Delayed lactogenesis II (DLII)—often referred to by parents as “milk coming in late”—is a clinical concern with meaningful implications for breastfeeding success. Defined as the onset of copious milk production occurring more than 72 hours postpartum, DLII has been associated with reduced breastfeeding duration and increased rates of early cessation of exclusive breastfeeding (Brownell et al., 2012). Understanding its causes and how to support parents at risk can help improve outcomes.

What Is Lactogenesis II

Lactogenesis II refers to the initiation of copious milk secretion and typically occurs between 48 and 72 hours postpartum. This physiological shift is triggered by the sharp drop in progesterone following placental delivery, allowing prolactin to act more effectively on mammary alveolar cells (Peng et al., 2024).

When this process is delayed beyond 72 hours postpartum, it’s termed DLII and is considered a risk factor for early breastfeeding difficulties and shorter breastfeeding duration (Brownell et al., 2012; Peng et al., 2024).

What Factors Influence Delayed Lactogenesis II?

A wide array of factors can contribute to DLII, many of which are modifiable. According to a 2024 meta-analysis, the global incidence of DLII is around 30%, and the following are among the most strongly associated risk factors (Peng et al., 2024):

Maternal Obesity and High BMI

Higher pre-pregnancy BMI has consistently been linked with delayed lactogenesis II (Ballesta-Castillejos et al., 2020; Huang et al., 2019). Obesity may reduce prolactin responsiveness or interfere with hormonal signaling necessary for secretory activation.

Gestational Weight Gain

Excessive gestational weight gain has also been associated with DLII, even independent of pre-pregnancy BMI (Huang et al., 2019).

Diabetes and Metabolic Conditions

Both gestational and pre-existing diabetes have been shown to delay the onset of lactogenesis II, possibly due to disrupted hormonal regulation (Moorhead et al., 2025; Mullen et al., 2022).

Cesarean Births—Especially at Night

Cesarean deliveries are a well-documented risk factor, and those conducted during night hours may carry an even higher risk due to disruption in maternal circadian rhythms (İlhan et al., 2018).

Delayed Initiation of Breastfeeding

Initiating breastfeeding or milk expression after more than two hours postpartum significantly increases the likelihood of DLII (Mullen et al., 2022).

Infant Factors

Prematurity, low birth weight, and infant separation can all impede early suckling or milk expression, contributing to delays (Parker et al., 2024).

Strategies to Mitigate Delayed Lactogenesis II

While DLII can be discouraging for new parents, there are proactive strategies that can make a substantial difference.

Encourage Early Initiation of Breastfeeding

Encouraging breastfeeding within the first hour of life, even after cesarean birth, can significantly reduce DLII risk (Fok et al., 2019).

Use Early and Frequent Milk Expression

For parents at high risk (e.g., after cesarean, with diabetes, or whose infants are in the NICU), initiating expression within one hour of birth and pumping 8+ times per day has been shown to promote earlier lactogenesis II and improve milk volume (Parker et al., 2024; Fok et al., 2019).

Provide Targeted Lactation Support

Routine screening for risk factors like obesity, diabetes, or delayed initiation can help providers flag dyads needing early intervention. These families may benefit from proactive lactation consults and follow-up within the first few days postpartum.

Educate Families About Milk Coming In

Reassuring families that some variability exists in the timing of milk increase and that supplementation, if needed, can be given in a breastfeeding-supportive way (e.g., with expressed milk or donor milk) helps preserve confidence and supply.

Address Hospital Practices

Ensuring skin-to-skin contact, minimizing separations, and avoiding non-medically necessary supplementation can reduce DLII risk (Henkel et al., 2023; Peng et al., 2024).

Final Thoughts

Delayed lactogenesis II is common—but not inevitable. By understanding the contributing factors and taking early, supportive action, we can give families the best chance at a strong breastfeeding start. Recognizing risk, offering early lactation support, and encouraging frequent milk removal are key to success.

References

Ballesta-Castillejos, A., Gomez-Salgado, J., Rodriguez-Almagro, J., Ortiz-Esquinas, I., & Hernandez-Martinez, A. (2020). Relationship between maternal body mass index with the onset of breastfeeding and its associated problems: An online survey. International Breastfeeding Journal, 15, 55. https://doi.org/10.1186/s13006-020-00298-5

Brownell, E., Howard, C. R., Lawrence, R. A., & Dozier, A. M. (2012). Does delayed onset lactogenesis II predict the cessation of any or exclusive breastfeeding? The Journal of Pediatrics, 161(4), 608–614. https://doi.org/10.1016/j.jpeds.2012.03.035

Fok, D., Aris, I. M., Ho, J., et al. (2019). Early initiation and regular breast milk expression reduces risk of lactogenesis II delay in at-risk Singaporean mothers in a randomised trial. Singapore Medical Journal, 60(2), 80–88. https://doi.org/10.11622/smedj.2018067

Henkel, A., Lerma, K., Reyes, G., et al. (2023). Lactogenesis and breastfeeding after immediate vs delayed birth-hospitalization insertion of etonogestrel contraceptive implant: A noninferiority trial. American Journal of Obstetrics and Gynecology, 228, 55.e1–9. https://doi.org/10.1016/j.ajog.2022.08.012

Huang, L., Chen, X., Zhang, Y., et al. (2019). Gestational weight gain is associated with delayed onset of lactogenesis in the TMCHC study: A prospective cohort study. Clinical Nutrition, 38(5), 2436–2441. https://doi.org/10.1016/j.clnu.2018.11.001

İlhan, G., Atmaca, F. V., Çümen, A., Zebitay, A. G., Güngör, E. S., & Karasu, A. F. G. (2018). Effects of daytime versus night-time cesarean deliveries on Stage II lactogenesis. Journal of Obstetrics and Gynaecology Research, 44(4), 717–722. https://doi.org/10.1111/jog.13562

Moorhead, A. M., Forster, D. A., Donath, S., De Bortoli, J., & Amir, L. H. (2025). Does antenatal expressing affect onset of lactogenesis for women with diabetes? Australian and New Zealand Journal of Obstetrics and Gynaecology, Advance online publication. https://doi.org/10.1111/ajo.13929

Mullen, A. J., O’Connor, D. L., Hanley, A. J., et al. (2022). Associations of metabolic and obstetric risk parameters with timing of lactogenesis II. Nutrients, 14(4), 876. https://doi.org/10.3390/nu14040876

Parker, L. A., Hoban, R., Bendixen, M. M., et al. (2024). Milk biomarkers of secretory activation in breast pump-dependent mothers of preterm infants: An integrative review. Breastfeeding Medicine, 19(1), 3–16. https://doi.org/10.1089/bfm.2023.0107

Peng, Y., Zhuang, K., & Huang, Y. (2024). Incidence and factors influencing delayed onset of lactation: A systematic review and meta-analysis. International Breastfeeding Journal, 19, 59. https://doi.org/10.1186/s13006-024-00666-5