Key Points español 中文 (chinese)
Does fetal growth restriction influence neurocognitive function in midchildhood after repeated antenatal betamethasone treatment?
In the 988 children followed up at 6 to 8 years of age in this secondary analysis of a placebo-controlled randomized clinical trial, exposure to repeated antenatal betamethasone treatment was not associated with adverse effects on survival free of any disability, death, or survival with moderate to severe disability, even in the presence of fetal growth restriction.
Health care professionals should use repeated doses of antenatal corticosteroids when indicated before preterm birth, regardless of fetal growth restriction, in view of the associated neonatal benefits and absence of later adverse effects.
Repeated doses of antenatal betamethasone are recommended for women at less than 32 weeks’ gestation with ongoing risk of preterm birth. However, concern that this therapy may be associated with adverse neurocognitive effects in children with fetal growth restriction (FGR) remains.
To determine the influence of FGR on the effects of repeated doses of antenatal betamethasone on neurocognitive function in midchildhood.
Design, Setting, and Participants
This preplanned secondary analysis of data from the multicenter Australasian Collaborative Trial of Repeat Doses of Corticosteroids (ACTORDS) included women at less than 32 weeks’ gestation with ongoing risk of preterm birth (<32 weeks) at least 7 days after an initial course of antenatal corticosteroids who were treated at 23 hospitals across Australia and New Zealand from April 1, 1998, through July 20, 2004. Participants were randomized to intramuscular betamethasone or saline placebo; treatment could be repeated weekly if the woman was judged to be at continued risk of preterm birth. All surviving children were invited to a midchildhood outcome study. Data for this study were collected from October 27, 2006, through March 18, 2011, and analyzed from June 1 through 30, 2018.
At 6 to 8 years of corrected age, children were assessed by a pediatrician and psychologist for neurosensory and cognitive function, and parents completed standardized questionnaires.
Main Outcomes and Measures
The prespecified primary outcomes were survival free of any disability and death or survival with moderate to severe disability.
Of 1059 eligible children, 988 (55.0% male; mean [SD] age at follow-up, 7.5 [1.1] years) were assessed at midchildhood. The FGR rate was 139 of 493 children (28.2%) in the repeated betamethasone treatment group and 122 of 495 (24.6%) in the placebo group (P = .20). Primary outcome rates were similar between treatment groups for the FGR and non-FGR subgroups, with no evidence of an interaction effect for survival free of any disability (FGR group, 108 of 144 [75.0%] for repeated betamethasone treatment vs 91 of 126 [72.2%] for placebo groups [odds ratio [OR], 1.1; 95% CI, 0.6-1.9]; non-FGR group, 267 of 335 [79.7%] for repeated betamethasone vs 283 of 358 [79.0%] for placebo groups [OR, 1.0; 95% CI, 0.7-1.5]; P = .77) and death or moderate to severe disability (FGR group, 21 of 144 [14.6%] for repeated betamethasone treatment vs 20 of 126 [15.9%] for placebo groups [OR, 0.9; 95% CI, 0.4-1.9]; non-FGR group, 29 of 335 [8.6%] for repeated betamethasone vs 36 of 358 [10.0%] for placebo [OR, 0.8; 95% CI, 0.4-1.3]; P = .84).
Conclusions and Relevance
In this study, repeated antenatal betamethasone treatment compared with placebo was not associated with adverse effects on neurocognitive function at 6 to 8 years of age, even in the presence of FGR. Physicians should use repeated doses of antenatal corticosteroids when indicated before preterm birth, regardless of FGR, in view of the associated neonatal benefits and absence of later adverse effects.
anzctr.org.au Identifier: ACTRN12606000318583
Antenatal corticosteroid therapy remains one of the most effective treatments for preterm infants, and administration of a repeated dose or doses in women who are at ongoing risk of preterm birth at least 7 days after an initial course results in additional neonatal benefits.1 These benefits include reduced risk of preterm lung disease (especially severe disease), other combined serious neonatal morbidity, and patent ductus arteriosus. The absolute benefits of repeated-dose therapy are similar to those of an initial course.2 These clinical data are supported by studies in animals and human fetal lung explants showing that optimal structural and functional maturation requires serial exposure of fetal tissues to corticosteroids.3
However, animal studies have also revealed the potential for adverse long-term effects on organ development with increasing fetal exposure to corticosteroids. This potential is of particular concern for neural tissues with demonstration in different species that repeated or higher doses of corticosteroids can result in reduced brain mass,4 compromised structural development and neuronal maturation,5 diminished cellular proliferation and differentiation,6 reduced population of hippocampal neurons,7,8 and adverse development of the hypothalamic-pituitary-adrenal axis.9 These findings have contributed to the cautious clinical recommendations on the use of repeated doses of antenatal corticosteroids.10
Recent evidence from the Australasian Collaborative Trial of Repeat Doses of Corticosteroids (ACTORDS) has shown that use of repeated doses of antenatal corticosteroids in humans is not associated with adverse effects in offspring at midchildhood, including neurocognitive function, learning, behavior, growth, lung function, and cardiometabolic function.11,12 Nevertheless, clinical uptake of repeated doses of corticosteroids has been limited, and concern remains about the safety of this therapy in the context of fetal growth restriction (FGR), which is commonly associated with very preterm birth.13,14 Preterm-born children with FGR are at increased risk of adverse long-term neurodevelopmental outcomes and behavioral dysfunction,15 but at present, no published data are available from randomized clinical trials on the efficacy and safety of repeated-dose corticosteroid therapy in this important clinical subgroup. Therefore, we undertook a secondary analysis of data from the ACTORDS to determine the influence of FGR on the effects of repeated doses of antenatal betamethasone on neurocognitive function and behavior in midchildhood.11
ACTORDS was a placebo-controlled, randomized clinical trial of repeated antenatal betamethasone treatment conducted at 23 collaborating hospitals across Australia and New Zealand.2 The full trial protocol appears in Supplement 1. Eligible women had a single, twin, or triplet pregnancy at less than 32 weeks’ gestation, with an ongoing risk of preterm birth at least 7 days after an initial course of antenatal corticosteroids. A total of 982 women (1146 fetuses) were randomized, via a central telephone service, to an intramuscular dose of betamethasone (Celestone Chronodose, consisting of 7.8 mg of betamethasone sodium phosphate and 6 mg of betamethasone acetate) or saline placebo. The treatment could be repeated each week if the woman was judged to be at continued risk of preterm birth, until 32 weeks’ gestation.2 At 2 years of corrected age, neurodevelopment, growth, and general health were similar between groups.16 Although the midchildhood assessment was not part of the original trial protocol, this assessment was planned before the completion of the 2-year follow-up owing to concerns about the potential for long-term adverse effects of fetal corticosteroid exposure.11 Written informed consent was obtained from caregivers, and children provided assent for assessment. The Midchildhood Outcomes Study was approved by the National Health and Disability Ethics Committee in New Zealand and by regional Health Research Ethics Committees in Australia. This report has been prepared according to the Consolidated Standards of Reporting Trials (CONSORT) reporting guidelines for clinical trials.
Midchildhood Outcomes Study
All surviving children of mothers who had participated in ACTORDS were invited to partake in the Midchildhood Outcomes Study of neurocognitive function and general health at 6 to 8 years of corrected age.11 Children were assessed by a pediatrician and a psychologist who were blinded to treatment allocation.11 The pediatric assessment included a physical and neurologic examination, vision and hearing screening, and tests of fine and gross motor function using the Movement Assessment Battery for Children, Second Edition (MABC-2).17 Several children underwent assessment using the earlier edition of the MABC. Cerebral palsy was defined as a nonprogressive loss of motor function with disordered muscle tone or tendon reflexes18 and was graded according to gross motor function criteria of Palisano et al19 (mild, grade 1; moderate, grades 2-3; and severe, grades 4-5). Blindness consisted of visual acuity of worse than 20/200 in the better eye. Deafness consisted of hearing loss requiring hearing aids or worse.
The psychological assessment included the Wechsler Abbreviated Scale of Intelligence.20 The full-scale IQ was derived from the Vocabulary, Similarities, Block Design, and Matrix Reasoning subtests. Scores were age standardized with a normative mean (SD) of 100 (15). Intellectual impairment was classified as mild (IQ of 1-2 SDs below the mean), moderate (IQ of >2 to 3 SDs below the mean), and severe (IQ of >3 SDs below the mean). Children with severe intellectual impairment who were unable to complete the Wechsler Abbreviated Scale of Intelligence were assigned an IQ score of 40.
Attention was assessed using subtests from the Test of Everyday Attention for Children.21 Selective visual attention was assessed using the Sky Search subtest; sustained attention, the Score! subtest; shifting attention, the Creature Counting subtest; and divided attention, the Sky Search Dual Task subtest. Scores in the Sky Search, Score!, and Creature Counting subtests were age standardized (test mean [SD], 10 ). Performance in the Sky Search Dual Task subtest was determined by the mean of the proportion of visual targets correctly identified plus the proportion of correct auditory counting games multiplied by 100.21 The range of possible values is 0 to 100, and although this scoring procedure has no published norms, the mean (SD) score in a study of 173 control children at 8 years of age was 80.3 (16.5).22
Executive function was assessed using the Rey Complex Figure Test23 and the Fruit Stroop Task.24 The Complex Figure Test assesses complex spatial organization; children’s copying of a complex geometrical figure was scored for accuracy (maximum score of 36)23 and strategic organization.25 The Fruit Stroop Task assessed impulse control, with performance determined by the number of correct responses in 45 seconds (naming the true color of fruit that was presented in conflicting colors).11 Academic skills were assessed using the word reading, spelling, and math computation subtests of the Wide Range Achievement Test, fourth edition.26 Each scale is age standardized with a normative mean (SD) of 100 (15).
Caregivers completed questionnaires, including the Strengths and Difficulties Questionnaire to assess general behavioral and emotional problems,27 the Behavior Rating Inventory of Executive Function to assess behavioral manifestations of inattention and executive function,28 and the Conners’ ADHD/DSM-IV Scales29 to assess for features of attention-deficit/hyperactivity disorder. Neurosensory disability included cerebral palsy, intellectual impairment, or blindness or deafness and was graded as mild (mild cerebral palsy or IQ of 70-84), moderate (deafness, moderate cerebral palsy, or IQ of 55-69), or severe (blindness, severe cerebral palsy, or IQ of <55).
Children who completed 1 or more of the neurocognitive tests at 6 to 8 years of corrected age were included in this secondary analysis of data from the midchildhood assessments of the ACTORDS.11 The prespecified primary outcomes for this study were survival free of any neurosensory disability and death or moderate to severe disability. To reduce the risk of type I error, the following secondary outcomes were selected a priori as key indicators of function in the each neurocognitive domain: (1) cognition using full-scale IQ and cognitive impairment (IQ <85); (2) motor using cerebral palsy and low motor function (MABC total score <15th centile); (3) attention using Test of Everyday Attention for Children subtest scores; (4) executive function using Rey Complex Figure Test accuracy and organization scores and the number of correct Fruit Stroop Task responses (trial 4); (5) educational achievement using Wide Range Achievement Test, edition 4, scores in reading, spelling, and mathematics; and (6) behavior using the Strengths and Difficulties Questionnaire Total Difficulties score (range, 0-40, with 14-16 indicating borderline and ≥17 abnormal),27 Behavior Rating Inventory of Executive Function Global Executive Composite t score (mean [SD], 50 ), and Conners’ ADHD/DSM-IV Scales ADHD Index t score (mean [SD], 50 ).
We hypothesized that exposure to repeated antenatal betamethasone treatment, compared with a single course of treatment, would have adverse effects on neurosensory function, general cognition, attention, executive function, academic performance, and behavior at 6 to 8 years of corrected age in children with FGR but not for those with normal prenatal growth. As previously described,30 FGR was defined a priori as 1 or more of the following: obstetric diagnosis of FGR at trial entry; cesarean delivery for FGR; or customized birth weight of no greater than the third centile (GROW, version 126.96.36.199; Perinatal Institute). Although this definition includes postrandomization factors, these were judged to be important because antenatal diagnosis of FGR substantially underrepresents the true incidence of FGR in the preterm population.14 However, we used a conservative birth weight threshold of the third centile. Customized centiles, which incorporate fetal growth curves and account for normal maternal constraint on fetal growth, were used because these have been shown to improve detection of FGR.31 Further, meta-analysis of randomized clinical trials has shown that repeated doses of corticosteroids do not increase the risk of being small for gestational age.1
Analyses were performed using SAS software (version 9.4; SAS Institute, Inc). Data are presented as number (percentage) or mean (SD). For all prespecified outcomes, treatment groups were compared using generalized linear models with adjustment for gestational age at trial entry, preterm prelabor rupture of membranes, antepartum hemorrhage, country of birth, and clustering of children from multiple pregnancy by generalized estimating equations.2 The influence of FGR on treatment effect was assessed by an interaction test. Treatment effects within the FGR and non-FGR subgroups are reported as odds ratios (ORs) for binary outcomes or mean difference (MD) for continuous outcomes with 95% CI. Two-tailed α < .05 was considered statistically significant.
Of the 1059 surviving children eligible for the Midchildhood Outcomes Study, 988 (445 [45.0%] female and 543 [55.0%] male; mean [SD] age at follow-up, 7.5 [1.1] years) completed 1 or more tests of neurocognitive function (repeated betamethasone treatment, 493 participants; placebo, 495 participants) (Figure).11 The rate of FGR was similar between those exposed to repeated betamethasone therapy (139 of 493 [28.2%]) and placebo (122 of 495 [24.6%]) (P = .20).
The FGR subgroup, compared with the non-FGR subgroup, was characterized by older mean maternal age (31.9 [5.8] vs 30.4 [5.9] years; P = .002), higher maternal parity (parity ≥4, 29 of 216 [13.4%] vs 54 of 673 [8.0%]; P = .02), and increased rates of multiple pregnancy (79 of 216 [36.6%] vs 93 of 673 [13.8%]; P < .001) and preeclampsia (67 of 216 [31.0%] vs 27 of 673 [4.0%]; P < .001) (Table 1). Fetal growth restriction was associated with lower rates of preterm prelabor rupture of membranes (35 of 216 [16.2%] vs 248 of 673 [36.8%]; P < .001), cervical incompetence (11 of 216 [5.1%] vs 67 of 673 [10.0%]; P = .03), antepartum hemorrhage (34 of 216 [15.7%] vs 218 of 673 [32.4%]; P < .001), and shorter mean gestation (31.8 [3.1] vs 32.9 [4.0] weeks; P < .001) (Table 1). Women in the FGR group were less likely to speak English at home (177 of /216 [81.9%] vs 594 of 673 [88.3%]; P = .02) (Table 1). Neonates with FGR had substantially reduced z scores for mean birth weight (−1.2 [0.8] vs 0.1 [0.7]; P < .001) and head circumference (−0.9 [0.9] vs 0.2 [1.1]; P < .001) and increased rates of mechanical ventilation (154 of 261 [59.0%] vs 344 of 727 [47.3%]; P = .002); and serious neonatal morbidity (78 of 261 [29.9%] vs 132 of 727 [18.2%]; P < .001) (Table 1).
In the FGR subgroup, those exposed to repeated-dose betamethasone therapy were more likely than those exposed to placebo to have received at least 4 trial treatments (38 of 118 [32.2%] vs 14 of 98 [14.3%]; P = .002) and to be born at a later mean gestational age (32.2 [3.2] vs 31.2 [3.0] weeks; P ≤ .001). Repeated betamethasone therapy reduced the incidence of respiratory distress syndrome, the severity of neonatal lung disease, and serious neonatal morbidity, as well as the need for mechanical ventilation, oxygen, and surfactant therapy (Table 1).
In the non-FGR subgroup, those exposed to repeated betamethasone treatment were less likely than those exposed to placebo to have preterm prelabor rupture of membranes (108 of 330 [32.7%] vs 140 of 343 [40.8%]; P = .03) as the main reason for being at risk of preterm birth. Repeated betamethasone therapy significantly reduced the severity of neonatal lung disease (Table 1).
For the primary outcomes at 6 to 8 years of corrected age, rates were similar between treatment groups in the FGR and non-FGR subgroups, with no evidence of an interaction effect for survival free of any disability (FGR, 108 of 144 [75.0%] with repeated betamethasone vs 91 of 126 [72.2%] with placebo [odds ratio (OR), 1.1; 95% CI, 0.6-1.9]; non-FGR, 267 of 335 [79.7%] with repeated betamethasone vs 283 of 358 [79.0%] with placebo [OR, 1.0; 95% CI, 0.7-1.5]; P = .77) or for death or moderate to severe disability (FGR, 21 of 144 [14.6%] with repeated betamethasone vs 20 of 126 [15.9%] with placebo [OR, 0.9; 95% CI, 0.4-1.9]; non-FGR, 29 of 335 [8.6%] with repeated betamethasone vs 36 of 358 [10.0%] with placebo [OR, 0.8; 95% CI, 0.4-1.3]; P = .84) (Table 2).
For the secondary outcomes of Sky Search Dual Task (divided attention) and Fruit Stroop Task (executive function), a significant interaction occurred for the effect of repeated antenatal betamethasone therapy and FGR. In the FGR subgroup, children exposed to repeated betamethasone performed better on the Sky Search Dual Task than those exposed to placebo; no significant difference was seen between treatment groups in the non-FGR subgroup (FGR MD, 7.1 [95% CI, −0.8 to 15.2]; non-FGR MD, −3.5 [95% CI, −8.4 to 1.3]; P = .02 for interaction) (Table 2). Conversely, in the non-FGR subgroup, children exposed to repeated betamethasone performed worse on the Fruit Stroop Task than those exposed to placebo; no significant difference was seen between treatment groups in the FGR subgroup for number correct (FGR MD, 1.0 [95% CI, −1.1 to 3.1]; non-FGR MD, −2.1 [95% CI, −3.5 to −0.8]; P = .02 for interaction) (Table 2). In post hoc analyses, these interactions remained significant after adjustment for maternal parity and number of trial treatments. For all other secondary outcomes, rates and scores were similar between the FGR and non-FGR subgroups, with no evidence of an interaction (Table 2, Table 3, and Table 4).
Regardless of treatment exposure, children with compared with those without FGR had an increased risk of death or moderate to severe disability (OR, 1.6; 95% CI, 1.1-1.4) and motor impairment (MABC total score <15th centile: OR, 1.5 [95% CI, 1.2-1.8) and had lower IQ (MD, −3.3; 95% CI, −5.8 to −0.8) and lower scores for measures of attention, executive function, and reading (eTable in Supplement 2).
In this secondary analysis of data from the midchildhood assessments of the ACTORDS randomized clinical trial,11 we found that exposure to repeated antenatal betamethasone treatment was not associated with adverse effects on survival free of any disability or on death or moderate to severe disability at 6 to 8 years of age, in children with and without FGR. Some evidence suggested a differential effect for several secondary outcomes, with better scores for selective and divided attention after exposure to repeated antenatal betamethasone in children with FGR, but poorer scores for impulse control in children without FGR. These effects were small and of uncertain clinical significance and may reflect type I error. For all other measures of neurocognitive function and learning, exposure to repeated antenatal betamethasone treatment did not alter performance in midchildhood, even in the presence of FGR.
For preterm- and term-born patients, FGR is associated with adverse neurodevelopmental outcomes in childhood and adulthood, including neurosensory disability, cognitive impairments, executive dysfunction, and emotional and behavioral difficulties.15,32 Imaging studies indicate that infants with FGR have abnormal structural and metabolic brain development,33-35 which may reflect suboptimal intrauterine conditions, including hypoxia-ischemia, nutritional deprivation, and/or perinatal injury. Preterm infants with FGR have decreased cortical growth36 and microstructural complexity, especially in the basal ganglia, brainstem, cerebellum, and frontal lobes.37,38 Neonatal morbidities such as chronic lung disease and necrotizing enterocolitis, which are more common in preterm infants with FGR, may exacerbate these changes.39
Therefore, that infants with FGR exhibit abnormal neurodevelopment is not surprising. School-aged children with FGR are reported to be more likely to have impaired social awareness, autistic mannerisms, and psychosocial issues.40 Concurrent with our data, cohort studies and meta-analyses have shown that children with FGR have significantly lower IQ scores and poorer overall educational achievement compared with children without FGR.41 By adulthood, those with FGR tend to have lower incomes because they are less likely to have professional or skilled employment.42 Furthermore, they also have a greater risk of adverse psychological outcomes, including schizophrenia, anxiety, and mood disorders.43
Although the benefits of repeated antenatal corticosteroid therapy are well established and human studies have demonstrated long-term safety,11,44 concerns remain about the use of this treatment in FGR, given reports from animal studies suggesting long-term adverse effects of treatment on neurosensory function.4,45 For example, in FGR sheep, antenatal betamethasone exposure was associated with significantly reduced expression of 5α-reductase and the subsequent concentration of the endogenous neuroprotective steroid allopregnanolone.46 Animal studies4,5,7 have also reported adverse effects, including reduced brain growth, disrupted expression of neuronal components involved with plasticity and apoptosis, and delayed glial cell maturation. Many of these studies administered corticosteroids at gestations analogous to 23 to 34 weeks’ pregnancy, a period in which severe FGR is common.14 On this basis, we hypothesized that repeated antenatal corticosteroid treatment may compound the adverse effects already imposed by FGR.
However, contrary to our hypothesis, we did not find any evidence of adverse effects of repeated-dose antenatal corticosteroid treatment on neurocognitive function in children with FGR. One explanation for this might be that infants with FGR appeared to have greater benefit from repeated antenatal corticosteroid therapy, with a nearly 2-fold reduction in serious neonatal morbidity. Thus, the decrease in serious postnatal complications may have counteracted any potential adverse effects of corticosteroid exposure. Cartwright et al30 have shown that exposure to repeated-dose antenatal corticosteroid treatment was associated with improved postnatal linear growth in children with FGR, which may have a positive influence on neurodevelopment. For example, low birth weight followed by rapid catch-up growth during infancy is associated with improved neurodevelopment at 2 years of age.47 Further, height in late childhood and early adulthood is positively associated with IQ,48 and improved linear growth during early childhood and late adolescence is independently and positively associated with later cognitive ability and educational attainment.49 Thus, several possible mechanisms may explain why effects on neurodevelopment in human trials may be different than those of animal studies, as Cartwright et al30 have shown for long-term cardiometabolic function.
One particular concern is whether use of repeated antenatal corticosteroids in FGR could increase the risk of attention-deficit/hyperactivity disorder. Attention-deficit/hyperactivity disorder is associated with altered concentration of neurotrophins, which regulate neuronal growth, morphology, migration, and apoptosis,50-53 and evidence suggests that neurotrophin expression is regulated by corticosteroids.54,55 Fetal growth restriction did not influence the parent-reported attention-deficit/hyperactivity disorder scale, but repeated betamethasone treatment had a small, positive association with the direct assessment of divided attention and possibly impulse control in children with FGR. Although a type I error cannot be excluded, this raises the possibility that treatment with antenatal corticosteroids could be neuroprotective in FGR. This possibility is supported by the finding of higher umbilical cord blood neurotrophin concentrations, such as brain-derived neurotrophic factor and neurotrophin-3, in infants exposed to antenatal corticosteroids.56 In infants with FGR, exposure to repeated-dose antenatal corticosteroid treatment was not associated with a change in head circumference z score at birth.
A key limitation of this study is the inherent risk of bias in subgroup analyses. Nevertheless, given the high rates of FGR among preterm infants and the ongoing concerns around efficacy and safety of repeated exposure to corticosteroid treatment in this subgroup, we believed that this exploratory analysis was important, particularly because further trials of repeated exposure to antenatal corticosteroid treatment are unlikely to be performed. Another potential source of bias in this study is the inclusion of birth weight in the definition of FGR because subgroup analysis should strictly only involve factors identified before randomization. However, we were concerned that the rate of FGR reported at trial entry (5%) underrepresented the actual degree of FGR in this high-risk cohort and could potentially obscure the effect of FGR on outcomes. We took a conservative approach, defining FGR as a birth weight less than the third centile rather than the more commonly used 10th centile, and used customized rather than population centiles because of the strong association between preterm birth and FGR. The key strengths of our study include the high follow-up rate and comprehensive assessment of participants.11
The findings of this study relate to single repeated doses of betamethasone and may not necessarily apply to other repeated-dose corticosteroid regimens. The relative effect of repeated-dose antenatal corticosteroid treatment at very early compared with later gestational ages, in the short and long terms, is also not known.
Repeated antenatal betamethasone treatment was not associated with adverse effects on survival free of any disability or on death or moderate to severe disability at 6 to 8 years of age, even in the presence of FGR. Physicians should use repeated doses of antenatal corticosteroids when indicated before preterm birth, regardless of FGR, in view of the associated neonatal benefits and absence of later adverse effects.
Accepted for Publication: December 10, 2018.
Published: February 1, 2019. doi:10.1001/jamanetworkopen.2018.7636
Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2019 Cartwright RD et al. JAMA Network Open.
Corresponding Author: Christopher J. D. McKinlay, PhD, Liggins Institute, University of Auckland, Private Bag 92019, Victoria Street West, Auckland 1142, New Zealand (email@example.com).
Author Contributions: Mr Cartwright and Dr McKinlay had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Doyle, McKinlay.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Cartwright, McKinlay.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Cartwright, McKinlay.
Obtained funding: Crowther, Harding.
Administrative, technical, or material support: Crowther, McKinlay.
Supervision: Anderson, Doyle, McKinlay.
Conflict of Interest Disclosures: Dr Doyle reported receiving grants from National Health and Medical Research Council of Australia during the conduct of the study. Dr McKinlay reported receiving grants from the Auckland Medical Research Foundation during the conduct of the study. No other disclosures were reported.
Funding/Support: This study was supported by the National Health Medical Research Council of Australia, the Health Research Council of New Zealand, and the Auckland Medical Research Foundation.
Role of the Funder/Sponsor: The sponsors had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Additional Contributions: We thank all the women and their children who participated in this study. Pat Ashwood, BSc, University of Adelaide, served as the study coordinator. Kristyn Willson, BSc, University of Adelaide, served as the trial biostatistician. Neither individual was financially compensated for these contributions.
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