TABLE 2.

Case-control studies of caffeine consumption and risk of preterm birth¹

Author, publication year, and country	No. of cases/no. of controls	Intake measurement	Trimester considered	Preterm definition	Comparisons made by authors	Risk estimate (95% CI)	Comparisons made in meta-analysis	Adjusted confounders
Chiaffarino et al, 2006, Italy (42)	502/1966	Coffee, tea, and cola (cups or glasses/d)	Third and throughout pregnancy	28–37 wk gestation	0 cups/d	1.0	0 mg/d	Age, education, parity, smoking during the first trimester of pregnancy, gestational hypertension, and history of preterm births
					1 cup (90 mg)/d	0.9 (0.6, 1.2)
					≥2 cups/d	0.9 (0.7, 1.3)	≥150 mg/d
de Souza and Sichieri, 2005, Brazil (45)	140/162	Coffee, tea, maté, and powdered chocolate (servings in mL or g); authors computed daily caffeine intake (mg/d)	Throughout pregnancy	<37 wk of gestation	<50 mg/d	1.00	<50 mg/d	NA
					50–99 mg/d	1.58 (0.88, 2.84)
					≥100 mg/d	1.35 (0.48, 3.80)	≥100 mg/d
Tough et al, 2003, Canada (47)	323/664	Coffee	Throughout pregnancy	Live born singleton infant at <37 wk of gestation	<1 cup/d	1.0	<100 mg/d	Prior conception experiences, emotional health, interpregnancy intervals, pregnancy complications, maternal complications during pregnancy
						1.38 (1.01, 1.88)	≥100 mg/d
		Caffeinated soft drinks			≥1 cup/d	1.0	<27 mg/d
						1.22 (0.89, 1.72)	≥27 mg/d
Bicalho and Filho, 2002, Brazil (46)	182/354	Coffee, soft drinks, and tea (servings in mL); authors computed daily caffeine intake (mg/d)	Throughout pregnancy	Delivery before 37 wk gestation	0 mg/d	1.0	0 mg/d	Mother's age, schooling, income, marital status, skin color, parity, smoking, previous low-birth-weight children, mother's prepregnancy weight, employment status, interval between pregnancies, prenatal care, and high blood pressure
					<300 mg/d	0.59 (0.32, 1.09)
					≥300mg/d	0.32 (0.15, 0.72)	≥300 mg/d
Pastore and Savitz 1995, USA (43)	408/490	Caffeinated coffee, tea, cola soft drinks, and non-cola caffeinated soft drinks (servings and preparation method); authors computed daily caffeine intake (mg/d)	Second and third	<37 wk of gestation	Second trimester: 0 mg/d >1 mg/d Third trimester: 0 mg/d >1 mg/d	Second trimester: 1.0 1.5 (1.0, 2.3) Third trimester: 1.0 0.8 (0.6, 1.2)	Second trimester: 0 mg/d >1 mg/d Third trimester: 0 mg/d >1 mg/d	None
Williams et al, 1992, USA (44)	488/2252	Coffee (cups/d)	First	Delivery before 37 wk gestation without premature rupture of membranes	0 cups/d	1.0	0 mg/d	Race, education, maternal age, welfare status, marijuana and alcohol use during pregnancy, parity, previous spontaneous or induced abortion, cervical incompetence, bleeding during pregnancy, prepregnancy BMI, and cigarette smoking
					1–2 cups/d	1.0 (0.8, 1.3)
					3 cups/d	1.4 (0.9, 2.3)
					4 cups/d	1.8 (0.9, 3.4)
					≥5 cups/d	1.1 (0.5, 2.1)	>400 mg/d
Berkowitz et al, 1982, USA (26)	166/299	Coffee and tea, including iced coffee and iced tea, separately (cups/d)	First	Singleton live birth before 37 wkof gestation not preceded by spontaneous labor or rupture of membranes	0 cups/d	1.0	0 mg/d	Race, socioeconomic status, infertility history, first trimester spotting or light bleeding, pregravid weight, maternal weight gain, previous induced abortion, leisure-time physical activity, and attitude toward pregnancy
					1 cup/d	0.7 (0.4, 1.3)
					2 cups/d	0.9 (0.5, 1.6)
					3 cups/d	1.6 (0.8, 3.3)
					≥4 cups/d	0.6 (0.3, 1.4)	≥320 mg/d
			Second		0 cups/d	1.0	0 mg/d
					1 cup/d	0.6 (0.4, 1.1)
					2 cups/d	0.8 (0.4, 1.4)
					3 cups/d	1.3 (0.7, 2.8)
					≥4 cups/d	0.6 (0.3, 1.3)	≥320 mg/d
			Third		0 cups/d	1.0	0 mg/d
					1 cup/d	0.6 (0.4, 1.1)
					2 cups/d	1.1 (0.6, 2.0)
					3 cups/d	1.5 (0.7, 3.0)
					≥4 cups/d	0.5 (0.2, 1.1)	≥320 mg/d

¹NA, not available.