Kim Min-hee says she breastfed on set — what the research says for mothers and babies

Actor Kim Min-hee's first public appearance since giving birth — during which she described breastfeeding and caring for her baby while filming — has renewed attention to the realities of postpartum work and nursing. Breastfeeding can benefit a baby's immune system and nutrition and may have positive effects on the mother's health as well, but experts caution that it should not be treated as an obligation every woman must fulfill.

Kim appeared Thursday (local time) at the 79th Locarno Film Festival in Switzerland for a screening of and audience discussion following director Hong Sang-soo's feature film "Nowhere to Lay My Eyes." It was her first public appearance since she gave birth to a son in April last year.

Kim spoke that day about returning to work after childbirth. "It was the first film I shot after taking about two years off following the birth of my baby, and my state of mind was very different from before, when I used to immerse myself entirely in the film," she said. She added that her baby had been on set with her. "I filmed while breastfeeding and making baby food," she said. "I would wake up incredibly early, finish all the preparations for the baby, and then get ready for the film. Looking back, I think that version of me was actually healthier."

Balancing nursing and work after childbirth is physically demanding. For breastfeeding women in particular, fatigue can vary greatly depending on feeding intervals, the baby's sleep patterns, whether pumping is involved, and the workplace environment. For this reason, experts say that when considering a postpartum return to work, it is important to look beyond physical recovery alone and also account for sleep, nutrition, emotional stability and access to caregiving support.

Breast milk supplies the nutrients a baby needs while also containing components that support immune function. Colostrum — produced in the first few days after birth — is especially rich in antibodies and immune-related compounds that can help newborns fight off external infections.

According to the US Centers for Disease Control and Prevention, breastfed babies may face a lower risk of certain infectious illnesses, including diarrhea, respiratory infections and ear infections. The World Health Organization also considers breastfeeding a key factor in infant survival and health, and recommends exclusive breastfeeding — with no water or other foods — for the first six months of life.

Breast milk also changes in composition as the baby grows. Colostrum, rich in immune components, gives way to milk whose ratios of fat, protein and sugars shift to match the infant's development. From around six months of age, complementary foods can be introduced while breastfeeding continues.

The American Academy of Pediatrics recommends exclusive breastfeeding for approximately the first six months, and says that after solid foods are introduced, breastfeeding can continue for two years or beyond if both mother and child wish. These are recommendations, however, not standards that apply uniformly to every situation.

The benefits of breastfeeding extend beyond the baby. According to the WHO and the CDC, breastfeeding may help lower a woman's risk of breast and ovarian cancer, and has been associated with a reduced risk of type 2 diabetes and high blood pressure.

In the immediate postpartum period, oxytocin released during nursing can help the uterus contract and return to its pre-pregnancy size. Breastfeeding also increases the time mother and baby spend in close physical contact, which can foster emotional bonding.

Breastfeeding may also support postpartum weight management, since producing milk requires energy. The American College of Obstetricians and Gynecologists notes that breastfeeding can aid postpartum weight loss. However, postpartum weight changes are influenced by many factors — including how much weight was gained during pregnancy, diet, sleep, activity level and hormonal shifts — so it is difficult to attribute weight loss to breastfeeding alone.

Nursing women should also pay close attention to nutrition. Extreme dietary restriction can worsen fatigue and dizziness and may make it harder to sustain breastfeeding. Adequate intake of protein, calcium, iron and fluids is recommended, while caffeine and alcohol consumption should be moderated. Breast pain, fever or red swelling may indicate mastitis, and medical attention is advisable in such cases.

Importantly, not breastfeeding does not mean a mother and baby will lack a strong bond. Whether a woman breastfeeds depends on a range of factors, including the health of both mother and child, medications, workplace conditions, family support and personal choice. Formula feeding and mixed feeding, when done appropriately, can also support a baby's growth and attachment.

Experts stress that promoting the benefits of breastfeeding must go hand in hand with creating conditions that make it sustainable. Women who wish to nurse or pump after returning to work should be guaranteed safe, hygienic spaces and adequate time to do so, and broader social support for postpartum recovery and maternal mental health is equally necessary, they say.