Indian Pediatrics 2002; 39:130-135
Effect of Delayed Cord Clamping on Iron Stores in Infants Born to Anemic Mothers: A Randomized Controlled Trial
THE public health magnitude of anemia amongst children in India has been brought to the fore by the recent NFHS survey(1), which has recorded that almost 70% of infants between 6-11 months are anemic. It has also demonstrated a strong association between maternal hemoglobin levels and prevalence of anemia amongst their children. Iron store at birth is a major factor influencing growth and the occurrence of iron deficiency anemia during infancy. These stores are determined by the transplacental iron transferred to the fetus and the blood transferred from the placenta at delivery. Various studies have shown that late clamping of cord provides the infant about 100 ml of blood (equivalent to about 56 mg of elemental iron)(2,3).
Delayed cord clamping has been suggested as a possible strategy for reducing anemia amongst toddlers. Not many random-ized controlled trials have been conducted to see the effect of this extra iron acquired at birth on iron stores during infancy and none in infants born to anemic mothers. The present study was, therefore, designed to test the hypothesis that delayed clamping of cord at birth would result in higher iron stores at 3 months in infants born to anemic mothers.
Subjects and Methods
A randomized controlled trial was designed to include hospital born term neonates born vaginally to pregnant women with hemoglobin (Hb) <100 g/L (used to define anemia in pregnant mothers at term) at time of delivery with no associated medical or pregnancy related complications, e.g., eclampsia, severe heart failure, severe antepartum hemorrhage or Rh-isoimmuniza-tion. Infants were excluded if they needed resuscitation at birth or had major congenital malformations.
Serum ferritin and hemoglobin in the infant at 3 months of age, was designated as the primary outcome variable.
Sample Size Estimates
To detect a difference in serum ferritin of 20 µg/L between early and delayed cord clamping groups at 3 months with a SD of 3 µg/L (based on observations from an earlier trial)(4), a power of 80% and probability of 5%, it was estimated that a total sample size of 60 infants would be required. Similarly, to detect a difference of 10 g/L in Hb at 3 months between the two groups with a SD of 8 g/L, a power of 80% and probability of 5%, it was estimated that a total sample size of 30 infants would be required. To allow for dropouts sufficient subjects were planned for initial enrolment such that atleast 30 infants were available in each group at 3 months of age.
Informed written consent was obtained from all women with anemia admitted in labor. The institutional research committee ethically cleared the study.
Randomization and Cord Clamping Technique
Computer generated random number sequences were placed in opaque sealed envelopes. The envelopes were opened when the women in labor, fulfilling the entry criteria, were about to deliver. The women assigned to the early cord-clamping group had their cords clamped immediately after the birth of the infant. In those women assigned to the delayed-cord clamping group, the cord was clamped after the placenta had descended into the vagina; during this time the newborn was held below but within 10 cm of the vaginal introitus and utmost care was taken to prevent hypothermia in the infant by adequate drying and wrapping the infant in dry, warm linen. Thereafter, the infant was placed under a preheated radiant warmer in the delivery room.
Collection of Blood Samples and Analytic Techniques
Maternal venous blood (4 ml) was collected at the time of delivery in plain tubes for serum ferritin estimation and in EDTA containing vial for hemoglobin estimation. In the infant, 4 ml of cord blood at birth and infant venous blood at 3 months of age were collected in plain tubes and EDTA containing vials for Hb and ferritin estimations. The samples for ferritin assay were centrifuged and the serum was separated into a sealed tube and was stored in deep freeze at –20şC till the assay was performed.
Hemoglobin was estimated by Cyan-methemoglobin method(5). Serum ferritin was estimated by micro ELISA technique using human ferritin enzyme immunoassay test kit (Diagnostic Automation, Inc., Calabasas). The ferritin quantitative test kit uses a solid phase enzyme linked immuno-sorbent assay technique. The assay was performed as per the manufacturer’s instructions.
Baseline maternal data with regard to age, medicinal iron intake, parity, socioeconomic status and infant’s data with regard to birth weight and gestation were recorded in all cases. Infants were followed up till 3 months of age. No medicinal iron was given to any of these infants till the end of the study. The feeding patterns, weight gain, intervening morbidities like respiratory infections and diarrhea during this period were carefully recorded.
Group means of continuous parametric variables was evaluated by Student’s t-test. Proportions were compared by Chi-square test. Ferritin values were transformed to logarithmic values prior to analysis. Analysis of Covariance (ANCOVA) was used to estimate the change in hemoglobin at three months after adjusting for covariates using the SPSS-PC software.
There were 102 mother-infant pairs enrolled into the study; 53 in the early clamping group and 49 in the delayed clamping group. At three months follow-up, there were 58 infants available; 29 each in the early and delayed clamping groups.
A comparison between the lost to follow-up (n = 44) with those available at 3 months (n = 58) revealed that the mothers in the loss to follow-up group had a significantly lower mean number of antenatal visits (2.8 ± 2.1) compared to women in the study group (4.2 ± 2.6). The maternal mean ferritin levels were also significantly lower in the lost of follow-up group (23.5 µg/L) compared to the study group (35.9 µg/L). These observations pro-bably suggest a lower motivation and poorer compliance to medical advise amongst women in the loss to follow-up group.
Table I provides a comparison of baseline characteristics between the two groups. The groups were comparable for maternal nutritional characteristics, antenatal care and medicinal iron intake, and infant’s weight, gestation, sex and breastfeeding pattern at 3 months. The groups were also comparable for their monthly family incomes.
Table II provides the maternal and infant hemoglobin and ferritin values at birth with no significant difference between the two groups. Infant’s hemoglobin and ferritin values at 3 months were significantly lower in early clamping group compared to those in the delayed clamping group. The change in hemoglobin at 3 months from birth, both unadjusted and adjusted (for significantly correlated factors – cord hemoglobin and timing of cord clamping) was significantly less in the delayed clamping group. The mean difference in hemoglobin change (g/dl) between the groups was significant after adjusting for co-variates (–1.097, 95% CI: –1.579 to –0.615, p <0.001).
The proportion of infants at 3 months who had Hb <100 g/L were significantly less in the delayed clamping group (44%) than in the early clamping group (86%; odds ratio 7.7, 95% CI, 1.84-34.9). Similarly, the proportion of infants who had low iron stores at 3 months (serum ferritin <50 µg/L) were significantly less in the delayed clamping group (3%) compared to the early clamping group (27%; odds ratio 10.67, 95% CI 1.1-249.5).
* All values are presented as means (SD), except where specifically indicated: p >0.05 for all values
Table II__Maternal and Infant Hemoglobin and Ferritin Values
* p <0.001, **p = 0.02, + p = 0.05
It has generally been observed that healthy breastfed infants are unlikely to become iron deficient before 6 months of age(6). This is possibly because of the high bioavailability of iron from breast milk and not much increase in utilization of body iron during this period(7). Between 4-12 months of age, body iron is expected to increase by 70%, thus making this a period vulnerable to iron deficiency anemia. The recent NFHS survey has reported very high prevalence of anemia both in mothers and their children in India, with almost a quarter of children of severely anemic mothers being also severely anemic.
Iron stores at birth correlate with iron stores at 6-12 months. Studies have observed that infants of mothers with moderate and severe anemia had significantly lower cord serum ferritin levels and hence lower iron stores at birth(8,9). It has also been observed that even in iron replete Indian mothers (serum ferritin >10 µg/L), the cord ferritin was significantly lower compared to western reports(9). Iron store at birth is an important determinant of anemia in infancy. Delayed clamping of cord at birth has been suggested as a possible strategy to prevent anemia in infants between 4-11 months of age(10). Two randomized controlled trials have evaluated the effect of delayed cord clamping on iron stores in infancy. A trial from Guatemala(11) randomized 69 neonates to one of three groups at delivery: (a) cord clamped immediately at delivery, (b) clamped when cord stopped pulsating with newborns placed at level of placenta, and (c) clamped when cord stopped pulsating with newborn placed below the level of placenta. At two months after delivery the group with delayed clamping had signifi-cantly higher hemoglobin levels than the early clamping group. The only other trial from India(5), randomized 107 term infants born to non-anemic mothers to either immediate clamping of cord at delivery or clamping delayed till descent of placenta into vagina with neonate placed below the level of the placenta. Three months after delivery the infants in both groups had similar hemoglobin levels. The serum ferritin was higher but insignificant, in the delayed clamping group.
There are, however, no studies to demons-trate the effect of delayed cord clamping on the iron status of infants born to anemic mothers. The hemoglobin and serum ferritin levels at 3 months were significantly higher in the delayed clamping group compared to the early claming group. The odds of developing anemia (Hb <100 g/L) and having deficient iron stores (ferritin <50 µg/L(12) at 3 months was 7 and 10 times higher respectively, in the early clamping than in the delayed clamping group.
Thus it appears that infants born to anemic mothers benefit more than those born to non-anemic mothers from the additional iron they derive from the blood passed from the placenta as a result of delayed clamping. These benefits appear to outweigh any risk that may result from delayed cord clamping (such as polycythemia or volume overload); none of the trials have demonstrated increased risks of these potential side effects. The findings of the present study have important implications for the developing countries. There is need to incorporate delayed cord clamping as a component of routine active labor management. This strategy can impact upon the existing high prevalence of anemia in infancy and early childhood.
It is suggested that recommending delay in cord clamping specially in infants born to anemic mothers could serve as an additional cost-effective intervention in our anemia prevention/control program.
Contributors: RG executed trial, collected data, helped in analysis and drafting manuscript. SR designed the study, analyzed the data and drafted manuscript; he will act as the guarantor for the manuscript.
Competing interests: None stated.