There are issues with "under 2 years MAM" that relate to under months children. These are (1) we do not tend to measure length in these children in surveys, (2) we have no clearly defined or agreed case-definitions for MAM in these children, and (3) we tend not to want to use supplementary or complementary feeding products or breast milk substitutes in these children and do so only in well-defined circumstances. I assume here that when we use the term "under 2 years MAM" we refer to children aged 6-23 months meeting either (or both) a WHZ or MUAC based case-definition for MAM. Estimation of prevalence in this age-group can be done using the same methods as for the 6-59 month age-group (e.g. SMART or RAM) but collecting data for children aged 6-23 months. You can use data from an existing SMART survey to do this. Just select the children aged 6-23 months (or delete older children) and have the ENA software report on the restricted dataset. The ENA software has an option (on the "Options" tab to limit analysis to a particular age-range). One problem with this approach is that the sample size will be about one third that of the original survey so the estimate will lack precision. You can improve precision by specifying a finite population correction (this is legitimate as the population sampled will be small) or by using a PROBIT estimator (as is used in RAM). Sometimes you may only have a report to work from. If you are lucky you may find that the SMART survey report gives prevalence in the 6-23 month age group. This used to be common practice. The report may give prevalence in year-centred age-groups (i.e. 6-17 months, 18-29 months, and so-on). In this case you could use the combined figures for the 6-17 months and 18-29 months age-groups. If all you have is an estimate for the 6-59 months age-group then you can apply a correction factor to this. If you use a W/H based case-definition you should use a locally derived correction factor as W/H varies with body shape which varies with age and MAM prevalence can appear to be very high in older children (and the healthiest older children will appear to have MAM). Where are you? I could use some old surveys to work out a correction factor for you. If this is a common problem then we could try to produce local correction factors for all countries for which we have data for. I hope this is of some help.