Relative Risk Of Preterm Delivery Research Articles

High birth weight and greater gestational age at birth in singletons born after frozen compared to fresh embryo transfer

ObjectiveWhile many studies agree that the fetal birth weight is higher after frozen embryo transfer (FET), few studies have explored the difference in fetal weight change during such pregnancies. This cohort study was to identify the difference in fetal birth weight and gestational age at birth between singletons born following fresh ET and those born following FET. Materials and methodsThis was a hospital-based cohort study using clinical data from the Kaohsiung Chang Gung Memorial Hospital Obstetric and Neonatal Database from January 1, 2007, to December 1, 2018. A sample of 784 eligible women who had singleton pregnancies and live-born deliveries after 428 fresh ET or 356 FET between January 2007 and December 2018. ResultsCompared with those in the fresh ET group, singletons in the FET group had higher birth weight (3137 g [2880–3441 g] vs. 3060 g [2710–3340 g], p < 0.05), were born later (39.0 weeks of gestation [38.0–40.0 weeks] vs. 38.0 weeks of gestation [37.0–39.0 weeks], p < 0.05), and had a lower incidence of preterm birth (10.4% vs. 15.2%, p < 0.05). The difference in birth weight was not associated with maternal body weight (BW) or body mass index, increase in maternal BW in the third trimester, but related to the total increase in maternal BW during pregnancy. ConclusionsThe birthweight of singletons born following FET and fresh ET became significant in the late third trimester. The main reason is that singletons conceived from FET were at a lower relative risk of preterm delivery and had a higher gestational age at birth.

Effect of bacterial vaginosis on preterm birth: a meta-analysis.

Bacterial vaginosis is a common genital tract disorder. It can lead to preterm birth, but its contribution is equivocal. Bacterial vaginosis is curable and, if diagnosed and appropriately treated, may reduce preterm births. The study desired to confirm the association between bacterial vaginosis and preterm birth. It was a meta-analysis. We included articles published from 2008 to 2022. The authors included studies that measured the association between bacterial vaginosis and preterm birth by relative risk/risk ratio (RR) or odds ratio (OR). We excluded studies with qualitative data. The study utilized five search engines, PubMed, Scopus, Google Scholar, Cochrane, and LILAC. We used the statistical package for social sciences (SPSS) to draw forest and funnel plots separately for RR and OR. Afteran extensive search, the study included20 articles yielding 26 relevant results with a total of 290,397 observations. This meta-analysis proves that bacterial vaginosis is undoubtedly associated with preterm birth. The overall relative risk of preterm delivery is about two-fold as overall OR1.79 (95% Confidence Interval 1.32-2.43). The overall RR of preterm birth is 1.44 (95% Confidence Interval 1.19-1.73). Our study shows a significant association between bacterial vaginosis and preterm birth. The study concludes that investigation for bacterial vaginosis and management should be a part of the routine examination of a pregnant woman. The health system must initiate this strategy soon to reduce the prevalence of preterm births and consequent neonatal mortality.

Increased risk of preterm delivery with high cortisol during pregnancy is modified by fetal sex: a cohort study

BackgroundPrevious studies show an association between maternal plasma and salivary cortisol and preterm birth but have been primarily conducted in high-income countries. It is unknown whether salivary cortisol is a risk factor for preterm birth in Ghana. Our objective was to determine whether maternal salivary cortisol during pregnancy was associated with pregnancy duration and preterm delivery in Ghana.MethodsWe conducted a cohort study of 783 pregnant women in Ghana. We measured salivary cortisol at baseline (mean 16 wk), 28 wk., and 36 wk. gestation. Pregnancy duration was determined primarily by ultrasound. We used adjusted linear regression models to examine the association between cortisol and pregnancy duration and Poisson regression models to determine the risk of preterm delivery among women with high cortisol at baseline or 28 wk. gestation.ResultsMean pregnancy duration was 39.4 ± 1.8 wk. and 6.6% had a preterm delivery. Mean maternal cortisol increased throughout pregnancy, from 4.9 ± 2.7 nmol/L at baseline (16 wk) to 6.4 ± 3.2 nmol/L at 28 wk. and 7.9 ± 3.0 nmol/L at 36 wk. gestation. In adjusted analyses, higher cortisol concentrations at baseline (β = − 0.39, p = .002) and 28 wk. (β = − 0.49, p = .001), but not 36 wk. (β = − 0.23, p = .084) were associated with a shorter pregnancy duration. Women with high cortisol at baseline (> 6.3 nmol/L) had an increased relative risk of preterm delivery (RR (95% CI): 1.96 (1.13, 3.40)), but the association between high cortisol at 28 wk. and preterm delivery was not significant. There was a significant interaction with fetal sex (p-for-interaction = 0.037): among women carrying male fetuses, high cortisol at baseline increased the risk of preterm delivery threefold (3.18 (1.51, 6.71)) while there was no association (1.17 (0.50, 2.74)) among women carrying female fetuses.ConclusionHigher maternal cortisol is associated with a shorter pregnancy duration and an increased risk of preterm delivery. Subgroup analysis by fetal sex revealed that this association is evident primarily among women carrying male fetuses. Future studies of cortisol and preterm delivery should include consideration of fetal sex as a potential effect modifier.

Cervical Length at 28–32 Weeks of Gestation Predicts Preterm Birth

Abstract Objective: To evaluate the ability of cervical length (CL) at 28–32 weeks of gestation to predict spontaneous preterm delivery and preterm premature rupture of membranes (PPROM). Methods: It was a retrospective cohort study that vaginal ultrasonography at approximately 28–32 weeks of gestation was performed in 14,953 women between 17–49 years old with singleton pregnancies who delivered after 28 weeks of gestation at the Peking University First Hospital from June 2008 to December 2012. The pregnancy outcomes were followed and the relationship between the CL and preterm delivery or PPROM was assessed. The relative risk was calculated to assess group differences in the likelihood of an event occurring. Results: The overall prevalence of preterm delivery was 5.7% (858/14,953); the incidence for therapeutic preterm delivery was 2.1% (318/14,953), for spontaneous preterm delivery was 0.9% (133/14,953), and for PPROM was 2.7% (407/14,953). Excluding the 318 women who had therapeutic preterm delivery, the relative risk of preterm delivery for women with a CL between 25 mm and &lt;30 mm, between 15 mm and &lt;25 mm, and &lt;15 mm was 3.7, 9.3, and 30.2, respectively. The sensitivity, specificity, and positive and negative predictive values of CL ≤25 mm at 28–32 weeks of gestation as the cut-off value for predicting preterm delivery were 19.8%, 97.5%, 23.4%, and 96.9%, respectively. For preterm delivery before 35 weeks of gestation, the sensitivity, specificity, and positive and negative predictive values of a CL ≤ 25 mm at 28–32 weeks of gestation as the cut-off value were 30.0%, 97.2%, 11.8%, and 99.1%, respectively. In addition, women with PPROM (n = 407) had significantly shorter CL (31.9 ± 7.4) mm at 28–32 weeks of gestation compared that of women without PPROM (34.0 ± 8.3) mm. The incidence of PPROM in women with a CL≤25 mm at 28–32 weeks of gestation (19.4%, 79/407) was significantly lower than that for women with a CL &gt;25 mm (80.6%, 328/407, P &lt; 0.05). Conclusion: CL at 28–32 weeks of gestation can predict spontaneous preterm delivery, and is valuable for predicting PPROM.

Term Complications and Subsequent Risk of Preterm Birth: Registry-Based Study

Abstract Objective To explore conditions and outcomes of a first delivery at term that might predict later preterm birth. Design Population based, prospective register based study. Setting Medical Birth Registry of Norway, 1999-2015. Participants 302 192 women giving birth (live or stillbirth) to a second singleton child between 1999 and 2015. Main outcome measures Main outcome was the relative risk of preterm delivery ( Results Women with any of the five complications at term showed a substantially increased risk of preterm delivery in the next pregnancy. The absolute risks for preterm delivery in a second pregnancy were 3.1% with none of the five term complications (8202/265 043), 6.1% after term pre-eclampsia (688/11 225), 7.3% after term placental abruption (41/562), 13.1% after term stillbirth (72/551), 10.0% after term neonatal death (22/219), and 6.7% after term small for gestational age (463/6939). The unadjusted relative risk for preterm birth after term pre-eclampsia was 2.0 (95% confidence interval 1.8 to 2.1), after term placental abruption was 2.3 (1.7 to 3.1), after term stillbirth was 4.2 (3.4 to 5.2), after term neonatal death was 3.2 (2.2 to 4.8), and after term small for gestational age was 2.2 (2.0 to 2.4). On average, the risk of preterm birth was increased 2.0-fold (1.9-fold to 2.1-fold) with one term complication in the first pregnancy, and 3.5-fold (2.9-fold to 4.2-fold) with two or more complications. The associations persisted after excluding recurrence of the specific complication in the second pregnancy. These links between term complications and preterm delivery were also seen in the reverse direction: preterm birth in the first pregnancy predicted complications in second pregnancies delivered at term. Conclusions Pre-eclampsia, placental abruption, stillbirth, neonatal death, or small for gestational age experienced in a first term pregnancy are associated with a substantially increased risk of subsequent preterm delivery. Term complications seem to share important underlying causes with preterm delivery that persist from pregnancy to pregnancy, perhaps related to a mother’s predisposition to disorders of placental function.

Term complications and subsequent risk of preterm birth: registry based study

ObjectiveTo explore conditions and outcomes of a first delivery at term that might predict later preterm birth.DesignPopulation based, prospective register based study.SettingMedical Birth Registry of Norway, 1999-2015.Participants302 192 women giving...

Perinatal outcome in context of the social determinants of health

The importance of recognition of the social determinants and the degree to which they influence the perinatal health is of utmost significance for the reproductive epidemiology and therefore they are important causes of the health inequalities within and between the countries. These facts have implied the aims of this study, to evaluate four frequent social determinants (level of education, employment status, parity and antenatal controls) and their influence on the two adverse perinatal outcomes – preterm/near term newborn of 35-37 gestational weeks, and small for gestational age baby (SGA). The research is a part of very extensive study, and by design it was prospective cohort study during which validated Questionnaire was used and extracted data from the maternal and neonatal history. As very relevant, the statistical parameters Relative Risk and Numbers Needed to Treat (NNT) were used for risk analysis. The Results have shown strong influence of the maternal education on the both perinatal outcomes. The Relative risk for preterm delivery in 35-37th gestational week in mother of uneducated mother is 14,963 (95%CI 4,54-49,27) compared to mother of academic level of education; the relative risk for SAG newborn is 3,204 (95%CI 2,12-4,84); in unemployed mother, the relative risk for preterm delivery is 4,585 of that in mother of academic level (95%CI 2,27-9,28), whereas for SGA baby is 4,799 (95%CI 3,17-7,26). No antenatal control in pregnancy is high risk for bad outcome, but in this study the Relative risk for preterm delivery was 1,293 (95%CI 0,67-2,47), and for SGA babies it was very low compared to full control in pregnancy, and was 1,041 (95%CI 0,84-1,29).&#x0D; According to these findings, it is obvious that the understanding of the social determinants of health priorities are the first and the most important step towards their gradual reduction, and this action is an entry point for global action to reach the health goals. Therefore, it is recommended such types of research studies to be conducted in extensive sample size, considering as much as possible social determinants, and performing multivariate analysis, in order to get higher statistical significance, which will help in creating strategies and activities for reduction of the most influential social determinants and improvement of the perinatal outcome of the newborns.

Risk Assessment for Preterm Delivery using the Fetal Fibronectin Test Associated with the Measurement of Uterine Cervix Length in Symptomatic Pregnant Women.

To analyze the use of the measurement of uterine cervix length (MUCL) and the fetal fibronectin (fFN) rapid test as predictors of preterm delivery (PTD) in symptomatic pregnant women assisted at the Santa Casa de Misericórdia de Sobral Maternity Hospital. This was a prospective and analytic study involving 53 parturients assisted between September of 2015 and July of 2016; the participants were between 24 and 34 weeks of gestational age (GA) and presented complaints related to preterm labor (PTL) prodromes. Vaginal secretion was collected for fFN testing, and the MUCL was obtained via transvaginal ultrasonography. A total of 58.49% of the subjects showed MUCL < 25 mm, and 41.51% were positive in the fFN rapid test. A total of 48 patients were followed-up until their delivery date, and 54.17% resulted in PTL. The relative risk (RR) for PTD in patients with MUCL < 25 mm was 1.83 (p = 0.09, 0.99-3.36, 95% confidence interval [CI]), with a mean time before delivery of 2.98 weeks. Based on fFN positive results, the RR was 3.50 (p = 0.002, 1.39-8.79, 95%CI) and the mean time until delivery was 1.94 weeks. The RR was 2.70 (p = 0.002, 1.08-6.72, 95%CI) when both tests were used. The RR of PTD within 48 hours, and 7 and 14 days were, respectively, 1.30 (p = 0.11, 95% CI 1.02-1.67), 1.43 (p = 0.12, 95% CI % 0.99-2.06), and 2.03 (p = 0.008, 95% CI 1.26-3.27), when based on the MUCL, and 1.75 (p = 0.0006, 95% CI 1.20-2.53), 2.88 (p = 0.0001, 95% CI, 1.57-5.31), and 3.57 (p = 0.0002, 95% CI 1.63-7.81) when based on positive fFN results. The RR at 48 hours and 7 and 14 days considering both tests was 1.74 (p = 0.0001, 95% CI 1.14-2.64), 2.22 (p = 0.0001, 95% CI 1.22-4.04), and 2.76 (p = 0.0002, 95% CI 1.27-5.96), respectively. In symptomatic pregnant women, we concluded that the MUCL < 25 mm associated with positive fFN rapid test indicate increased the risk for PTD. Further studies with larger sample sizes could contribute in supporting the results presented in the current study.

Significance of Initial Maternal Hemoglobin Concentration during Pregnancy in Birth Weight and Preterm Delivery in Sri Lanka

Objective: The study was conducted to investigate the influence of initial hemoglobin (Hb) concentration of Sri Lankan pregnant mothers on baby’s birth weight and preterm delivery. Methods: For this retrospective study, 3867 primigravid pregnant women in Sri Lanka were followed till they deliver the baby. Sampling method was cluster sampling where all the pregnant mothers giving singleton birth in the selected 15 health division were followed for three years. Mothers’ initial Hb concentration, weight gain during the pregnancy and neonatal outcomes were assessed. Results: Severe iron deficiency anemia at the initial stage of pregnancy had 3.9 - 14.4 folder higher relative risk of low birth weight (LBW) and 3.0 - 8.1 folder higher relative risk of preterm delivery at 95% confidence interval. The minimum incidence of preterm delivery and maximum weight gain of mothers occurs in association with an initial Hb concentration of 105 - 125 g/L. Conclusion: The excess level of initial iron content at pregnancy does not contribute for any adverse effect on pregnancy outcome as like in the later part of pregnancy and therefore supplement of iron during the initial pregnancy for mothers can be carried out regardless of whether the mother is anemic.

Relation of body mass index to frequency of recurrent preterm birth in women treated with 17-alpha hydroxyprogesterone caproate

The standard weekly dose of 17-alpha hydroxyprogesterone caproate (17OHP-C; 250 mg/wk) to reduce the risk of recurrent preterm birth was adopted without regard to patient characteristics. We examined the relationship between prepregnancy body mass index (BMI) and gestational age at birth after 17OHP-C prophylaxis. We hypothesized that rates of births before 32, 35, and 37 weeks of gestation would be increased in women with a BMI of 25 kg/m(2) or greater. A retrospective cohort study was conducted from a deidentified database of women treated with 17OHP-C for prior spontaneous preterm birth. The frequency of recurrent preterm delivery before 32, 35, and 37 weeks of gestation was investigated for women with a BMI less than 25 kg/m(2) compared with women with a BMI of 25 kg/m(2) or greater. The adjusted relative risk of preterm delivery was estimated through a modified Poisson regression approach. Of 390 women who met inclusion criteria, 60 (15.4%) delivered before 32 weeks, 89 (22.8%) before 35 weeks, and 156 (40.0%) before 37 weeks. A total of 174 women had a BMI less than 25 kg/m(2) (mean [SD], 21.2 [2.5]) and 216 had a BMI of 25 kg/m(2) or greater (mean [SD], 33.5 [6.7]). Risk of birth before 32 weeks was 1.7 times higher on average (adjusted relative risk, 1.7; 95% confidence interval, 1.05-2.77) in overweight women than in women with a BMI less than 25 kg/m(2), adjusting for age, race, smoking, and short cervix. There was no difference in the risk of preterm birth before 35 or 37 weeks. Among pregnant women receiving 17OHP-C prophylaxis for a prior preterm birth, recurrent preterm birth before 32 weeks was significantly more common in those women whose prepregnancy BMI was 25 kg/m(2) or greater than in women with BMI less than 25 kg/m(2). This observation is consistent with pharmacological studies suggesting that dosing regimens of 17OHP-C may affect efficacy.

Associations of adherence to the New Nordic Diet with risk of preeclampsia and preterm delivery in the Norwegian Mother and Child Cohort Study (MoBa).

Preeclampsia and preterm delivery are serious complications of pregnancy and leading causes of perinatal mortality and morbidity worldwide. Dietary factors might be associated with these adverse outcomes. We investigated whether adherence to the New Nordic Diet (NND) was associated with preeclampsia and preterm delivery risks in the Norwegian Mother and Child Cohort Study (MoBa). Participants were recruited from all over Norway during the period 1999-2008. A previously constructed diet score assessing meal frequency, and the consumption of Nordic fruits, root vegetables, cabbages, potatoes, oatmeal porridge, whole grains, wild fish, game, berries, milk and water, was used to assess NND adherence. Associations between NND adherence and the outcomes were estimated in adjusted multivariate logistic regression models. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. A total of 72,072 women was included in the study. High versus low NND adherence was associated with lower risk of total preeclampsia (OR0.86; 95% CI 0.78-0.95) and early preeclampsia (OR 0.71; 95% CI 0.52-0.96). High compared with low NND adherence was associated with a lower risk of spontaneous preterm delivery among nulliparous women (OR 0.77; 95% CI 0.66-0.89), whereas multiparous women with high NND adherence had a marginally significant higher risk of preterm delivery (OR 1.24; 95% CI 1.00-1.53). High NND adherence was associated with a lower relative risk of preeclampsia and of spontaneous preterm delivery among nulliparous women; however, among multiparous women there was a higher relative risk of preterm delivery.

Measurement of cervical biometry using transvaginal ultrasonography in predicting preterm labor.

Context:Preterm delivery is associated with high perinatal mortality and morbidity. Although detection of fetal fibronectin in cervical can predict preterm labor, but it is not available in lower source setting area. So, cervical length measurement by ultrasound can be used as an alternative to fetal fibronectin for predicting preterm labor.Aims:To find out the effectiveness of assessment of cervical length by endovaginal ultrasonography in predicting preterm delivery.Settings and Design:The study was conducted in the infertility clinic of Mahatma Gandhi Medical College and Research Institute, Pondicherry from January 2010 to July 2011.Materials and Methods:A total of 130 women with singleton gestation were studied with transvaginal ultrasonography (TVS) to assess the cervical changes (cervical length, dilation of internal os, presence of funneling) between 22 weeks and 24 weeks of gestation. The gestational age at delivery in women with cervical length with ≥25 mm were compared with those of <25 mm.Statistical Analysis Used:Statistical analysis was done using Chi-square test. The P value is <0.001 which is statistically significant.Results:The mean cervical length in the study population was 33.16 mm. 16 women had cervical length <25 mm at mid trimesters can out of which 13 (40.62%) went for spontaneous preterm delivery. The relative risk of preterm delivery increased as the length of the cervix decreased. The P value is <0.001 which is statistically significant. A significant difference was found between multigravida at risk of preterm being 62.5% compared to primigravida which was 37.5%.Conclusions:The risk of spontaneous preterm delivery is increased in women who are found to have a short cervix by TVS during pregnancy and it is a sensitive, simple and cost effective method of assessing risk of preterm delivery.

Obstetric and Perinatal Outcomes in Women with Type 1 Diabetes Mellitus

Abstract Background and aims: Pregnancy in women with type 1 diabetes mellitus (T1DM) is associated with increased risk of maternal and fetal complications. The aim of this study was to examine and to compare pregnancy outcomes between women with T1DM and a control group of non diabetic women. Material and method: The present study included all pregnancies in T1DM women followed at Diabetes Clinic, Emergency County Clinical Hospital, Timişoara, from 1990 to 2010. Results: We found a relative risk of spontaneous abortions of 1.85 (95%CI 1.01-3.39; p=0.05) and a relative risk of major congenital malformations of 4.32 (95%CI 1.55-12; p=0.005) in T1DM pregnancies compared to the control group. We also observed that the rate of stillbirth was more frequent in type 1 diabetic pregnancies (p=0.02). The offspring of T1DM women were more likely to be delivered preterm (32%) compared with the control group (9.5%). The relative risk of preterm delivery was 3.38 higher (95%CI 2.93-5.6; p&lt;0.0001) in T1DM pregnancies compared with non diabetic mothers. There was a statistically significant difference in the proportion of macrosomic offspring between T1DM (17.3%) and non diabetic mothers (6.5%) Conclusions: The present study demonstrated that pregnancy outcome and perinatal complications are still high in T1DM pregnancies.

Predictive value of cervical length by transvaginal sonography for preterm pregnancy during mid- and late-trimester of pregnancy

To study the value of cervical length (CL) by transvaginal sonography in the mid-trimester and late-trimester for the prediction of preterm delivery. The CL was measured by transvaginal sonography for 5277 pregnant women between 22 - 24 weeks and 28 - 32 weeks gestation, who were prenatal cared and delivered at the First Hospital of Peking University from June 2008 to November 2009. The pregnancy outcomes were followed, and the relationship between CL and preterm delivery and preterm premature rupture of membrane was studied. (1) The incidence of preterm delivery was 5.4% (289/5370) total, among of them the incidence of therapeutic preterm delivery was 1.7% (93/5370), spontaneously preterm delivery was 1.2% (62/5370), and preterm premature rupture of membrane was 2.5% (134/5370). There are 4 cases (4/5370) who occured late abortion. (2) Excluding the 93 women who had therapeutic preterm delivery, the mean CL of 22 - 24 weeks was (38.8 ± 4.0) mm. The relative risk for preterm delivery when the CL < 30 mm was 5.2, when CL < 25 mm, the relative risk was 11.1, and when CL < 15 mm the relative risk for preterm delivery was 13.8. The average CL during 28-32 weeks of gestation was (34.6 ± 4.8) mm, was significantly shorter than that of 22 - 24 weeks (P < 0.05). During this period the relative risk for preterm delivery when the CL < 30 mm was 6.9, when CL < 25 mm, the relative risk was 11.1, and when CL < 15 mm the relative risk for preterm delivery was 20.0. (3) A CL < 30 mm as the cut-off value for predicting preterm delivery during 22 - 24 weeks of gestation has only a 3% sensitivity and 19% positive predictive value, but had a 99% specificity and 96% negative predictive value. The sensitivity, positive predictive value, specificity and negative predictive value for a CL < 30 mm as the cut-off value for predicting preterm delivery during 28 - 32 weeks of gestation was 33%, 21%, 95% and 97% respectively. (4) The total number of preterm premature rupture of membrane pregnant women was 134 (2.5%), who had a mean CL of (38.4 ± 4.7) mm during 22 - 24 weeks of gestation, was similar with the women without preterm premature rupture of membrane (PPROM), but during 28 - 32 weeks of gestation the women who occured PPROM had a mean cervical length of (30.6 ± 8.1) mm, and was significantly shorter than that of women without PPROM (34.7 ± 4.6) mm. (1) CL in 28 - 32 weeks of gestation is significantly shorter than that of in the mid-gestation, but more than 90% of women has a CL ≥ 30 mm. (2) The shorter the CL is, the greater the relative risk of preterm delivery. According to different CL for clinical consulting objective relative risk could be provide. (3) The CL during 28 - 32 weeks of gestation can also predict preterm delivery, the sensitivity is obviously better than that of 22 - 24 weeks of gestation. (4) The CL during 28 - 32 weeks of gestation is valuable for predicting of PPROM.

A meta-analysis of adverse perinatal outcomes in women with asthma

Asthma is a common condition during pregnancy and may be associated with adverse perinatal outcomes. This meta-analysis sought to establish if maternal asthma is associated with an increased risk of adverse perinatal outcomes, and to determine the size of these effects. Electronic databases were searched for the following terms: (asthma or wheeze) and (pregnan* or perinat* or obstet*). Cohort studies published between 1975 and March 2009 were considered for inclusion. Studies were included if they reported at least one perinatal outcome in pregnant women with and without asthma. A total of 103 articles were identified, and of these 40 publications involving 1,637,180 subjects were included. Meta-analysis was conducted with subgroup analyses by study design and active asthma management. Maternal asthma was associated with an increased risk of low birthweight (RR 1.46, 95% CI 1.22-1.75), small for gestational age (RR 1.22, 95% CI 1.14-1.31), preterm delivery (RR 1.41, 95% CI 1.22-1.61) and pre-eclampsia (RR 1.54, 95% CI 1.32-1.81). The relative risk of preterm delivery and preterm labour were reduced to non-significant levels by active asthma management (RR 1.07, 95% CI 0.91-1.26 for preterm delivery; RR 0.96, 95% CI 0.73-1.26 for preterm labour). Pregnant women with asthma are at increased risk of perinatal complications, including pre-eclampsia and outcomes that affect the baby's size and timing of birth. Active asthma management with a view to reducing the exacerbation rate may be clinically useful in reducing the risk of perinatal complications, particularly preterm delivery.

Obstetric management of women after treatment for CIN

Preterm delivery is a major cause of neonatal morbidity and mortality that is increasing in incidence, and a major economic burden. The cost of preterm birth in England and Wales has recently been estimated at £2.9 billion a year. There is increasing evidence that excisional procedures for treatment of cervical intraepithelial neoplasia (CIN) are associated with preterm delivery and subsequent perinatal mortality. The two original articles in this issue add to the existing data and highlight the problem of obstetric management in pregnancies subsequent to excisional cervical surgery. The small but detailed study by Van de Vijver et al., on women in Belgium found that conisation of the cervix was associated with a seven times higher relative risk of preterm birth before 37 weeks. Because of its small sample size, it did not have enough power to detect a statistically significant increased risk of more serious preterm delivery, before 34 weeks. However, although delivery between 34 and 37 weeks is rarely associated with significant sequelae, the study does add weight to the findings of a recent meta-analysis that found a significant association between excisional cervical surgery and preterm birth and consequent perinatal mortality. A larger study also reported in this issue by Ortoft et al., from Denmark also supports the meta-analysis by finding a three-fold increased risk of preterm delivery before 37 weeks after one cervical conisation and a ten-fold increased risk after two conisations. These Danish data add evidence to the concept that the more cervix that is removed the worse the risk of preterm labour. Importantly, they report similarly increased risks for severe preterm delivery (before 28 weeks of gestation) and perinatal mortality. A potential problem with the reported association between cervical surgery for CIN and preterm birth is that of confounding factors as both preterm birth and CIN are known to be more prevalent in smokers and women of poor social economic class. However, Ortoft et al., accounted for these confounding factors in their regression analysis and compared pregnancy outcomes in the same women before and after cervical surgery and still found an increased risk of preterm birth. Consequently, both studies in this issue support the concept that it is excisional cervical treatment (as opposed to ablation) that is associated with preterm labour and delivery. The mechanism by which this association occurs is not yet clarified. Ascending infection, from the vagina into the fetal–placental unit is commonly seen and presumed to be causative in preterm labour. The cervix is thought to be an important physical and immunological barrier to ascending infection, hence any weakening of the cervical barrier could increase the risk of infection and preterm labour and delivery. The question that arises is how should obstetricians manage women who have had excisional cervical treatment for CIN in any subsequent pregnancy? The twoto ten-fold increased relative risk of preterm delivery in these women is very similar in magnitude to that of women with a past history of previous preterm birth. In current UK obstetric practice, women with a past history of preterm birth are treated as high-risk patients and given a package of care that can include warning of the risk of recurrence, referral for serial transvaginal cervical scanning and/or fetal fibronectin screening, and preventative treatments such as cervical cerclage, progesterone, bed rest and antenatal corticosteroid therapy. The problem with this screen-andtreat approach is that it has not been shown to improve pregnancy outcome, and is therefore probably not cost effective; further research in this area has been recommended. Warning women of an increased risk of preterm birth may increase their anxiety but also increase the likelihood that they seek medical help should symptoms of preterm labour occur. A short cervical length, as detected by transvaginal ultrasound scan in second-trimester, is known to be a good predictor of preterm birth,

Treatment for cervical intraepithelial neoplasia and subsequent IVF deliveries

The aim was to study whether the treatment of cervical intraepithelial neoplasia (CIN) is associated with a subsequent increase in the use of IVF to achieve deliveries and whether women with cervical treatment and IVF have increased rates of preterm delivery. This was a register-based retrospective cohort (n = 822 183 deliveries) study from Finland whose main outcome measures were the rates of IVF and preterm deliveries in different CIN treatment groups. Of all deliveries in Finland, 1.5% (12 240) resulted from IVF treatment. This proportion was 1.6% for women who had undergone any cervical procedure [n = 150, risk ratio (RR): 1.21, confidence interval (CI): 1.04-1.42]. The risk for IVF was not increased after cervical conization, whether by loop or laser (1.6%), or ablation (1.8%). An increased number of IVF deliveries (2.7%) was observed following other excisional treatments, even when adjusted for year of delivery (RR: 1.83, CI: 1.16-2.89) or parity (RR: 1.95, CI: 1.25-3.04). Although women who had undergone any cervical procedure and IVF appeared to have an increased relative risk for preterm delivery (3.42-fold, CI: 2.18-5.37) when compared with women with neither, this was explained by maternal age and parity. The proportion of IVF deliveries was not increased after cervical conization or ablation. This is reassuring for young women who undergo such treatments.

Familial Patterns of Preterm Delivery: Maternal and Fetal Contributions

Women who deliver preterm (<37 completed weeks' gestation) are at high risk for recurrence. This has prompted exploration of candidate genes (both maternal and fetal) associated with preterm delivery. Epidemiologists can use recurrence patterns of preterm delivery across generations to assess the relative contributions of maternal and fetal genes. The authors used data from the Medical Birth Registry of Norway (1967-2004) to identify 191,282 mothers and 127,830 fathers who subsequently had at least one singleton offspring. The authors stratified parents according to whether or not they had been born preterm and calculated the risk of preterm delivery among their firstborn. Mothers born preterm had a relative risk for preterm delivery of 1.54 (95% confidence interval (CI): 1.42, 1.67). This association was weaker for fathers born preterm (relative risk (RR) = 1.12, 95% CI: 1.01, 1.25). Among early preterm births (<35 weeks), the effect became stronger for mothers (RR = 1.85, 95% CI: 1.52, 2.27) and weaker for fathers (RR = 1.06, 95% CI: 0.77, 1.44). These data suggest that paternal genes have little, if any, effect on preterm delivery risk. This argues against major contributions of fetal genes inherited from either parent. The increased risk of preterm delivery among mothers born preterm is consistent with heritable maternal phenotypes that confer a propensity to deliver preterm.

Pregnancy outcome in women before and after cervical conisation: population based cohort study

Objectives To examine the consequences of cervical conisation in terms of adverse outcome in subsequent pregnancies.Design Population based cohort study.Data sources Data on cervical conisation derived from the Cancer Registry...

Bacterial Infection Promotes DNA Hypermethylation

Maternal oral infection, caused by bacteria such as C. rectus or P. gingivalis, has been implicated as a potential source of placental and fetal infection and inflammatory challenge, which increases the relative risk for pre-term delivery and growth restriction. Intra-uterine growth restriction has also been reported in various animal models infected with oral organisms. Analyzing placental tissues of infected growth-restricted mice, we found down-regulation of the imprinted Igf2 gene. Epigenetic modification of imprinted genes via changes in DNA methylation plays a critical role in fetal growth and development programming. Here, we assessed whether C. rectus infection mediates changes in the murine placenta Igf2 methylation patterns. We found that infection induced hypermethylation in the promoter region-P0 of the Igf2 gene. This novel finding, correlating infection with epigenetic alterations, provides a mechanism linking environmental signals to placental phenotype, with consequences for development.