A mother and her baby daughter who were on Social Services' radar had been dead for at least a week before their bodies were discovered, an inquest has heard.
Joanne Thomas was found in her bed alongside four-month-old Harper at their terraced home in Troedyrhiw, South Wales, last July.
Aberdare Coroner's Court heard concerns had been raised weeks before, after 27-year-old Miss Thomas failed to take Harper for her injections.
A social worker told acting coroner Andrew Barkley he tried to visit Miss Thomas on three occasions before their bodies were found, as well as sending out letters and attempting to contact her family.
The bodies were eventually formally identified via dental records and DNA testing - with a top pathologist saying it was "impossible" to say who had died first.
Police later ruled out foul play, as well as discounting the possibility of carbon monoxide poisoning - after "slightly raised levels" were found in the blood of smoker Miss Thomas' blood and her baby.
A coroner was told Miss Thomas regularly complained of feeling unwell in the weeks leading up to her death and may have been vomiting blood.
Joanne Thomas and her four-month-old baby Harper were found dead at their home in Merthyr Tydfil in July. An open verdict has been recorded.
Police add there is 'no evidence to date' to suggest carbon monoxide killed the two, believed to be a mother and her four-month-old baby.