Pregnancy is not a risk factor for gallstone disease: Results of a randomly selected population sample

Table 1 Classical risk factors of cholecystolithiasis in multiple logistic regression

Classical risk factors	Odds ratio (OR)	95%CI	P
Age (per yr)	1.06	1.05–1.08	<0.001
Female sex	2.78	1.91–4.07	<0.001
BMI (per kg/m2)	1.12	1.08–1.15	<0.001
Positive family history	1.89	1.30–2.75	<0.001

Table 2 History of pregnancy and the number of prior pregnancies in the multiple logistic regression model (only females)

Factor tested	Odds ratio (OR)	95%CI	P
Age (per yr)	1.06	1.04–1.08	<0.001
BMI (per kg/m2)	1.11	1.07–1.15	<0.001
Positive family history	1.99	1.28–3.07	0.002
Positive history of pregnancy	0.76	0.44–1.31	0.321

Table 3 Number of pregnancies in the multiple logistic regression model (only females)

Factor tested	Odds ratio (OR)	95%CI	P
Age (per yr)	1.06	1.04–1.08	<0.001
BMI (per kg/m2)	1.11	1.07–1.15	<0.001
Positive family history	2.09	1.34–3.25	<0.001
Number of pregnancies			0.104
One or two vs none	0.65	0.37–1.15
Three or more vs none	1.04	0.56–1.94

Table 4 Relative risk for gall bladder stones in relation to selection of study population

Place/region	Populationselection	n	Sex distributionmale:female
Chiayi[23]	Random sample	923	1:1.0
Rome[32]	Factory	2 325	1:1.1
Bergen[40]	Random sample	1 371	1:1.1
Ulm[19]	Blood donors	1 116	1:1.1
Copenhagen[44]	Random sample	4 807	1:1.4
Chiang Mai[38]	Random sample	6 146	1:1.5
Schwedt[41]	Factory	1 616	1:1.6
Okinawa[17]	Inhabitants of an island	2 584	1:1.7
Jiaotong[14]	Random sample	15 856	1:2.0
M.I.C.O.L[24]	Random sample	29 739	1:2.0
Römerstein[20]	Total survey	2 498	1:2.1
Sirmione[21]	Total survey	1 911	1:2.2
Cianciano[22]	Total survey	1 804	1:2.3
Leutkirch	Random sample	2 401	1:2.3

Table 5 Review of published studies addressing the effect of the factor “pregnancy” on the prevalence of gallbladder stones

Factor by which the prevalence of gallstone diseasein women with prior pregnancy is increased	1.0–1.5 times	1.6–2.5 times	2.6–10 times	11 – 50 times
Studies showing a quantitative relation between cholecystolithiasis and pregnancy	1966 Framingham[42] 1988 Sirmione[21] 1985 San Antonio[45] 1985 Maastricht[46]	1982 Oxford[47] 1982 Kopenhagen[44]	1979 Stockholm[48] 1982 Rom[32] 1986 Schwedt[41] 1986 Chianciano[22] 1991 Santiago[49]	1988 Srinagar[15]
Studies not showing a quantitative relation between cholecystolithiasis and pregnancy	1956 Birmingham[50] 1970 Pima reservation[51] 1980 Boston[52] 1982 Oberpfuss[53] 1983 Oxford[54] 1984 Adelaide[55] 1989 Soweto[12] 1990 Dublin[43] 1995 Ulm[19] 1996 Römerstein[20] 2002 Leutkirch