To analyze the risk factors of lactational mastitis (LM) in primiparas and build a risk prediction model of nomogram.

The clinical data of 186 primiparas who delivered their baby in our hospital from June 2021 to June 2022 were retrospectively analyzed, and the incidence of LM in primiparas was statistically analyzed. The logistic regression analysis was applied to find the risk factors of LM in primiparas. The R3.6.3 software was applied to construct the nomogram for predicting LM in primiparas, and the receiver operating characteristic (ROC) curve and calibration curve were used to verify the nomogram.

Among 186 primiparas in lactation period, 42 patients developed mastitis, with an incidence of 22.6% (42/186). Logistic regression analysis showed that breast trauma history (OR=9.470, 95%CI: 3.450-25.996, P<0.001), milk stasis (OR=8.734, 95%CI: 3.241-23.534, P<0.001), cracked nipple (OR=5.540, 95%CI: 1.949-15.743, P=0.001) and abnormal lingual frenulum in infants (OR=7.121, 95%CI: 2.673-18.975, P<0.001) were independent risk factors for LM in primiparas. The area under the ROC curve was 0.867 (95%CI: 0.804-0.930). The slope of calibration curve was close to 1 (goodness-of-fit test: χ²=7.910, P=0.341).

The primiparas with breast trauma history, milk stasis, cracked nipples and infants with abnormal lingual frenulum are in high risk of LM. The nomogram based on these four factors can provide guidance for clinical prediction of LM in primiparas and implementation of corresponding interventions.