Table 4.

Multivariable logistic model showing effect of family size at the time of twin birth on adjusted odds ratio of association between birth of twins and divorce, US Census data, 1980

Position of twins in birth order	Odds ratio of divorce [95% CI]	Effect of twins on divorce at first through third births compared to twins at fourth birth (p-value)
No. observations	841,442
First birth	1.14 [1.06–1.22]	0.04
Second birth	1.11 [1.03–1.23]	0.04
Third birth	1.12 [1.01–1.25]	0.04
Fourth birth	1.36 [1.08–1.65]

Note: Adjusted for age of mother at first birth, age at marriage, and indicators for college attendance and being white. Reported p-values reflect comparisons of ORs of divorce among mothers with twins at fourth birth compared to mothers with twins at first through third births.