Maternal Age and Breastfeeding at 1 Month After Delivery at a Japanese Hospital

Dear Editor:

Exclusive breastfeeding for the first 6 months of life has been recommended because of important health, medical, social, and developmental benefits to both mothers and babies. ¹ Older women (especially those older than 25 years) have been reported to be more likely to initiate and continue breastfeeding than younger women. ² Recently, the maternal age has been rising significantly in Japan. If older women have a tendency to breastfeed, the rise in maternal age in Japan may be a desirable trend to increase the rate of exclusive breastfeeding; however, it is questionable whether older women simply intend to breastfeed because breastfeeding requires physical strength that older women may not have. Therefore, we examined the difference in the rate of exclusive breastfeeding at 1 month after delivery by maternal age in Japanese women at our hospital.

We reviewed the obstetric records of all Japanese women with a singleton delivery at our hospital between 2011 and 2012. A face-to-face interview was conducted to ask them whether or not they intended to perform exclusive breastfeeding for their babies on admission for delivery, and an additional interview was conducted to ask about their feeding methods at 1 month after birth. The definition of “exclusive breastfeeding” in this study is that an infant receives only breastmilk without additional liquids such as artificial baby milk, other than water for medications or vitamins. In this study, we also examined their parity, in vitro fertilization/intracytoplasmic sperm injection use, delivery modes, gestational age at delivery, and neonatal outcomes because these factors have been reported to be associated with the rate of exclusive breastfeeding.^2,3

During this period, in total, 3,140 women met the above-mentioned conditions. Of these, 1,457 women (46%) performed exclusive breastfeeding for their babies at 1 month after delivery. In this study, they were classified into seven groups by their age at delivery, presented in Table 1.

As shown in Table 1, compared with women 25–29 years of age, the rates of nulliparity and no intention of breastfeeding in teenaged women were significantly higher (p<0.01 and p<0.01, respectively), and the rates of exclusive breastfeeding in women of 40 years of age or older were significantly lower on univariate analysis by the χ² test (40–42 years, p<0.01; 43 years or older, p<0.01). The rate of pregnancy following in vitro fertilization/intracytoplasmic sperm injection increased with advancing maternal age (p<0.01). On multivariate analysis, the rate of no intention of breastfeeding was associated with nulliparity in teenaged women. However, the rates of exclusive breastfeeding in women 40 years of age or older were significantly lower independently (40–42 years, adjusted odds ratio 0.70, 95% confidence interval 0.48–0.94, p<0.01; 43 years or older, adjusted odds ratio 0.40, 95% confidence interval 0.20–0.82, p<0.01).

In this study, the exclusive breastfeeding rate in young women was not low, contrary to some previous observations. ² Teenaged Japanese women did not desire to initiate exclusive breastfeeding compared with women 20 years of age or older. The reasons may be social and/or economic problems in some of the teenaged women. ⁴ On the other hand, unfortunately, the current results indicate that an advanced maternal age of 40 years or older is independently associated with a decreased rate of exclusive breastfeeding. Some obstetric factors considered in this study, such as nulliparity, in vitro fertilization/intracytoplasmic sperm injection use, cesarean delivery, preterm delivery, and neonatal admission, did not seem to affect the difference in exclusive breastfeeding rates between women 25–29 years of age and those 40 years of age or older.

Based on the current results, milk production of younger mothers may be greater than that of older mothers. Considering exclusive breastfeeding, therefore, optimal delivery ages may be present in Japan. In addition, the benefits of breastfeeding should be taught to young Japanese mothers.