Abstract
Aim:
The total duration of lactation was studied in mothers of preterm infants in our NICU at the National Hospital in Oslo, Norway (comparable to level III nurseries in USA). The duration of lactation was studied also in subgroups of mothers (grouped according to infants' birthweight).
Definition of lactation:
Feeding at breast (partial or total) and/or feeding mother's expressed milk.
Subjects:
108 mothers were included, and 59.3% had a Caesarian Section. The infants stayed median 46.5 days at the hospital, their gestational age at birth was median 30.5 weeks (23–36 weeks), and their birth weight was median 1447.5 g (600–2480g). 68% of the infants needed oxygen supply for median 12 days, and 50% of the infants needed ventilator-connection for median 5.5 days. Twenty-seven percent of the infants had a birthweight of 1000 g or below.
Methods:
A structured interview based on open-ended questions was used at the time of the infants' discharge. The mothers were asked following main-questions: Do you have breastmilk for your baby? If not, how long did you have breastmilk? Phone calls were used later to those mothers who still lactated at their infant's discharge. Existing sources of data were used for infant variables as birthweight, and a registration-schedule was used for close contact, as initial sucking and skin to skin holding. The Wilcoxon Rank Sum test (Z) was used to test differences between subgroups. The Spearman Rank Correlation test (rs) was used to test relationship between variables.
Results:
The mothers lactated for a median of 122 days (= 4 months) (mean 168.3 days = 5.6 months, variation 2 – 713 days). Mothers who had previously breastfed, continued lactation significantly longer than those who had not (p= 0.029). Mothers who smoked post birth had a significantly shorter lactation period compared to nonsmoking mothers (p= 0.0006), respectively median 53 and 153 days. A longer lactation period showed a significant relationship with early skin to skin holding of infants (p= 0.0055), and with increasing length of education (p= 0.0001). A shorter period of lactation showed a significant relationship with low gestational weeks (p= 0.0001), and with low birthweight (p= 0.0001). Lactation in 4 groups of mothers (grouped according to infant birthweight) were as follows: group A (infants to and including 999 g): median 56 days (= 1.8 months), group B (1000 – 1499 g): median 72.5 days (= 2.4 months), group C (1500 – 1999 g): median 273 days (= 9.1 months), and in group D (2000 – 2499 g): median 227 days (= 7.5 months).
Additional findings.
Mothers who smoked during pregnancy (n= 37) delivered their infants at a significantly lower gestation week (p= 0.026) (difference: median 2.5 week), and their infants had significantly lower birth weights (p= 0,038) (difference: median 195 g), compared to mothers who did not smoke (tables and figure in English).