Postpartum haemorrhage

Chapter 6 Table 19: Performance of indicators for pre-eclampsia. Asterisked indicators, having met the selection criteria, are considered candidates for 'best' indicator. Pre-eclampsia Indicator Counta Min Sea Max Sea 1. Maternal height 3/8 0.31 0.47 2. Pre-pregnancy weight 2/6 0.36 0.50 3. Attained weight by month 5 2/8 0.35 0.38 4. Attained weight by month 7 1/8 0.54 0.54 5. Attained weight by month 9 0/9 6. Mid-upper-arm circumference 0/9 7. Weight gain: months 5 to 7 0/6 8. Weight gain: months 5 to 9 0/6 9. Weight gain: months 7 to 9 0/7 10. Weight gain: pp to month 5 0/6 11. Weight gain: pp to month 7 0/6 12. Weight gain: pp to month 9 0/6 13. Pre-pregnancy BMI 3/5* 0.31 0.50 14. BMI month 5 1/8 0.35 0.35 15. BMI month 7 1/7 0.50 0.50 16. BMI month 9 0/7 a 'Count' gives the fraction of data sets in which the Se/Sp cri- teria was met. The asterisk denotes that the indicator met this criterion (Se >0.3, Sp >0.7) in over 40% of the studies. The observed maximum and minimum sensitivities across studies that meet the Se/Sp criterion are recorded in the final two columns. Where only one study has met the criteria, the min and max figure for Se will be the same. Postpartum haemorrhage Definition. Bleeding during the first 24 hours post- partum. As with prematurity, there is no known bio- logical basis for a relationship between maternal nutritional status and postpartum haemorrhage. Maternal anthropometric indicators are therefore examined solely for any predictive capacity. The six studies that had uniformly defined infor- mation on this condition are identified in Table 8, Chapter 3 (page 16), where it will be seen that the prevalence of this condition across studies is very low: 0.5-4.4%. Table 20 provides a summary of the combined odds ratios derived from the eligible stud- ies. As with assisted delivery and pre-eclampsia, all estimated ORs are below 1 with the exception of attained BMI indicators which show a marginal ele- vated risk (but with 95% CIs embracing 1.0) (Fig. 21). Apart from attained weight by month 9 and MUAC, confidence intervals for all other indicators include 1, suggesting that these are neutral in respect of risk prediction. Attained weight by month 9 has an OR of 0.6 with a 95% CI of 0.4-0.8 and MUAC has an OR of 0.6 with a 95% CI of 0.5-0.8, implying prediction Table 20: Summary of the combined odds ratios for each indicator. The ORs refer to the relative risk for post- partum haemorrhage for the lower quartile versus the upper quartile of the indicator's distribution. Odds ratio for postpartum Indicator haemorrhage Maternal height 0.7 Mid-upper-arm circumference 0.6 Pre-pregnancy weight 0.6 Attained weight by month 5 0.9 Attained weight by month 7 0.9 Attained weight by month 9 0.6 Pre-pregnancy BMI 0.8 BMI month 5 1.2 BMI month 7 1.1 BMI month 9 1.0 Weight gain: Pre-pregnancy to month 5 0.5 Pre-pregnancy to month 7 0.7 Pre-pregnancy to month 9 0.6 Month 5 to month 7 0.9 Month 5 to month 9 0.9 Month 7 to month 9 0.7 of a reduced risk, but more data would be required before this could be considered to be reliably deter- mined. For this reason a larger number of studies of Fig. 21. The combined OR profiles for attained weight and postpartum haemorrhage are shown. Means (with 95% confidence interval) are estimated as: WTpp: 0.6 (0.4-1.1); WT/5: 0.9 (0.4-1.7); WT/7: 0.9 (0.6-1.5); and WT/9: 0.6 (0.4-0.8). The ORs are for weight below the lowest quartile versus weight above the highest quartile. Pre-pregnancy Month 9 Month 7 Month 5 0 0.75 1.0 1.5 2.25 3.0 Odds ratio 36 WHO Bulletin OMS: Supplement Vol. 73 1995 Maternal outcomes sufficient size will need to be incorporated into the meta-analysis before more precise estimates can be obtained for this outcome and thus provide a clearer indication of the predictive power of these indica- tors. The profile for attained weight at month 9 is based on all six studies and has a low OR of 0.6 with a confidence interval in the 0-1 range. This reduced risk-finding parallels that for MUAC (OR, 0.6; 95% CI, 0.5-0.8) and the same interpretation and caution must be applied to both. Postpartum haemorrhage is a serious and life- threatening condition requiring immediate and effec- tive response. Most of the indicators examined here are of insufficient strength and reliability to be useful predictors of increased risk from a service point of view. Of the two that potentially indicate reduced risk, the evidence is insufficient to justify any assumptions of more favourable status in respect of this outcome. Sensitivity and specificity Accepting these limitations on predictive capacity, Se/Sp analysis is rather academic, but for the record the results are shown in Fig. 22 and Table 21. Sensi- tivities will be seen to vary substantially across the few available studies for many of the indicators; a Fig. 22. Ranges in computed sensitivity (left side) and specificity (right side) across all relevant data sets for all indicators for postpartum haemorrhage. The indica- tors are numbered 1 to 16 and follow the sequence shown in Table 21. 10 10. 0.9 K-- --- a 0.9 0.8 -- -.8------ ----------i 0.7 ---------------------------------------0.7 0.1 -- ..........;;;;00.5 .5 10) .2 .3 .3 0 5 10 15 0 5 10 15 Indicators WHO 95100 Table 21: Performance of indicators for postpartum haemorrhage. Asterisked indicators having met the selec- tion criteria, are considered candidates for 'best' indicator. Post-partum haemorrhage Indicator Counta Min Sea Max Sea 1. Maternal height 0/7 2. Pre-pregnancy weight 1/5 0.36 0.36 3. Attained weight by month 5 0/4 4. Attained weight by month 7 2/5* 0.43 0.50 5. Attained weight by month 9 0/7 6. Mid-upper-arm circumference 0/4 7. Weight gain: months 5 to 7 1/3 0.50 0.50 8. Weight gain: months 5 to 9 0/3 9. Weight gain: months 7 to 9 1/4 0.33 0.33 10. Weight gain: pp to month 5 0/3 11. Weight gain: pp to month 7 1/2* 0.38 0.38 12. Weight gain: pp to month 9 0/4 13. Pre-pregnancy BMI 2/5* 0.31 0.50 14. BMI month 5 0/5 15. BMI month 7 2/6 0.32 0.50 16. BMI month 9 1/6 0.45 0.45 a 'Count' gives the fraction of data sets in which the Se/Sp cri- terion was met. The asterisk denotes that the indicator met this criterion (Se >0.3, Sp >0.7) in over 40% of the studies. The observed maximum and minimum sensitivities across studies that meet the Se/Sp criterion are recorded in the final two col- umns. Where only one study has met the criteria, the min and max figure for Se will be the same. single study can exaggerate the range considerably. For example, Se for indicator number 10 (WTg/pp-5) will be seen to encompass a range from just above 0.1 to almost 1.0; the latter point is due to a single atypical outlier. Most study sensitivities are below the cut-off point of 0.3. In contrast, the ma- jority of the study specificities exceed 0.7. It will be seen from Table 21 that the indicators meeting the study criteria are: weight attained by month 7, weight gain from pre-pregnancy to month 7, and pre-pregnancy BMI. However, as the numbers of studies available for this summary are very limit- ed indeed, there can be little or no confidence in the selection criteria in this instance. In addition, it will be recalled that all of these indicators had already been excluded as potential predictors because the confidence intervals for associated ORs included 1, implying no evidence for a risk relationship with this outcome. WHO Bulletin OMS: Supplement Vol. 73 1995 37