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Regression problems in which predictors are measured with error have been studied by statisticians and researchers for many years. Measurement error in predictors creates biases in estimated regression coefficients, and hence models that address this are extremely important. These models are especially important in perinatal research since errors in gestational age can have serious effects. / The presence of measurement error in gestational age can lead to poor estimation of fetal growth and risk of mortality and morbidity, and can compromise statistical analyses [32, 39]. Since various obstetric choices are made based on birth weight distributions by gestational age, it is important to obtain plausible birthweight-gestational-age combinations. / Berry et al. [3] propose a Bayesian approach to modeling a flexible regression function in the presence of measurement error, where the regression function is modeled using smoothing splines and regression P-splines. These methods are applied to population-based data from U.S. birth certificates, which results in realistic birthweight-gestational age combinations.

Diss. (sammanfattning) Uppsala : Univ., 2003. / Härtill 5 uppsatser.

A research report submitted to the Faculty of Health Sciences in partial fulfilment of the requirements for the degree of Master in Family Medicine Department of Family Medicine University of the Witwatersrand, Johannesburg, 2017. / Background Research has shown that women who do not obtain adequate prenatal care significantly reduce their chances of a favourable pregnancy outcome. Despite antenatal care services being provided free of charge in South Africa, only 53.9% of women attend antenatal care before the gestational age of 20 weeks or less as recommended by the World Health Organisation (WHO) and National Department of Health (NDOH).The interventions aimed at reducing unfavourable pregnancy outcomes are most effective during prenatal care, it is crucial to identify factors that prevent pregnant mothers from presenting early. It is believed that the findings of this study will give us an insight into the rate of early ANC attendance and will also be useful to policymakers and facility managers, especially at the Primary Health Care (PHC) level, in optimising patient care and improving healthcare services. Aims and objectives Therefore, the objectives of this study were: 1 To establish the gestational age at which pregnant women present to first antenatal visit in Maquassi Hills sub district. 2 To describe participants’ socio-demographic profile, health status and obstetrical characteristics 3 To explore knowledge and attitudes that affect timing of first presentation. 4 To determine any association between first ANC presentation and socio-demographic, obstetric factors, knowledge and attitudes towards ANC. 5 To determine predictors for first antenatal attendance. Method This was a cross-sectional study conducted in four publicly funded primary health facilities in the Maquassi Hills sub district, between August and October 2015. A total of 127 participants were directly interviewed using a structured questionnaire to obtain information about their socio-economic characteristics, ANC and services rendered. Most of the information required for the study was obtained from the Maternity booklet. This included demographic data, obstetric history, medical history, and gestational age. Data analysis was done using Microsoft Excel 2014. A chi-square test was used to determine associations between time of the first presentation and each variable; and a multiple variable regression was used to determine predictors of early attendance. Results Most participants interviewed were: Tswana speaking (72.4%), with a mean age of 26.5 years (SD = 5.9), had a high school education (84.6%) and were mostly single (70.6%). This study showed that 68.9% of the respondents presented to their first antenatal booking within the recommended time of less than 20 weeks. The average period of presentation was 16.3 weeks (SD = 6.0). No statistically significant association was found between socio- demographic, obstetrical characteristics and the timing of the first antenatal visit. All the participants knew that the right time to book an appointment was before 20 weeks as the best perceived time for initiation of ANC. However, there was a statistically significant difference in the best perceived time between those who booked early (2 months [1.99 months (SD =1.145)]) compared with those who booked later (3 months [2.83months (SD = 1.595)]) (p = 0.006). The multivariate analysis showed that participants who perceived three months as the best time for booking were 1.5 times more likely to book later (OR= 1.589, 95% CI 1.227-2.059) compared with those who perceived that the best time was at two months. The most frequent reason given for booking early was to confirm pregnancy (64.0%) and (31.1%) initiated ANC because they were ill. Long waiting times and staff attitude were reported by participants (91.3%) and (5%) respectively as barriers to early ANC visit. Conclusion The findings of this study show that most participants booked antenatal care timely and all participants knew the right time to initiate ANC. However, there is incongruity between knowledge and practice for the 30% who presented late. This could be attributed to the long waiting time and staff attitude mentioned by some of the participants. There is a need therefore to address the demotivating factors such as long waiting time, and staff attitude in order to promote early ANC booking/attendance. / LG2018

Trisomies 18 and 13 are rare genetic conditions (occurring around 1 in 6,000 and 10,000 newborns respectively) which are caused by an extra copy of either chromosome 18 or 13, similar to trisomy 21 (Down syndrome). The only known risk factor for these syndromes is maternal age, however previous cluster analyses have linked trisomy risk to a number of alternate factors, including radiation exposure and infection. Cases of trisomies 18 and 13 from the National Down Syndrome Cytogenetic Register (NDSCR) were scanned for temporal and spatial clusters throughout England and Wales between 2004 and 2010. No temporal clusters were detected, however there were multiple significant spatial clusters detected for both trisomies in London. These clusters were likely caused by advanced maternal age in the region, and it is also possible that regional differences in gestational age at the time of prenatal screening could have contributed to these clusters. In order to account for maternal age and gestational age at diagnosis, a novel method was developed in R to directly weight cases based on these factors. Applying weights to cases directly allowed both factors to be simultaneously accounted for by multiplying weights together. This method was evaluated using synthetic data and compared with an alternate method in the widely used program SaTScan. Both programs returned similar results when the weighting method was mild, but when extreme weights were applied at random significant clusters were observed in SaTScan but not in R. The NDSCR data was weighted and then rescanned for spatial clusters in both programs. No evidence of clustering was detected using the novel method, while SaTScan returned multiple highly significant clusters. These findings, combined with those obtained using the synthetic data, indicate that the novel method produces more reliable results than SaTScan when extreme adjustment is applied.

A Dissertation that is being submitted for an MMed in Obstetrics and Gynaecology in partial fulfilment of the FCOG (SA) Part II 07 April 2015 / Objectives: The main objective of this study was to characterise women who presented at Chris Hani Baragwanath Academic Hospital (CHBAH) between 12 and 20 weeks for termination of pregnancy (TOP). Secondary objectives were to determine time to abortion, compare sonar gestational age to gestational age by dates and reasons for late presentation. Method: This was a prospective cohort study of women over the age of 18 who were referred to CHBAH for second trimester TOP between August 2012 and May 2013. The exclusion criteria were pregnancies more advanced than 20 weeks gestation. Data was collected from the medical file and by interview. Demographics and reasons to terminate were extracted from the files. Outcome variables included bleeding, pain, and time to abortion. Results: One hundred and ninety one women (91.39%) aborted. The median age of women was 25.00 (IQR=21.00-31.00), range (18-43). Women older than 25 years were 33% less likely to abort than women less than 25 years of age. Ninety nine women (47.14%) bled severely. One woman had a uterine perforation following evacuation of the uterus. The median gestational age by sonar was14.71 (IQR=13.86-16.14), range (13.00-20.00). The median gestational age by dates was13.57 (IQR=12.29-15.00), range (4.14-26.28). One hundred and thirty five women (63.98%) had an MVA for RPOC using analgesia following medical induction. Two women (0.95%) needed hysterotomy following failed TOP. The median time to abortion was 11.50(IQR=8.67-17.92), range (3.50-69.33) and incidence rate of 0.5 per hour or 1 per 2hours. Conclusion: The majority of women (91%) aborted within 72 hours following medical induction with less complication rate and short induction to abortion time. This affirm misoprostol efficacy as the suitable drug for conducting second trimester medical TOP. / MT2016

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M.S.)--University of Delaware, 2006. / Principal faculty advisor: Leta P. Aljadir, Dept. of Health, Nutrition and Exercise. Includes bibliographical references.

BACKGROUND: Over two-thirds of the United States population is considered overweight or obese. Bariatric surgery is often used when conservative weight loss measures fail. The majority of bariatric surgeries are performed on women of childbearing age. Women who become pregnant following bariatric surgery have a decreased occurrence of gestational diabetes, hypertensive disorders and macrosomia, but they also have an increased risk of small for gestational age infants (SGA), with the greatest risk of SGA infants following malabsorptive and mixed bariatric surgery procedures. STUDY: A gap in the literature exists regarding the risks of SGA and intrauterine growth restriction (IUGR) following Roux-en-Y gastric bypass (RYGB) compared to sleeve gastrectomy (SG), the two most common procedures in the United States in 2014. This study will be a multi-center retrospective cohort study that will identify the risk of IUGR following RYGB and SG. CONCLUSION: This study will improve our understanding of the effects on pregnancy following RYGB and SG. The most innovative, and hardest, part of this study will be the collection of data on as many SG women as possible. This will be the biggest hurdle because SG is a relatively new procedure, so the prevalence of pregnancy following SG is low. PUBLIC HEALTH SIGNIFICANCE: A better understanding of the effects of the most common bariatric procedural types on pregnancy is important given the prevalence of bariatric surgery among women of childbearing age. It will allow bariatric surgeons to better council their patients on a surgery type for those that may be considering pregnancy afterwards, and enable obstetricians to have a better understanding of the risks associated with their patient’s pregnancy.

Preterm delivery (PTD) is a leading cause of infant death, and surviving infants are at risk for poor health. Data from the Iowa Health in Pregnancy Study, a case-control study of maternal stress on risk of PTD and small for gestational age (SGA) deliveries were used to address three aims: 1) develop a method to correct for error in ultrasound measurement among suspected SGA infants, 2) estimate the association of occupational stress on risk of PTD, and 3) examine injury-related risk factors for PTD. Estimates of gestational age using ultrasound can be biased if the fetus is growth-restricted, yielding underestimates due to the small stature of the fetus. Multivariate linear regression modeling was used to estimate and correct for this bias among subjects with a suspected SGA infant who 1) began prenatal care in the first trimester, 2) reported a last menstrual period and 3) had an ultrasound examination between 7-21 weeks. To correct for this bias, an average of 1.5 weeks was added to the ultrasound gestational age. Following the correction, the proportion of PTD cases decreased from 29.1% to 26.5% while SGA cases increased from 23.7% to 31.3%. Using this PTD classification, occupational physical and psychosocial stressors were studied. Continuous employment over the first 20 weeks of pregnancy was associated with a 30% increased risk of PTD versus not working. Working women reporting highly repetitive tasks (aOR=1.47(1.10-1.98)) or inadequate breaks (aOR=1.67(1.03-2.73)) were at increased risk of PTD. Working women who reported high lifting in the home had double the risk of PTD. Over 5% of control subjects reported an injury during pregnancy, and injured women tended to be younger, unmarried, less educated, and have lower incomes. Women with injuries involving >1 body part (aOR=2.50(1.14-5.49)), or injuries to the abdomen and other regions of the body (OR=1.75(0.59-5.23)) were at increased risk of PTD. Our findings provide a statistical approach to assess and correct for underestimates of ultrasound gestational age in case-control studies of PTD and SGA. The analyses of occupational exposures and injury during pregnancy indicate the need for studies that incorporate specific and standardized assessments of these exposures.