objective: To identify associations between second-trimester serum inflammatory biomarkers and preterm birth among obese women.

Methods: In this nested case-control study, we compared 65 serum inflammatory biomarkers in obese women whose pregnancies resulted in early spontaneous preterm birth (<32 weeks gestation, n?=?34) to obese women whose pregnancies resulted in term birth (n?=?34). These women were selected from a larger population-based California cohort. Random forest and classification and regression tree techniques were employed to identify biomarkers of importance, and adjusted odds ratios (aORs) and 95% confidence intervals (CI) were estimated using logistic regression.

Results: Random forest and classification and regression tree techniques found that soluble vascular endothelial growth factor receptor-3 (sVEGFR3), soluble interleukin-2 receptor alpha-chain (sIL-2RA) and soluble tumor necrosis factor receptor-1 (sTNFR1) were related to preterm birth. Using multivariable logistic regression to compare preterm cases and term controls, decreased serum levels of sVEGFR3 and increased serum levels of sIL-2RA and sTNFR1 were associated with increased risk of preterm birth among obese women, aOR?=?3.2 (95% CI: 1.0–9.9), aOR?=?2.8 (95% CI: 0.9–9.0), and aOR?=?4.1 (95% CI: 1.2–14.1), respectively.

Conclusions: In this pilot study, we identified three serum biomarkers indicative of inflammation to be associated with spontaneous preterm birth among obese women: sVEGFR3, sIL-2RA and sTNFR1.     

不同阶段自发早产临床分析

目的　探讨不同阶段的自发性早产对结局的影响。方法　回顾性分析于我院分娩的孕龄在2 8～ 36周的 1 36例自然早产者。分为早期早产 (earlypretermbirth)组 ,孕龄为 2 8～ 31 6周 ,(32 / 1 36 ,2 3 5 3% ) ,中度早产 (moderatepretermbirth)组孕龄为 32～ 33 6周 (31 / 1 36 ,2 2 79% ) ,轻型早产 (mildpretermbirth)组孕龄为 34～ 36周 (73/ 1 36 ,5 3 6 8% )。分析治疗和孕龄延长时间、早产儿结局和医疗费用。结果　我院早产发生率为1 0 30 % ,其中自发性早产发生率为 6 6 4 0 %。早期早产组新生儿发病率及死亡率均高于其他两组 (P <0 0 1 ) ,且医疗费用也明显高于其他两组 (P <0 0 0 1 )。Logistic多因素回归分析显示孕龄是影响早产儿结局的重要因素。结论　早期早产与新生儿预后密切相关 ,应加强对早期早产的重视