Postpartum Exposure: Amenorrhea, Abstinence, and Insusceptibility

1) Percentage of live births and stillbirths in the 3 years preceding the survey for which the mothers are postpartum amenorrheic.

2) Percentage of live births and stillbirths in the 3 years preceding the survey for which the mothers are postpartum abstaining from sexual intercourse.

3) Percentage of live births and stillbirths in the 3 years preceding the survey for which the mothers are insusceptible to pregnancy.

Population base: All live births and stillbirths within the time period preceding the survey (NR file)

Time period: Current status at the time of the survey (interview date) for births within the three years (0-35 months) preceding the survey

1) Number of live births and stillbirths at specified times before the survey for which the mother is postpartum amenorrheic (i.e., her menstrual period has not resumed since the birth, and she is not currently pregnant) (m6 = 96 & v213 ≠ 1)

2) Number of live births and stillbirths at specified times before the survey for which the mother is postpartum abstaining (i.e., mother has not resumed sexual intercourse since the birth) (m8 = 96)

3) Number of live births and stillbirths at specified times before the survey for which the mother is either postpartum amenorrheic or abstaining ((m6 = 96 & v213 ≠ 1) or m8 = 96)

Denominator: Number of live births and stillbirths at specified times (typically three years) preceding the survey (b19 < 36)

Calculation

For the purposes of analysis of DHS data, a live birth is a pregnancy outcome that resulted in a live born child including children who cried, breathed, or moved, but later died, irrespective of the duration of pregnancy. A stillbirth is defined as any pregnancy of 28 weeks or more or 7 or more months duration that resulted in an outcome other than a live birth.

Number of last births where the mother is amenorrheic since the birth (m6=96) and the mother is not currently pregnant (v213≠1). For last birth, amenorrhea status is from the mother’s report of her status at the time of the interview. For all other births, the mother is assumed not to be amenorrheic since the birth. Includes live births and stillbirths for which mothers are either still amenorrheic or still abstaining (or both) following birth

Number of last births where the mother has abstained from sexual intercourse since the birth (m8=96). For last birth, abstinence status is from the mother’s report of her status at the time of the interview. For all other births, the mother is assumed not to have been abstaining since the birth.

Number of last births where the mother is either amenorrheic or has abstained from sexual intercourse since the birth (m6=96 or m8=96). For last birth, insusceptibility is from the mother’s report of her amenorrhea and sexual abstinence status at the time of the interview. For all other births, the mother is assumed not to have been insusceptible since the birth.

Births are grouped by two-month intervals before the survey, as determined by difference in interview date and birth date (p19).

Denominator: Number of all births in the three years preceding the survey (p19 < 36), including last and prior births, grouped by two-month intervals before survey ( int( p19/2 ) ), as determined by difference in interview date and birth date.

Handling of Missing Values

Birth dates were imputed if missing. Dates of interview are not allowed to have missing data.

Women with missing reports of amenorrhea or sexual abstinence are considered to be not amenorrheic or not abstaining, respectively.

Notes and Considerations

Only the last of multiple births are considered (caseid ≠ caseid[_n-1] or p3 ≠ p3[_n-1]). The other births are ignored in both numerators and denominator. Births of both living and dead children are included. Survival status is ignored.

Changes over Time

The calculation of the number of months since the birth changed in DHS-7 compared to prior rounds of The DHS Program. This indicator uses the variable b19 (months since birth) calculated using the full date of birth of the child and the full date of interview, while in earlier rounds of The DHS Program, the number of months since birth was calculated using the century month code of the date of birth and the century month code of the date of interview as v008 - b3. See Age of Children in Chapter 1 for more information. The main effect for this indicator is that the number of months since the birth is roughly half a month shorter on average than presented in prior rounds of The DHS Program, so care should be taken when comparing results between surveys.

The calculation of this indicator further changed in DHS-8 to include both live births and stillbirths.

Resources

Median and mean durations of postpartum amenorrhea, abstinence, and insusceptibility

Definition

Population base: All births within the time period (0-35 months) preceding the survey (NR file)

1) Number of births at specified times before the survey for which the mother is postpartum amenorrheic (i.e., her menstrual period has not resumed since the birth, and she is not currently pregnant) (m6 = 96 & v213 ≠ 1)

2) Number of births at specified times before the survey for which the mother is postpartum abstaining (i.e., mother has not resumed sexual intercourse since the birth) (m8 = 96)

3) Number of births at specified times before the survey for which the mother is either postpartum amenorrheic or abstaining (m6 = 96 or m8 = 96)

Denominator: Number of births at specified times in the three years preceding the survey (p19 < 36)

Calculation

Utilize the numerators and denominators calculated for the Percentage of live births and stillbirths for which mothers are postpartum amenorrheic, abstaining from sexual intercourse and insusceptible to pregnancy, by time since birth, as given above. Numerators and denominators are each smoothed by a three-group moving average. For example, the value of the numerator and denominators for births that occurred 4-5 months before the interview is the average of groups 2-3, 4-5, and 6-7 months. Groups < 2 months and 34-35 months are not smoothed. Smoothed proportions are calculated by dividing the smoothed numerator values by the smoothed denominator values of each two-month group.

Beginning with the lowest time-since-birth group, each group is examined to see whether the proportion amenorrheic, abstaining, or insusceptible is less than 0.5. Value of median is determined by linear interpolation of percentage of first group below 0.5 and previous group percentage using the following formula:

where p_i is the proportion amenorrheic, abstaining, or insusceptible for the first group, where the proportion is below 0.5, p_i-1 is the proportion amenorrheic, abstaining, or insusceptible for the preceding group, m_i-1 is the midpoint value for the preceding group, and w_i is the time width of the group taken as the difference between the midpoint value of the current group and the preceding group.

Prior to DHS-7: In The DHS Program rounds prior to DHS-7, for all groups except the first, the midpoint values are one-half month above the lower limit. This midpoint value comes about because the time since birth is calculated as the difference between birth dates and date of interview that are accurate for month only (day of month is not ascertained), and month 0 effectively contains on average only half a month’s births.

For example, if the date of interview were April 2018, the interview could have occurred at any time during the month, from the 1^st to the 30^th. The same holds true for a birth that occurred in January 2018, at any time between the 1^st and the 31^st of the month. Thus, the difference in time between the date of birth and the date of interview could be between 60 days and 120 days. Assuming a constant distribution by day of month for interviews and for births, the midpoint is 90 days or three months, which is the value of the difference in the century-month codes of the dates. The midpoint value for the group of the difference of 2 months and 3 months together is therefore 2.5.

The first group is special. The value of the previous group is assumed to be 100 percent since all women are assumed to be amenorrheic and abstaining on the day of birth. Moreover, births that occur in the month of interview can only come before the date of interview, rather than on any day of the month of interview. Based on simulations, 0.75 is chosen as the midpoint value for the group < 2 months (i.e., 0-1). The midpoint of the previous group is 0 (day of interview).

DHS-7 and later: The midpoint values are at the midpoints of the range as the difference between the births dates and date of interview are accurate to the day, and month 0 now contains a full month of births.

Using the example above, if the date of interview were April 2018, the interview could have occurred at any time during the month, from the 1^st to the 30^th. The same holds true for a birth that occurred in January 2018, at any time between the 1^st and the 31^st of the month. With the day of interview known, and the day of birth known, or imputed, it is possible to calculate the exact age of the child to the day and the age would be between 2.0 months and just less than 4.0 months and would be either 2 month or 3 months when truncated. Similarly, a child born in February 2018 would either be 1 or 2 months old. Combining all date combinations together, a child categorized as 2 months old would on average be 2.5 month, and a child categorized as 3 months old would on average be 3.5 months old. The midpoint value for the group of the difference of 2 months and 3 months together is therefore 3.0.

In DHS-7, the first group is still special, and the value of the previous group is still assumed to be 100 percent since all women are assumed to be amenorrheic and abstaining on the day of birth. However, because births in the month 0 group now come from births in the month of interview and in the preceding month, the midpoint of the month 0 group is 0.5 and the month 1 group is 1.5, so for the group 0-1 months, the midpoint is 1.0.

Example:

DHS-7				Rounds prior to DHS-7
Group	Pi	Midpoint	Width	Group	Pi	Midpoint	Width
<2	0.88	1.0	1.0	<2	0.90	0.75	0.75
2–3	0.67	3.0	2.0	2–3	0.70	2.5	1.75
4–5	0.52	5.0	2.0	4–5	0.55	4.5	2.00
6–7	0.40	7.0	2.0	6–7	0.43	6.5	2.00

Note that the proportions in age each group are not the same between the DHS-7 approach and the prior approach as the calculation of months since birth has changed in DHS-7 to provide a more accurate estimate, thus requiring the change in the method of calculating the median.

Note also that due to a number of factors including the different calculation of the age groups, and the application of the three-month moving average, the actual calculations are unlikely to result in exactly the same estimates (as the example does) from the two approaches, but they should be quite close. In general, the DHS-7 approach is a more accurate estimate.

Mean

The mean duration is the accumulation over all groups of the proportions amenorrheic, abstaining, or insusceptible (p_i) multiplied by the width of the time-since-birth group (w_i).

The calculation of the mean is also affected by the change in approach in the calculation of the time-since-birth groups, which will result in slightly different proportions in each group, and a change in the width of the first two groups.

Handling of Missing Values

Birth dates were imputed if missing. Dates of interview are not allowed to have missing data.

Women with missing reports of amenorrhea or sexual abstinence are considered to be not amenorrheic or not abstaining, respectively.

Notes and Considerations

Medians and means are based on current status of mothers of the births. The distributions of the proportions of births by month of birth of the child are analogous to the l_x column of the synthetic life table. The basic assumption is that there has been no change in the proportions amenorrheic, abstaining, and insusceptible over time so that proportions that are calculated from births with small times since birth are the same as those of births that occurred earlier, when those earlier births had those durations. For the short period of 36 months, this assumption is very likely to be approximately correct. The proportions are assumed to be 1 at the time of birth and to decrease monotonically with time since birth. The time at which the proportions decline to 0.5 is taken as the median. The mean is taken similarly from the l_x column of the life table, which in this case is the series of proportions by time since birth. Because the sum of proportions equals 1, there is no need to divide the sum of the proportions times the width of the interval.

Because of the relatively small number of births in each month before the interview, the months are first grouped and then smoothed to reduce random fluctuations due to sampling variance.

Truncated Mean: Because of the limitation to births that occurred within the three years preceding the survey, the mean is truncated if there are mothers who are amenorrheic or abstaining longer than three years after their last birth. It is very unlikely that the proportions are more than negligible after 35 months since birth, except for those women who are not really postpartum amenorrheic or abstaining (more likely for older women whose postpartum amenorrhea blended into menopause or whose postpartum sexual abstinence blended into terminal abstinence). Therefore, it is felt that the truncated mean is very close to the full mean.

The measures are based on all births that occurred within the three years preceding the interview, including last and other births, surviving or not.

Current status medians and means are used instead of measures based on the recall of durations because of the severe heaping (digit preference) on multiples of 3 and 6 months in the recall data.

In the current calculation of median and mean durations, a woman can contribute more than once if she had more than one birth in the three years preceding the survey. An alternative calculation would be to base the medians and means on women rather than births. In this alternative, each woman is represented only once, which is equivalent to durations based on only the last birth. Estimates of durations based on last births (open interval durations) are thought to overestimate average durations of amenorrhea and abstinence since they almost always exceed those based on recall after other births (closed interval durations).

Changes over Time

As described above under the median calculation the change in the calculation of time since birth required changes in the calculation of the current status median from the proportions amenorrheic, abstaining or insusceptible. See Age of Children in Chapter 1 for more information on the change in the calculation of time since birth.

In DHS-8 the calculation of this indicator was changed to include amenorrhea, postpartum abstinence, and insusceptibility following live births and stillbirths.

Resources

FE_PPIS_W_MDA, FE_PPIS_W_MDB, FE_PPIS_W_MDI, E_PPIS_W_MNA, FE_PPIS_W_MNB, FE_PPIS_W_MNI

p0	Twin
p3	CMC date of birth
p19	Months since birth
m6	Duration of amenorrhea (96 = still amenorrheic)
m8	Duration of abstinence (96 = still abstaining)
v005	Woman’s individual sample weight

p0	Twin
p3	CMC date of birth
p19	Months since birth
m6	Duration of amenorrhea (96 = still amenorrheic)
m8	Duration of abstinence (96 = still abstaining)
v005	Woman’s individual sample weight