ROTARY WINGED TFC FLIES IMC IN VFR FLT DURING EMS SVC.

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I OPERATE AN IFR HELI IN EMS OPS. ON THE DAY OF THIS OCCURRENCE THE AUTOPLT WAS MEL'ED DUE TO ANTI-TORQUE PEDAL CREEP IN THE COUPLED MODE. THIS PROB HAD BEEN INTERMITTENT. ON MY PREVIOUS 3 FLTS; THIS PROB WAS NOT PRESENT. HOWEVER; THE MEL RESTR THE ACFT TO VFR ONLY. AT XA30 I DEPARTED HOSPITAL ENRTE TO ZZZ TO PICK UP A PREGNANT WOMAN PENDING A PREMATURE DELIVERY. WX RPTS IN THE VICINITY OF THE DEP POINT AND PICK UP POINT WERE WELL ABOVE MY 500/1 AND 800/2 VFR MINIMUMS (DAY/NIGHT RESPECTIVELY). IN FACT; ZZZ RPTED CLR CSF AND 5 MI FOG; XYZ RPTED 1700 FT OVCST AND 7 MI AND XYY CLR BELOW 12000 FT AND 10 MI. FORECAST FOR THE AREA INDICATED GENERALLY 1500 FT OVCST 5 MI FOG WITH OCCASIONAL 2 MI FOG. XYY AWOS CONTINUED TO RPT CLR BELOW 12000 FT AND BETTER THAN 10 MI. XYY IS APPROX 10 NM S OF MY PICKUP POINT. ABOUT 5 MI S OF MY PICKUP POINT I SAW AN AREA OF UNFORECAST GND FOG SPREADING FROM OVER THE PICKUP POINT TO THE NE AS FAR AS I COULD SEE. I HAD THE MEDICAL CREW MAKE ARRANGEMENTS TO PICK UP THE PATIENT AT A HWY ROAD WAYSIDE. LAW ENFORCEMENT SECURED THE AREA. WE PICKED UP THE PATIENT AND DEPARTED WITHOUT FURTHER PROBS. I CALLED MY DISPATCHER AND ASKED HER TO CALL THE ASOS AT XYZ. (THIS ASOS HAS BEEN IN PLACE FOR NEARLY 2 YRS BUT ISN'T CERTIFIED YET. WE USE IT AS A SOURCE OF INFO BUT NOT FOR PLANNING OR TO EXECUTE APCHS.) THIS ASOS RPTED 800 FT OVCST AND 5 MI FOG. THIS DIDN'T CORRESPOND WITH THE INFLT CONDITIONS I ENCOUNTERED ENRTE. I FOUND MYSELF DSNDING TO 500 FT AGL WITH A COUPLE OF MI VISIBILITY. I CLBED IN VFR TO 4000 FT; CALLED FSS TO VERIFY THERE WAS NO ICE FORECAST IN THE CLOUDS. THERE WASN'T. I THEN HAD THE DISPATCHER CALL XYY TO SEE IF AN OBSERVER WAS ON DUTY; THERE WAS. I THEN ELECTED TO REQUEST AN IFR CLRNC TO EXECUTE THE RWY 34 APCH AT XYY. I DID THIS THEN PROCEEDED THE 2.3 MI VFR TO THE HOSPITAL. ALTHOUGH RPTED VISIBILITY WAS 5 MI FOG I FOUND IT TO BE CLOSER TO 1 1/2 - 2 MI FOG. PRIOR TO OBTAINING THE CLRNC WHEN I DSNDED; I DID SO DUE TO DECREASING INFLT VISIBILITY. THE CLOUDS WERE STILL IN FRONT OF ME. ONCE I DETERMINED NO ICE WAS FORECAST I FELT IT WOULD BE SAFER TO EXECUTE AN IFR APCH RATHER THAN 'SCUD RUN' TO THE HOSPITAL. (I WOULD HAVE TO FLY OVER A MARSH AREA THAT ROUTINELY HAS LOWER CLOUDS AND VISIBILITY. THIS AREA IS JUST N OF MY HOME HOSPITAL.) DESPITE THE MEL I STILL FEEL I CONDUCTED A MUCH SAFER OP BASED ON MY KNOWLEDGE OF THE LCL AREA AND WX. 2 LAST NOTES: 1) I DID PICK UP TRACE RIME ICE IN THE CLOUDS DURING THE APCH. 2) THE PATIENT HAD STARTED TO DELIVER (WHICH SHE DID SOON AFTER WE ARRIVED AT THE HOSPITAL). IF I HAD LANDED SHORT RATHER THAN 'SCUD RUN' OR GO IFR; THE MEDICAL CREW WOULD NOT ONLY HAD THE MOM TO CARE FOR BUT A 24 WK PREMATURE BABY.