Outcomes of Congenital Diaphragmatic Hernia among Preterm Infants: Inverse Probability of Treatment Weighting Analysis

doi:10.21203/rs.3.rs-2218210/v1

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Outcomes of Congenital Diaphragmatic Hernia among Preterm Infants: Inverse Probability of Treatment Weighting Analysis

https://doi.org/10.21203/rs.3.rs-2218210/v1

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Journal Publication

published 13 Apr, 2023

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Objectives

To evaluate the survival and intact-survival rates among preterm infants with congenital diaphragm hernia (CDH).

Study Design

Multicenter retrospective cohort study of 849 infants born between 2006 and 2020 at 15 Japanese CDH study group facilities. Multivariate logistic regression analysis adjusted using inverse probability treatment weighting (IPTW) method was used. We also compare trends of intact-survival rates among term and preterm infants with CDH.

Results

After adjusting using the IPTW method for CDH severity, sex, APGAR score at 5 min, and cesarean delivery, preterm infants had a significantly lower survival rate [odds ratio (OR), 0.46; 95% confidence interval (CI), 0.22–0.95] and lower intact-survival rate [OR, 0.48; 95% CI, 0.32–0.74] compared with term infants. Trends of intact-survival rates for preterm infants had changed little unlike term infants.

Conclusion

Prematurity was a significant risk factor for survival and intact-survival among infants with CDH, regardless of adjustment for CDH severity.

Health sciences/Medical research/Outcomes research

Health sciences/Risk factors

congenital diaphragmatic hernia

preterm infant

survival rate

intact survival

inverse probability of treatment weighting

Congenital diaphragmatic hernia (CDH) is a fetal abnormality that occurs in 2.7–4.9 per 10,000 live births¹. The pathophysiology of CDH is a diaphragmatic defect accompanied by complications, such as lung hypoplasia, gastroesophageal reflux disease, and thoracic deformity, which may occur and significantly affect a child's life². Although the survival rate has improved dramatically over the years, owing to prenatal diagnosis and advances in various treatments^{3, 4}, there are still several problems to be solved, including severe cases and complications.

Prematurity is an essential factor among the various factors that affect the prognosis of CDH. Preterm birth hurts the forecast for all weeks of life and newborn developmental outcomes. Survival rates for preterm births are improving worldwide, and as the survival rate increases, the proportion of children who require long-term medical care increases^{5, 6, 7, 8}. Although data in the U.S. showed that the prognosis for preterm CDH naturally improves with increasing weeks of gestation⁹; however, this is not the case in Japan.

It is unknown how many preterm infants with CDH will require medical care. Many cases have reported life expectancy; however, complications have not yet been reported. Preterm birth outcomes have improved over the years, but there are no data on changes over time. Additionally, these data do not account for disease severity, and the evidence is insufficient.

In this study, we hypothesized that preterm infants with CDH would have a lower survival rate and require additional medical care than term infants with CDH. The survival rate of preterm infants with CDH and extent of medical care needed at discharge were examined using the IPTW method according to the severity of CDH.

Study design and population

This multicenter, retrospective cohort study was conducted among infants with CDH born between 2006 and 2020 at 15 Japanese CDH study group facilities. The study enrolled 1037 infants with CDH registered in the Japanese CDH group database. Outborn infants, those receiving palliative care, and those with an unknown gestational age (GA) were excluded. We first excluded those who were outborn because of lack of markers to assess CDH severity, such as lung area to head circumference ratio (LHR) and liver-up. We also excluded patients who underwent fetal endoscopic tracheal occlusion (FETO) because it is not yet widely used and can only be performed at some of the 15 participating facilities in Japan. Infants were categorized, as shown in the flowchart in Fig. 1. The institutional ethics committee approved the study protocol of Osaka Women’s and Children’s Hospital (No. 11017), and the institutional review board of all the participating institutions. We also adopted an opt-out system and posted a study summary on each institutional website; individuals had the right to decline participation. The study was performed in accordance with the principles of the Declaration of Helsinki and ethical guidelines for medical and health research involving human participants.

Outcomes

Primary outcomes were survival and intact-survival rates among preterm infants with CDH at discharge. Intact-survival patients did not require medical care at discharge, such as supplementary oxygen, mechanical ventilator, tracheostomy, tube feeding, central venous feeding, or pulmonary vasodilators. Baseline characteristics contained perinatal factors, such as GA, birth weight (BW), sex, APGAR score at 5 min, mode of delivery, chromosomal abnormalities, congenital heart disease, small for GA (≤-1.5 SD) (Table 1). Clinical coarse as treatment and complications showed Table 2 as antenatal steroids, polyhydramnios, hydrops, surfactant administration, shunt direction at the ductus within 24 h after birth, use of high-frequency oscillation ventilation (HFO), inhaled nitric oxide (iNO), and extracorporeal membrane oxygenation (ECMO) and central nervous system abnormality (CNS). We defined CNS as intraventricular hemorrhage (IVH), periventricular leukomalacia (PVL), hydrocephalus, and hypoxic-ischemic encephalopathy. We also examined outcomes related to CDH on surgery day, pneumothorax, chylothorax, pulmonary hemorrhage, surgical wound infection, observed/expected LHR (o/e LHR), lung-to-thorax transverse area ratio (L/T ratio), and liver-up presence into the thorax. As not all cases of prenatal diagnosis had been performed, we first investigated whether prenatal diagnosis had been completed, and then examined these factors. Liver-up was defined as prenatally detected liver herniation occupying more than one-third of the thoracic space¹⁰. A cut-off point of 25% for o/e LHR was set based on the results of a previous report ¹¹. We defined the severity of CDH, with liver-up or o/e LHR ≤ 25%, respectively.

Table 1

Characteristics of preterm infants with CDH
	Frequency (%)
Characteristics
Gestational age, weeks
≤28	4 (2.4)
29–32	5 (3.0)
33–34	39 (23.3)
35–36	119 (71.3)
Birth weight, g
< 1000	5 (3.0)
1000–1499	13 (7.8)
1500–2499	87 (52.1)
≤2500	58 (34.7)
Missing data	4 (2.4)
Sex
Male	81 (48.5)
Female	86 (51.5)
Missing data	0 (0.0)
APGAR score at 5 min
0–3	55 (32.5)
4–6	57 (34.1)
7–10	47 (28.1)
Missing data	8 (4.8)
C-section delivery
Yes	135 (80.8)
No	32 (19.2)
Missing data	0 (0.0)
Cardiac anomalies
Yes	48 (28.7)
No	119 (71.3)
Missing data	0 (0.0)
Data are expressed as number (%).

Table 2

Outcomes of all preterm infants with CDH according to gestational age
weeks	≤32 (n = 9)		33–36 (n = 156)	37–41 (n = 679)
Survival at discharge	5 (55.5)		106 (67.1)	560 (82.4)
Side of hernia, left	6 (55.5)		135 (85.4)	623 (91.4)
Prenatal diagnosis	6 (66.6)		141 (89.2)	615 (90.2)
Liver-up	3/8 (37.5)		68/133 (51.1)	186/585 (31.8)
o/e LHR ≤25%	3/6 (50.0)		17/76 (22.3)	45/371 (12.1)
Polyhydramnios	3 (33.3)		68 (43.0)	143 (21.0)
Antenatal steroids	2 (22.2)		16 (10.1)	16 (2.4)
Administration of surfactant	4 (44.4)		59 (37.3)	16 (2.4)
R to L shunting within 24hrs	3 (33.3)		74 (46.8)	266 (44.5)
Chromosomal anomalies	1 (11.1)	25 (15.8)		31 (4.6)
Small for gestational age	3 (33.3)	31 (19.6)		74 (11.8)
Surgery performed	5 (55.6)	132 (83.5)		623 (91.4)
Day of surgery	1 (0, 4)		1 (0, 3)	1 (0,3)
Use of iNO	6 (66.6)		128 (81.0)	509 (74.6)
Use of ECMO	0 (0.0)		15 (9.4)	51 (7.5)
Use of HFOV	5 (55.5)		101 (63.9)	412 (60.7)
Hydrops	3 (33.3)		12 (7.5)	13 (2.0)
Chylothorax	2 (22.2)		29 (18.3)	96 (14.1)
Pulmonary hemorrhage	1 (11.1)		8 (5.1)	9 (1.3)
Pneumothorax	0 (0.0)		11 (7.0)	82 (12.1)
Wound infection	0 (0.0)		2 (1.2)	8 (1.2)
Central nervous system abnormality	5 (55.5)		12 (7.7)	49 (7.2)
Intact-survival at discharge	2/8 (25.0)		50/132 (37.8)	335/566 (59.2)
O2 use	2/8 (25.0)		32/121 (26.4)	100/539 (18.5)
Respirator use	1/9 (11.1)		15/122 (12.3)	47/580 (8.1)
Tracheostomy	1/9 (11.1)		12/122 (9.8)	15/587 (2.6)
Tube feeding	1/8 (12.5)		36/107 (33.7)	80/507 (15.8)
Parenteral nutrition	1/8 (12.5)		6/108 (5.6)	22/512 (4.3)
Pulmonary vasodilator	1/8 (12.5)		16/120 (13.3)	56/585 (9.6)
*Data are expressed as numbers (%).

We examined perinatal factors, CDH-related factors, and the proportion of infants who needed medical care at discharge for each GA group (≤32 weeks, 33–36 weeks, and ≥ 37 weeks). We investigated the trend in the percentage of intact survival of preterm infants with CDH over five years.

In the multivariable analysis, we compared the survival and intact-survival rates between preterm (33–36 weeks GA) and full-term (≥ 37 weeks) infants matched for CDH severity and perinatal background, excluding infants less than or equal to 32 weeks GA because of the small sample size.

Statistical analysis

We compared the baseline characteristics and outcomes of preterm and term infants. Multiple imputations were performed before multiple logistic regression analysis because some data were missing from our dataset. Inverse probability of treatment weighting-adjusted regression analysis using propensity scores (PSs) was performed to model the impact of CDH preterm infants on survival and intact survival rates, while adjusting for baseline neonatal characteristics and CDH severity and reweighting the data to account for the unbalanced nature of observational data. The PSs were estimated using a logistic regression model that included all possible prenatal confounders likely to have affected neonatal characteristics, including sex, APGAR score at 5 min, cesarean delivery, and CDH severity. The weights of patients in the preterm CDH group were the inverse of the PS, and those of patients in the term group were the inverse of (1-PS)¹². Prenatal diagnosis was not performed in all the patients, and some missing values were found.

Data management and statistical analyses were performed using the R statistical software (version 3.4.1(The R Foundation for Statistical Computing, Vienna, Australia). Inverse probability of treatment weighting was conducted using Survey (V.3.37). All reported p values were two-sided, and values of p < 0.05 were considered statistically significant. Data are presented as medians (interquartile range) or numbers (%).

In our study, 849 infants with CDH were enrolled. Outborn infants (n = 136), infants with unknown GA (n = 3), infants receiving palliative care (n = 35), and infants undergoing FETO (n = 15) were excluded, and one infant was administered palliative care and FETO. We studied 167 (19.7%) preterm infants and 682 term infants with CDH (Fig. 1). Table 1 presents detailed infant characteristics, showing that late preterm infants constitute a large percentage.

The survival and intact survival rates increased with increasing GA (Table 2). Additionally, fetal hydrops tended to grow, and CDH repair surgery cases decreased, lowering the GA.

As for the age trend, the intact-survival rates of CDH for term groups have gradually increased ,but for preterm infants have changed little in recent 15 years (Fig. 2).

Using the IPTW method based on CDH severity based on CDH severity and perinatal factors, preterm infants had a significantly lower survival rate [odds ratio (OR), 0.46; 95% confidence interval (CI), 0.22–0.95] and lower intact-survival rate [OR, 0.48; 95% CI, 0.32–0.74)] compared with term infants (Table 3).

Table 3

Comparison of neonatal survival and intact-survival rates between preterm (33–36 weeks) and term (37≤ weeks) infants using IPTW.
	Preterm (33–36 weeks) (n = 156)	Term (37≤ weeks) (n = 679)	OR (95% CI)
Survival	106 (67.9)	563 (82.9)	0.46 (0.22–0.95)
missing data	2 (1.3)	3 (0.4)
Intact Survival	49 (31.4)	335 (49.3)	0.48 (0.32–0.74)
missing data	26 (16.6)	116 (17.1)
*IPTW, inverse probability of treatment weighting.
*IPTW-adjusted regression analysis was performed using the propensity score (PSs). The PSs were estimated using a logistic regression model that included confounders, such as CDH severity, sex, APGAR score at 5 min, and cesarean section delivery.

Using data from a multicenter study in Japan, our study evaluated survival and intact-survival rates at discharge among preterm infants with CDH matched for CDH severity. The results showed that preterm infants with CDH had significantly lower survival and intact-survival rates at discharge than did full-term infants. The trends showed that the intact survival rates increased only slightly.

Prematurity decreased the survival rate of infants with CDH, regardless of the severity of CDH, which is consistent with previous reports. In a previously reported study in the U.S., survival rate of CDH preterm infants increased linearly with increasing weeks of gestation [32.1% (GA 28 weeks), 36.5% (29–32 weeks), 49.7% (33–34 weeks), and 62.3% (35–36 weeks)]. We obtained similar results, although there were fewer categories of GA. The Neonatal Research Network of Japan, a Japanese neonatal database that registers babies born in Japan at 32 weeks or less, also found that the survival rate of 30,973 babies over a ten-year period from 2003 to 2012 increased as the number of weeks of gestation increased¹³. The trend for infants with CDH appears to be similar to that for preterm infants. Peluso et al.⁹ reported a survival rate of 49% for 2,356 CDH preterm infants, while our figures were 55.5% for 32 weeks or less and 67.1% for 33–36 weeks, slightly higher than previously reported. In our study, it is difficult to determine whether these rates were higher because of the small number of patients enrolled at 32 weeks or less. We excluded only 8% of patients with CDH severity at 32 weeks or less when matching for CDH severity. The comparison population comprised almost exclusively late-preterm patients between 33 and 36 weeks of age, with poor outcomes of survival and development compared with term infants¹⁴. This finding is consistent with the results of our study.

In this study, we found that preterm infants with CDH had an increased need for medical care at discharge from the hospital, even if the severity of CDH was matched. To the best of our knowledge, this has not been reported yet. Neurodevelopmental impairment is an important complication in preterm infants with CDH^{15, 16, 17, 18, 19}. Although the detailed mechanism is unknown, there are reports of central nervous system (CNS) abnormalities in CDH^{20, 21, 22}. Congenital diaphragmatic hernia is a risk factor for hypoxic acidosis, which is a risk factor for CNS abnormalities during the disease. There are various reports on the medical care needed at discharge for CDH²³, but very few are available. There have been several studies on each medical care category, and our investigation is consistent with these studies. Baroudi et al.²⁴ reported that lower GA was a risk factor for tracheostomy in univariate analysis, but not in multivariate analysis. These findings require additional cases and further investigations.

We defined CDH severity based on two criteria: liver elevation and o/e LHR. The importance of liver-up has been shown in a meta-analysis²⁵ to help predict survival rates and respiratory disease in infants with isolated left-sided CDH. Observed/expected LHR was also an attractive risk predictor²⁶, and low o/e LHR was a sensitive predictor of lower survival and higher incidence of ECMO²⁷. Terui et al. reported that a combination of factors, including o/e LHR < 25%, liver-up, thoracic stomach, right-side CDH, and severe malformations were sensitive in predicting risk²⁸. Liver-up and o/e LHR were combined to determine severity, which is reasonable, considering the evidence obtained in previous studies. In our multicenter study, we used the L/T ratio to estimate illness severity in actual practice. Masahata et al.²⁹ found that a combination of L/T ratio and liver-up was significantly associated with postnatal severity in a single-center study, and Usui et al.³⁰ reported an linear relationship between the L/T ratio and o/e LHR in early pregnancy. Although our group used L/T ratio for diagnosis of CDH severity, because several international reports used LHR to assess CDH severity, and because we considered preterm as exposure, we adopted o/e LHR could be corrected by gestational weeks.

This study has several limitations. First, this was a multicenter retrospective study. Therefore, the therapeutic strategies for preterm infants with CDH depended on attending physicians in each facility. Consequently, there is a possible bias in survival and intact survival among CDH preterm infants. Second, this study lacked information after hospital discharge and did not allow long-term follow-up. Our database has many categories for long-term outcomes; therefore, further research is needed to enforce evidence about preterm infants with CDH. Third, we analyzed the effects, including chromosomal and cardiac abnormalities. Non-isolated CDH seems worse than isolated CDH, but we intended to assess outcomes among all preterm infants with CDH. In addition, this study did not evaluate neonatal morbidity under admission for bronchopulmonary dysplasia or intraventricular hemorrhage. Our database lacked this information, and we could not assess the association between neonatal morbidity and preterm infants with CDH. Finally, in our study, preterm infants with CDH showed poor improvement in intact-survival rates at 5-year intervals compared to term infants. The cause of this difference could not be clearly shown, although the influence of CDH was more pronounced in preterm infants. Our study covered only 15 year period, and the number of preterm births per 5-year period was small, and the selection bias was significant. It is necessary to further expand the sample size and conduct more studies in the future.

In conclusion, survival and intact survival rates at discharge for preterm infants with CDH were lower than those for term infants with CDH after matching for CDH severity. Further evaluation of the impact of immaturity on CDH will require more studies on long-term neurodevelopmental outcomes.

Statement of Ethics

The study protocol was reviewed and approved by the institutional ethics committee of Osaka Women’s and Children’s Hospital (No.11017) and the institutional review board of all participating institutions.

Conflict of Interest Statement

The authors have no conflicts of interest to declare.

Funding Sources

This work was supported by a grant from the Ministry of Health, Labor and Welfare of Japan (Grant No.20FC1017).

Author Contributions

YI and NU were involved in study design and data interpretation. YI and NU were involved in the data analysis. All authors critically revised the report, commented on the manuscript drafts, and approved the final manuscript.

Data Availability Statement

The research data obtained from the included articles are available and can be requested from corresponding author and will be made available when requested.

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There is NO conflict of interest to disclose.

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Outcomes of Congenital Diaphragmatic Hernia among Preterm Infants: Inverse Probability of Treatment Weighting Analysis

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Study Design

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Introduction

Materials And Methods

Study design and population

Outcomes

Statistical analysis

Results

Discussion/conclusion

Declarations

Statement of Ethics

Conflict of Interest Statement

Funding Sources

Author Contributions

Data Availability Statement

References

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