SUDANESE JOURNAL OF PAEDIATRICS

2023; Vol 23, Issue No. 1

ORIGINAL ARTICLE

Trends in long term growth outcome: comparison of two birth cohorts (year 2007–08 and year 2015–16)

Kallem Venkat Reddy (1), Challa V. S. Lakshmi (2), Sai Kiran (1), Srinivas Murki (1)

(1) DNB Resident, Fernandez Hospital Hyderguda, Hyderabad, India

(2) Cradle Hospital, Hyderabad, India

Correspondence to:

Kallem Venkat Reddy

DNB Resident, Fernandez Hospital Hyderguda, Hyderabad, India.

Email: venkat467 [at] gmail.com

Received: 12 June 2019 | Accepted: 03 April 2023

How to cite this article:

Reddy KV, Lakshmi CVS, Kiran S, Murki S. Trends in long term growth outcome: comparison of two birth cohorts (year 2007-08 and year 2015-16). Sudan J Paediatr. 2023;23(1):68–73. https://doi.org/10.24911/SJP.106-1560160872

ABSTRACT

Very low birth weight (VLBW) infants comprise between 4% and 8% of live-births and about one-third of deaths during the neonatal period. The objective of the study is to evaluate and compare the long-term growth outcomes of VLBW infants among two different birth cohorts: Cohort 2007–08 (cohort 1) and cohort 2015–16 (cohort 2), in a cross-sectional observational study. The neonatal and perinatal data of cohort 1 was collected from available trial data and the same data from cohort 2 was collected from patient case files and patient history. The primary outcome of the study was to compare the growth outcomes of VLBW infants attending the follow-up clinic between 12 and 18 months of corrected age from two different birth cohorts. Respectively, 238 and 268 infants were eligible for inclusion in cohort 1 and 2. Among the eligible infants, 148 infants in cohort 1 and 178 infants in cohort 2 were available for primary outcome assessment during the recruitment phase. The weight and length at corrected age (12 to 18 months) is significantly higher in cohort 2 compared to that in cohorts 1 although the mean age at assessment is similar between the two groups. There is a significant reduction in the incidence of underweight in infants that belonged to cohort 2. The proportions of infants who are underweight at follow-up were significantly lower in cohort 2 when compared to cohort 1, and there were no significant differences in the incidence of stunting and microcephaly among both the cohorts.

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Keywords:

Very low birth weight; Growth; Trend.

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INTRODUCTION

Very low birth weight (VLBW) infants comprise between 4% and 8% of live-births and about one-third of deaths during the neonatal period [1,2]. Achieving optimum growth plays an important role in the care of VLBW infants as inadequate early nutrition and consequent growth deficits adversely impact long-term outcomes, leading to short stature and impaired neurodevelopment [3]. Nutritional practices vary among different neonatal intensive care units and have improved over the last decades. Though the survival of VLBW infants is improving in India [4,5]; however, there is a paucity of published data on the trends in long-term growth outcomes among VLBW infants. Hence, we designed this study to evaluate and compare the long-term growth outcomes of VLBW infants among two different birth cohorts: Cohort 2007–08 and Cohort 2015–16.

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MATERIALS AND METHODS

This is a cross-sectional observational study comparing growth outcomes between two different birth cohorts with a time gap of 8 years. VLBW infants born during the period January 2007 to December 08 and January 2015 to December 2016 were eligible for inclusion in cohort 1 and 2, respectively. Infants with major congenital malformation were excluded. The study included all eligible infants (VLBW infants born during the time frame) who were attending the follow-up clinic in Fernandez Hospital at 12–18 months of corrected age. Infants from cohort 1 are part of a previous trial whose short-term outcomes are published elsewhere [6]. The neonatal and perinatal data of cohort 1 was collected from available trial data and the same data of cohort 2 is collected from patient case files and patient history. The data collected included birth weight, gestation, sex, intrauterine growth retardation (IUGR) status (based on Fenton chart), antenatal steroid coverage, antenatal Doppler assessment, mode of delivery, singleton/multiple pregnancy, neonatal morbidities and discharge outcomes and anthropometry. In both the cohorts the follow-up details during infancy included duration of breastfeeding, time of initiation of complementary feeding and type of complimentary feeding.

The two cohorts differed in the following care practices (Table 1). Other interventions such as antenatal steroid coverage, indications for caesarean delivery, indications for use of empirical antibiotics, failure criteria for continuous positive airway pressure (CPAP) and post-natal steroid use remained the same during both periods.

The primary outcome of the study was to compare the growth outcomes of VLBW infants attending the follow-up clinic between 12 and 18 months of corrected age from two different birth cohorts (Table 2). A trained nurse, as per pre-existing protocol in the unit, assessed weight, length and head circumference in all enrolled infants.

Both the cohorts were compared for neonatal, perinatal and feeding characteristics and outcome variables. Statistical analyses were performed by using SPSS (Version 16.0 for Windows, SPSS Inc., Chicago, IL). Data were presented as mean with SD or proportions as appropriate. All descriptive data were expressed as mean and SD and compared using Student t test. All categorical variables were compared using chi square test. Finally, the calculated value was compared with the tabulated value at a particular degree of freedom and the level of significance was found out. A ‘p-value’ < 0.05 was taken as significant. Linear regression analysis with weight at 12 to 18 months as the dependent variable and birth weight, IUGR status at birth, sex, multiple pregnancy, antenatal steroid usage and cohort group as the independent variables were done to find an independent association of cohort group on follow up weight. Logistic regression models were also done for underweight, stunting and microcephaly as the dependent variables, respectively.

Table 1. Care practices among the two cohorts.

Care practice	Cohort 1	Cohort 2
Magnesium sulphate for neuroprotection	Absent	Present
Neonatal resuscitation	NRP 2005 guidelines	NRP 2010 guidelines
Labor room CPAP	Nil	Universal coverage for all eligible infants
Surfactant therapy	FiO2 >0.40 and bubble CPAP if gestation <34 weeks	FiO2 >0.30 or on bubble CPAP if gestation <34 weeks
Colostrum within 12 hours of birth	Nil	50% compliance
Aggressive parenteral nutrition	No	Yes
Infection control	No HICC	HICC active
VAP bundle	Not existent	Active
Apnea therapy	Aminophylline	Caffeine
PDA treatment	Selective clinical PDA	Selective Echo or clinical PDA

CPAP, Continuous positive airway pressure; HICC, Hospital Infection Control Committee; NRP, Neonatal Resuscitation Program; PDA, Patent ductus arteriosus; VAP, Ventilator associated pneumonia.

Table 2. Definitions of outcomes.

Outcome	Definition
Underweight	Weight for age Z-score < −2.00 (WHO growth chart)
Stunting	Length for age Z-score < −2.00 (WHO growth chart)
Microcephaly	Head circumference for age Z-score < −3.00 (WHO growth chart)

WHO, World Health Organization.

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RESULTS

Two hundred thirty-eight infants and 268 infants were eligible for inclusion in cohort 1 and 2, respectively. Among the eligible infants, 148 infants in cohort 1 and 178 infants in cohort 2 were available for primary outcome assessment during the recruitment phase. The mean weight and the mean gestation age at birth among the cohorts 1 and 2 are 1,154.693 ± 230.818 versus 1,078.181 ± 227.230 g and 31 ± 1.97 versus 29.854 ± 1.994 weeks, respectively (Table 3). Among the morbidities during birth hospitalization, need for CPAP, bronchopulmonary dysplasia (BPD), time to reach full feeds and duration of hospitalization were significantly higher in the infants that belonged to cohort 2. Although the mean gestation at discharge was similar between the two cohorts, the mean discharge weight and the mean discharge length were significantly higher in cohort 2. Both the cohorts were similar in the feeding parameters at discharge and during infancy.

Primary outcome

The weight and length at corrected age (12 to 18 months) are significantly higher in cohort 2 compared to that in cohorts 1 although the mean age at assessment is similar between the two groups (Table 4). After adjustment for birth weight, sex, IUGR status, multiple pregnancy and antenatal steroid coverage infants in cohort 2 had a mean weight and mean length of 936 (499–1,373) g and 4.57 (2.8–6.2) cm higher than infants in cohort 1. Discharge weight had an independent positive effect on the infant growth at 12 to 18 months of follow up. Also, there is a significant reduction in the incidence of underweight in infants that belonged to cohort 2. The proportion of infants who are underweight at follow up were significantly lower in cohort 2 compared to cohort 1 when adjusted for birth weight, sex, IUGR status, multiple pregnancy and antenatal steroid coverage with an odds of 0.47 (0.23–0.94). There were no significant differences in the incidence of stunting and microcephaly among both the cohorts.

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DISCUSSION

This is a cross-sectional observational study done at follow-up clinic at Fernandez hospital with an aim to compare growth outcomes in VLBW infants at 12–18 months of corrected age among two different birth cohorts with a time gap of 8 years (2007–08 and 2015–16). We have observed that the infants in cohort 2 had better weights and lengths and also lesser underweight than infants in cohort 1 at 12–18 months of corrected age. These improved growth parameters were seen although babies in cohort 2 were more immature and had lesser weight at birth. Although infants in cohort 2 had more morbidities and greater sickness as evidenced by a higher incidence of culture-positive sepsis and BPD, this did not translate to poor weight at hospital discharge. The improved growth outcomes at discharge and at follow up might be attributed to neonatal care practices including aggressive enteral and parenteral nutrition, the trend towards increased use of non-invasive respiratory support and strict infection control measures. A higher discharge weight with comparable gestational age at discharge is proof of possible better in-hospital nutrition in cohort 2. Our study did not have the power to identify the differences in incidence of stunting and microcephaly in follow up. Sharma et al. [7] published growth and neurological outcomes of VLBW infants at 18 months of corrected age. Out of 55 infants followed till 18 months of corrected age 17 (30.9%; 95% CI 18.3% to 43.5%) infants were undernourished, 28 (50.9%; 95% CI 37.3% to 64.6%) were stunted, 8 (14.5%; 95% CI 0 to 24) were wasted and 14 (25.4%; 95% CI 13.6% to 37.3%) had microcephaly. The mean gestational age and mean weight at birth were higher when compared to our study cohorts. The incidence of underweight was similar to the outcome in cohort 2, stunting and microcephaly were higher when compared to both of our study cohorts. Ernst et al. [8] published growth patterns of weight, length, and occipital frontal circumference (OFC) complete through 12 months corrected age were determined for 122 VLBW infants. The incidences of underweight, stunting and microcephaly were found to be 30%, 21% and 14%, respectively. This study was conducted in 1982–83 and over these last 3 decades significant changes occurred in the neonatal care practices. The difference in growth outcomes with our study may have occurred due to differences in baseline birth weights and care practices. Wang et al. [9] presented the growth outcome of VLBW infants at 5 years of age from Taiwan. Of the 224 VLBW infants 126 were followed till 5 years of age. The incidences of underweight, stunting and microcephaly were 10.3%, 8.7% and 16%, respectively. Though these were done at 5 years of age the mean weight, length, and head circumference at 12 months of age were comparable to our study cohort 2. Sangtawesin et al. [10] presented growth and developmental outcomes of VLBW infants at 18–24 months of corrected age. Out of 111 eligible infants 30 infants were followed up at 18–24 months of corrected age. The incidence of underweight (3.33%) and microcephaly (10%) were less when compared to our study cohorts. The follow-up rate of this study is very low compared to the expected standards. Though there are many research articles over the comparison of different birth cohorts regarding neurodevelopmental outcomes, there were no articles regarding the trends in growth outcomes among the different birth outcomes.

Table 3. Baseline variables between the two cohorts.

Variable	Birth cohort 1 (2007–08)	Birth cohort 2 (2015–16)	OR (95% CI)/Mean difference (95% CI)
Mean weight	1,154.693 ± 230.818 g	1,078.181 ± 227.230 g	−75.512 (−142.89; −8.126) g
Mean gestation age	31 ± 1.97 weeks	29.854 ± 1.994 weeks	−1.146 (−1.72; −0.56) weeks
Sex (male)	46.6%	52.7%	0.79(0.44;1.42)
SGA	43.2%	34.5%	1.48(0.80;2.72)
Abnormal Doppler (AREDF)	44.5%	38.1%	1.28(0.70;2.33)
Singleton pregnancy	78.99%	74.54%	1.21(0.60;2.41)
Antenatal steroids	85.4%	90.7%	0.60(0.23;1.57)
Mode of delivery (LSCS)	92%	94.5%	0.73(0.22;2.36)
PPV at birth	19.3%	27.2%	0.61(0.31;1.22)
Culture positive sepsis	16.8%	27.2%	0.826(0.407–1.673)
Mechanical ventilation	12.6%	16.8%	0.734(0.327; 1.647)
CPAP	24.7%	44.7%	0.421(0.227; 0.779)
NEC ≥ 2A	10%	5.4%	1.746(0.556;5.482)
BPD	1.6%	10.9%	0.173(0.043;0.695)
Time to reach full feeds	7.946 ± 3.896 days	10.490 ± 6.139 days	2.544 days (1.168;3.920)
Duration of hospital stay	21.599 ± 20.12 days	29.552 ± 23.372 days	7.953 days (1.746;14.159)
Discharge gestation	34.257 ± 1.817 weeks	34.740 ± 2.359 weeks	0.483 weeeks (−0.102;1.068)
Discharge weight	1,311.159 ± 168.739 g	1,500 ± 154.428 g	188.841 g (140.58;237.101)
Discharge length	39.560 ± 2.311 cm	40.254 ± 1.712 cm	0.694 cm (0.062;1.326)
Discharge OFC	29.144 ± 1.947 cm	29.272 ± 1.487 cm	0.128 cm (−0.405;0.661)
Any BF at discharge	75.63%	69.4%	1.36 (0.70;2.62)
Any BF at 6 months	63%	61%	1.12 (0.61;2.06)
Complementary feeds (Home based foods and mixed feeds)	44.9%	56.4%	0.64 (0.35;1.15)

AREDF, Absent/reversed end diastolic flow; BF; Breast feeding; BPD, Bronchopulmonary dysplasia; CPAP, Continuous positive respiratory support; LSCS, Lower segment cesarean section; NEC, Necrotizing enterocolitis; OFC, Occipital frontal circumference; PPV, Positive pressure ventilation; SGA, Small for gestational age.

Table 4. Outcome variables between the two cohorts.

Variable	Cohort I (2007–08)	Cohort II (2015–16)	Mean difference (95%CI)/OR (95%CI)
Mean age at follow up	14.269 ± 4.88 months	13.878 ± 2.13 months	−0.391 months (−1.634;0.852)
Mean weight	7.96 ± 1.20 kg	8.627 ± 1.670 kg	0.667 kg (0.268;1.065)
Mean length	72.125 ± 5.00 cm	74.458 ± 6.221 cm	1.333 cm (−0.250;2.916)
Mean OFC	44.482 ± 3.65 cm	44.385 ± 2.016 cm	−0.097 cm (−1.048;0.854)
Underweight	43.83%	29%	0.47* (0.237–0.941)
Stunting	42.1%	38.1%	0.76* (0.39–1.47)
Microcephaly	10.6%	5.4%	0.55* (0.16–1.83)

*Adjusted odds ratio.

OFC, Occipital frontal circumference.

Strengths of the study

Comparison of two prospectively collected data.

Most data collection and outcomes were standardized during both the times.

Significant changes occurred in care practices during the two epochs.

Limitations of the study

Differences in baseline parameters.

Patient enrollment in second cohort is ongoing.

The compliance of care parameters during the two epochs is not well documented.

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CONCLUSION

There is the trend of increased growth outcomes including better weights, better length and less under nutrition when VLBW infants are compared across two birth cohorts separated by a gap of 8 years.

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CONFLICT OF INTEREST

The authors declare that they have no conflict of interests.

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FUNDING

None.

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ETHICAL APPROVAL

The study was approved and received ethical clearance from Institutional Ethics Committee (Fernandez Hospital). An informed consent for participation was obtained from all parents or guardians. Confidentiality was maintained at all levels.

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