Is there an association between the primary mode of lactation support received (digital/telehealth versus face-to-face peer support) and exclusive breastfeeding at 6–8 weeks postpartum among mothers who delivered during pandemic-related social restrictions, after adjusting for maternal age, parity, education, mode of delivery, prior breastfeeding experience, and intended breastfeeding duration?

Mothers who delivered live singleton infants at ≥37 weeks' gestation during the COVID-19 pandemic social restriction period (defined operationally as March 2020–December 2021, aligning with [[1]]) and who received structured lactation support — either digital/telehealth lactation support or face-to-face peer support — during the first 6–8 weeks postpartum. Exclusion criteria: multiple gestation, preterm delivery (<37 weeks), NICU admission >7 days, maternal conditions contraindicating breastfeeding, or relocation out of the catchment area within 8 weeks postpartum.

A single tertiary maternity hospital (or a defined network of 2–3 facilities in one metropolitan area) that maintained systematic records of both the mode of lactation support provided and breastfeeding outcomes during the pandemic restriction period. The facility must have offered both digital/telehealth and face-to-face peer support options during the study window so that both exposure groups are representable from the same source population, minimising selection bias from differential site practices.

Systematic sampling from the hospital's electronic postpartum records: all eligible mothers who delivered during the restriction period will be enumerated chronologically and every k-th record selected, where k = N/n, with a random start. If the eligible pool is smaller than the required sample, a census of all eligible records will be attempted. This approach reduces the selection bias inherent in convenience sampling while remaining operationally feasible for a retrospective review.

Cochran's two-proportion formula: n per group = [Z_{α/2}√(2p̄(1−p̄)) + Z_β√(p₁(1−p₁)+p₂(1−p₂))]² / (p₁−p₂)². Assumptions: two-sided α = 0.05 (Z_{α/2} = 1.96), power = 0.80 (Z_β = 0.84), expected exclusive breastfeeding proportion in the face-to-face peer support group p₁ = 0.60, expected proportion in the digital/telehealth group p₂ = 0.45 (a 15-percentage-point difference considered the minimum clinically meaningful difference), p̄ = 0.525. This yields n ≈ 135 per group. Adjusting for 20% incomplete records/non-response gives approximately 170 per group (340 total). If the eligible population is smaller, the study will report the achieved power and minimum detectable difference transparently.

Retrospective hospital maternity and lactation service records (for exposure ascertainment, delivery details, early postpartum breastfeeding status, and covariates available in clinical records); structured telephone or online follow-up survey administered at the time of study contact (for 6–8-week exclusivity outcome if not available in records, and for covariates such as return-to-work, education, prior breastfeeding experience, and intended duration). The survey will use validated breastfeeding exclusivity items consistent with WHO definitions, as applied in breastfeeding intervention studies [[2]]. To address potential recall bias, the time frame for survey items will be anchored to the 6–8-week postpartum period, and records will be the primary source for exposure classification.

6–8 months: 1–2 months for ethics approval and record identification; 2–3 months for chart abstraction and participant contact/survey administration; 2–3 months for data cleaning, analysis, and write-up.

Low-to-moderate. Primary costs are researcher time for chart review, telephone/online survey platform, and participant reimbursement (e.g., mobile data vouchers equivalent to ~USD 2–5 per respondent). No new intervention delivery costs. Estimated total: USD 2,000–5,000 depending on setting.

IRB approval required. Retrospective chart review component requires waiver or modification of consent for record access; the follow-up survey component requires informed consent. Privacy protections for health data and COVID-19 status must comply with local data protection regulations. No intervention is administered; risk is minimal.