The effect of labour induction on the risk of caesarean delivery: using propensity scores to control confounding by indication.

OBJECTIVE: To use propensity score methods to control for confounding by indication in the association between labour induction and caesarean delivery. DESIGN: Cross-sectional analysis of administrative hospital discharge data supplemented by medical record information. SETTING: Fourteen US member hospitals of the National Perinatal Information Center. SAMPLE: A cohort of 166 559 singleton liveborn deliveries in the period 2007-2012. METHODS: We used propensity scores (PSs) to balance 83 covariates between induced and non-induced women, and compared estimates with traditional covariate adjustment. We estimated PSs for labour induction versus expectant management of pregnancy each week from 34 to 42 weeks of gestation. We estimated risk ratios (RRs) for the association between labour induction and primary caesarean delivery from models with no adjustment, traditional adjustment of five covariates, matched PS, and adjustment for continuous PS. MAIN OUTCOME MEASURE: Caesarean delivery in current or subsequent week of gestation. RESULTS: In crude models labour induction increased the risk of caesarean delivery in all weeks (RR 1.06-1.52), excepting 39 weeks of gestation (RR 0.89). After matching on PS, the analysis showed a significantly decreased risk of caesarean delivery with labour induction during weeks 35-39 (RR 0.77-0.92), and a significantly elevated risk at weeks 40 (RR 1.22) and 41 (RR 1.39). Traditional covariate and PS adjustment resulted in RRs between those from crude and PS-matched models. CONCLUSIONS: There is evidence of considerable confounding by indication in the association of labour induction and caesarean delivery, particularly for preterm deliveries. Using PS methods, we found a reduced risk of caesarean delivery with labour induction before 40 weeks of gestation, and an elevated risk for weeks 40-42. TWEETABLE ABSTRACT: With confounding adjustment, labour induction does not increase the risk of caesarean at 34-39 weeks of gestation.

Effects of dalfampridine on multi-dimensional aspects of gait and dexterity in multiple sclerosis among timed walk responders and non-responders.

BACKGROUND: Dalfampridine extended release 10mg tablets (D-ER) have demonstrated improvement in walking for ambulatory persons with multiple sclerosis (pwMS), termed "responders." OBJECTIVE: This study examined the extent additional aspects of gait and dexterity change for patients prescribed D-ER. METHODS: Over 14-weeks, walking endurance, dynamic gait, self-report walking ability and fine and gross dexterity were examined in pwMS prescribed D-ER as a part of routine clinical care. RESULTS: The final results (n=39) validate that a subset of pwMS improve walking speed (Time 25-Foot Walk Test, p<0.0001). Significant improvements in gait and dexterity were observed even among participants who did not improve walking speed. Improvements were evident in gait and dexterity domains including Six Minute Walk Test, p=0.007, Six-Spot Step Test, p<0.0001, Multiple Sclerosis Walking Scale-12, p<0.0001, Nine Hole Peg Test, p<0.0001 dominant and non-dominant sides, and Box and Blocks Test, p=0.005 and 0.002, dominant and non-dominant sides, respectively. CONCLUSIONS: These findings suggest that D-ER may be a potential treatment for gait impairments, beyond walking speed and dexterity in pwMS. Further investigation regarding D-ER response is warranted.

Preterm delivery and risk of subsequent cardiovascular morbidity and type-II diabetes in the mother.

OBJECTIVE: Preterm delivery has been shown to be associated with subsequent maternal cardiovascular morbidity. However, the impact of the severity and recurrence of preterm delivery on the risk of specific cardiovascular events and the metabolic syndrome in the mother, have not been investigated. DESIGN: National registry-based retrospective cohort study. SETTING: Women delivering in Denmark from 1978 to 2007. POPULATION: Women with a first singleton delivery (n = 782 287), and with a first and second singleton delivery (n = 536 419). METHODS: Cox proportional hazard models, with the gestational age stratified into four groups as primary exposure. We made adjustments for maternal age, year of delivery, hypertensive pregnancy disorders, fetal growth deviation, placental abruption and stillbirth. MAIN OUTCOME MEASURES: Subsequent maternal hypertension, ischaemic heart diseases, thromboembolism and type-II diabetes. RESULTS: After a first delivery at 32-36 completed weeks of gestation, the adjusted risk of subsequent type-II diabetes increased 1.89-fold (1.69-2.10) and the risk of thromboembolism increased 1.42-fold (1.24-1.62). Women having a preterm delivery in the first pregnancy and a term delivery in the second had a 1.58-fold (1.34-1.86) increased risk of type-II diabetes and a 1.18-fold (0.96-1.44) increased risk of thromboembolism. Women having two preterm deliveries had a 2.30-fold (1.71-3.10) increased risk of type-II diabetes and a 1.80-fold (1.29-2.50) increased risk of thromboembolism. CONCLUSIONS: Preterm delivery is independent of other pregnancy complications associated with subsequent maternal overt type-II diabetes and thromboembolism. The recurrence of preterm delivery will augment these risks.

Genetic influences on smoking cessation and relapse in pregnant women.

Cigarette smoking during pregnancy continues to be a significant public health concern. Maternal smoking during pregnancy has been associated with low birth weight (<2500 g), fetal growth restriction, placental problems, pre-term delivery and spontaneous abortion. Mothers who smoke during pregnancy are twice as likely to give birth to low birth weight infants, and smoking during pregnancy is estimated to be responsible for 20-30% of all low birth weight infants. Smoking during pregnancy not only affects placental function, thus causing obstetrical complications, but nicotine also crosses the placenta and acts as a neuroteratogen. This in turn, elevates the risk of cognitive and auditory processing deficits, and has also been found to be negatively associated with long-term consequences on offspring behaviour. In addition, smoking has negative long-term health consequences for both mother and child, including respiratory conditions, cancer and cardiovascular problems. This review provides insight into the genetic influences on smoking behaviour in pregnant women. In particular, the roles of genes in the neurotransmitter pathways are highlighted. It also emphasises the need for further research in this area, and provides rationale for the importance of focusing on pregnant women who are highly motivated to quit when researching smoking behaviours in women.

The influence of air conditioning, humidity, temperature and other household characteristics on mite allergen concentrations in the northeastern United States.

BACKGROUND: Information about the influence of housing and occupant characteristics on mite allergen concentrations is crucial to determine which methods could be used to decrease exposure of susceptible subjects. OBJECTIVES: To identify housing and occupant characteristics that are associated with mite allergen concentrations in house dust collected from living rooms and mattresses. METHODS: We collected dust samples from 750 homes in the northeastern US. The influence of various characteristics on concentrations of mite allergens (Der p 1 and Der f 1) was studied using multiple linear regression analysis. RESULTS: Some characteristics, like absence of air conditioners, the presence of mold or mildew, and a lower temperature were consistently associated with higher concentrations of both mite allergens in dust from all sampling locations. However, none of these factors changed Der p 1 or Der f 1 concentrations by more than a factor of 2. People of white ethnic background had roughly two times higher mite allergen concentrations, while family income, family size, and education level only marginally influenced mite allergen concentrations. CONCLUSIONS: Various housing characteristics have some influence on mite allergen concentrations, and could possibly be used to decrease exposure of susceptible subjects. However, only a limited percentage of the variation in mite allergen concentrations was explained by these characteristics.

Risk factors for asthma prevalence among urban and nonurban African American children.

Urban residence is a risk factor for asthma. We examined multiple risk factors simultaneously among African American children. We interviewed 2409 African American mothers of newborns who had at least 1 child at home under 18 years of age. Sixteen percent reported at least 1 child with physician-diagnosed asthma. Significantly associated with an asthmatic child were maternal asthma and allergies, maternal cigarette smoking, a humidifying device, and a gas range or oven in the home. Urban residence was related to asthma but became nonsignificant once other factors were controlled for. Asthma associated with urban residence may be explained by identifiable factors.

Model for the analysis of binary time series of respiratory symptoms.

Environmental epidemiologic research on respiratory symptoms presents unique types of data, typically requiring simultaneous analysis of both time- and person-varying factors. In this paper, the authors propose a new, simple model that incorporates such factors and controls for each person's prior history of symptoms. The Yale Mother and Infant Health Study was undertaken to investigate the effects of ambient pollutant concentrations, meteorologic changes, and demographic variables on daily respiratory symptoms in both mothers and infants. This analysis was restricted to 673 mothers followed in southwestern Virginia from June 10 to August 31, 1995. Of the person-varying factors, husband's level of education, nested within marital status, and having pets in the home were related to an increased likelihood of new episodes; however, neither was related to duration of symptoms. Interestingly, women who were unmarried were least likely to have new episodes of respiratory symptoms, while those with the most highly educated spouses were most likely to have new episodes. Having pets in the home increased the likelihood of a new episode. Having a history of allergies and having children in day care were found to be related to the symptom of a runny or stuffy nose, in terms of both incidence and duration. The level of coarse particles was related to the incidence of new episodes of runny or stuffy nose, and a higher level prolonged the duration of symptoms. Sulfate level was not related to the incidence of new episodes but was associated with the duration of the episodes.

Abortion and its effect on risk of preeclampsia and transient hypertension.

We examined the effect of abortion type, number, and gestational age on the risk of preeclampsia and transient hypertension among women who received prenatal care from 13 obstetric practices in southern Connecticut between April 1988 and December 1991 (N = 2,739). Subjects were interviewed before 16 weeks' gestation regarding reproductive history and pregnancy-related risk factors. We estimated the risk of preeclampsia (N = 44) and transient hypertension (N = 172) among nulliparous women who had had one or more abortions, with nulliparous women with no abortion as the referent group. Similar effects were seen for one spontaneous or induced abortion, when analyzed separately. A single prior abortion was associated with a decreased risk of preeclampsia [odds ratio (OR) = 0.35; 95% exact confidence interval (CI) = 0.09-1.01]. One abortion had only a small association with risk of transient hypertension (OR = 1.09, 95% exact CI = 0.68-1.72); however, a history of two or more abortions was associated with a decreased risk (OR = 0.42, 95% exact CI = 0.16-0.94). Among nulliparous women with a history of one abortion, a decreased risk of both hypertensive disorders was observed among women whose aborted pregnancy ended at > or =3 months gestation. These findings suggest that a history of abortion in nulliparous women is a protective factor against the risk of preeclampsia in the subsequent pregnancy.

Healthy women's PEF variations with ambient summer concentrations of PM10, PM2.5, SO42-, H+, and O3.

The relationship between ambient air pollution and daily change in peak expiratory flow (PEF) was studied in a sample of 473 nonsmoking women (age 19 to 43 yr) in Virginia over summers 1995- 1996. Daily 24-h averages of particulate matter (PM2.5 and PM10), fine particulate sulfate (SO42-) and strong acid (H+), hourly ozone (O3), and select meteorologic variables (e.g., temperature) were collected at a regional outdoor monitoring site. Subjects took PEF measurements twice daily for a 2-wk period using a standard MiniWright peak flow meter. Concurrent measures for summer periods of 24-h PM2.5 (micrograms/m3) ranged from 3.5 to 59.7; H+ (nmol/m3) from 0 to 250; maximal daily 8-h average O3 (ppb) from 17.0 to 87.6. Morning PEF decrements were significantly associated with H+ and PM2. 5. An increase of 50 etamol/m3 of H+ and 10 micrograms/m3 of PM2.5 related to decreases of 0.89 (95% CI = 0.21 to 1.57) and 0.73 (95% CI = 0.07 to 1.38) L/min in morning PEF, respectively. Ozone was the only exposure related to evening PEF with 5-d cumulative lag exposure showing the greatest effect; 7.65 L/ min (95% CI = 2.25 to 13.0) decrease per 30 ppb O3 increase. Separate physiologic effects were observed for summer ambient concentrations of two different pollutants (PEF decrements related to PM2.5 in morning and O3 in evening) at concentrations below the new U.S. EPA 24-h ambient air quality standard for PM2.5 and 8-h standard for O3.

Correlates of residential wiring code used in studies of health effects of residential electromagnetic fields.

The home wiring code is the most widely used metric for studies of residential electromagnetic field (EMF) exposure and health effects. Despite the fact that wiring code often shows stronger correlations with disease outcome than more direct EMF home assessments, little is known about potential confounders of the wiring code association. In a study carried out in southern Connecticut in 1988-1991, the authors used strict and widely used criteria to assess the wiring codes of 3,259 homes in which respondents lived. They also collected other home characteristics from the tax assessor's office, estimated traffic density around the home from state data, and interviewed each subject (2,967 mothers of reproductive age) for personal characteristics. Women who lived in very high current configuration wiring coded homes were more likely to be in manual jobs and their homes were older (built before 1949, odds ratio (OR) = 73.24, 95% confidence interval (CI) 29.53-181.65) and had lower assessed value and higher traffic densities (highest density quartile, OR = 3.99, 95% CI 1.17-13.62). Because some of these variables have themselves been associated with health outcomes, the possibility of confounding of the wiring code associations must be rigorously evaluated in future EMF research.