Racial/ethnic standards for fetal growth: the NICHD Fetal Growth Studies

OBJECTIVE

Fetal growth is associated with long-term health yet no appropriate standards exist for the early identification of undergrown or overgrown fetuses. We sought to develop contemporary fetal growth standards for 4 self-identified US racial/ethnic groups.

STUDY DESIGN

We recruited for prospective follow-up 2334 healthy women with low-risk, singleton pregnancies from 12 community and perinatal centers from July 2009 through January 2013. The cohort comprised: 614 (26%) non-Hispanic whites, 611 (26%) non-Hispanic blacks, 649 (28%) Hispanics, and 460 (20%) Asians. Women were screened at 8w0d to 13w6d for maternal health status associated with presumably normal fetal growth (aged 18-40 years; body mass index 19.0-29.9 kg/m(2); healthy lifestyles and living conditions; low-risk medical and obstetrical history); 92% of recruited women completed the protocol. Women were randomized among 4 ultrasonography schedules for longitudinal fetal measurement using the Voluson E8 (GE Healthcare, Milwaukee, WI). In-person interviews and anthropometric assessments were conducted at each visit; medical records were abstracted. The fetuses of 1737 (74%) women continued to be low risk (uncomplicated pregnancy, absent anomalies) at birth, and their measurements were included in the standards. Racial/ethnic-specific fetal growth curves were estimated using linear mixed models with cubic splines. Estimated fetal weight (EFW) and biometric parameter percentiles (5th, 50th, 95th) were determined for each gestational week and comparisons made by race/ethnicity, with and without adjustment for maternal and sociodemographic factors.

RESULTS

EFW differed significantly by race/ethnicity >20 weeks. Specifically at 39 weeks, the 5th, 50th, and 95th percentiles were 2790, 3505, and 4402 g for white; 2633, 3336, and 4226 g for Hispanic; 2621, 3270, and 4078 g for Asian; and 2622, 3260, and 4053 g for black women (adjusted global P < .001). For individual parameters, racial/ethnic differences by order of detection were: humerus and femur lengths (10 weeks), abdominal circumference (16 weeks), head circumference (21 weeks), and biparietal diameter (27 weeks). The study-derived standard based solely on the white group erroneously classifies as much as 15% of non-white fetuses as growth restricted (EFW <5th percentile).

CONCLUSION

Significant differences in fetal growth were found among the 4 groups. Racial/ethnic-specific standards improve the precision in evaluating fetal growth.

An Inverse Relationship Between Weight and Free Thyroxine During Early Gestation Among Women Treated for Hypothyroidism

BACKGROUND

Following treatment sufficient to normalize thyrotropin (TSH), nonpregnant hypothyroid adults display higher free thyroxine (FT(4)) concentrations than a reference population. Our aim is to determine whether FT(4) concentrations are higher during pregnancy among women treated for hypothyroidism and whether their weight is associated with FT(4) levels. Weight/FT(4) relationships have not previously been reported in treated hypothyroid adults (either pregnant or nonpregnant).

METHODS

Thyroid-related measurements were available from over 10,000 women at two early pregnancy time periods from the FaSTER (First and Second Trimester Evaluation of Risk for Fetal aneuploidy) trial (1999-2002). All women were receiving routine prenatal care. Present analyses were restricted to 9267 reference women and 306 treated, hypothyroid women with TSH between the 2nd and 98th reference percentiles. We compared FT(4) values between those groups at 11-14 and 15-18 weeks' gestation, using linear regression to estimate FT(4)/maternal weight relationships, after accounting for treatment and other potential covariates.

RESULTS

In comparison to reference women, median FT(4) values and percent of FT(4) values ≥95th reference percentile were significantly higher in treated women at both 11-14 and 15-18 weeks' gestation (p<0.001) overall and after stratification by weight into tertiles. Among both treated and reference women, median FT(4) decreased monotonically with increasing weight, regardless of anti-thyroperoxidase antibody status. Maternal age, maternal weight, and treatment status were important predictors of FT(4) levels (p<0.001, defined by partial r(2) values of 1% or higher). Anti-thyroperoxidase antibody status, TSH values (after logarithmic transformation), and all interaction terms were well below an r(2) of 1%. FT(4) levels were 1.45 pmol/L higher in treated than reference women, independent of other factors. Maternal age and weight reduced FT(4) levels by 0.0694 pmol/L/y and 0.0208 pmol/L/kg, respectively.

CONCLUSIONS

FT(4) concentrations are higher among treated hypothyroid pregnant women than among reference women, and higher maternal weight is associated with lower FT(4) levels, regardless of treatment status. This inverse relationship is not associated with higher TSH levels. While no immediate clinical implications are attached to the current observations, increased peripheral deiodinase activity in the presence of higher weight might explain these findings. Further investigation appears worthy of attention.

An economic analysis of trial of labor after cesarean delivery

OBJECTIVE

Given that cesarean delivery is one of the most commonly performed surgical procedures in the United States and an important contributor to obstetric care costs, this analysis sought to examine maternal hospital costs associated with trial of labor after cesarean delivery (TOLAC) versus repeat cesarean delivery (RCD).

METHODS

A national sample was used to identify women with singleton pregnancy who underwent either TOLAC or RCD from 2006 to 2012. Women with diagnoses that could confound cost via extended hospital length of stay prior to delivery were excluded. Other medical and obstetric covariates that could influence cost were included in an adjusted model.

RESULTS

A total of 485,247 women were identified, including 365,596 (75.3%) cesarean deliveries without labor, 41,988 (8.6%) successful and 77,663 (16.0%) unsuccessful TOLAC deliveries. The inflation-adjusted median costs in this cohort were $5512 for cesarean without labor, $4175 for successful TOLAC, $5166 for all TOLAC attempts, and $5759 for failed TOLAC. In a multivariable model, hospital region was a major predictor of median cost as were demographic variables and medical comorbidities.

CONCLUSION

TOLAC is associated with modest reductions of cost for maternal hospitalizations. However, other medical, demographic and hospital factors appear to be more important factors.

Patterns of use and predictors of receipt of antibiotics in women undergoing cesarean delivery

OBJECTIVE

Perioperative antibiotics are recommended during cesarean delivery to reduce the risk of postoperative infections and resulting maternal morbidity. We examined the patterns of use and predictors of receipt of antibiotics in women undergoing cesarean delivery.

METHODS

We identified a national cohort of women who underwent a cesarean delivery between 2003 and 2010 using a commercial hospitalization database. Women who received antibiotics on the day of cesarean delivery were classified as having received perioperative antibiotics. Multivariable regression models were developed to account for patient, obstetric, physician, and hospital factors on receipt of antibiotics. Between-hospital variation was calculated using generalized linear mixed models.

RESULTS

Among 1,137,804 women who underwent cesarean delivery, 59.5% received perioperative antibiotics. The proportion of patients receiving antibiotics increased over time from 52.5% in 2003 to 63.1% in 2010 (P<.001) and varied significantly by geographic region. Women who did not labor were more likely to receive antibiotics than those who had a cesarean delivery after labor (66% compared with 44%, P<.001). Age, race, and insurance status were not major determinants of the use of perioperative antibiotics.

CONCLUSION

Among women undergoing cesarean delivery, compliance with the recommendation for universal perioperative antibiotic prophylaxis is poor. Coordinated efforts are needed to enhance use of guideline-based perioperative antibiotic prophylaxis for women undergoing cesarean delivery.

LEVEL OF EVIDENCE

III.

Advancing research transdisciplinarity within our discipline

Advancing biomedical knowledge is crucial to the understanding of disease pathophysiology, diagnosis, treatment, and the maintenance of health. Whereas collaborative pursuits among basic and translational scientists, clinical researchers, and clinicians should advance biomedical progress and its translation to better medicine. The field of obstetrics and gynecology and its subspecialties has not escaped this problem. Obstetrics and gynecology specialists and subspecialists have limited opportunities to interact with translational or basic investigators, and cross-fertilization and collaborations are further challenged by the current healthcare and funding climate. This opinion manuscript focuses on the field of maternal-fetal medicine, serving as an example that illustrates the risks and opportunities that might exist within our obstetrics and gynecology academic community. A Pregnancy Task Force recently sought to identify ways to overcome hurdles related to research training, and ensure a sufficient pool of physician-scientists pursuing pertinent questions in the field. The group discussed strategies to promote a culture of intellectual curiosity and research excellence, securing additional resources for trainees, and attracting current and next generation basic, translational, and clinical scholars to our field. Recommendations encompassed activities within annual academic meetings, training initiatives, and additional funding opportunities. Inferences from these discussions can be made to all obstetrics and gynecology subspecialty areas.

Implications of High Free Thyroxine (FT4) concentrations in euthyroid pregnancies: the FaSTER trial

CONTEXT

Lower birth weight has been reported in conjunction with high maternal free T4 (FT4) in euthyroid pregnancies, raising concerns for suboptimal outcomes.

OBJECTIVE

The objective of the study was to explore the relationships between high maternal FT4 and pregnancy complications in euthyroid women and to further examine the relationships among maternal size, FT4, and birth weight.

DESIGN

This was an observational multicenter cohort study.

SETTING

The study was conducted at prenatal clinics.

STUDY SUBJECTS

A total of 9209 euthyroid women with singleton pregnancies participated in the study.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

Relationships between second-trimester high maternal FT4 and pregnancy/delivery complications and, among FT4, maternal weight and birth weight were measured.

RESULTS

Women in the highest FT4 quintile are younger and weigh less than women in quintiles 1-4; gestational diabetes and preeclampsia occur less often (P = < .001, P < .001, P < .001, and P = .05, respectively). Lowest median birth weight occurs among women in the highest FT4 quintile (P = < .001), but deliveries less than 37 weeks' gestation are not increased. Labor/delivery complications do not differ by FT4 quintile. Restricting analyses to maternal weight-adjusted small-for-gestational-age deliveries yields similar results, except for preeclampsia. In the highest maternal weight decile, adjusted median birth weight is 266 g higher (8.3%) than in the lowest weight decile; adjusted median FT4 is 0.91 pmol/L lower (6.8%). Among women in the highest FT4 decile, adjusted median birth weight is 46 g lower (1.3%) than in the lowest FT4 decile. All three relationships are statistically significant (P < .001, P < .001, and P = .004, respectively).

CONCLUSIONS

Lower median birth weight among euthyroid women with high FT4 is not associated with adverse pregnancy outcomes. Further investigation is indicated to determine how the variations in thyroid hormone concentration influence birth weight.

Practice patterns and preferences of obstetricians and gynecologists regarding thromboprophylaxis at the time of Cesarean section

OBJECTIVE

Our survey aimed to identify knowledge and application of guidelines in the United States by assessing practicing obstetricians and gynecologists (OBGYN) use of thromboprophylaxis, preferred methods and whether their type of practice influenced their choices.

STUDY DESIGN

A cross-sectional survey of fellows of the American College of Obstetricians and Gynecologists (ACOG) was performed. A 21-item paper and electronic questionnaire was sent to each participant. A total of three mailings were carried out.

RESULTS

In total, 400 OBGYN were invited to participate. Questionnaires were returned by 209 (52.3%), 157 (75.1%) of whom provided prenatal care within the last year. All respondents used at least one method of thromboprophylaxis routinely. About 92.4% used pneumatic compression devices. An equal proportion used unfractionated heparin and low molecular weight heparin routinely (17.8%). About 19.1% routinely used combination prophylaxis. In total, 77.1% (n = 121) used the ACOG guidelines. Local hospital guidelines were referenced by 38.2% (n = 60). Other guidelines referenced were the ACCP guideline (n = 34, 21.7%) and several international guidelines (n = 5, 3.3%).

CONCLUSION

Awareness of the risk of thromboembolism around delivery by cesarean section is high among OBGYN practitioners. Broadening guidelines to encompass all deliveries, not only cesareans, with a focus on identifying the patient at risk, would likely be successful.

The case for an electronic fetal heart rate monitoring credentialing examination

The Perinatal Quality Foundation has created an examination containing both knowledge-based and judgment questions relating to the interpretation of electronic fetal heart rate monitoring for credentialing all medical and nursing personnel working on a labor and delivery floor. A description of the examination and the rationale for its use throughout the United States is presented.

Safety of conservative management of ovarian masses during pregnancy

OBJECTIVE

To determine the clinical outcomes and risk factors for persistence of ovarian cysts in pregnant women. With the increased use of ultrasound in pregnancy, the identification of incidental ovarian masses is becoming more common.

STUDY DESIGN

An observational study of women with ovarian masses identified before 24 weeks of pregnancy was performed. Only women who underwent follow-up imaging or surgery were included. Factors associated with persistence and outcomes of women who underwent surgery were analyzed.

RESULTS

Of the 803 women with available follow-up, the cysts resolved in 707 (88.1%) patients. Fifty (6.2%) women underwent surgical intervention. Women with persistent cysts were younger, more often Hispanic, detected at a later gestational age, had larger cysts, and more often had complex or solid components (p < 0.05 for all). Overall, 1 (0.1%) malignancy was diagnosed (a patient with a B-cell lymphoma), while 3 (0.4%) women had borderline epithelial ovarian tumors.

CONCLUSION

Ovarian masses identified during pregnancy have a low risk of malignancy. The majority of women can be serially monitored without intervention.

Pulmonary embolus in pregnancy

Venous thromboembolism remains in the top three leading causes of maternal death in the US, representing 10.2% of pregnancy-related deaths. Risk of developing a pulmonary embolus appears to increase throughout pregnancy, with a peak in incidence in the early postpartum period. Overall the incidence of VTE is 0.6-1.8 VTEs per 1000 deliveries. Diagnosis and management of pulmonary embolus can prove challenging, but the aim should be to optimize maternal outcome while minimizing hemorrhagic complications. Low-molecular-weight heparin is a safe and effective treatment for the majority of cases of pregnancy-related pulmonary embolus.

Opinions and practice patterns of obstetricians-gynecologists in the United States regarding amniocentesis in twins

OBJECTIVE

Accurate amniocentesis-related pregnancy loss (ARL) rates for twin gestations remains elusive because of varying ARL definitions in the literature. We examined how OB/GYNs define/counsel women carrying twins about ARL.

METHODS

A random sample of 1000 American College of OB/GYN (ACOG) fellows and ACOG Collaborative Ambulatory Research Network (CARN) members were mailed surveys about their opinions/practice patterns regarding amniocentesis in twins. There were 208/400 (52%) CARN members and 166/600 (27%) ACOG fellows who returned the survey (37% response rate).

RESULTS

Of respondents, 80.8% practiced general OB/GYN, and 9.1% practiced maternal fetal medicine. Of respondents, 72% discussed amniocentesis for prenatal diagnosis. Of these, 91.7% discuss the risk of ARL; however, 47.4% do not quote an ARL rate. Of those who discuss ARL rates, 65% quote a rate greater than for singletons. Regarding monochorionic-diamniotic twins, 12.1% of respondents said the ARL rate was less, 39.6% said equal to, and 38.9% said greater than for dichorionic twins. Table 1 lists the most common clinical definitions/time intervals used to describe ARL.

CONCLUSION

Various definitions/ARL rates are used when counseling about ARL in twins. Further studies using a widely accepted definition of ARL are necessary to improve the counseling of women considering amniocentesis for prenatal diagnosis in twins.

Putting the "M" back in maternal-fetal medicine

Although maternal death remains rare in the United States, the rate has not decreased for 3 decades. The rate of severe maternal morbidity, a more prevalent problem, is also rising. Rise in maternal age, in rates of obesity, and in cesarean deliveries as well as more pregnant women with chronic medical conditions all contribute to maternal mortality and morbidity in the United States. We believe it is the responsibility of maternal-fetal medicine (MFM) subspecialists to lead a national effort to decrease maternal mortality and morbidity. In doing so, we hope to reestablish the vital role of MFM subspecialists to take the lead in the performance and coordination of care in complicated obstetrical cases. This article will summarize our initial recommendations to enhance MFM education and training, to establish national standards to improve maternal care and management, and to address critical research gaps in maternal medicine.

Practice patterns and knowledge of obstetricians and gynecologists regarding placenta accreta

OBJECTIVE

We surveyed obstetricians to determine their knowledge, patterns of care and treatment preferences for women with placenta accreta.

METHODS

A 27-item survey was mailed to fellows of the American College of Obstetricians and Gynecologists. The survey included demographics, questions regarding knowledge and items to examine practice patterns.

RESULTS

Among 994 surveyed practitioners 508 responded including 338 who practiced obstetrics. Among generalists, 23.8% of respondents referred patients with placenta accreta to a sub-specialist. Overall, 20.4% referred women to the nearest tertiary center, and 7.1% referred to a regional center. Delivery was recommended at 34-36 weeks by 41.2%. Adjuvant interventions including ureteral stents (26.3%), iliac artery embolization catheters (28.1%), and balloon occlusion catheters (20.1%) were used infrequently. Six or more units of blood were crossed for delivery by only 29.0% of practitioners.

CONCLUSION

There is widespread variation in the care of women with or at risk for placenta accreta.

Impact of adjusting for the reciprocal relationship between maternal weight and free thyroxine during early pregnancy

BACKGROUND

Among euthyroid pregnant women in a large clinical trial, free thyroxine (FT4) measurements below the 2.5th centile were associated with a 17 lb higher weight (2.9 kg/m(2)) than in the overall study population. We explore this relationship further.

METHODS

Among 9351 women with second trimester thyrotropin (TSH) measurements between 1st and 98th centiles, we examine: (i) the weight/FT4 relationship; (ii) percentages of women in three weight categories at each FT4 decile; (iii) FT4 concentrations in three weight categories at each TSH decile; and (iv) impact of adjusting FT4 for weight--in the reference group and in 190 additional women with elevated TSH measurements.

RESULTS

FT4 values decrease steadily as weight increases (p<0.0001 by ANOVA) among women in the reference group (TSH 0.05-3.8 IU/L). TSH follows no consistent pattern with weight. When stratified into weight tertiles, 48% of women at the lowest FT4 decile are heavy; the percentage decreases steadily to 22% at the highest FT4 decile. Median FT4 is lowest in heaviest women regardless of the TSH level. In the reference group, weight adjustment reduces overall variance by 2.9%. Fewer FT4 measurements are at either extreme (below the 5th FT4 centile: 4.8% before adjustment, 4.7% after adjustment; above the 95th FT4 centile: 5.0% and 4.7%, respectively). Adjustment places more light weight women and fewer heavy women below the 5th FT4 centile; the converse above the 95th centile. Between TSH 3.8 and 5 IU/L, the FT4 percentage below the 5th FT4 centile is not elevated (3.8% before adjustment, 3.1% after adjustment). Percentage of FT4 values above the 95th centile, however, is lower (1.5% before adjustment, 0.8% after adjustment). Above TSH 5 IU/L, 25% of women have FT4 values below the 5th FT4 centile; weight adjustment raises this to 30%; no FT4 values remain above the 95th FT4 centile.

CONCLUSIONS

During early pregnancy, TSH values are not associated with weight, unlike nonpregnant adults. Lower average FT4 values among heavy women at all TSH deciles partially explain interindividual differences in FT4 reference ranges. The continuous reciprocal relationship between weight and FT4 explains lower FT4 with higher weight. Weight adjustment refines FT4 interpretation.

Effectiveness of timing strategies for delivery of monochorionic diamniotic twins

OBJECTIVE

The purpose of this study was to compare strategies for delivery timing of uncomplicated monochorionic diamniotic twin pregnancies.

STUDY DESIGN

A decision tree compared 9 strategies that included scheduled delivery between 32 and 38 weeks' gestation, with or without confirmation of fetal lung maturity. Outcomes in the model included fetal death, infant death, respiratory distress syndrome, mental retardation, and cerebral palsy.

RESULTS

A scheduled delivery at 38 weeks' gestation was the preferred strategy, which resulted in the highest quality adjusted life years under base-case assumptions. Decreased, but comparable, quality adjusted life years estimates resulted from scheduled deliveries at 36 and 37 weeks' gestation, with or without amniocentesis. Sensitivity analyses demonstrated that the optimal gestational age for delivery was always ≥36 weeks' gestation.

CONCLUSION

This decision analysis suggests that, for women with uncomplicated monochorionic twins, delivery between 36 and 38 weeks' gestation is the preferred strategy for timing of delivery.

Prenatal diagnosis in twin gestations

Twin gestations face an increased risk of structural abnormalities compared with singleton gestations, as well as an increased risk of aneuploidy. Accordingly, there is a need for accurate prenatal diagnosis of fetal genetic disorders and structural anomalies in twin gestations. Given the increased risk of congenital anomalies, a detailed sonographic survey of fetal anatomy is recommended in the early second trimester of twin gestations. In addition, fetal echocardiography should be considered in monochorionic twin gestations and in dichorionic twin pregnancies conceived using assisted reproductive technologies given the increased risk of congenital heart disease in these populations. Although first- and second-trimester aneuploidy screening in twin gestations is available, screening is less accurate than in singleton gestations. Invasive prenatal diagnosis in twin pregnancies is associated with a risk of pregnancy loss that is higher than the baseline risk of loss among twin gestations. Precise procedure-related loss rates in twin gestations undergoing chorionic villus sampling or amniocentesis, however, remain unclear because of methodological differences between published studies investigating diagnostic procedures in twins.