“worked last time”

[sitifan]

Breastfeeding exclusivity
Among participants who reported prenatal intent to breastfeed, 73.3% (63 of 86) were exclusively doing so on the postnatal unit. Unplanned formula supplementation was described as easing the maternal ‘burden’ of breastfeeding. For experienced mothers, combination feeding of human and artificial milk “worked last time” which they would rather do than have the newborns “crying all night.” Some mothers used formula in an effort to settle their infants so that they could obtain more rest.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4451198/
In the above passage, what does “worked last time” mean?

[tedmc]

In the above passage, what does “worked last time” mean?

The combination of human and artificial milk feeding kept their babies happy, without crying, which eased the burden of the mothers feeding them solely with human milk.

[sitifan]

Breastfeeding exclusivity
Among participants who reported prenatal intent to breastfeed, 73.3% (63 of 86) were exclusively doing so on the postnatal unit. Unplanned formula supplementation was described as easing the maternal ‘burden’ of breastfeeding. For experienced mothers, combination feeding of human and artificial milk “worked last time” which they would rather do than have the newborns “crying all night.” Some mothers used formula in an effort to settle their infants so that they could obtain more rest.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4451198/

What is the antecedent of which in the quoted passage?

[emsr2d2]

"Combination feeding".

[Tdol]

And it worked last time,because they are experienced mothers who have done this before.