Breastfeeding Intensity and Exclusivity of Early Term Infants at Birth and 1 Month

Abstract

Objective:

To examine breastfeeding exclusivity and intensity of early term (ET) infants, born at 37–38 weeks, and term infants, born at 39–41 weeks, during the postpartum hospitalization and the first month of life.

Materials and Methods:

This was a prospective cohort study of 358 mothers of ET and term infants during the first 72 hours after birth and at 1 month of age. Logistic analysis was used to calculate unadjusted and adjusted odds ratios (aORs) and control for confounding variables.

Results:

ET infants had significantly lower breastfeeding in the first hour (aOR = 0.43, 95% confidence interval [CI] = 0.21–0.87), lower exclusive breastfeeding in the hospital and at 1 month (aOR = 0.46, 95% CI = 0.27–0.71 and aOR = 0.40, 95% CI = 0.22–0.71), and lower rates of high breastfeeding intensity in the hospital and at 1 month (aOR = 0.39, 95% CI = 0.22–0.71 and aOR = 0.33, 95% CI = 0.15–0.72), after controlling for confounding variables. ET infants had more emergency room (ER) visits in the first month (OR = 7.6, 95% CI = 1.01–60.6), and all ET infants who had ER visits were exclusively breastfed.

Conclusions:

ET infants had lower breastfeeding in the hospital and at 1 month. They should be regarded as a group at risk for breastfeeding challenges and infant morbidity.

Introduction

Although 37 weeks is traditionally considered term, evidence has emerged that early term (ET) infants, defined as infants born 37⁺⁰ to 38⁺⁶ weeks, are more immature than term infants born at 39⁺⁰ to 41⁺⁶ weeks.^1,2 Literature regarding ET infants has demonstrated that they have higher rates of respiratory distress, admission to Neonatal Intensive Care Unit (NICU), length of hospital stay, and hospital readmission than their term counterparts.^3–7 Recent reports reveal that the long-term consequences of ET births include increased childhood asthma, cardiovascular disease, diabetes and obesity, health care-related costs during early childhood, need for early intervention, decreased cognitive scores, speech and/or language delay, and worse school performance at 7 years of age than their peers.^6,8–15

The neurological immaturity of these infants also extends to difficulties in breastfeeding.^4,6,16–18 There is, however, limited literature regarding the effects of ET birth on exclusive breastfeeding and no studies that examined breastfeeding intensity. The purpose of this study was to prospectively study breastfeeding exclusivity and breastfeeding intensity of ET infants compared with term infants during their postpartum hospitalization and the first month of life.

Materials and Methods

Study design

This was a prospective cohort study conducted from April 2013 to July 2014 at the Hadassah Medical Center, a major teaching and referral center in Israel. During the study period, there were no differences in hospital policies for ET or term infants, and there were a total of 9,015 births. There is no Baby Friendly Hospital in Israel. The study composed of a convenience sample. A power analysis was performed for sample size, which was calculated to achieve a power of 0.80 for α of 0.05. Due to the prospective design of the study, the intention was to enroll 207 ET infants and 158 term infants to account for an attrition of 30% at 1 month.

Inclusion criteria included singleton newborns born between 37⁺⁰ and 41⁺⁶ weeks, whose mothers intended to breastfeed, who did not need admission to the NICU, were appropriate for gestational age, and were born to mothers aged 18–45 years. Exclusion criteria were any breastfeeding contraindications (e.g., HIV, Human T-cell lymphotropic virus [HTLV] HTLV-1, HTLV-2).

ET infants were those born from 37⁺⁰ to 38⁺⁶ weeks. For this study, we defined term infants as those born from 39⁺⁰ to 41⁺⁶ weeks. Gestational age was assessed by early first trimester ultrasound and, when unavailable, by last menstrual age.

Instruments

The instruments used for this study were the Baseline In-Hospital Interview, the One-Month Follow-Up Interview questionnaires, and the Dennis' Breastfeeding Self-Efficacy Scale–Short Form (BSES-SF).

The Baseline In-Hospital Interview questionnaire was adapted for the present study by the primary investigators (A.N. and L.N.) from the Centers for Disease Control and Prevention Infant Feeding Practices Study II.¹⁹ Mothers were interviewed by a research assistant within the first 72 hours after birth during the postpartum hospitalization. The initial interview took between 15 and 20 minutes. The One-Month Follow-Up Interview questionnaire used selected questions from the Infant Feeding Practices Study II.¹⁹ The research assistant contacted the mother by phone and conducted a phone interview, which took 10 minutes. All data for the study, including breastfeeding rates, were obtained from the maternal oral interviews.

Dennis' BSES-SF consists of 14 statements that measure breastfeeding self-efficacy (BSE) using a five-point Likert scale ranging from 1 to 5 (not at all confident—very confident), with scores ranging from 14 to 70.²⁰ The higher the score, the higher the level of BSE. Dennis reported a Cronbach's alpha of 0.94. For the present study, the BSE was measured at both the postpartum hospitalization and 1-month interviews, and Cronbach's alpha at both times was 0.91.

Outcome assessment

Breastfeeding rates for this study included several variables: breastfeeding in the first hour of life, age of infant at breastfeeding initiation, any breastfeeding, exclusive breastfeeding, and breastfeeding intensity during the postpartum hospitalization and at 1 month. Breastfeeding in the first hour was defined as infant's receiving any breast milk in the first hour of life. Breastfeeding rates at 1 month of age were calculated with a feeding history for the 7 days before the phone interview. Any breastfeeding was defined as receiving any breast milk either at the breast or pumped milk. Exclusive breastfeeding for this study was defined as receiving only mother's milk via the breast or pumped milk. Exclusive breastfeeding at 1 month was defined as exclusive breastfeeding for the 7 days before the 1-month interview. Breastfeeding intensity was defined as the percentage of all feedings that were breast milk. High breastfeeding intensity was defined as a breastfeeding intensity >80%.

Statistical analysis

Data were analyzed using SPSS 24. Descriptive statistics were used to summarize the data and identify characteristics of the mothers and newborns in the two groups, and t-tests, Pearson correlation, chi-square, Fisher exact, and Mann–Whitney U tests were performed for interval, nominal, and ordinal variables, respectively. The relationship between background and clinical variables was analyzed using Pearson correlations. Logistic analysis was used to calculate the unadjusted and adjusted odds ratios (aORs) for breastfeeding outcomes in the ET and term groups. Maternal immigrant status, marital status, obese/overweight, work intention in the first year, study intention in the first year, gravida, was breastfed, breastfed in the past, delivery type, and epidural were included as confounding variables in the adjusted analysis. The study received approval from the Internal Review Board at the Hadassah Medical Organization, and the study participants signed an informed consent form.

Results

The study sample composed of 370 infants; 12 mothers declined to consent for the study. Of the 358 remaining infants, 200 were classified as ET infants and 158 were term infants. The mean maternal age was 31 years, and 98% of all mothers were married. The mothers' highest educational degree was: 19% of mothers graduated high school, 4% post-high school certificate, 40% had a Bachelor's degree, 21% had a Master's degree, and 4% had a Doctoral degree. Eighty-two percent of the mothers intended to work in the first year and 27% intended to return to school. There were no significant differences between the groups for education (Mann–Whitney U = 14,992, p = 0.780) or income levels (U = 14,638, p = 0.26). The background variables for the two groups are given in Table 1. Of note, less ET mothers intended to return to school in the first year and less delivered vaginally. As expected, birth weight was lower among ET infants (3,082 [318] g versus 3,313 [317] g, p < 0.001). There were no differences between the groups in maternal health problems, including diabetes and pre-eclampsia.

Table 1.

Maternal and Birth Characteristics for Early Term and Term Mothers

Characteristic	ET^a (n = 200)	Term^a (n = 158)	p
Maternal age, years
<25	16 (8)	20 (13)	0.207
25–34	125 (63)	101 (64)
>34	59 (29)	37 (23)
Married	196 (98)	156 (99)	0.211
Immigrant	68 (34)	60 (38)	0.284
Work intention <1 year	160 (80)	133 (84)	0.640
Study intention <1 year	42 (21)	55 (35)	0.004
Maternal health problem	20 (10)	24 (15)	0.188
Maternal overweight/obese	54 (27)	32 (20)	0.170
Mother was breastfed	152 (76)	133 (84)	0.147
Primiparous	46 (23)	35 (22)	0.899
Breastfed prior child	146 (73)	115 (73)	0.846
Vaginal delivery	140 (70)	145 (92)	0.000
Vaginal induction	4 (2)	6 (4)	0.144
Vaginal epidural	92 (46)	79 (50)	0.450

Chi-square analysis.

Data are presented as n (%).

Two hundred twenty-three of the 358 mothers in the study breastfed in the first hour of life (62%), 348 (97%) breastfed in the hospital, and 162 (45%) exclusively breastfed in the hospital. ET mothers were less likely to breastfeed in the first hour (Table 2), and the age of the first breastfeeding was higher in ET infants than in term infants (3.0 [2.2] hours versus 1.9 [1.6] hours, p < 0.001). ET infants were more likely to receive formula in the first day of life (41% versus 32%, p = 0.04, odds ratio [OR] = 1.50, 95% confidence interval [CI] = 1.16–2.33). ET infants had lower any breastfeeding rates in the hospital (95% versus 100%, p = 0.007). In this cohort of mothers who all intended to breastfeed, all term mothers initiated breastfeeding in the hospital, whereas eight ET mothers did not. In addition, ET infants had significantly lower exclusive breastfeeding (Table 2), lower breastfeeding intensity (76 [28]% versus 87 [20]%, p = 0.000), and lower rates of high breastfeeding intensity (Table 2) in the hospital.

Table 2.

Unadjusted Odds of Breastfeeding Outcomes of Early Term at Birth and 1 Month

	ET ^a	Term ^a	p	OR (95% CI)
In hospital	n = 200	n = 158
Breastfeeding in the first hour	101 (51)	122 (77)	0.000	0.30 (0.19–0.48)
Any breastfeeding	190 (95)	158 (100)	0.026	0.12 (0.02–0.96)
Exclusive breastfeeding	73 (37)	89 (56)	0.000	0.45 (0.29–0.68)
High breastfeeding intensity^b	121 (61)	126 (80)	0.000	0.39 (0.24–0.63)
1 Month	n = 188	n = 153
Any breastfeeding	178 (95)	140 (97)	NS
Exclusive breastfeeding	127 (68)	125 (82)	0.003	0.47 (0.28–0.78)
High breastfeeding intensity^b	147 (78)	137 (90)	0.006	0.42 (0.23–0.78)

Univariate logistic regression analysis.

Data are presented as n (%).

High breastfeeding intensity is defined as a BFI >80%. BFI is defined as the percentage of all feedings that were breast milk.

BFI, breastfeeding intensity; CI, confidence interval; OR, odds ratio.

One-month data were obtained on 341 infants (95% of original cohort), 188 ET and 153 term. There were no significant differences in any breastfeeding rates between the two groups at 1 month. Two hundred fifty-two of the 341 mothers were exclusively breastfeeding at 1 month. ET infants, however, had significantly lower exclusive breastfeeding (Table 2), lower breastfeeding intensity (85 [28]% versus 93 [21]%, p = 0.006), and lower rates of high breastfeeding intensity (Table 2) at 1 month.

Subgroup analysis revealed that both 37- and 38-week infants had lower breastfeeding rates in the hospital and 1 month than term infants. Thirty-seven- and 38-week infants had lower breastfeeding rates in the hospital than term infants for exclusive breastfeeding (29% versus 56%, p = 0.001; 39% versus 56%, p = 00.002), breastfeeding intensity (76 [23]% versus 87 [20]%, p = 0.000; 76 [30]% versus 87 [20]%, p = 0.000), and high breastfeeding intensity (46% versus 67%, p = 0.008; 55% versus 67%, p = 0.045) and had lower breastfeeding rates at 1 month for exclusive breastfeeding (61% versus 82%, p = 0.019; 69% versus 82%, p = 0.004), breastfeeding intensity (81 [32]% versus 93 [21]%, p = 0.019; 87 [27]% versus 93 [21]%, p = 0.035), and high breastfeeding intensity (71% versus 88%, p = 0.004; 80% versus 88%, 0.031).

Multivariable logistic regression analysis, controlling for confounding variables, including intension to return to school and caesarean delivery, demonstrated that ET infants had significantly lower breastfeeding in the first hour (aOR = 0.43, 95% CI = 0.21–0.87), lower exclusive breastfeeding in the hospital and at 1 month (aOR = 0.46, 95% CI = 0.27–0.71 and aOR = 0.40, 95% CI = 0.22–0.71), and lower rates of high breastfeeding intensity in the hospital and at 1 month (aOR = 0.39, 95% CI = 0.22–0.71 and aOR = 0.33, 95% CI = 0.15–0.72) (Table 3).

Table 3.

Adjusted Odds of Breastfeeding Outcomes of Early Term Infants

	p	aOR (95% CI)
In-hospital
Breastfeeding in the first hour	0.018	0.43 (0.21–0.87)
Any breastfeeding	NS
Exclusive breastfeeding	0.000	0.46 (0.27–0.71)
High breastfeeding intensity^a	0.002	0.39 (0.22–0.71)
1 Month
Any breastfeeding	NS
Exclusive breastfeeding	0.005	0.40 (0.21–0.76)
High breastfeeding intensity^a	0.005	0.33 (0.15–0.72)

Adjusted for maternal immigrant status, marital status, obese/overweight, work intention in the first year, study intention in the first year, gravida, was breastfed, breastfed in the past, delivery type, and epidural. Multivariable logistic regression analysis.

High breastfeeding intensity is defined as a BFI >80%. BFI is defined as the percentage of all feedings that were breast milk.

aOR, adjusted odds ratio; CI, confidence interval.

BSE scores in the hospital and at 1 month did not differ between the two groups. The BSE in the hospital correlated with breastfeeding intensity in the hospital (r = 0.338, p < 0.001) and exclusive breastfeeding in the hospital (53 [11] versus 48 [13], p = 0.000). The BSE in the hospital correlated with breastfeeding intensity at 1 month (r = 0.302, p < 0.001) and exclusive breastfeeding at 1 month (52 [10] versus 45 [15], p = 0.000). The BSE at 1 month also correlated with breastfeeding intensity at 1 month (r = 0.626, p < 0.001) and exclusive breastfeeding at 1 month (58 [8] versus 45 [15], p = 0.000). In addition, the BSE in the hospital was negatively correlated with the age of first breastfeeding (r = −0.225, p < 0.001).

Ancillary outcomes

Breastfeeding in the first hour of life was associated with increased exclusive breastfeeding in the hospital (62% versus 26%, p < 0.001) and at 1 month (82% versus 66%, p = 0.001) and increased breastfeeding intensity in the hospital (90% [18] versus 65% [31], p < 0.001) and at 1 month (93% [21] versus 86% [28], p = 0.02). Breastfeeding support, whether defined by observing a breastfeeding session, helping breastfeed or support by a lactation consultant, in the hospital or outpatient, did not differ between the two groups.

More mothers of ET infants reported breastfeeding difficulties related to infants not waking up enough to breastfeed (12% versus 3%, p = 0.002, OR = 4.2, 95% CI = 1.5–11.2). In the first month of age, while there was no difference in the number of hospitalizations or sick clinic visits, ET infants had more emergency room (ER) visits (5% versus 1%, p = 0.02, OR = 7.6, 95% CI = 1.01–60.6). Reasons given for ER visits were jaundice (33%), fever (22%), and lethargy (11%). Infants who had ER visits had higher breastfeeding intensity in the hospital (91 [11]% versus 80 [20]%, p = 0.02) and at 1 month (100 [0]% versus 90 [25]%, p < 0.001). All the infants who had ER visits were exclusively breastfed at 1 month, and only one was receiving pumped milk.

Discussion

This prospective study provides evidence that ET infants have significantly lower breastfeeding and exclusive breastfeeding initiation rates and 1-month continuation rates, a finding that is consistent with previous studies. A 2013 retrospective large study found that ET infants had lower breastfeeding initiation rates.¹⁸ A 2014 survey of mothers performed at an average of 11 months postpartum found lower, but nonsignificant, any breastfeeding and exclusive breastfeeding rates of ET infants at 1-week postpartum.¹⁶ A 2016 secondary analysis of a large study found that ET infants had decreased breastfeeding rates at 1 month of age, defined as any breastfeeding or feeding of pumped milk.¹⁷ A 2013 retrospective PRAMS study found that ET infants had significantly lower breastfeeding initiation and breastfeeding continuation at 10 weeks, defined as any breastfeeding or feeding of pumped breast milk.⁴ Our prospective study analyzed any breastfeeding, exclusive breastfeeding, and breastfeeding intensity. The study found that ET infants had lower hospital any breastfeeding, lower hospital exclusive breastfeeding, lower hospital breastfeeding intensity, lower hospital rates of high breastfeeding intensity, lower breastfeeding in the first hour, higher age of first breastfeeding, lower 1-month exclusive breastfeeding, lower 1-month breastfeeding intensity, and lower 1-month rates of high breastfeeding intensity. Multivariable logistic regression analysis demonstrated that ET infants had significantly lower breastfeeding in the first hour, lower exclusive breastfeeding in the hospital and at 1 month, and lower rates of high breastfeeding intensity in the hospital and at 1 month, after controlling for confounding variables.

The higher formula use on the first day of life and lower breastfeeding intensity in the hospital and at 1 month among ET infants reported in this study is concerning due to the growing evidence that lack of exclusive breastfeeding increased childhood morbidity and mortality.²¹ The present study found that delayed breastfeeding initiation past the first hour of life, which was increased in ET infants, was associated with lower breastfeeding rates in the hospital and at 1 month. This delayed breastfeeding initiation is also concerning due to evidence that breastfeeding initiation beyond the first hour of life doubled the risk of neonatal mortality²² and increased infant morbidity.²³

The present study did not find a significant decrease in any breastfeeding of ET infants at 1 month (Table 2). This differed from the studies of Hackman et al.¹⁷ and Hwang et al.,⁴ which found significant differences at 1 month and 10 weeks, respectively. The lack of a difference in the present study may be secondary to the very high breastfeeding rates in both groups at 1 month of age, >95%. These high rates may be due to the study's inclusion criteria of mothers who intended to breastfeed their infants and exclusion of infants admitted to the NICU. We speculate that the high rates may also be secondary to the 15-week mandatory paid maternity leave in Israel, compared with the other studies, which were performed in the United States, with no guaranteed paid maternity leave.²⁴

This is the first study to compare BSE scores of ET and term mothers. While there were no differences in BSE scores between ET and term mothers, the BSE was associated with most of the breastfeeding outcomes. We speculate that the lack of difference in BSE scores between the groups was because most mothers in both groups were multiparous (78%) with past breastfeeding experience (73%). The BSE is a measure of maternal confidence and depends on many factors, one of the most important is previous breastfeeding experience.^25,26 The finding in the present study pertaining to the BSE and breastfeeding outcomes suggests that BSE assessment during the postpartum stay should be considered for identification of ET and term mothers who are at risk for lactation difficulties.

The present study found that ET infants had more ER visits in the first month. Of note, those infants who had ER visits breastfed more; they had higher breastfeeding intensity in the hospital, all were exclusively breastfed at 1 month, and only one was receiving pumped milk. The most common reasons for the ER visits were jaundice, fever, and lethargy. This is consistent with data by Dietz et al. that ET infants had higher rates of sick/ER visits in the first year of life.⁵ It is also consistent with studies that ET infants have higher rates of readmissions in the first 2 weeks of life, with the most common reasons being jaundice and feeding problems,^5,27 both of which are related to breastfeeding difficulties. A similar finding was found in late preterm infants that those who breastfed were 1.8 times more likely than term infants to require hospital-related care, whereas no differences were found between late preterm and term infants who were not breastfed.²⁸ This suggests that special follow-up may be needed to prevent neonatal morbidity among ET breastfed infants, who may have more difficulty in establishing breastfeeding due to immaturity.

The strengths of this study are that it is a prospective study with 93% follow-up at 1-month follow-up. Limitations are that it is a single-center study, which used a convenience sample. The present study, although powered for breastfeeding rates, was not powered for morbidity. As with all studies that request that participants answer a questionnaire, participants may have answered questions with answers thought to be desirable to the research assistant.

Conclusions

This prospective cohort study provides evidence that breastfeeding of ET infants is not the same as term infants. In the hospital, ET infants had lower any breastfeeding, lower exclusive breastfeeding, lower breastfeeding intensity, lower rates of high breastfeeding intensity, and lower breastfeeding in the first hour. At 1 month, ET infants had lower exclusive breastfeeding, lower breastfeeding intensity, and lower rates of high breastfeeding intensity. In addition, ET infants had more ER visits in the first month. The infants who had ER visits had higher breastfeeding intensity in the hospital, and all were exclusively breastfed at 1 month. We suggest that health care professionals identify the ET maternal–infant dyad during labor to ensure lactation support in the immediate postpartum period and improve first hour breastfeeding.²⁹ ET infants should continue to receive tailored lactation and medical support throughout the first month to improve breastfeeding and decrease morbidity.

Prior Publications

There are no prior publications or submissions with any overlapping information, including studies and patients. Preliminary results of this study have been presented at the Pediatric Academic Societies and Academy of Breastfeeding Medicine annual meetings.

Footnotes

Disclosure Statement

No competing financial interests exist.

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