Table 4.

Shapley additive explanation (SHAP) values.

Variables	SHAP values
	PTB vs. FTB			SPTB vs. FTB
	Min	Max	Mean	Min	Max	Mean
Maternal age	− 0.0805	0.0990	− 0.0036	− 0.0551	0.0756	0.0023
Pre-pregnancy BMI	− 0.1640	0.1997	0.0071	− 0.0572	0.1038	0.0042
In vitro fertilization	− 0.0445	0.0191	0.0005	− 0.0609	0.0272	0.0023
Prior preterm birth	− 0.0173	0.0132	− 0.0006	− 0.0054	0.0350	− 0.0006
Preeclampsia	− 0.0578	0.1312	0.0000	− 0.0214	0.0053	0.0012
Chronic hypertension	− 0.0800	0.0091	0.0028	− 0.0248	0.0077	0.0017
Gestational diabetes mellitus	− 0.0350	0.0352	− 0.0001	− 0.0080	0.0020	0.0006
PROM	− 0.0577	0.2256	− 0.0029	− 0.0989	0.3005	− 0.0041
CAM	− 0.0184	0.1057	− 0.0030	− 0.0266	0.1637	− 0.0044
CAM stage	− 0.0192	0.1176	− 0.0041	− 0.0300	0.1617	− 0.0085
Periodontitis stage	− 0.0268	0.0323	0.0010	− 0.0189	0.0161	0.0025
MGI	− 0.1190	0.1274	− 0.0005	− 0.0681	0.1306	0.0023
MGI ≥ 2	− 0.0752	0.0889	− 0.0032	− 0.0192	0.0283	− 0.0015
Plaque index ≥ 2	− 0.0637	0.0620	0.0001	− 0.0073	0.0119	− 0.0007
DMFT-index	− 0.0909	0.0837	− 0.0004	− 0.0839	0.1171	0.0024

The SHAP values of top-5 predictors are highlighted in Bold.

BMI, body mass index; PROM, prelabor rupture of the membranes; CAM, chorioamnionitis; MGI, modified gingival index; DMFT, decayed, missing, filled teeth; PTB, preterm birth; FTB, full-term birth; SPTB, spontaneous preterm birth.