First, you can help baby's digestion with tummy massages using olive oil, as the Prophet ﷺ mentioned in the hadiths. In addition, the mother can make breastfeeding her ally, by drinking fenugreek and anise herbal teas, and the baby will be soothed digestively.
What the science says: reflux and the stomach in children
What published research says about the remedies mentioned above, for context only — the studies address material causes, while healing belongs to Allah.
In children
In infants, the probiotic Lactobacillus reuteri reduces colic-related crying according to a meta-analysis (Pediatrics, 2018) (Acta Paediatr, 2024); in children, honey soothes nighttime coughing (after age one) (Cochrane, 2018), fiber and hydration treat constipation (J Pediatr, 2022), and omega-3s are being studied for hyperactivity (Neuropsychopharmacology, 2018). Precaution: never give honey before age one, no essential oils before age 3 (age 6 for peppermint), doses adjusted to weight; any fever in an infant under 3 months old is an emergency.
Reflux and the stomach
Gastroesophageal reflux responds first to lifestyle habits: light meals eaten early, an elevated head of the bed, a healthy weight, quitting smoking, and less coffee and fat (JAMA, 2020) (Ther Clin Risk Manag, 2021); traditional medicine plants (licorice, chamomile, ginger) are being evaluated for dyspepsia (Curr Drug Discov Technol, 2021). Precaution: licorice raises blood pressure; persistent heartburn, difficulty swallowing, or unexplained weight loss should be examined by a doctor.