An "unanticipated increase" in children being put up for adoption has prompted an urgent recruitment drive to find suitable parents to give them a home.
In the south east Wales region, some 280 children were referred for adoption in 2016-17 - a 66% increase in a year.
It is a trend which the National Adoption Service (NAS) said was replicated around Wales.
The service said it was looking in particular for adoptive parents for harder-to-place sibling groups.
Suzanne Griffiths, director of operations at NAS for Wales, said demand for adoption had fallen between 2014 and 2016 but it suddenly rose last year to about 300 children in Wales on the waiting list.
That is expected to rise by 23% to about 370 when statistics are released by the Welsh Government later this month.
Ms Griffiths said the increase was "unanticipated" and put it down to both the way an earlier court ruling on adoptions was being interpreted and a rise in children being taken into care.
"Ultimately we tailor our resources to demand, so when that went down, so did our recruitment of parents," she added.
"Now we really need to find suitable people who will meet the needs of the children we have."
The Vale, Valleys and Cardiff Adoption Collaborative (VVC) - one of the five regional collaboratives covering Wales which the NAS oversees - said the demand was adding to "increased workloads and capacity issues".
In its annual report from April 2016 to March 2017, it said some people were waiting over a year from making an initial enquiry to being assessed and approved as adoptive parents.
The Welsh Government target is eight months and around Wales the average wait is 11.1 months.
Ms Griffiths said part of this was down to making sure parents were properly prepared before proceeding with an adoption.
But a spokesman for the VVC - which oversees adoption for councils in the area - said it was clear the increase in adoption referrals, coupled with more demand for support services, was "having an impact on performance in other areas, particularly the recruitment and assessment of adopters".
"Coming at a time when the number of enquiries from potential adopters is also falling, this impact has been particularly noticeable," he added.
"This is why, in line with the priorities of the National Adoption Service for Wales, we have made the recruitment of adopters a key priority for the service."
Adrian, of Pembrokeshire, has two adopted children, a girl aged 10 and a boy aged seven.
He said any person considering adoption should be prepared for challenges but also for love, joy and fulfilment, adding: "I just find it the most complete family I could ever imagine."
The focus on National Adoption Week, which has run this week, has been on finding parents willing to take on groups of siblings.
Ms Griffiths added: "Taking on a sibling group can have complexities but it can have positives. Some of the children will have been through bad times and their sense of security comes from being together.
"And whoever takes them on can move into a more-developed family life quickly."
The Welsh Government said it was working closely with the NAS "to monitor progress, priorities and performance".