According to a study done in France on 1,400 pregnant women in 2006, there was no observable effect on pregnancy outcomes. This study compared 628 uninfected women with 658 infected during pregnancy, 27 infected before pregnancy and 87 infected on unknown dates.
Fritel, X., et.al. Chikungunya Virus Infection during Pregnancy, Reunion, France, 2006. Emerging Infectious Disease. 16(3):418-425. March 2010.