PURPOSE: Advances in surgical techniques allow implantation of intraocular lenses (IOL) with cataract extraction, even in young children. However, there are several challenges unique to the pediatric population that result in greater degrees of postoperative refractive error compared to adults. METHODS: Literature review of the techniques and outcomes of pediatric cataract surgery with IOL implantation. RESULTS: Pediatric cataract surgery is associated with several sources of postoperative refractive error. These include planned refractive error based on age or fellow eye status, loss of accommodation, and unexpected refractive errors due to inaccuracies in biometry technique, use of IOL power formulas based on adult normative values, and late refractive changes due to unpredictable eye growth. CONCLUSIONS: Several factors can preclude the achievement of optimal refractive status following pediatric cataract extraction with IOL implantation. There is a need for new technology to reduce postoperative refractive surprises and address refractive adjustment in a growing eye.
: During normal foveal development there is a close interaction between the neurosensory and vascular elements of the fovea making it vulnerable to prematurity and retinopathy of prematurity (ROP). We aim to assess this potential effect on foveal development in preterms evaluated simultaneously with both optical coherence tomography (OCT) and OCT angiography (OCTA).: Unrestricted literature search in the PubMed and Cochrane library databases yielded 20 distinct citations. Fifteen were relevant and reviewed.: In preterms, OCTA demonstrated a significant decrease in the foveal avascular zone area and an increase in foveal vessel density. OCT showed a decrease in foveal pit depth and an increase in the thickness of the subfoveal retinal layers. Some studies correlated these changes with reduced vision.: Changes in the vascular and neurosensory retina were found in premature children. It remains unclear whether this is related to prematurity alone or ROP and its treatment.
Glaucoma is a common and sight-threatening complication of pediatric cataract surgery Reported incidence varies due to variability in study designs and length of follow-up. Consistent and replicable risk factors for developing glaucoma following cataract surgery (GFCS) are early age at the time of surgery, microcornea, and additional surgical interventions. The exact mechanism for GFCS has yet to be completely elucidated. While medical therapy is the first line for treatment of GFCS, many eyes require surgical intervention, with various surgical modalities each posing a unique host of risks and benefits. Angle surgical techniques include goniotomy and trabeculotomy, with trabeculotomy demonstrating increased success over goniotomy as an initial procedure in pediatric eyes with GFCS given the success demonstrated throughout the literature in reducing IOP and number of IOP-lowering medications required post-operatively. The advent of microcatheter facilitated circumferential trabeculotomies lead to increased success compared to traditional <180° rigid probe trabeculotomy in GFCS. The advent of two-site rigid-probe trabeculotomy indicated that similar results could be attained without the use of the more expensive microcatheter system. Further studies of larger scale, with increased follow-up, and utilizing randomization would be beneficial in determining optimum surgical management of pediatric GFCS.
Variants in multiple tubulin genes have been implicated in neurodevelopmental disorders, including malformations of cortical development (MCD) and congenital fibrosis of the extraocular muscles (CFEOM). Distinct missense variants in the beta-tubulin encoding genes TUBB3 and TUBB2B cause MCD, CFEOM, or both, suggesting substitution-specific mechanisms. Variants in the alpha tubulin-encoding gene TUBA1A have been associated with MCD, but not with CFEOM. Using exome sequencing (ES) and genome sequencing (GS), we identified 3 unrelated probands with CFEOM who harbored novel heterozygous TUBA1A missense variants c.1216C>G, p.(His406Asp); c.467G>A, p.(Arg156His); and c.1193T>G, p.(Met398Arg). MRI revealed small oculomotor-innervated muscles and asymmetrical caudate heads and lateral ventricles with or without corpus callosal thinning. Two of the three probands had MCD. Mutated amino acid residues localize either to the longitudinal interface at which α and β tubulins heterodimerize (Met398, His406) or to the lateral interface at which tubulin protofilaments interact (Arg156), and His406 interacts with the motor domain of kinesin-1. This series of individuals supports TUBA1A variants as a cause of CFEOM and expands our knowledge of tubulinopathies.
OBJECTIVE: Steady state insulin-like growth factor-1 (IGF-1) levels vary significantly during continuous intravenous infusion of recombinant human insulin-like growth factor-1/recombinant human insulin-like growth factor binding protein-3 (rhIGF-1/rhIGFBP-3) in the first weeks of life in extremely preterm infants. We evaluated interleukin-6 (IL-6) and insulin-like growth factor binding protein-1 (IGFBP-1) levels as predictors of low IGF-1 levels. METHODS: Nineteen extremely preterm infants were enrolled in a trial, 9 received rhIGF-1/rhIGFBP-3 and 10 received standard neonatal care. Blood samples were analyzed daily for IGF-1, IL-6 and IGFBP-1 during intervention with rhIGF-1/rhIGFBP-3. RESULTS: Thirty seven percent of IGF-1 values during active treatment were <20 μg/L. Among treated infants, higher levels of IL-6, one and two days before sampled IGF-1, were associated with IGF-1 < 20 μg/L, gestational age adjusted OR 1.30 (95% CI 1.03-1.63), p = .026, and 1.57 (95% CI 1.26-1.97), p < .001 respectively. Higher levels of IGFBP-1 one day before sampled IGF-1 was also associated with IGF-1 < 20 μg/L, gestational age adjusted OR 1.74 (95% CI 1.19-2.53), p = .004. CONCLUSION: In preterm infants receiving continuous infusion of rhIGF-1/rhIGFBP-3, higher levels of IL-6 and IGFBP-1 preceded lower levels of circulating IGF-1. These findings demonstrate a need to further evaluate if inflammation and/or infection suppress serum IGF-1 levels. The trial is registered at ClinicalTrials.gov (NCT01096784).
OBJECTIVES: To examine differences in growth patterns in preterm infants developing major morbidities including retinopathy of prematurity (ROP), bronchopulmonary dysplasia (BPD), necrotising enterocolitis (NEC) and intraventricular haemorrhage (IVH). STUDY DESIGN: Cohort study of 2521 infants born at a gestational age (GA) of 23-30 weeks from 11 level III neonatal intensive care units in USA and Canada, and 3 Swedish population-based cohorts. OUTCOMES: Birth weight and postnatal weight gain were examined relative to birth GA and ROP, BPD, NEC and IVH development. RESULTS: Among infants with a birth GA of 25-30 weeks, birth weight SD score and postnatal weight were lower in those developing ROP and BPD. Infants developing ROP showed lower growth rates during postnatal weeks 7-9 in the 23-24 weeks GA group, during weeks 4-6 in the 25-26 weeks GA group and during weeks 1-5 in the 27-30 weeks GA group. Infants with BPD born at 27-30 weeks GA showed lower growth rates during postnatal weeks 3-5. Infants with NEC had lower growth rates after postnatal week 6 in all GA groups, with no significant differences in birth weight SD score. IVH was not associated with prenatal or postnatal growth. CONCLUSIONS: In this cohort study of extremely preterm infants, we found that the postnatal growth pattern was associated with morbidities such as ROP, BPD and NEC as well as with gestational age at birth.
OBJECTIVES: Surveys are an important tool to assess the impact of research on physicians' approach to patient care. This survey was conducted to assess current practice patterns in the management of infantile cataracts in light of the findings of the Infant Aphakia Treatment Study. METHODS: Pediatric ophthalmologists were emailed a link to the survey using newsletters from American Association of Pediatric Ophthalmology and Strabismus, World Society of Pediatric Ophthalmology and Strabismus, and the Pediatric Listserv. The 17-question survey was anonymous and active during July to August 2016. RESULTS: One hundred twenty-five respondents (North America, 65%; Asia, 12%; Europe, 9%; and other, 14%) reported operating on pediatric cataracts. Most practice in a university setting (55%). There was a strong consensus that unilateral cataract surgery should be performed between ages 4 to 6 weeks and aphakic contact lenses should be used to optically correct their eyes, particularly in children ≤6 months of age. For bilateral cataracts, there was a trend for surgeons to perform cataract surgery at an older age than unilateral cataract surgery. Surgeons who performed less than 5 versus greater than 20 pediatric cataract surgeries/year were more likely to use aphakic contact lenses in children undergoing cataract surgery more than 6 months of age (62% vs. 35%, P=0.04). Most respondents (73%) indicated that the Infant Aphakia Treatment Study had changed how they manage unilateral congenital cataracts. CONCLUSION: Most pediatric cataract surgeons perform congenital cataract surgery between ages 4 to 6 weeks and use aphakic contact lenses for initial optical correction in infants less than 6 months. Surgeons have equal preference for intraocular lenses and contact lenses in infants more than 6 months of age.
PURPOSE: To characterize the risk and risk factors for intraocular pressure (IOP) elevation in pediatric noninfectious uveitis. DESIGN: Multicenter retrospective cohort study. PARTICIPANTS: Nine hundred sixteen children (1593 eyes) younger than 18 years at presentation with noninfectious uveitis followed up between January 1978 and December 2007 at 5 academic uveitis centers in the United States. METHODS: Medical records review by trained, certified experts. MAIN OUTCOME MEASURES: Prevalence and incidence of IOP of 21 mmHg or more and 30 mmHg or more and incidence of a rise in IOP by 10 mmHg or more. To avoid underascertainment, outcomes were counted as present when IOP-lowering therapies were in use. RESULTS: Initially, 251 (15.8%) and 46 eyes (2.9%) had IOP ≥21 mmHg and ≥30 mmHg, respectively. Factors significantly associated with presenting IOP elevation included age of 6 to 12 years (versus other pediatric ages), prior cataract surgery, pars plana vitrectomy, duration of uveitis ≥6 months, contralateral IOP elevation, presenting visual acuity worse than 20/40, and topical corticosteroid use (in a dose-response relationship). The median follow-up was 1.25 years (interquartile range, 0.4-3.66). The estimated incidence of any observed IOP elevation to ≥21 mmHg, to ≥30 mmHg, and increase in IOP by ≥10 mmHg was 33.4%, 14.8%, and 24.4%, respectively, within 2 years. Factors associated with IOP elevation included pars plana vitrectomy, contralateral IOP elevation (adjusted hazard ratio [aHR], up to 9.54; P < 0.001), and the use of topical (aHR, up to 8.77 that followed a dose-response relationship; P < 0.001), periocular (aHR, up to 7.96; P < 0.001), and intraocular (aHR, up to 19.7; P < 0.001) corticosteroids. CONCLUSIONS: Intraocular pressure elevation affects a large minority of children with noninfectious uveitis. Statistically significant risk factors include IOP elevation or use of IOP-lowering treatment in the contralateral eye and local corticosteroid use that demonstrated a dose-and route of administration-dependent relationship. In contrast, use of immunosuppressive drug therapy did not increase such risk. Pediatric eyes with noninfectious uveitis should be followed up closely for IOP elevation, especially when strong risk factors such as the use of local corticosteroids and contralateral IOP elevation are present.
Cerebral/cortical visual impairment (CVI) is characterized by higher order visual dysfunction caused by injury to the retrogeniculate visual pathways and brain structures which subserve visual processing. CVI has become the leading cause of significant vision loss in children in developed countries, but continues to be an under-recognized cause of visual disability with respect to services aimed at maximizing visual development. Current criteria which are used to define visual disability rely on measures of visual acuity and visual field. Many children who require specialized vision services do not qualify, because these standard definitions of vision impairment do not account for CVI. In order to appropriately identify patients with CVI and offer the resources which may positively impact functional use of vision, the definition of visual impairment and blindness needs to be modified. This commentary calls for a change in the definition of visual impairment and blindness to acknowledge those persons with brain-based vision impairment.
PURPOSE: To measure binocular interaction in amblyopes using a rapid and patient-friendly computer-based method, and to test the feasibility of the assessment in the clinic. METHODS: Binocular interaction was assessed in subjects with strabismic amblyopia (n = 7), anisometropic amblyopia (n = 6), strabismus without amblyopia (n = 15) and normal vision (n = 40). Binocular interaction was measured with a dichoptic phase matching task in which subjects matched the position of a binocular probe to the cyclopean perceived phase of a dichoptic pair of gratings whose contrast ratios were systematically varied. The resulting effective contrast ratio of the weak eye was taken as an indicator of interocular imbalance. Testing was performed in an ophthalmology clinic under 8 mins. We examined the relationships between our binocular interaction measure and standard clinical measures indicating abnormal binocularity such as interocular acuity difference and stereoacuity. The test-retest reliability of the testing method was also evaluated. RESULTS: Compared to normally-sighted controls, amblyopes exhibited significantly reduced effective contrast (∼20%) of the weak eye, suggesting a higher contrast requirement for the amblyopic eye compared to the fellow eye. We found that the effective contrast ratio of the weak eye covaried with standard clincal measures of binocular vision. Our results showed that there was a high correlation between the 1st and 2nd measurements (r = 0.94, p<0.001) but without any significant bias between the two. CONCLUSIONS: Our findings demonstrate that abnormal binocular interaction can be reliably captured by measuring the effective contrast ratio of the weak eye and quantitative assessment of binocular interaction is a quick and simple test that can be performed in the clinic. We believe that reliable and timely assessment of deficits in a binocular interaction may improve detection and treatment of amblyopia.
PURPOSE: To compare the visual outcomes and adverse events associated with optical correction using an intraocular lens (IOL), contact lenses, or spectacles after cataract surgery in children 2 years of age or younger. METHODS: Literature searches were conducted in PubMed, the Cochrane Library, and the databases of clinical trials in February 2019, without date or language restrictions. The search resulted in 194 potentially relevant citations, and 34 were selected for full-text review. Fourteen studies were determined to be relevant to the assessment criteria and were selected for inclusion in this assessment. The panel methodologist then assigned a level of evidence rating to these studies. RESULTS: Intraocular lenses were associated with visual outcomes similar to outcomes for contact lenses or spectacles for children who had both bilateral and unilateral cataracts. Intraocular lenses were also associated with an increased risk of visual axis opacities. All treatments were associated with a similar incidence of glaucoma. Although ocular growth was similar for all treatments, infants younger than 6 months who underwent IOL implantation had large myopic shifts that often resulted in high myopia or severe anisometropia later in childhood. Corneal endothelial cell counts were lower in eyes that underwent IOL implantation. The incidence of strabismus was similar with all treatments. CONCLUSIONS: Intraocular lens implantation is not recommended for children 6 months of age or younger because there is a higher incidence of visual axis opacities with this treatment compared with aphakia. The best available evidence suggests that IOL implantation can be done safely with acceptable side effects in children older than 6 months of age. However, the unpredictability of ocular growth means that these children will often have large refractive errors later in childhood that may necessitate an IOL exchange or wearing spectacles or contact lenses with a large refractive correction. In addition, the training and experience of the surgeon as well as ocular and systemic comorbidities should be taken into consideration when deciding whether IOL implantation would be appropriate.
PURPOSE: To review the published literature to assess the visual outcomes and adverse events associated with the 2 most commonly used contact lenses for treating aphakia in children: silicone elastomer (SE) and rigid gas permeable (RGP). METHODS: Literature searches were last conducted in January 2018 in the PubMed, Cochrane Library, and ClinicalTrials.gov databases with no date or language restrictions. These combined searches yielded 167 citations, 27 of which were reviewed in full text. Of these, 10 articles were deemed appropriate for inclusion in this assessment and subsequently assigned a level of evidence rating by the panel methodologist. RESULTS: The literature search identified 4 level II studies and 6 level III studies. There were insufficient data to compare visual outcomes for eyes treated using SE lenses versus RGP lenses. Silicone elastomer lenses have the advantage that they can be worn on an extended-wear basis, but they were associated with more adverse events than RGP lenses. These adverse events included microbial keratitis, corneal infiltrates, corneal edema, corneal scars, lenses adhering to the cornea, superficial punctate keratopathy, lid swelling, and conjunctival hyperemia. The lens replacement rate was approximately 50% higher for RGP lenses in the only study that directly compared SE and RGP lenses. CONCLUSIONS: Limited evidence was found in the literature on this topic. Silicone elastomer and RGP contact lenses were found to be effective for treating aphakia in children. Silicone elastomer lenses are easier to fit and may be worn on an extended-wear basis. Rigid gas permeable lenses must be removed every night and require a more customized fit, but they are associated with fewer adverse events. The choice of which lens a practitioner prescribes should be based on the particular needs of each patient.
OBJECTIVE: To evaluate to what extent indicators of placenta insufficiency are associated with low concentrations of insulin-like growth factor 1 (IGF-1) and IGF-1-binding protein-1 (IGFBP-1) in neonatal blood, and to what extent the concentrations of these growth factors are associated with concentrations of proteins with inflammatory, neurotrophic, or angiogenic properties. STUDY DESIGN: Using multiplex immunoassays, we measured the concentrations of IGF-1 and IGFBP-1, as well as 25 other proteins in blood spots collected weekly from ≥ 880 infants born before the 28th week of gestation, and sought correlates of concentrations in the top and bottom quartiles for gestational age and day the specimen was collected. RESULTS: Medically indicated delivery and severe fetal growth restriction (sFGR) were associated with low concentrations of IGF-1 on the first postnatal day and with high concentrations of IGFBP-1 on almost all days. Elevated concentrations of IGF-1 and IGFBP-1 were accompanied by elevated concentrations of many other proteins with inflammatory, neurotrophic, or angiogenic properties. CONCLUSION: Disorders associated with impaired placenta implantation and sFGR appear to account for a relative paucity of IGF-1 on the first postnatal day. Elevated concentrations of IGF-1 and especially IGFBP-1 were associated with same-day elevated concentrations of inflammatory, neurotrophic, and angiogenic proteins.
Ley D, Hallberg B, Hansen-Pupp I, Dani C, Ramenghi LA, Marlow N, Beardsall K, Bhatti F, Dunger D, Higginson JD, Mahaveer A, Mezu-Ndubuisi OJ, Reynolds P, Giannantonio C, van Weissenbruch M, Barton N, Tocoian A, Hamdani M, Jochim E, Mangili A, Chung J-K, Turner MA, Smith LEH, Hellström A, Hellström A. rhIGF-1/rhIGFBP-3 in Preterm Infants: A Phase 2 Randomized Controlled Trial. J Pediatr 2019;206:56-65.e8.Abstract
OBJECTIVE: To investigate recombinant human insulin-like growth factor 1 complexed with its binding protein (rhIGF-1/rhIGFBP-3) for the prevention of retinopathy of prematurity (ROP) and other complications of prematurity among extremely preterm infants. STUDY DESIGN: This phase 2 trial was conducted from September 2014 to March 2016. Infants born at a gestational age of 23 weeks to 27 weeks were randomly allocated to rhIGF-1/rhIGFBP-3 (250 µg/kg/ 24 hours, continuous intravenous infusion from <24 hours of birth to postmenstrual age 29 weeks) or standard neonatal care, with follow-up to a postmenstrual age of 40 weeks. Target exposure was ≥70% IGF-1 measurements within 28-109 µg/L and ≥70% intended therapy duration. The primary endpoint was maximum severity of ROP. Secondary endpoints included time to discharge from neonatal care, bronchopulmonary dysplasia, intraventricular hemorrhage, and growth measures. RESULTS: Overall, 61 infants were allocated to rhIGF-1/rhIGFBP-3, 60 to standard care (full analysis set); 24 of 61 treated infants achieved target exposure (evaluable set). rhIGF-1/rhIGFBP-3 did not decrease ROP severity or ROP occurrence. There was, however, a 53% decrease in severe bronchopulmonary dysplasia in the full analysis set (21.3% treated vs 44.9% standard care), and an 89% decrease in the evaluable set (4.8% vs 44.9%; P = .04 and P = .02, respectively) for severity distribution between groups. There was also a nonsignificant trend toward decrease in grades 3-4 intraventricular hemorrhage in the full analysis set (13.1% vs 23.3%) and in the evaluable set (8.3% vs 23.3%). Fatal serious adverse events were reported in 19.7% of treated infants (12/61) and 11.7% of control infants (7/60). No effect was observed on time to discharge from neonatal care/growth measures. CONCLUSIONS: rhIGF-1/rhIGFBP-3 did not affect development of ROP, but decreased the occurrence of severe bronchopulmonary dysplasia, with a nonsignificant decrease in grades 3-4 intraventricular hemorrhage. TRIAL REGISTRATION: ClinicalTrials.gov: NCT01096784.
The retina is part of the central nervous system and both the retina as well as the brain can suffer from severe damage after very preterm birth. Retinopathy of prematurity is one of the major causes of blindness in these children and brain neuronal impairments including cognitive defects, cerebral palsy and intraventricular hemorrhage (IVH) are also complications of very preterm birth. Insulin-like growth factor 1 (IGF-1) acts to promote proliferation, maturation, growth and survival of neural cells. Low levels of circulating IGF-1 are associated with ROP and defects in the IGF-1 gene are associated with CNS disorders including learning deficits and brain growth restriction. Treatment of preterm infants with recombinant IGF-1 may potentially prevent ROP and CNS disorders. This review compares the role of IGF-1 in ROP and CNS disorders. A recent phase 2 study showed a positive effect of IGF-1 on the severity of IVH but no effect on ROP. A phase 3 trial is planned.
Importance: Mice with oxygen-induced retinopathy fed matched diets except for ω-3 long-chain polyunsaturated fatty acids (LC-PUFAs) vs ω-6 LC-PUFAs demonstrate relative antiangiogenic and neuroprotective associations of ω-3 LC-PUFAs. However, supplementing preterm infants with LC-PUFAs has been inconsistent in reducing major preterm morbidities. However, few studies measured serum lipid levels after supplementation.
Objective: To examine the associated risk of retinopathy of prematurity (ROP) from the levels of circulating ω-3 and ω-6 LC-PUFAs.
Design, Setting, and Participants: This longitudinal clinical study was a further analysis of serum lipid levels from a randomized controlled trial cohort of 90 infants born at gestational age (GA) less than 28 weeks. From April 4, 2013, to September 22, 2015, cord blood samples, followed by venous blood samples, were obtained at birth and at 1, 7, 14, and 28 days after birth and then at postmenstrual age (PMA) 32, 36, and 40 weeks at the neonatal intensive care unit at Sahlgrenska University Hospital in Göteborg, Sweden.
Main Outcomes and Measures: Serum phospholipid fatty acids were transmethylated and measured by gas chromatography-mass spectrometry. Mann-Whitney test, logistic regression Spearman rank correlation, and receiver operating characteristic curve analysis were used to compare differences between infants with no ROP and infants who developed ROP.
Results: Serum levels from 78 infants (43 male [55%]; mean [SD] GA, 25.5 [1.4] weeks) with a known ROP outcome were evaluated. Lower area under the curve (AUC) of arachidonic acid (AA) (20:4 ω-6) was seen in infants with a later diagnosis of ROP compared with infants with no ROP in the first month of life (mean, 34.05 [95% CI, 32.10-36.00] vs 37.15 [95% CI, 34.85-39.46]; P < .05). In addition, lower levels of AA at 32 weeks' PMA were seen in infants with later severe ROP compared with in those without ROP (mean, 7.06 [95% CI, 6.60-7.52] vs 8.74 [95% CI, 7.80-9.67]; P < .001). In logistic modeling, low postnatal serum levels of AA and GA at birth identified with a sensitivity greater than 90% of infants who developed ROP.
Conclusions and Relevance: Low postnatal levels of the ω-6 LC-PUFAs (AA) are strongly associated with ROP development. Evaluating postnatal AA fraction after birth in addition to GA may be useful for ROP prediction.
Trial Registration: clinicaltrials.gov Identifier: NCT02760472.
BACKGROUND/AIMS: To determine whether timing of ophthalmic screening influences prevalence of neonatal fundus haemorrhages. We compared the prevalence of fundus haemorrhages in two populations: term newborns screened early (less than 72 hours) and preterm newborns screened late (4-11 weeks). Additionally, we reviewed the literature on timing and prevalence of newborn haemorrhages. METHODS: Retrospective observational cohort study. Infants who underwent wide-angle ophthalmic digital imaging over one overlapping year in the Newborn Eye Screen Testing (NEST) or Stanford University Network for Diagnosis of Retinopathy of Prematurity (SUNDROP) programme were included. The PubMed database was filtered to include English-language articles dating back to 1950. Nine articles were selected for review based on inclusion of the prevalence of newborn fundus haemorrhages at multiple time points. RESULTS: A total of 202 patients received early imaging in the NEST cohort and 73 patients received late imaging in the SUNDROP cohort. In the NEST cohort, 20.2% of newborns had haemorrhages. In contrast, we found haemorrhages in only one case or 1.4% of the SUNDROP cohort. Using prevalence data from nine additional studies, we developed a predicted probabilities model of newborn haemorrhages. Per this model, the probability of seeing a haemorrhage if you screen an infant at 1 hour is 18.8%, at 2 weeks is 2.9% and at 1 month is 0.28%. CONCLUSION: We found a significant difference in the prevalence of fundus haemorrhages between the early-screened NEST cohort and the late-screened, preterm SUNDROP cohort. Likely, this difference is due to the transient nature of most newborn haemorrhages.