There are some very good D.O. OB programs out there (and you can still match an ACGME fellowship although it might be more difficult).
Some good ones to look into are:
St Joseph Mercy oakland, Ponitac MI
Warren MI
Doctors, OH
Geisinger, PA
Metro, MI
Mercy St Vincent, OH
Genesys, Grand Blanc, MI
There is a MD/DO program in Buffalo NY
I did a Sub-I at Warren and Genesys and was very impressed by both programs in terms of people, training and surgical numbers.