Physical activity during pregnancy and adverse birth outcome: a prospective cohort study in China

Figures & data

Figure 1. Directed acyclic graph for the association between physical activity and birth weight z-scores and gestational age. Minimally sufficient adjustment sets: age, occupation, pre-pregnancy BMI, folic acid supplementation during pregnancy, passive smoking during pregnancy, gravidity, and parity. Potential mediator was birth length.

Table 1. Characteristics of the included and overall participants.

Characteristics	Including* (n = 11292)	Overall* (n = 17315)
Maternal characteristics
Age (years)
≤24	2615 (23.2)	2807 (23.2)
25 ∼ 29	3802 (33.7)	4100 (33.8)
30 ∼ 34	3254 (28.8)	3467 (28.6)
≥35	1621 (14.4)	1745 (14.4)
Missing (n)	0	5196
Ethnicity
Zhuang	9857 (91.6)	15124 (91.0)
None of the above	902 (8.4)	1491 (9.0)
Missing (n)	533	700
Occupation
Farmer	3650 (34.0)	5926 (35.8)
Non-farmer	7084 (66.0)	10638 (64.2)
Missing (n)	558	751
Residential area
Rural	10244 (91.7)	14998 (91.7)
Urban	927 (8.3)	1352 (8.3)
Missing (n)	125	965
BMI (kg/cm^2)
Underweight	1719 (21.3)	2689 (21.0)
Normal	5195 (64.4)	8279 (64.6)
Overweight	1147 (14.3)	1852 (14.4)
Missing (n)	3231	4495
Smoking history
No	10570 (99.6)	16353 (99.5)
Yes	40 (0.4)	79 (0.5)
Missing (n)	682	883
Drinking during pregnancy
No	11241 (99.5)	17232 (99.5)
Yes	51 (0.5)	83 (0.5)
Passive smoking during pregnancy
No	5778 (57.3)	8978 (57.2)
Yes	4301 (42.7)	6717 (42.8)
Missing (n)	1213	1620
Folic acid supplement during pregnancy
No	1988 (21.9)	2824 (19.6)
Yes	7075 (78.1)	11581 (80.4)
Missing (n)	2229	2910
Gravidity
≤2	6045 (53.5)	7885 (50.3)
>2	5247 (46.5)	7795 (49.7)
Missing (n)	0	1635
Parity
Primiparous	4561 (40.4)	6686 (42.6)
Multiparous	6731 (59.6)	8994 (57.4)
Missing (n)	0	1635
Gestational age at enrollment
First trimester	6097 (66.0)	6796 (67.5)
Second trimester	2474 (26.8)	2605 (25.9)
Third trimester	661 (7.2)	662 (6.6)
Missing (n)	2060	7252
Infants’ characteristics
Fetal sex
Male	5971 (52.9)	6385 (52.7)
Female	5325 (47.1)	5733 (47.3)
Missing (n)	0	5197
Mode of delivery
Spontaneous vaginal	8153 (72.2)	8687 (71.7)
Cesarean section	3113 (27.6)	3394 (28.0)
Instrumental delivery	27 (0.2)	37 (0.3)
Missing (n)	0	5196

BMI: body mass index. Reported as number (%).

*Missing data were not included when calculate the constituent ratios.

Table 2. Adjusted association of maternal exercise during pregnancy and birth outcomes.

Model	PA during pregnancy	β (95%CI)		OR (95%CI)
		Z-score	Gestational age	SGA	PTB
PA status
Model1	No regular PA	ref	ref	ref	ref
	Regular PA	0.037 (–0.006,0.080)	0.022 (–0.037,0.081)	1.00 (0.89,1.13)	0.93 (0.78,1.12)
Model2	No regular PA	ref	ref	ref	ref
	Regular PA	0.022 (–0.020,0.063)	0.019 (–0.041,0.078)	1.04 (0.92,1.18)	0.95 (0.79,1.14)
Activity intensity
Model1	No regular PA	ref	ref	ref	ref
	Low	0.024 (–0.024,0.071)	0.011 (–0.055,0.077)	1.04 (0.91,1.18)	1.01 (0.83,1.22)
	MVPA	0.077 (0.002,0.152)	0.053 (–0.050,0.157)	0.90 (0.73,1.12)	0.72 (0.50,1.02)
Model2	No regular PA	ref	ref	ref	ref
	Low	0.015 (–0.031,0.061)	0.004 (–0.063,0.070)	1.06 (0.93,1.21)	1.03 (0.84,1.25)
	MVPA	0.041 (–0.032,0.114)	0.063 (–0.041,0.167)	0.98 (0.79,1.22)	0.73 (0.51,1.05)
Adequacy of PA
Model1	No regular PA	ref	ref	ref	ref
	Inadequate	0.003 (–0.043,0.050)	0.009 (–0.055,0.073)	1.02 (0.91,1.15)	0.96 (0.80,1.15)
	Adequate	0.070 (–0.009,0.148)	0.046 (–0.063,0.155)	0.70 (0.43,1.13)	0.53 (0.24,1.21)
Model2	No regular PA	ref	ref	ref	ref
	Inadequate	–0.002 (–0.047,0.043)	0.000 (–0.064,0.065)	1.06 (0.94,1.20)	0.98 (0.81,1.18)
	Adequate	0.038 (–0.038,0.115)	0.062 (–0.047,0.171)	0.76 (0.47,1.24)	0.53 (0.23,1.21)

PA: physical activity; MVPA: moderate to vigorous PA; SGA: small-for-gestational-age; PTB: preterm birth.

Model 1 did not adjust any factors.

Model 2 adjusted mother characteristics, including age, occupation, pre-pregnancy BMI, folic acid supplementation during pregnancy, passive smoking during pregnancy, gravidity, and parity.

Figure 2. Restricted cubic spline with 3 knots was performed to determine the relationship of total weekly activity MET with risk of small-for-gestational age (SGA, A) and preterm birth (PTB, B). Adjusted factors were variables, including mother age, occupation, pre-pregnancy BMI, folic acid supplementation during pregnancy, passive smoking during pregnancy, gravidity, parity.