No personal experience here, but I found some links for you - maybe too much information ;->. My non-expert summary is that there is some data concerning the risks of multiple shots (over weeks and weeks - and Caryn points out those studies are likely "confounded" by other prematurity factors) BUT so far the research shows the precautionary dose you'll be getting has no risks to baby or you!
Antenatal betamethasone: reassuring long-term data.
Maternal steroid injections shortly before premature delivery reduce the risk of neonatal respiratory distress syndrome. A 30-year follow-up study of subjects exposed to betamethasone in utero showed no impact of this treatment on cardiovascular, mental, pulmonary or bone function.
Incidence of respiratory disorders in neonates born between 34 and 36 weeks of gestation following exposure to antenatal corticosteroids between 24 and 34 weeks of gestation.
The beneficial effects of corticosteroids were similar in both genders. It appears that the exposure of singleton pregnancies to antenatal corticosteroids between 24 and 34 weeks of gestation is associated with a significantly lower incidence of respiratory disorders among neonates born at 34 to 36 weeks of gestation.
Steroids for accelerating fetal lung maturity are given as either two injections 24 hours apart (betamethasone), or 4-8 injections every 6-12 hours (dexamethasone). The betamethasone regimen is preferred. The maximum benefit for fetal lung maturation is seen 24 hours after the last dose is given and persists for at least 7 days. At present, repetitive dosing is not recommended. Corticosteroids at these doses will adversely affect blood sugar, but adjusting insulin dosage will control this and the fetal benefits tend outweigh the maternal metabolic risks. Blood glucose control will usually return to near baseline levels within 4-5 days.
http://www.preeclampsia.org/forum/viewtopic.php?t=28153 - Can Steroid shot hurt baby?
http://www.preeclampsia.org/forum/viewtopic.php?t=7693 - Steroids for babies' lungs questions
I'm glad your new doc is so proactive! Hang in there!