Investigating the Shape and Strength of the Relationship Between Maternal Weight Gain and Gestational Age at Delivery in Twin and Singleton Pregnancies.

Both inadequate and excessive maternal weight gain are correlated with preterm delivery in singleton pregnancies, yet this relationship has not been adequately studied in twins. We investigated the relationship between time-varying maternal weight gain and gestational age at delivery in twin pregnancies and compared it with that in singletons delivered in the same study population. We used serial weight measurements abstracted from charts for twin and singleton pregnancies delivered during 1998-2013 in Pittsburgh, Pennsylvania. Our exposure was time-varying weight gain z score, calculated using gestational age-standardized and prepregnancy body mass index-stratified twin- and singleton-specific charts, and our outcome was gestational age at delivery. Our analyses used a flexible extension of the Cox proportional hazards model that allowed for nonlinear and time-dependent effects. We found a U-shaped relationship between weight gain z score and gestational age at delivery among twin pregnancies (lowest hazard of delivery observed at z score = 1.2), which we attributed to increased hazard of early preterm spontaneous delivery among pregnancies with low weight gain and increased hazard of late preterm delivery without labor among pregnancies with high weight gain. Our findings may be useful for updating provisional guidelines for maternal weight gain in twin pregnancies.

Severe Maternal Morbidity in Twins.

OBJECTIVE: While twin gestations are at increased risk of severe maternal morbidity (SMM), there is limited information about timing and causes of SMM in twins. Furthermore, existing data rely on screening definitions of SMM because a gold standard approach requires chart review. We sought to determine the timing and cause of SMM in twins using a gold standard definition outlined by the American College of Obstetricians and Gynecologists (ACOG). STUDY DESIGN: We used a perinatal database to identify all twin deliveries from 1998 to 2013 at a single academic medical center (n = 2,367). Deliveries were classified as screen positive for SMM if they met any of the following criteria: (1) one of the Centers for Disease Control and Prevention (CDC) International Classification of Diseases Ninth Revision diagnosis and procedure codes for SMM; (2) a prolonged postpartum length of stay (>3 standard deviations beyond mean length of stay by mode of delivery); or (3) maternal intensive care unit admission. We identified true cases of SMM through medical record review of all screen-positive deliveries using the definition of SMM outlined in the ACOG Obstetric Care Consensus. We also determined cause and timing of SMM. RESULTS: A total of 165 (7%) of twin deliveries screened positive for SMM. After chart review of all screen-positive cases, 2.4% (n = 56) were classified as a true case of SMM using the ACOG definition for a positive predictive value of 34%. The majority of SMM occurred postpartum (65%). Hemorrhage was the most common cause of SMM, followed by hypertensive and pulmonary etiologies. CONCLUSION: Commonly used approaches to screen for SMM perform poorly in twins. This has important implications for quality initiatives and epidemiologic studies that rely on screening definitions of maternal morbidity. Our study demonstrates that the immediate postpartum period is a critical time for maternal health among women with twin pregnancies. KEY POINTS: · Screening approaches for SMM have low positive predictive value in twins.. · Hemorrhage, hypertensive, and pulmonary complications were the most common morbidities.. · SMM was most common postpartum..

Early Gestational Weight Gain and the Risk of Preeclampsia in Dichorionic Twin Pregnancies.

OBJECTIVE: The purpose of our study was to evaluate the body mass index (BMI)-specific association between early gestational weight gain (GWG) in dichorionic twin pregnancies and the risk of preeclampsia. STUDY DESIGN: We conducted a retrospective cohort study of all dichorionic twin pregnancies from 1998 to 2013. Data were obtained from a perinatal database and chart abstraction. Prepregnancy BMI was categorized as normal (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2), and obese (≥30 kg/m2). Early GWG was defined as the last measured weight from 160/7 to 196/7weeks' gestation minus prepregnancy weight. GWG was standardized for gestational duration using BMI-specific z-score charts for dichorionic pregnancies. Preeclampsia was diagnosed using American College of Obstetricians and Gynecologists criteria and identified with International Classification of Diseases-9 coding. Early GWG z-score was modeled as a three-level categorical variable (≤ - 1 standard deviation [SD], 0, 3 +1 SD), where -1 to +1 was the referent group. We estimated risk differences and 95% confidence intervals (CIs) via marginal standardization. RESULTS: We included 1,693 dichorionic twin pregnancies in the cohort. In adjusted analysis, the incidence of preeclampsia increased with increasing early GWG among women with normal BMI. Women with normal BMI and a GWG z-score < - 1 (equivalent to 2.6 kg by 20 weeks) had 2.5 fewer cases of preeclampsia per 100 births (95% CI: -4.7 to - 0.3) compared with the referent; those with GWG z-score > +1 (equivalent to gaining 9.8 kg by 20 weeks) had 2.8 more cases of preeclampsia per 100 (95 % CI: 0.1-5.5) compared with the referent. In adjusted analyses, early GWG had minimal impact on the risk of preeclampsia in women with overweight or obesity. CONCLUSION: GWG of 2.6 kg or less by 20 weeks was associated with a decreased risk of preeclampsia among women pregnant with dichorionic twins and normal prepregnancy BMI. Current GWG guidelines focus on optimizing fetal weight and gestational length. Our findings demonstrate the importance of considering other outcomes when making GWG recommendations for twin pregnancy. KEY POINTS: · Early GWG decreased with increasing BMI category.. · Among women with normal weight, as early GWG increased so did the risk of preeclampsia.. · There was no association between early GWG and preeclampsia among women with overweight or obesity..

Adverse Cardiovascular Events Following Severe Maternal Morbidity.

Severe maternal morbidity (SMM) affects 50,000 women annually in the United States, but its consequences are not well understood. We aimed to estimate the association between SMM and risk of adverse cardiovascular events during the 2 years postpartum. We analyzed 137,140 deliveries covered by the Pennsylvania Medicaid program (2016-2018), weighted with inverse probability of censoring weights to account for nonrandom loss to follow-up. SMM was defined as any diagnosis on the Centers for Disease Control and Prevention list of SMM diagnoses and procedures and/or intensive care unit admission occurring at any point from conception through 42 days postdelivery. Outcomes included heart failure, ischemic heart disease, and stroke/transient ischemic attack up to 2 years postpartum. We used marginal standardization to estimate average treatment effects. We found that SMM was associated with increased risk of each adverse cardiovascular event across the follow-up period. Per 1,000 deliveries, relative to no SMM, SMM was associated with 12.1 (95% confidence interval (CI): 6.2, 18.0) excess cases of heart failure, 6.4 (95% CI: 1.7, 11.2) excess cases of ischemic heart disease, and 8.2 (95% CI: 3.2, 13.1) excess cases of stroke/transient ischemic attack at 26 months of follow-up. These results suggest that SMM identifies a group of women who are at high risk of adverse cardiovascular events after delivery. Women who survive SMM may benefit from more comprehensive postpartum care linked to well-woman care.

Use of a Doubly Robust Machine-Learning-Based Approach to Evaluate Body Mass Index as a Modifier of the Association Between Fruit and Vegetable Intake and Preeclampsia.

The Dietary Guidelines for Americans rely on summaries of the effect of dietary pattern on disease risk, independent of other population characteristics. We explored the modifying effect of prepregnancy body mass index (BMI; weight (kg)/height (m)2) on the relationship between fruit and vegetable density (cup-equivalents/1,000 kcal) and preeclampsia using data from a pregnancy cohort study conducted at 8 US medical centers (n = 9,412; 2010-2013). Usual daily periconceptional intake of total fruits and total vegetables was estimated from a food frequency questionnaire. We quantified the effects of diets with a high density of fruits (≥1.2 cups/1,000 kcal/day vs. <1.2 cups/1,000 kcal/day) and vegetables (≥1.3 cups/1,000 kcal/day vs. <1.3 cups/1,000 kcal/day) on preeclampsia risk, conditional on BMI, using a doubly robust estimator implemented in 2 stages. We found that the protective association of higher fruit density declined approximately linearly from a BMI of 20 to a BMI of 32, by 0.25 cases per 100 women per each BMI unit, and then flattened. The protective association of higher vegetable density strengthened in a linear fashion, by 0.3 cases per 100 women for every unit increase in BMI, up to a BMI of 30, where it plateaued. Dietary patterns with a high periconceptional density of fruits and vegetables appear more protective against preeclampsia for women with higher BMI than for leaner women.

Can Ensemble Machine Learning Improve the Accuracy of Severe Maternal Morbidity Screening in a Perinatal Database?

BACKGROUND: Severe maternal morbidity (SMM) is an important maternal health indicator, but existing tools to identify SMM have substantial limitations. Our objective was to retrospectively identify true SMM status using ensemble machine learning in a hospital database and to compare machine learning algorithm performance with existing tools for SMM identification. METHODS: We screened all deliveries occurring at Magee-Womens Hospital, Pittsburgh, PA (2010-2011 and 2013-2017) using the Centers for Disease Control and Prevention list of diagnoses and procedures for SMM, intensive care unit admission, and/or prolonged postpartum length of stay. We performed a detailed medical record review to confirm case status. We trained ensemble machine learning (SuperLearner) algorithms, which "stack" predictions from multiple algorithms to obtain optimal predictions, on 171 SMM cases and 506 non-cases from 2010 to 2011, then evaluated the performance of these algorithms on 160 SMM cases and 337 non-cases from 2013 to 2017. RESULTS: Some SuperLearner algorithms performed better than existing screening criteria in terms of positive predictive value (0.77 vs. 0.64, respectively) and balanced accuracy (0.99 vs. 0.86, respectively). However, they did not perform as well as the screening criteria in terms of true-positive detection rate (0.008 vs. 0.32, respectively) and performed similarly in terms of negative predictive value. The most important predictor variables were intensive care unit admission and prolonged postpartum length of stay. CONCLUSIONS: Ensemble machine learning did not globally improve the ascertainment of true SMM cases. Our results suggest that accurate identification of SMM likely will remain a challenge in the absence of a universal definition of SMM or national obstetric surveillance systems.

Gestational Diabetes in Twin Versus Singleton Pregnancies With Normal Weight or Overweight Pre-Pregnancy Body Mass Index: The Mediating Role of Mid-Pregnancy Weight Gain.

BACKGROUND: Gestational diabetes might be more common in twin versus singleton pregnancies, yet the reasons for this are unclear. We evaluated the extent to which this relationship is explained by higher mid-pregnancy weight gain within normal weight and overweight pre-pregnancy body mass index (BMI) strata. METHODS: We analyzed serial weights and glucose screening and diagnostic data abstracted from medical charts for twin (n = 1397) and singleton (n = 3117) pregnancies with normal or overweight pre-pregnancy BMI delivered from 1998 to 2013 at Magee-Womens Hospital in Pennsylvania. We used causal mediation analyses to estimate the total effect of twin versus singleton pregnancy on gestational diabetes, as well as those mediated (natural indirect effect) and not mediated (natural and controlled direct effects) by pathways involving mid-pregnancy weight gain. RESULTS: Odds of gestational diabetes were higher among twin pregnancies [odds ratios (ORs) for total effect = 2.83 (95% CI = 1.54, 5.19) for normal weight and 2.09 (95% CI = 1.16, 3.75) for overweight pre pregnancy BMI], yet there was limited evidence that this relationship was mediated by mid-pregnancy weight gain [ORs for natural indirect effect = 1.21 (95% CI = 0.90, 1.24) for normal weight and 1.06 (95% CI = 0.92, 1.21) for overweight pre-pregnancy BMI] and more evidence of mediation via other pathways [ORs for natural direct effect = 2.34 (95% CI = 1.24, 4.40) for normal weight and 1.97 (95% CI = 1.08, 3.60) for overweight pre-pregnancy BMI]. CONCLUSIONS: While twin pregnancies with normal weight or overweight pre-pregnancy BMI experienced higher odds of gestational diabetes versus singletons, most of this effect was explained by pathways not involving mid-pregnancy weight gain.

Optimizing reproductive health management in lupus and Sjogren's syndrome.

PURPOSE OF REVIEW: People with childbearing capacity who are diagnosed with systemic lupus erythematosus (SLE) and Sjogren's syndrome (SS) have specific and important reproductive health considerations. RECENT FINDINGS: Recommendations from the European League Against Rheumatism (EULAR) and the American College of Rheumatology (ACR) provide rheumatologists and other clinicians with guidance for reproductive health management of patients with rheumatic diseases. Patient-centered reproductive health counseling can help clinicians to operationalize the EULAR and ACR guidelines and enhance patient care. SUMMARY: Disease activity monitoring, risk factor stratification, and prescription of pregnancy-compatible medications during pregnancy help to anticipate complications and enhance pregnancy outcomes in SLE and SS. Assisted reproductive technologies are also safe among people with well-controlled disease. Safe and effective contraceptive methods are available for patients with SLE and SS, and pregnancy termination appears to be safe among these patients.

Pregnancy weight gain in twin gestations and maternal and child health outcomes at 5 years.

OBJECTIVE: Current guidelines for maternal weight gain in twin pregnancy were established in the absence of evidence on its longer-term consequences for maternal and child health. We evaluated the association between weight gain in twin pregnancies and the risk of excess maternal postpartum weight increase, childhood obesity, and child cognitive ability. METHODS: We used 5-year follow-up data from 1000 twins born to 450 mothers in the Early Childhood Longitudinal Study-Birth Cohort, a nationally representative U.S. cohort of births in 2001. Pregnancy weight gain was standardized into gestational age- and prepregnancy body mass index (BMI)-specific z-scores. Excess postpartum weight increase was defined as ≥10 kg increase from prepregnancy weight. We defined child overweight/obesity as BMI ≥ 85th percentile, and low reading and math achievement as scores one standard deviation below the mean. We used survey-weighted multivariable modified Poisson models with a log link to relate gestational weight gain z-score with each outcome. RESULTS: Excess postpartum weight increase occurred in 40% of mothers. Approximately 28% of twins were affected by overweight/obesity, and 16 and 14% had low reading and low math scores. There was a positive linear relationship between pregnancy weight gain and both excess postpartum weight increase and childhood overweight/obesity. Compared with a gestational weight gain z-score 0 SD (equivalent to 20 kg at 37 weeks gestation), a weight gain z-score of +1 SD (27 kg) was associated with 6.3 (0.71, 12) cases of excess weight increase per 1000 women and 4.5 (0.81, 8.2) excess cases of child overweight/obesity per 100 twins. Gestational weight gain was not related to kindergarten academic readiness. CONCLUSIONS: The high prevalence of excess postpartum weight increase and childhood overweight/obesity within the recommended ranges of gestational weight gain for twin pregnancies suggests that these guidelines could be inadvertently contributing to longer-term maternal and child obesity.

A New Approach for Classifying Fetal Growth Restriction.

BACKGROUND: Fetal growth restriction is commonly defined using small for gestational age (SGA) birth (birthweight < 10th percentile) as a proxy, but this approach is problematic because most SGA infants are small but healthy. In this proof-of-concept study, we sought to develop a new approach for identifying fetal growth restriction at birth that combines information on multiple, imperfect measures of fetal growth restriction in a probabilistic manner. METHODS: We combined information on birthweight, placental weight, placental malperfusion lesions, maternal disease, and fetal acidemia using latent profile analysis to classify fetal growth in births at the Royal Victoria Hospital in Montreal, Canada, 2001-2009. We examined the clinical characteristics and health outcomes of infants classified as growth-restricted and nongrowth-restricted by our model, and among the subgroup of growth-restricted infants who had a birthweight ≥10th percentile (i.e., would have been missed by the conventional SGA proxy). RESULTS: Among 26,077 births, 345 (1.3%) were classified as growth-restricted by our latent profile model. Growth-restricted infants were more likely than nongrowth-restricted infants to have an Apgar score <7 (10% vs. 2%), have hypoglycemia at birth (17% vs. 3%), require neonatal intensive care unit admission (59% vs. 6%), die in the perinatal period (3.8% vs. 0.2%), and require an emergency cesarean delivery (42% vs. 15%). Risks remained elevated in growth-restricted infants who were not SGA, suggesting our model identified at-risk infants not detected using the SGA proxy. CONCLUSIONS: Latent profile analysis is a promising strategy for classifying growth restriction at birth in fetal growth restriction research.

Rating the seriousness of maternal and child health outcomes linked with pregnancy weight gain.

BACKGROUND: Current pregnancy weight gain guidelines were developed based on implicit assumptions of a small group of experts about the relative seriousness of adverse health outcomes. Therefore, they will not necessarily reflect the values of women. OBJECTIVE: To estimate the seriousness of 11 maternal and child health outcomes that have been consistently associated with pregnancy weight gain by engaging patients and health professionals. METHODS: We collected data using an online panel approach with a modified Delphi structure. We selected a purposeful sample of maternal and child health professionals (n = 84) and women who were pregnant or recently postpartum (patients) (n = 82) in the United States as panellists. We conducted three concurrent panels: professionals only, patients only, and patients and professionals. During a 3-round online modified Delphi process, participants rated the seriousness of health outcomes (Round 1), reviewed and discussed the initial results (Round 2), and revised their original ratings (Round 3). Panellists assigned seriousness ratings (0, [not serious] to 100 [most serious]) for infant death, stillbirth, preterm birth, gestational diabetes, preeclampsia, small-for-gestational-age (SGA) birth, large-for-gestational-age (LGA) birth, unplanned caesarean delivery, maternal obesity, childhood obesity, and maternal metabolic syndrome. RESULTS: Each panel individually came to a consensus on all seriousness ratings. The final median seriousness ratings combined across all panels were highest for infant death (100), stillbirth (95), preterm birth (80), and preeclampsia (80). Obesity in children, metabolic syndrome in women, obesity in women, and gestational diabetes had median seriousness ratings ranging from 55 to 65. The lowest seriousness ratings were for SGA birth, LGA birth, and unplanned caesarean delivery (30-40). CONCLUSION: Professionals and women rate some adverse outcomes as being more serious than others. These ratings can be used to establish the range of pregnancy weight gain associated with the lowest risk of a broad range of maternal and child health outcomes.

The impact of setting a pregnancy weight gain goal on total weight gain.

BACKGROUND: Expert groups recommend that women set a pregnancy weight gain goal with their care provider to optimise weight gain. OBJECTIVE: Our aim was to describe the concordance between first-trimester personal and provider pregnancy weight gain goals with the Institute of Medicine (IOM) recommendations and to determine the association between these goals and total weight gain. METHODS: We used data from 9353 women in the Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be. In the first trimester, women reported their personal pregnancy weight gain goal and their provider weight gain goal, and we categorised personal and provider weight gain goals and total weight gain according to IOM recommendations. We used log-binomial or linear regression models to relate goals to total weight gain, adjusting for confounders including race/ethnicity, maternal age, education, smoking, marital status and planned pregnancy. RESULTS: Approximately 37% of women reported no weight gain goals, while 24% had personal and provider goals, 31% had only a personal goal, and 8% had only a provider goal. Personal and provider goals were outside the recommended ranges in 12%-23% of normal-weight women, 31%-41% of overweight women and 47%-63% of women with obesity. Women with both personal and provider pregnancy weight gain goals were 6%-14% more likely than their counterparts to have a goal within IOM-recommended ranges. Having any goal or a goal within the IOM-recommended ranges was unrelated to pregnancy weight gain. Excessive weight gain occurred in approximately half of normal-weight or obese women and three-quarters of overweight women, regardless of goal setting group. CONCLUSIONS: These findings do not support the effectiveness of early-pregnancy personal or provider gestational weight gain goal setting alone in optimising weight gain. Multifaceted interventions that address a number of mediators of goal setting success may assist women in achieving weight gain consistent with their goals.

Validation of criteria to identify severe maternal morbidity.

BACKGROUND: Epidemiologic research on severe maternal morbidity often relies on a screening definition of the outcome because a gold standard approach requires medical record review. OBJECTIVE: To determine the validity of screening or identification criteria to classify cases of severe maternal morbidity using the definition of severe maternal morbidity proposed by the American College of Obstetricians and Gynecologists (ACOG). METHODS: From all singleton deliveries at Magee-Womens Hospital in Pittsburgh, Pennsylvania (2010-2011; n = 19 307), we selected all deliveries that had at least one screening or identification criteria for severe maternal morbidity (n = 349) and a random sample of deliveries with no case identification criteria (n = 349). Screen-positive deliveries were a delivery with any of the following: Centers for Disease Control and Prevention International Classification of Diseases 9th Revision diagnosis and procedure codes for the identification of severe maternal morbidity; prolonged post-partum length of stay; or maternal intensive care unit admission. We identified true cases through detailed chart review using the suggested diagnoses in the 2016 ACOG and SMFM Obstetric Care Consensus on severe maternal morbidity. We calculated the positive and negative predictive values of the screening criteria. RESULTS: Approximately 1.8% of deliveries screened positive for severe maternal morbidity. After medical record review, 166 screen-positive deliveries were true cases (48% positive predictive value), and 347 screen-negative cases were true negatives (99% negative predictive value). Two screen-negative cases were false negatives. If we applied the negative predictive value to the population, 109 true cases would be missed with these criteria. CONCLUSION: The criteria we used to identify potential cases of severe acute maternal morbidity had poor performance in our cohort. In the absence of resources to apply the gold standard outcome definition to a large population, validation data and analytic strategies that incorporate measurement error are essential to estimate the direction and magnitude of the resulting bias.

Comparison of Parametric and Nonparametric Estimators for the Association Between Incident Prepregnancy Obesity and Stillbirth in a Population-Based Cohort Study.

While prepregnancy obesity increases risk of stillbirth, few studies have evaluated the role of newly developed obesity independent of long-standing obesity. Additionally, researchers have relied almost exclusively on parametric models, which require correct specification of an unknown function for consistent estimation. We estimated the association between incident obesity and stillbirth in a cohort constructed from linked birth and death records in Pennsylvania (2003-2013). Incident obesity was defined as body mass index (weight (kg)/height (m)2) greater than or equal to 30. We used parametric G-computation, semiparametric inverse-probability weighting, and parametric/nonparametric targeted minimum loss-based estimation (TMLE) to estimate the association between incident prepregnancy obesity and stillbirth. Compared with pregnancies from women who stayed nonobese, women who became obese prior to their next pregnancy were estimated to have 2.0 (95% confidence interval (CI): 0.5, 3.5) more stillbirths per 1,000 pregnancies using parametric G-computation. However, despite well-behaved stabilized inverse probability weights, risk differences estimated from inverse-probability weighting, nonparametric TMLE, and parametric TMLE represented 6.9 (95% CI: 3.7, 10.0), 0.4 (95% CI: 0.1, 0.7), and 2.9 (95% CI: 1.5, 4.2) excess stillbirths per 1,000 pregnancies, respectively. These results, particularly those derived from nonparametric TMLE, were highly sensitive to covariates included in the propensity score models. Our results suggest that caution is warranted when using nonparametric estimators to quantify exposure effects.

"It gave me so much confidence": First-time U.S. mothers' experiences with antenatal milk expression.

Antenatal milk expression (AME) involves maternal hand-expression, collection, and storage of breast milk during pregnancy for the purposes of reducing the early formula use in breastfed infants. AME is not widely practiced in the United States, despite its growing popularity elsewhere. In this study, we examined the experiences of first-time mothers recruited from a U.S. midwife practice who engaged in AME within the context of a pilot randomized controlled trial. The AME intervention involved demonstration and practice of AME with a lactation consultant beginning at 37 weeks of gestation, reinforcement at weekly study visits until delivery, and daily home practice. Nineteen women participated in a semistructured interview at 1-2 weeks postpartum regarding their study experiences. Major themes included (1) perceived benefits and impact of AME, (b) AME implementation, and (c) use of AME milk. Women perceived multiple benefits of AME, most notably that it increased their confidence that they would be able to make milk and breastfeed successfully postpartum. Women expressed some concern that no/little milk expressed could be indicative of postpartum milk production problems. Regarding implementation, women found that the AME protocol fit well into their daily routine. There was mixed feedback regarding comfort with practicing AME in the presence of partners. Reasons for postpartum use of AME milk varied; barriers to provision included inadequate milk storage options at the birth hospital and unsupportive hospital providers/staff. With few caveats, AME appears to be an acceptable breastfeeding support intervention among a sociodemographically homogeneous group of first-time mothers in the United States.

Pregnancy Weight Gain by Gestational Age in Women with Uncomplicated Dichorionic Twin Pregnancies.

BACKGROUND: Twin pregnancies are at increased risk for adverse outcomes and are associated with greater gestational weight gain compared to singleton pregnancies. Studies that disentangle the relationship between gestational duration, weight gain and adverse outcomes are needed to inform weight gain guidelines. We created charts of the mean, standard deviation and select percentiles of maternal weight gain-for-gestational age in twin pregnancies and compared them to singleton curves. METHODS: We abstracted serial prenatal weight measurements of women delivering uncomplicated twin pregnancies at Magee-Womens Hospital (Pittsburgh, PA, 1998-2013) and merged them with the hospital's perinatal database. Hierarchical linear regression was used to express pregnancy weight gain as a smoothed function of gestational age according to pre-pregnancy BMI category. Charts of week- and day-specific values for the mean, standard deviation, and percentiles of maternal weight gain were created. RESULTS: Prenatal weight measurements (median: 11 [interquartile range: 9, 13] per woman) were available for 1109 women (573 normal weight, 287 overweight, and 249 obese). The slope of weight gain was most pronounced in normal weight women and flattened with increasing pre-pregnancy BMI (e.g. 50th percentiles of 6.8, 5.7, and 3.6 kg at 20 weeks and 19.8, 18.1, and 14.4 at 37 weeks in normal weight, overweight, and obese women, respectively). Weight gain patterns in twins diverged from singletons after 17-19 weeks. CONCLUSIONS: Our charts provide a tool for the classification of maternal weight gain in twin pregnancies. Future work is needed to identify the range of weight gain associated with optimal pregnancy health outcomes.

Delayed Lactogenesis II and potential utility of antenatal milk expression in women developing late-onset preeclampsia: a case series.

BACKGROUND: Preeclampsia is a multi-system, hypertensive disorder of pregnancy that increases a woman's risk of later-life cardiovascular disease. Breastfeeding may counteract the negative cardiovascular sequela associated with preeclampsia; however, women who develop preeclampsia may be at-risk for suboptimal breastfeeding rates. In this case series, we present three cases of late-onset preeclampsia and one case of severe gestational hypertension that illustrate a potential association between hypertensive disorders of pregnancy and suboptimal breastfeeding outcomes, including delayed onset of lactogenesis II and in-hospital formula supplementation. CASE PRESENTATION: All cases were drawn from an ongoing pilot randomized controlled trial investigating the impact of antenatal milk expression versus an education control on breastfeeding outcomes. All study participants were healthy nulliparous women recruited at 34-366/7 gestational weeks from a hospital-based midwife practice. The variability in clinical presentation among the four cases suggests that any effect of hypertensive disorders on breastfeeding outcomes is likely multifactorial in nature, and may include both primary (e.g., preeclampsia disease course itself) and secondary (e.g., magnesium sulfate therapy, delayed at-breast feeding due to maternal-infant separation) etiologies. We further describe the use of antenatal milk expression (AME), or milk expression and storage beginning around 37 weeks of gestation, as a potential intervention to mitigate suboptimal breastfeeding outcomes in women at risk for preeclampsia and other hypertensive disorders of pregnancy. CONCLUSIONS: Additional research is needed to address incidence, etiology, and interventions, including AME, for breastfeeding issues among a larger sample of women who develop hypertensive disorders of pregnancy.

Patterns of Gestational Weight Gain in Early Pregnancy and Risk of Gestational Diabetes Mellitus.

BACKGROUND: Despite a call to study the effect of weight gain pattern on development of gestational diabetes mellitus, few studies have correctly adjusted for independent effects of gain after the first trimester. We used a conditional percentile approach to model the independent association between first and second trimester weight gain trajectories and development of gestational diabetes. METHODS: We sampled women delivering singleton infants from 1998 to 2010 at Magee-Womens Hospital in Pittsburgh, PA, (n = 124,590) using a case-cohort design. We modeled weight gain trajectories in the first and second trimesters of pregnancy using conditional weight gain percentiles, and used multivariable logistic regression to assess independent associations of the trajectory with gestational diabetes. We studied associations separately by prepregnancy body mass index category. RESULTS: The final cohort included 806 women with gestational diabetes and 4,819 randomly sampled women who delivered without gestational diabetes. In normal-weight women, every SD increase in weight gain in the first trimester above her predicted gain was associated with a 23% increased odds of gestational diabetes (95% confidence interval: 0.2%, 51%). Second trimester gain trajectory was not associated with gestational diabetes (odds ratio: 1.1, [95% confidence interval: 0.9, 1.3]) although the direction of effect was positive. This pattern was similar in obese class I and II but not in overweight and obese class III women. CONCLUSIONS: An upward weight gain trajectory in the first trimester was positively associated with gestational diabetes for women of most prepregnancy BMI categories. Second trimester weight gain trajectory was not associated with gestational diabetes for any group.

Low Gestational Weight Gain and Risk of Adverse Perinatal Outcomes in Obese and Severely Obese Women.

BACKGROUND: Our objective was to estimate associations between gestational weight gain z scores and preterm birth, neonatal intensive care unit admission, large- and small-for-gestational age birth, and cesarean delivery among grades 1, 2, and 3 obese women. METHODS: We included singleton infants born in Pennsylvania (2003-2011) to grade 1 (body mass index 30-34.9 kg/m, n = 148,335), grade 2 (35-39.9 kg/m, n = 72,032), or grade 3 (≥40 kg/m, n = 47,494) obese mothers. Total pregnancy weight gain (kg) was converted to gestational age-standardized z scores. Multivariable Poisson regression models stratified by obesity grade were used to estimate associations between z scores and outcomes. A probabilistic bias analysis, informed by an internal validation study, evaluated the impact of body mass index and weight gain misclassification. RESULTS: Risks of adverse outcomes did not substantially vary within the range of z scores equivalent to 40-week weight gains of -4.3 to 9 kg for grade 1 obese, -8.2 to 5.6 kg for grade 2 obese, and -12 to -2.3 kg for grade 3 obese women. As gestational weight gain increased beyond these z score ranges, there were slight declines in risk of small-for-gestational age birth but rapid rises in cesarean delivery and large-for-gestational age birth. Risks of preterm birth and neonatal intensive care unit admission were weakly associated with weight gain. The bias analysis supported the validity of the conventional analysis. CONCLUSIONS: Gestational weight gain below national recommendations for obese mothers (5-9 kg) may not be adversely associated with fetal growth, gestational age at delivery, or mode of delivery.

Predictor characteristics necessary for building a clinically useful risk prediction model: a simulation study.

BACKGROUND: Compelled by the intuitive appeal of predicting each individual patient's risk of an outcome, there is a growing interest in risk prediction models. While the statistical methods used to build prediction models are increasingly well understood, the literature offers little insight to researchers seeking to gauge a priori whether a prediction model is likely to perform well for their particular research question. The objective of this study was to inform the development of new risk prediction models by evaluating model performance under a wide range of predictor characteristics. METHODS: Data from all births to overweight or obese women in British Columbia, Canada from 2004 to 2012 (n = 75,225) were used to build a risk prediction model for preeclampsia. The data were then augmented with simulated predictors of the outcome with pre-set prevalence values and univariable odds ratios. We built 120 risk prediction models that included known demographic and clinical predictors, and one, three, or five of the simulated variables. Finally, we evaluated standard model performance criteria (discrimination, risk stratification capacity, calibration, and Nagelkerke's r2) for each model. RESULTS: Findings from our models built with simulated predictors demonstrated the predictor characteristics required for a risk prediction model to adequately discriminate cases from non-cases and to adequately classify patients into clinically distinct risk groups. Several predictor characteristics can yield well performing risk prediction models; however, these characteristics are not typical of predictor-outcome relationships in many population-based or clinical data sets. Novel predictors must be both strongly associated with the outcome and prevalent in the population to be useful for clinical prediction modeling (e.g., one predictor with prevalence ≥20 % and odds ratio ≥8, or 3 predictors with prevalence ≥10 % and odds ratios ≥4). Area under the receiver operating characteristic curve values of >0.8 were necessary to achieve reasonable risk stratification capacity. CONCLUSIONS: Our findings provide a guide for researchers to estimate the expected performance of a prediction model before a model has been built based on the characteristics of available predictors.