The NICE guidelines state:
1.2.3 Prelabour rupture of membranes at term
1.2.3.1Women with prelabour rupture of membranes at term (at or over 37 weeks) should be offered a choice of induction of labour with vaginal PGE2[3] or expectant management.
According to the Homebirth reference page, the guidance pre-2008 was that up to 96 hours with rupture of membranes was appropriate, it was changed in 2008 to state that induction should be offered (not recommended) after 24 hours.
This is the more detailed NICE guidance:
1.11 Prelabour rupture of membranes at term
1.11.1 Do not carry out a speculum examination if it is certain that the membranes have ruptured. [2007]
1.11.2 If it is uncertain whether prelabour rupture of the membranes has occurred, offer the woman a speculum examination to determine whether the membranes have ruptured. Avoid digital vaginal examination in the absence of contractions. [2007]
1.11.3 Advise women presenting with prelabour rupture of the membranes at term that:
the risk of serious neonatal infection is 1%, rather than 0.5% for women with intact membranes
60% of women with prelabour rupture of the membranes will go into labour within 24 hours
induction of labour[4] is appropriate approximately 24 hours after rupture of the membranes. [2007]
1.11.4 Until the induction is started or if expectant management beyond 24 hours is chosen by the woman:
do not offer lower vaginal swabs and measurement of maternal C‑reactive protein
to detect any infection that may be developing, advise the woman to record her temperature every 4 hours during waking hours and to report immediately any change in the colour or smell of her vaginal loss
inform the woman that bathing or showering is not associated with an increase in infection, but that having sexual intercourse may be. [2007]
1.11.5 Assess fetal movement and heart rate at initial contact and then every 24 hours after rupture of the membranes while the woman is not in labour, and advise the woman to report immediately any decrease in fetal movements. [2007]
1.11.6 If labour has not started 24 hours after rupture of the membranes, advise the woman to give birth where there is access to neonatal services and to stay in hospital for at least 12 hours after the birth. [2007]