This paper uses data from the baseline Fragile Families and Child Well-bein
g Study to examine the level and effects of father-involvement on child's b
irth weight and mother's health behavior during pregnancy (prenatal care, d
rinking, drug use and smoking). The findings indicate that most fathers, in
cluding unwed fathers, are involved with their children at birth and have i
ntentions to remain involved. The effects of father involvement on health a
nd health behavior depend, however, on how the construct is measured. When
measured as parents' relationship status (married, cohabiting, romantic or
non-romantic), the effects of marriage are beneficial for all but one outco
me, the effects of cohabitation are positive for prenatal care only, and th
e effects of romantic involvement are negative for child's birth weight. Wh
en measured as paternity acknowledgement, contributions during pregnancy an
d intentions to contribute, unmarried father involvement has no effect on c
hild's birth weight, a strong effect on early prenatal care and a variable
but overall positive effect on mothers' health behaviors. Furthermore, the
effects of father involvement do not vary systematically by fathers' earnin
gs potential and psychosocial attributes. While these results support the n
otion that fathers can influence mothers to maintain or adopt healthy pregn
ancy behaviors, they do not indicate that father-involvement improves birth
outcomes.