The Association Between Exercise During Pregnancy and the Risk of Preterm Birth

Figures & data

Table 1 Characteristics of the Study Population by PTB Status

Covariates	Preterm (n=285)		Full-Term (n=6216)		PTB Rates (%)	Χ^2	P-value
	n	%	n	%
Mother
Age (years)						11.229	0.004*
<25	17	5.96	520	8.37	3.17
25–30	106	37.19	2785	44.80	3.67
>30	162	56.84	2911	46.83	5.27
Occupation						5.200	0.023*
Other	210	73.68	4940	79.47	4.08
Housewife	75	26.32	1276	20.53	5.55
Education (years)						3.719	0.156
≤9	27	9.47	568	9.14	4.54
10–12	61	21.40	1064	17.12	5.42
>12	197	69.12	4584	73.75	4.12
Pregnancy
Parity						4.554	0.033*
Primiparous	122	42.81	3074	49.45	3.82
Multiparous	163	57.19	3142	50.55	4.93
Delivery mode						24.499	<0.001*
Natural birth	114	40.00	3426	55.12	3.22
Cesarean	171	60.00	2790	44.88	5.78
Complications						80.40	<0.001*
Yes	46	16.14	268	4.31	14.65
No	239	83.86	5948	95.69	3.86
Work						<0.001	0.997
Yes	175	61.40	3829	61.60	4.45
No	110	38.60	2387	38.40	4.41
Tobacco exposure						0.0688	0.793
Yes	41	14.39	941	15.14	4.18
No	244	85.61	5275	84.86	4.42
Infant
Gender						1.639	0.200
Male	164	57.54	3209	51.62	4.86
Female	121	42.46	3007	48.38	3.87
Family
Income (yuan/month)						5.415	0.020*
<6000	49	17.19	767	12.34	6.00
≥6000	236	82.81	5449	87.66	4.15

Note: *P<0.05.

Abbreviation: PTB, preterm birth.

Figure 1 Directed acyclic graph of the association between exercise during pregnancy and PTB.

Table 2 Association Between PTB and Exercise During Pregnancy

During Pregnancy	PTB Rate (%)	Preterm	Full-Term	Unadjusted		Adjusted^a
		(n)	(n)	OR	95% CI	OR	95% CI
Exercise
No	5.37	103	36.14	1.00		1.00
Yes	3.97	182	63.86	0.73*	0.57–0.94	0.74*	0.58–0.95
Time spent on exercise per week
None and low	5.28	112	39.30	1.00		1.00
Moderate	3.79	125	43.86	0.71*	0.54–0.92	0.72*	0.55–0.94
High	4.44	48	16.84	0.83	0.59–1.17	0.82	0.58–1.16
Energy expenditure per week
None and low	4.99	145	50.88	1.00		1.00
Moderate	3.76	113	39.65	0.74*	0.58–0.95	0.75*	0.58–0.96
High	4.58	27	9.47	0.91	0.59–1.37	0.89	0.57–1.33

Notes: ^aAdjusted for maternal age, maternal occupation, parity, and family income; *P<0.05.

Abbreviations: PTB, preterm birth; OR, odds ratio; CI, confidence interval.

Figure 2 Association between PTB and exercise during each trimester.

Table 3 Association Between PTB and Exercise During Pregnancy in Subgroup Analysis

Complication	Exercise During Pregnancy	Preterm Rates (%)	Preterm	Full-Term	Unadjusted		Adjusted^a
			n	n	OR	95% CI	OR	95% CI
Yes	No	14.95	16	91	1.00		1.00
	Yes	14.49	30	177	0.96	0.51–1.90	0.87	0.45–1.74
No	No	4.81	87	1723	1.00		1.00
	Yes	3.47	152	4225	0.71*	0.55–0.94	0.72*	0.55–0.95

Notes: ^aAdjusted for maternal age, maternal occupation, parity, and family income; *P<0.05.

Abbreviations: OR, odds ratio; CI, confidence interval.