Table I.

Response rates for all family types at each phase of the study.

Child's age (years)	Donor insemination	Egg donation
1	50	51
2	46	48
% original sample	92%	94%
3	41	41
% original sample	82%	80%
7	36	32
% original sample	72%	67%
10	34	30
% original sample	68%	59%

Sample sizes need not always decrease over time, as in some cases families were unable to participate during one phase of the study (e.g. a family event, moving house) but were then able to participate at a later phase.