AFAIK there is no study comparing the rates of birth defects in new births every year by state, though just about every state tracks it, rather most states only get rated by number of infant mortalities which is a different stat: only 1 in 4 fatalities are from birth defects.

My comment was just a big sharp jab at North Dakota for its policies, but if there was any truth to it that was because of methane emissions correlating highly. ND has the second largerst emissions per capita in 2017 according to World Research Institute and those emissions are further concentrated to specific counties involved in the oilfield. Articles talking about emissions impacts on public health like This One point out that 80% of Fracking is done in Texas and North Dakota, and articles like This Other Article which also mentions North Dakota specifically. NRDC also has a write up about reduced weight as a result of emissions and exposure, and it again mentions North Dakota by name.

Unfortunately, though, no. I don’t have data to back up my earlier claim.