There ARE Disadvantages to sweeps:
Discomfort or actual PAIN
Mw might not even be able to reach cervix to perform it, which leads to severe demoralisation (I've got the T-shirt)
Mw might accidently break waters which sets the clock ticking, if baby is not ready to arrive yet labour might not kick in and so you end up on the intervention slippery path
Bacteria can be taken up from vagina to cervix and increase risk of infection
not to mention the indignity, the having to trek to mw to get it done when you could be relaxing at home....
Sweeps are only supposed to work if you were going to go into labour anyway so why put yourself through it?
Far better to enjoy the twilight of your pg, relax, get a massage from dh, enjoy a nice soak in bath or shower, use lavender and other nice smellies, enjoy some comfort food, have a little glass of wine before bed, get early nights, drink plenty of fluids, take gentle excercise, swimming is great for relaxing the heavily pg body... lunch with your mates, book some manicure/pedicures...
Certainly, I wouldn't recommend attempting one till at least 41 wks, closer to 42