A co-twin study of the relative effect of birth weight and gestational age on retinopathy of prematurity

Respiratory outcomes in preterm infants following intravitreal bevacizumab for retinopathy of prematurity-a 10-year matched case study

OBJECTIVES

To evaluate respiratory outcomes in preterm infants with retinopathy of prematurity (ROP) following intravitreal bevacizumab injection (IVB).

METHODS

This single-centre study enroled preterm infants with a gestational age (GA) < 34 weeks or a birth weight (BW) < 1500 g with bilateral type 1 ROP who received a single IVB, and a treatment-free control group matched by GA, postmenstrual age, and respiratory status at the time of the IVB. The primary outcome was serial respiratory changes in mean airway pressure (MAP), fraction of inspired oxygen (FiO2), and respiratory severity score (RSS, MAP x FiO2) during the 28-day post-IVB/matching period and overall respiratory improvement at day 28 and at discharge. The duration of supplemental oxygen therapy following IVB/matching was documented.

RESULTS

A total of 5578 infants were included. Seventy-eight infants were enroled in the IVB group, and another 78 infants were matched as the control group. Both groups had downward trends in the MAP, FiO2, and RSS over the study period (all P < 0.001), but there were no between-group differences in these measures. The percentage of overall respiratory improvement was similar between the IVB and control groups, so was the duration of invasive and in-hospital oxygen ventilation. A lower percentage of oxygen dependence at discharge in the IVB group (P = 0.03) remained significant after adjusting for GA and BW.

CONCLUSIONS

This is a matched case study to evaluate respiratory outcomes in preterm infants following IVB for ROP. We found that the IVBs did not compromise respiratory outcomes in preterm infants during the 28-day post-IVB period and at discharge.

Association between fetal growth-restriction and retinopathy of prematurity using a unique identical twin model

BACKGROUND

Research in singletons identified fetal growth restriction (FGR) as a risk factor for retinopathy of prematurity (ROP), but is generally subject to confounding by genetic, obstetric, and maternal factors. We investigated the effect of FGR on ROP in growth-discordant identical twins, thereby controlling for confounding factors.

METHODS

All data of monochorionic (MC) twin pairs with a birth weight discordance ≥20% born in our center between 2010 and 2021 were retrospectively reviewed for the presence of ROP. Potential risk factors for ROP were analyzed. Outcomes were compared between the smaller and larger twin.

RESULTS

We included 88 MC twin pairs with growth discordance. In 34% (30/88), both neonates were at risk of ROP. Prevalence of ROP was higher among the smaller twin compared to the larger twin, 30% (9/30) versus 13% (4/30), respectively (OR 2.8, 95% CI: 1.2-6.6). The smaller twin had a longer duration of mechanical ventilation (8 (1-20) versus 2 (1-4) days) and received their first red blood cell transfusion at an earlier postmenstrual age (29.6 (28.1-31.6) versus 30.4 (29.7-32.6) weeks).

CONCLUSIONS

In this identical twin model, FGR is associated with almost tripled odds of ROP development, suggesting that both unfavorable antenatal growth conditions and adverse neonatal outcomes affect postnatal retinal vascular proliferation.

IMPACT

Fetal growth restriction in growth-discordant identical twins is associated with almost tripled odds of developing retinopathy of prematurity in the smaller twin. Since these twins do not only differ in birth weight but also duration of mechanical ventilation and timing of the first red blood cell transfusion, both unfavorable antenatal growth conditions and adverse neonatal outcomes can affect postnatal retinal vascular proliferation. More attention for preventing retinopathy of prematurity is needed in those with fetal growth restriction who received prolonged duration of mechanical ventilation, oxygen supplementation, or a first red blood cell transfusion <32 weeks postmenstrual age.

Treatment for Retinopathy of Prematurity in Twins: The Small Twin without High Birth Weight Discordant Is Not at Increased Risk

Purpose: As common retinopathy is observed in low-birth infants, the characteristics of ROP in twins are worth exploring. The present study tried to demonstrate the risk factors of treatment for retinopathy of prematurity (ROP) in twins both diagnosed with ROP. Methods: A retrospective, institution-based cohort study of 62 premature ROP twin pairs with a mean gestational age (GA) younger than 35 weeks and a birth weight (BW) lower than 2500 g. Only infants with a follow-up period longer than 6 months and complete treatment records were included. The demographic data, treatment requirements and further rescue treatments were all collected and analyzed for all infants according to whether they accepted treatments. Moreover, all twin infants were divided into small and large twin groups according to birth weight, and they were also categorized as three groups according to the treatment requirement including both twins receiving treatment (BT group), one of the twins receiving treatment (ST group) and none of the twins receiving treatment (NT group). Comparisons of demographic data, treatment requirements and further rescue treatments were all conducted according to the different grouping methods. Results: The mean GA of the enrolled infants was (29.29 ± 2.45) weeks with a mean BW of (1335.77 ± 390.36) grams. Among them, 110 infants were mechanically ventilated. Fifty-one of the infants did not receive any treatment and 73 infants received laser or intravitreal injection of anti-VEGF agents. In total, 64 infants only underwent intravitreal injection of anti-VEGF agents or laser treatment, while the other nine infants received scleral buckling or vitrectomy as a necessary treatment when the retinal detachment was observed. No significantly different mechanical ventilation or treatment requirements could be observed between the small twin group and the large twin group (p = 0.73, 0.94). The twins in the BT groups showed the lowest BW, while the NT group infants had the highest BW. The GA for the BT, ST and NT groups were (27.86 ± 1.87) weeks, (29.60 ± 1.52) weeks and (31.33 ± 2.39) weeks, respectively, and showed significant differences as well (p < 0.001). Conclusion: Being a small twin in twin-paired ROP without a high BW discordant will not increase the risk for treatment requirement or additional surgery necessity with a much more severe stage of ROP.

Clinical features of premature twin babies with intersibling asymmetry of retinopathy of prematurity severity

OBJECTIVE

To report the clinical features of premature twin babies showing intersibling asymmetry in their severity of retinopathy of prematurity (ROP) and analyze risk factors associated with development of severe ROP between twin siblings with discordant ROP severity.

METHODS

A retrospective study of records of 105 premature twin pairs was conducted. The criteria for discordant ROP with an intersibling difference in ROP severity were as follows: (i) two or more stages of difference in ROP between siblings, (ii) one sibling having treatment-requiring ROP and the other having no ROP or ROP that regressed spontaneously, or (iii) one sibling having aggressive posterior ROP and the other having staged or no ROP. Twin siblings were classified into two groups according to the severity of ROP (no or less ROP and more severe ROP). We examined ocular features in twins having intersibling asymmetry of ROP and analyzed perinatal risk factors for ROP.

RESULTS

Of 105 twin pairs, 32 pairs (30.5%) showed intersibling asymmetry of ROP severity, and 15 pairs (14.3%) showed ROP asymmetry in terms of need for ROP treatment. The development of more severe ROP was associated with longer duration of oxygen supplementation and greater frequency of total blood and packed red blood cell transfusion (p = 0.020, p = 0.045, and p = 0.036, respectively). Longer duration of oxygen supplementation remained a statistically independent risk factor of severe ROP using multivariate logistic regression analysis.

CONCLUSIONS

Ophthalmologists caring for premature infants should be aware of the variable courses and progressions of ROP between twin babies. Longer duration of oxygen supplementation and greater frequency of blood transfusions were associated with higher ROP severity in twins.

Effect of birth weight on retinopathy of prematurity in discordant twin pairs

Purpose:

Since twin pairs with discordance have equal gestational age (GA), discordant twins may constitute an appropriate group to investigate the specific effect that birth weight (BW) has on the development of retinopathy of prematurity (ROP). The present study aims to investigate the effect of BW on any and severe stages of ROP development in twin pairs.

Methods:

Fifty-two discordant twin pairs (104 preterms) born ≤32 gestational weeks, who were diagnosed with a minimum of 18% discordance between their BWs, were retrospectively analyzed. Twin pairs were separated into two groups based on the BW of each pair. The rate of any stage of ROP, Type 1 ROP, and perinatal risk factors were compared statistically among twin pairs.

Results:

The rate of any stage of ROP and Type 1 ROP was 24.0% and 4.8% in the whole group, respectively. A statistically significant difference was shown between lower and higher BW groups at any stage of ROP development (34.6% vs. 13.4%, P = 0.02). However, no difference was observed in Type 1 ROP development (7.7% vs. 1.9%, P = 0.17). No significant differences were found between twin pairs regarding neonatal morbidities. The number of small GA (SGA) infants in the smaller twin group was statistically higher than larger group and regression analysis showed that being SGA had significant correlation with any stage of ROP (odds ratio: 4.98, P = 0.02).

Conclusion:

This study showed that BW serves an effective role at any stage of ROP development in discordant twin pairs; however, no significant difference in terms of Type 1 ROP.

Retinopathy of prematurity: A comprehensive risk analysis for prevention and prediction of disease

BACKGROUND

Retinopathy of prematurity (ROP) is a blinding morbidity of preterm infants. Our current screening criteria have remained unchanged since their inception and lack the ability to identify those at greatest risk.

OBJECTIVES

We sought to comprehensively analyze numerous proposed maternal, infant, and environmental ROP risk variables in a robustly phenotyped population using logistic regression to determine the most predictive model for ROP development and severity. We further sought to determine the statistical interaction between significant ROP risk variables, which has not previously been done in the field of ROP. We hypothesize that our comprehensive analysis will allow for better identification of risk variables that independently correlate with ROP disease. Going forward, this may allow for improved infant risk stratification along a time continuum from prenatal to postnatal development, making prevention more feasible.

METHODS

We performed a retrospective cohort analysis of preterm infants referred for ROP screening in one neonatal intensive care unit from 2010-2015. The primary outcome measure was presence of ROP. Secondary outcome measures were ROP requiring treatment and severe ROP not clearly meeting current treatment criteria. Univariate, stepwise regression and statistical interaction analyses of 57 proposed ROP risk variables was performed to identify variables which were significantly associated with each outcome measure.

RESULTS

We identified 457 infants meeting our inclusion criteria. Within this cohort, numerous factors showed a significant individual association with our ROP outcome measures; however, stepwise regression analysis found the most predictive model for overall ROP risk included estimated gestational age, birth weight, the need for any surgery, and maternal magnesium prophylaxis. The corresponding Area Under the Curve (AUC) for this model was 0.8641, while the traditional model of gestational age and birth weight predicted ROP disease less well with an AUC of 0.8489. Development of severe ROP was best predicted by estimated gestational age (week), the need for any surgery and increased probability of death or moderate-severe BPD at 7 days. Finally, the model most predictive for type 1 ROP included estimated gestational age (week) and the presence of severe chronic lung disease. No significant statistical interaction was found between variables.

CONCLUSIONS

Our work is unique as we report comprehensive analysis of the greatest number of proposed ROP risk variables to date in a robustly phenotyped population. We describe novel risk models for our ROP outcome measures and demonstrate independence of these variables using statistical modeling not previously applied to ROP. This may better allow for individual infant risk stratification and importantly mitigation of future risk.

Treatment of retinopathy of prematurity in Northern Ireland, 2000-2011: a population-based study

PURPOSE

To evaluate the incidence of treatment-requiring retinopathy of prematurity (ROP) over a 12-year-period in Northern Ireland.

METHODS

The medical records of all infants treated for ROP from January 2000 to December 2011 were retrospectively reviewed and cross-referenced with the Neonatal Intensive Care Outcomes Research and Evaluation (NICORE) database.

RESULTS

The Northern Ireland population data showed an increase in the number of live births from 2000 to 2011. The proportion of babies born with a birth weight <1501 g and/or <32 weeks' gestational age remained constant (χ(2) trend = 3.220, P = 0.0727), although the proportion of these babies who died prior to 42 weeks' gestation decreased from 2000 to 2011 (P = 0.0196 using χ(2) for trend = 5.445; P = 0.0354 using χ(2) = 20.809). The prevalence of treatment-requiring ROP in these infants increased from 1.05% in 2000 to 5.78% in 2011 (P < 0.001 using χ(2) trend = 16.309; P < 0.001 using χ(2) = 31.378).

CONCLUSIONS

The present population-based study highlights that the incidence of treatment- requiring ROP is increasing in Northern Ireland. The increasing number of infants requiring treatment will need to be taken into consideration in the commissioning process for ROP services in Northern Ireland.

Risk factors for retinopathy of prematurity in extremely preterm Chinese infants

To investigate the incidence and risk factors of retinopathy of prematurity (ROP) and Type 1 ROP in extremely preterm Chinese infants. A retrospective review of medical records was performed of all extremely preterm neonates (gestational age, GA≤28 weeks) screened for ROP from 2007 to 2012 at an ophthalmology centre in Hong Kong. Thirty-three maternal and neonatal covariates were analyzed using univariate and multivariate regression analyses for both ROP and Type 1 ROP. The mean gestational age (GA) was 26.4±1.3 weeks and the birth weight (BW) was 855.0±199.0 g. The incidence of ROP development was 60.7% and 16.2% for Type 1 ROP. On univariate analysis, 6 risk factors were identified for ROP development including: lighter BW; lower GA; postnatal hypotension; inotrope use; surfactant use; and invasive mechanical ventilation (all P≤0.01). On multivariate analysis, neonatal congenital heart disease and greater GA were protective factors for ROP development (P≤0.04). On the other hand, 4 risk factors were associated with Type 1 ROP development in univariate analysis, including: lower GA, lighter BW, multiple pregnancies, and invasive mechanical ventilation (all P≤0.02); while there was no significant risk factors on multivariate analysis. A lighter BW and lower GA were the only common independent risk factors for both ROP and Type 1 ROP while neonatal congenital heart disease and greater GA were the protective factors against ROP.

Differences in risk factors for retinopathy of prematurity development in paired twins: a Chinese population study

Purpose. To determine the differences in risk factors for retinopathy of prematurity (ROP) in paired twins. Methods. A retrospective medical record review was performed for all paired twins screened for ROP between 2007 and 2012. Screening was offered to very low birth weight (≤1500 grams) and preterm (≤32 weeks) neonates. Twins 1 and 2 were categorized based on the order of delivery. Maternal and neonatal covariates were analyzed using univariate and multivariate regression analyses for both ROP and Type 1 ROP. Results. In 34 pairs of Chinese twins, the mean gestational age (GA) was 30.2 ± 2.0 weeks. In Twin 1, smaller GA (OR = 0.44, P = 0.02), higher mean oxygen concentration (OR = 1.34, P = 0.03), presence of thrombocytopenia (OR = 1429.60, P < 0.0001), and intraventricular hemorrhage (OR = 18.67, P = 0.03) were significant risk factors for ROP. For Twin 2, a smaller GA (OR = 0.45, P = 0.03) was the only risk factor. There were no significant risk factors for ROP in Twin 1 or Twin 2 on multivariate analysis. Conclusion. In Chinese twin pairs, smaller GA was the only common risk factor for ROP while Twin 1 was more susceptible to the postnatal risks for ROP.

Low birth weight is a risk factor for severe retinopathy of prematurity depending on gestational age

Objective

To evaluate the impact of low birth weight as a risk factor for retinopathy of prematurity (ROP) that will require treatment in correlation with gestational age at birth (GA).

Study design

In total, 2941 infants born <32 weeks GA were eligible from five cohorts of preterm infants previously collected for analysis in WINROP (Weight IGF-I Neonatal ROP) from the following locations: Sweden (EXPRESS) (n = 426), North America (n = 1772), Boston (n = 338), Lund (n = 52), and Gothenburg (n = 353). Data regarding GA at birth, birth weight (BW), gender, and need for ROP treatment were retrieved. Birth weight standard deviation scores (BWSDS) were calculated with Swedish as well as Canadian reference models. Small for gestational age (SGA) was defined as BWSDS less than −2.0 SDS using the Swedish reference and as BW below the 10^th percentile using the Canadian reference charts.

Results

Univariate analysis showed that low GA (p<0.001), low BW (p<0.001), male gender (p<0.05), low BWSDS_Canada (p<0.001), and SGA_Canada (p<0.01) were risk factors for ROP that will require treatment. In multivariable logistic regression analysis, low GA (p<0.0001), male gender (p<0.01 and p<0.05), and an interaction term of BWSDS*GA group (p<0.001), regardless of reference chart, were risk factors. Low BWSDS was less important as a risk factor in infants born at GA <26 weeks compared with infants born at GA ≥26 weeks calculated with both reference charts (BWSDS_Sweden, OR = 0.80 vs 0.56; and BWSDS_Canada, OR = 0.72 vs 0.41).

Conclusions

Low BWSDS as a risk factor for vision-threatening ROP is dependent on the infant's degree of immaturity. In more mature infants (GA ≥26 weeks), low BWSDS becomes a major risk factor for developing ROP that will require treatment. These results persist even when calculating BW deficit with different well-established approaches.

Incidence of retinopathy of prematurity in extremely premature infants

Purpose. To investigate the incidence and the severity of retinopathy of prematurity (ROP) in extremely preterm infants born before 28 weeks of gestation in southeastern Turkey. Methods. A retrospective chart review was performed for infants born before 28 weeks of gestation. The following data were reviewed: gender, gestational age (GA), birth weight (BW), zone and stage of ROP, presence of plus disease, and treatment for ROP if needed. Infants were divided into 2 groups according to GA as follows: group 1 included infants of GAs 25 weeks and under; group 2 included infants of GAs less than 28 weeks and over 25 weeks. Results. The incidence of any ROP in the whole cohort, in group 1, and in group 2, was 66.0%, 95.5%, and 58.6%, respectively. Incidence of any ROP was significantly associated with BW and GA (P = 0.014 and P = 0.002, resp.). The overall incidence of type 1 ROP was 35.8% (59.1% in group 1 and 29.9% in group 2). Development of type 1 ROP was independently associated with GA. Conclusion. Any ROP was significantly associated with BW and GA. Extremely premature infants with lower GA were found to be more likely to develop type 1 ROP. BW cannot predict the development of type 1 ROP.

Dopamine-resistant hypotension and severe retinopathy of prematurity

OBJECTIVE

To examine the relationship between the cause or severity of hypotension and the development of severe ROP (sROP) (≥stage 3 or stage 2 with plus disease in zone I or II).

STUDY DESIGN

Infants (<28 weeks' gestation, n = 242) were observed for hypotension and treated with a standardized hypotension-treatment protocol. Hypotension was classified as resulting from one of the following causes: (1) culture-positive infection and/or necrotizing enterocolitis; (2) patent ductus arteriosus ligation; or (3) "idiopathic" (no cause identified other than prematurity), and as being either dopamine responsive or dopamine resistant. Cortisol levels were measured for infants with dopamine-resistant hypotension. Eye examinations were performed until the retinopathy of prematurity resolved or the vasculature matured. Multivariable logistic regression analysis was performed to determine the relationship between the cause/severity of hypotension and sROP.

RESULTS

Overall, 66% of infants developed hypotension (41% were dopamine responsive and 25% were dopamine resistant). sROP developed in 19% of infants. "Idiopathic" dopamine-resistant hypotension was the only cause significantly related to sROP. Of the infants with dopamine-resistant hypotension, 66% had low serum cortisol (≤10 μg/dL). Low cortisol, in the presence of dopamine-resistant hypotension, was significantly associated with sROP and accounted for the relationship between "idiopathic" hypotension and sROP. When low cortisol was included in statistical models, other known risk factors, such as immature gestation, were no longer significantly related to sROP.

CONCLUSION

Low cortisol, in the presence of dopamine-resistant hypotension, has the greatest magnitude of association with sROP.

Effect(s) of preterm birth on normal retinal vascular development and oxygen-induced retinopathy in the neonatal rat

PURPOSE

Maturity is a critical factor in the pathogenesis of retinopathy of prematurity (ROP). One widely used method for studying this condition is that of oxygen-induced retinopathy (OIR). The general conditions of an OIR term animal, both at the time of birth and following birth, differ from those of the preterm infant. This, to simulate preterm conditions and to provide a basis for further studies on ROP, we investigated the effect(s) of preterm birth on retinal vascularization using the neonatal rat.

MATERIALS AND METHODS

Sprague-Dawley (SD) rats were delivered preterm by caesarean section on the day 19 of gestation. Term pups were used as controls. On the day of birth, preterm and term pups were housed under conditions of room air or cyclic oxygen. Retinas of pups housed in room air on days 4, 7, 10, 14, 18 and 22, as well as pups housed in oxygen on days 14, 18, and 22 were whole-mounted and stained with isolectin-B4. On day 18, cross-sections of the retina were cut and stained with hematoxylin and eosin for the identification of preretinal neovascular tufts. Images of avascular and neovascular areas were compared using light and fluorescence microscopy.

RESULTS

Preterm pups had significantly larger avascular retinal areas than term rats on the various postnatal days. After exposure to cyclic oxygen, preterm pups demonstrated significantly larger avascular (days 14 and 18) and neovascular areas (day 18) compared with term rats. On day 22, residual retinopathy of preterm pups was greater than that of term pups.

CONCLUSIONS

Preterm birth of rats, which are comparable in their physiology to humans, had negative effects on retinal vascularization. The impaired retinal vascular development and subsequent vasoproliferation resulting from hyperoxia in preterm pups is more severe and enduring.

[Pathogenesis of retinopathy of prematurity]

Retinopathy of prematurity (ROP) is a complex disease with a multifactorial pathogenetic cascade that is still only partially understood. Important pathogenetic factors are gestational age at birth and birth weight. Potent postnatal factors are exposure to supplemental oxygen, slow weight gain and expression of angiogenic growth factors. Some of these crucial aspects of ROP pathogenesis will be discussed in this article and put into clinical context. With the introduction of intravitreal anti-VEGF (vascular endothelial growth factor) treatment into ROP therapy, the pathomechanistic role of VEGF in ROP deserves a special focus. Apart from VEGF, other factors will be discussed that may precede VEGF upregulation and thus may represent targets for an earlier and potentially protective intervention. Among these insulin-like growth factor 1 (IGF-1) appears to be most prominent. Finally, factors such as postnatal weight gain will be discussed in light of their potential role as screening parameters and their ability to predict ROP severity.