Title: Impact of the Momentum pilot project on male involvement in maternal health and
newborn care in Kinshasa, Democratic Republic of the Congo: a quasi-experimental study
Version: 1 Date: 25 Mar 2022
Reviewer:  Michèle Dramaix
Reviewer's report:
The topic and the project analyzed in this article are very interesting. My comments and
questions relate mainly to the methodology and the results.
Introduction:
p. 4, L 85-87: DHS RDC: last one in 2013-14. No more recent assessment of maternal and infant
mortality?
p. 4, L88-89: “indicated by the high adolescent birth rate (138 per 1,000 live births)” : what
is 138 per 1000 live births? It’s not a birth rate. Is it the proportion of babies whose mother is
adolescent?
“short birth intervals among adolescent girls (27% of birth intervals)”: short birth interval: does
it means less than 2 years? Does the sentence mean that among adolescent girls, 27% of the birth
intervals are short? Same reference 15 ?
Methods
p. 6 What’s “Program P” (also mentioned in the introduction): program targeted at fathers and
Program M at mothers?
Sample size estimation
I suggest using the usual terminology to the sample size calculation features and just giving the
values for alpha “signification level” and 1-beta, power and specifying that the tests applied are
two-tailed. Why choose a design effect of 2, is it based on literature? Has the design effect been
taken into account in the analyses?
p.7-8 : “the prevalence of newborns’ first prenatal check in the first two days of birth” isn't this
rather the first postnatal check-up? Does the value 6.5% come from reference 15?
p. 8: To what correspond “10-15 percentage-point change on key behavioral indicators”? Is it a
a relative or absolute difference? There is only a calculation for first postnatal check, the other
indicators are not mentioned and it’s not possible to see if the sample size estimate is correct.
“Confidence” usually applies to confidence intervals and none are involved in calculating sample
size. I used a sample size calculator (STATA) but I was unable to find the same sample size
estimate as yours. Could you precise the difference you used from the base proportion you
mentioned (6.5%), confirm that you used a power of 99% (much higher than usually chosen)
and give the reference of the formula you are using?
p. 9, L204: 1766, is less than the estimated sample size? 1276 male partners were completely
interviewed in the end-line survey but 1248 were included in the analysis. What happened to the
28 missing? Of the 1766 male partners interviewed in the baseline survey, 1204 were included
in the analysis. Did the 562 lost subjects have similar characteristics to those with complete data
or do they differ in certain characteristics?
p. 10-11: what was the proportion or cumulative proportion of variance accounted for by the
factors retained in the various factor analyses (only eigenvalues are given)?
p. 10: how was the GEM index constructed? And what was the range of this index?
p. 10-11: Male involvement: why were additive indexes built and why were the factor scores
not used?
Statistical methods
p. 13, L320-21: What are the “already-existing differences (at baseline) between intervention
and comparison health zones”? The zones were chosen with similar characteristics?
“Difference-in-difference” regressions are mentioned in the abstract but don’t appear in the
statistical methodology.
P. 15, L355: “Analysis restricted to male partners with live-born babies”:, the final composition
of the sample is described p. 9, lines 204-214 but the restriction to male partners with live-born
babies is not included in this description. A flowchart might be helpful.
Results
What tests are used in table 1? What’s the objective of the analysis comparing the characteristics
of lost to follow-up in the intervention and control groups?
p. 15, L363-365: the attrition rate was already given p. 9, line 211 and it was specified that it was
the same in both study arms. Lines 363-365 in the results should be moved to the methodology.
Table 1: “These differential attrition rates led to varying changes in the characteristics of those
remaining in the sample. For example, in comparison health zones, fewer of those remaining
in the sample had always lived in the locality.” However, among  those lost to follow-up, the
proportion of those who “always lived in the locality” hardly differ between the two groups
(35.6% vs 37.1%). The number of subjects is not listed in table 1 but should be helpful. ? For
this variable “Always lived in the locality”, I don’t understand the % in the whole sample (all
male partners) because they are closer to those in the lost to follow-up, the smallest group.
p. 16: the sentence in lines 375-76 seems to be a methodological element.
The cutoffs used the  “Gender Relations Power sub-Scale” are not described in the methodology.
p. 16-17, L397-399: can we find the % quoted in the text, in table 2?
Tables 2 and 3, why was the analysis stratified by age? I don’t think it’s explained in the
methodology. P12, L295, just says that “Age was included as reported” .
Could you please in a footnote, indicate which statistical methods were used in tables 3 and table
4. In table 3, the number of subjects would be helpful.
p. 18, comments to table 4, lines 447, 450, 451, 460: are the value 0.15, 0.65, 0.60, 0.42 and
0.56 in the table?
Table 5: same remarks as above: it would be useful to specify the number of subjects and the
statistical methods in a footnote.
p. 21, L 515-516: “ the index of involvement in birth planning would have been significantly
higher (ATE=1.241; 95% CI: 0.326, 2.144) (see the last column of Table 5)” isn't that "Male
Engagement in Newborn Care"?
The sample size estimate was based on the “ the prevalence of newborns’ first prenatal check in
the first two days of birth” (6.5%) but this outcome is not analyzed.
The estimated sample size was 1213 subjects aged 15-24 years in each group. The number of
subjects is much lower and not limited to 15-24. Can you explain why the sample size calculation
does not correspond to the sample finally constituted?