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A Comparison of Intakes of Breast-Fed and Bottle-Fed Infants during the First Two Days of Life

The Department of Neonatology, Lis Maternity Hospital, Tel Aviv Sourasky Medical Center, Tel Aviv, ISRAEL

Address reprint requests to: Shaul Dollberg, MD, The Department of Neonatology, Lis Maternity Hospital, Tel Aviv Sourasky Medical Center, 6 Weizman Street, Tel Aviv 64239, ISRAEL. E-mail: mimouni{at}tasmc.health.gov.il

	ABSTRACT

TOP ABSTRACT INTRODUCTION PATIENTS AND METHODS RESULTS DISCUSSION REFERENCES

 
Objective: In the first days of life, breast-fed infants consume minimal amounts of milk; this may be explained by substrate limitation (limited milk output) and/or by self-limitation (through low appetite and/or suck-swallow competency). The spontaneous milk intake of unrestricted formula-fed infants has not been studied to date. We compared the spontaneous formula intake of unrestricted formula-fed infants to that of breast-fed infants over the first 48 hours of life. We hypothesized that 1) spontaneous formula intake of unrestricted infants is much higher than that of breast-fed infants and 2) spontaneous formula intake correlates positively with gestational age or birthweight.

Methods: We studied 43 healthy, term infants. By maternal choice, 15 infants were exclusively breast-fed and 28 were formula-fed ad libitum every four hours. Breast-fed infants were weighed before and one hour after initiation of feeding, and intake was calculated from the difference between the measurements and corrected individually for the infant’s normal postnatal decrease in body weight. Bottles offered to formula-fed infants contained 60 cc, and the remainder was carefully measured. Intakes were expressed as cc/kg/d, and weight changes as % of birthweight. Statistical methods included Student’s t tests and stepwise regression analysis.

Results: Breast feeding on Day 1 was 9.6±10.3 (mean±SD) vs. 18.5±9.6 cc/kg/d in formula-fed infants (p=0.011); on Day 2 it was 13.0±11.3 vs. 42.2±14.2 cc/kg/d (p<0.001). Breast-fed infants lost significantly more weight on Day 2 (p=0.015). In multiple regression, when the dependent variable was the second-day intake, the significant independent variables were group (higher intake in the formula-fed group), weight loss (the higher the weight loss, the lower the intake), and first-day intake (the higher the first-day intake, the higher the second-day intake).

Conclusion: Newborn infants offered formula ad libitum every four hours consumed much larger amounts than breast-fed infants fed according to the same schedule. In addition, weight loss was more marked in breast-fed infants on Day 2 of life.

Key words: infants, term, appetite, breast-feeding

	INTRODUCTION

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In the first days of life, breast-fed infants consume minimal amounts of milk, as little as 13 mL/kg/day on Day 1 and 40 mL/kg/day on Day 2 of life [1]. In theory, such small amounts may be due to low maternal colostrum output from a breast in transition from pregnancy to lactation. It is known, however, that the breast milk production adjusts itself to the infant’s requirements [2]. Whether low colostrum or milk output of the first two days of life is primarily due to a relative lack of readiness to lactate or is secondary to low consumption by the infant is unknown. We aimed to evaluate the spontaneous intake of infants fed formula (by maternal choice) ad libitum. We hypothesized that such infants consume greater amounts of milk in the first two days of life than breast-fed infants.

	PATIENTS AND METHODS

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We recruited 43 healthy, singleton term, (38 to 41 weeks’ gestation), appropriate for gestational age (using the curves of Lubchenco [3]) newborn infants concurrently born after uncomplicated pregnancy, labor and delivery; maternal analgesia during labor was solely by epidural bupivacaine. All infants had an Apgar score of more than 7 at 1 and at 5 minutes and were delivered by spontaneous vaginal vertex delivery.

By maternal choice, 28 were formula-fed and 15 breast-fed; in both groups, infants were fed every four hours, by hospital protocol, starting as early as two and as late as ten hours, as soon as the mother was ready to feed the infant. No baby was roomed-in. Formula-fed infants received ready-to-feed Similac (20 cal/oz, Ross laboratories, Columbus OH). Any remainder of the 60 mL bottle was carefully measured, and results were rounded to the closest mL. In the breast-fed group, every infants was weighed, fully clothed, before and one hour after initiation of feeding at the breast using an electronic scale (Seca Model 727, Hamburg, Germany). Intake was calculated from the difference between the two measurements. Correction for the normal postnatal decrease in body weight during the time spent at the breast, suggested by Salarya et al. [4], was based upon the daily weight loss of each individual infant. Specifically, we used the 24-hour weight loss of each child and divided it by the time spent at the breast in order to provide an adequate correction. In both groups, patients were weighed every 24 hours using an electronic scale. All regurgitations were noted on a collection form.

Statistical Analyses
Intakes were calculated as mL/kg/day and weight changes as % of birthweight. Results are expressed as mean±SD. Paired t tests (for normally distributed variables), were used to test the difference between Day 1 and Day 2 intakes. The Kruskal-Wallis test was used for non-normally distributed variables. The chi-square test was used to determine the difference between the groups for discrete variables (such as gender). Backward stepwise regression analysis was used to study the effect of selected variables on Day 1 or Day 2 intakes.

	RESULTS

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Twenty boys and 23 girls were recruited in the study. All mothers were middle-class, healthy women aged 24 to 41 years with an average parity of 2.4 (range 1 to 6). All infants were Israeli Jews, most of them of mixed Sepharadic and Ashkenazi origin. There were no significant differences between the breast-fed and the formula-fed group in terms of gestational age, birth weight or Apgar scores (Table 1).

	DISCUSSION

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We showed that formula-fed infants offered formula ad libitum on Day 1 and Day 2 of life have an intake of 18.5±9 mL/kg/day on Day 1, which increases to 42±14 mL/kg/day on Day 2. Significant regurgitations were not reported in either group, and we do not believe that unreported regurgitations may have biased significantly our results. Nevertheless, these values are significantly higher than those found in our control, breast-fed group. This observation may be interpreted possibly as being due to substrate limitation in breast-fed infants or, alternatively, to "overfeeding" in formula-fed infants. While it may very well be that infants fed formula ad libitum are "overfed" when compared to breast-fed infants, it is possible that reduced maternal milk production in our hospital settings may have played a role. Indeed, none of the infants in our study was roomed-in, and, although they were fed ad libitum, it was according to a strict every-four-hours schedule. In such circumstances, establishment of colostrum production may be slower and less efficient than when the infant is roomed-in [5]. In fact, the values found in formula-fed infants were close to those found by Casey et al. (13±16 mL/kg/day on Day 1 and 40±23 mL/kg/day on Day 2) in strictly breast-fed infants, although the rooming-in situation of these infants was not described [1]. In Casey’s study, all infants were breast-fed for the first time within the first two hours of life, a circumstance which may also have led to greater human milk production than in our patients, whose age at first feed, a variable which proved influential on intake, ranged between two and ten hours of life. Although the difference in age at first feed between the two groups was significantly different, in regression analysis, this difference of approximately three hours did not significantly affect the intake on Day 1 or Day 2.

Regardless of the feeding group, the values found in this study were much lower than those reported between the ages of eight and 30 days, when the median intake is 196 mL/kg/day [6]. There can be no suspicion that the formula-fed group was substrate-limited. Thus, lower intake in the first days of life must be interpreted as due to self-limitation by the infant. This self limitation could possibly be due to lower appetite and/or thirst, decreased sucking and swallowing competency or decreased alertness level and may be aggravated by iatrogenic factors such as opiate analgesics. In our study, the latter is not likely, as all infants were delivered after bupivacaine epidural analgesia, which has little effect on neonatal behavior [7].

The fluid intakes reported in this study as well as in that of Casey are well below what is advised in major neonatology textbooks, which suggest a true water requirement of 60 to 65 mL/kg/day at birth [8,9]. Thus, published recommendations may exceed the neonate’s physiological needs. However, when fluid or caloric requirements are increased, such as in hypoglycemia or hyperviscosity, the infant’s spontaneous intake may be insufficient. Nevertheless, while weight loss was similar on Day 1 of life in breast and formula-fed infants, it was more marked in breast-fed infants on the second day of life. Second-day weight loss correlated inversely with first-day intake, which itself correlated with age at first feed. Thus, it may very well be that, regardless of the group, one way to reduce excessive postnatal weight loss is to introduce an early feeding policy. In our opinion, the fact that first-day intake had an influence on the second-day intake is in support of the speculation that the infant "experience" (competency in sucking and swallowing) might be a factor even more important than "appetite".

Received January 25, 2000. Revised August 3, 2000. Accepted August 3, 2000.

	REFERENCES

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1. Casey CE, Neifert MR, Seacat JM, Neville MC: Nutrient intake by breast-fed infants during the first five days after birth. Am J Dis Child 140: 933–936, 1986.[Abstract]
2. Daly SE, Hartmann PE: Infant demand and milk supply. Part 1: Infant demand and milk production in lactating women. J Hum Lact 11: 21–26, 1995.[Abstract/Free Full Text]
3. Lubchenco LO, Hansman C, Dressler M, Boyd E: Intrauterine growth as estimated from live-born birth weight data at 24 to 42 weeks gestation. Pediatrics 32: 793–799, 1963.[Abstract/Free Full Text]
4. Salarya EM, Easton PM, Cater JL: Duration of breast-feeding after early initiation and frequent feeding. Lancet 2: 1141–1142, 1978.[Medline]
5. Perez-Escamilla R, Pollitt E, Lonnerdal B, Dewey KG: Infant feeding policies in maternity wards and their effect on breast-feeding success: an analytical overview. Am J Public Health 84: 89–97, 1994.[Abstract/Free Full Text]
6. Fomon SJ, Owen GM, Thomas LN: Milk or formula volume ingested by infants fed ad libitum. Am J Dis Child 108: 601–604, 1964.
7. Rosenblatt DB, Belsey EM, Lieberman BA, Redshaw M, Caldwell J, Notarianni L, Smith RL, Beard RW: The influence of maternal analgesia on neonatal behavior: II. Epidural bupivacaine. Br J Obstet Gynaecol 88: 407–413, 1981.[Medline]
8. Bell EF, Oh W: Fluid and electrolyte management. In Avery GB, Fletcher MA, MacDonald MG (eds): "Neonatology," 4th ed. Philadelphia: J.B. Lippincott, pp 312–339, 1994.
9. Liechty EA: Water requirements. In Polin RA, Fox WW (eds): "Fetal and Neonatal Physiology," 2nd ed. Philadelphia: W.B. Saunders, pp 305–307, 1998

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