Lost to follow-up among pregnant women in a multi-site community based maternal and newborn health registry: a prospective study

The 42-day LTFU rate in the MNHR was low, at 1.7%, in this community-based pregnancy
registry study. The complete follow up rates of 98.3% surpasses by far the recommended
follow up thresholds of between 60-80 percent for cohort studies 1]. However, it must be mentioned that the outcomes of interest are of relatively low
incidence, so a very low LTFU rate is crucial, as missing a single rare adverse outcome
disproportionately affects the conclusions. A meta-analysis of several antiretroviral
therapy (ART) programs in resource limited settings showed that an average of 21%
of patients had been LTFU in the first six months after starting ART 3]. These programs, however, were implemented in a clinic setting where clients were
enrolled and followed up within a health facility. Long waiting lines, lack of confidentiality
and privacy may have affected clients’ willingness to return for follow-up in clinic
settings 4,12,13]. This is unlikely to occur in community-based registries, such as the MNHR, where
follow-up is typically done in the participant’s home by the RA. However, some MNHR
follow-up activities also took place where women received antenatal and postpartum
care. The fact that women who most frequently utilized a government hospital or clinic
for ANC also showed higher rates of LTFU may be explained by the type of care received
at those locations and deserves additional investigation.

In studies like the present, some subjects are not able to be located by the study
personnel. Some pregnant mothers may leave their matrimonial homes and return to their
birth homes and remain there until they deliver by custom or for economic necessity.
This movement has been a commonly reported phenomenon in Indian and African studies
of pregnant women 5,7] and the paper in this supplement from India also documents a very high rate of movement
for delivery 6]. Such migration contributes to LTFU, especially if a tracking mechanism is not in
place to capture out of area births. Other potential reasons for a subject not being
located include incorrect addresses or insufficient information in study logs regarding
subjects’ places of residence. This is especially true in studies conducted in rural
areas of low-income countries, where few subjects have a physical street address.
Reliable phone contacts, head of household’s name and a notation of a landmark close
to where the subject lives improve the chances of locating the participant for follow
up 8].

While none of the sites had a large LTFU rate, Pakistan’s LTFU rate of 4.2% was higher
than that of the other sites and considerably higher than the Indian sites and especially
Belgaum’s LTFU rate. By virtually any measure of the health care system or women’s
education, Pakistan performs poorly compared to the other Global Network sites, while
in Belgaum, every effort is made to track women and ensure that they receive appropriate
care. These differences, documented in 2 papers in this supplement, likely explain
the differences in the LTFU rate between these sites 6,10].

Various techniques were employed in the different sites to ensure retention of mothers
in the registry. For instance, the Kenya site gave mobile phones to village elders
to improve communication between the village elders and MNHR RAs 11]. The elders were also provided with platform weighing scales to weigh all babies
delivered in their villages. This culturally appropriate method to engage the village
elders in the study improved the Kenya LTFU rate, and ensured that all mothers who
delivered at home had accurate infant weight recorded. In addition, the village elders
assisted the study personnel in contacting mothers as soon as possible after delivery
11]. In Belgaum, India, the site has worked closely with the Ministry of Health and the
existing community health workers to conduct monthly visits to check on the mother’s
status and track resident women who leave the area to give birth in a matrimonial
home outside the cluster 6]. As another example, the Guatemala team has engaged the traditional birth attendants
to help increase community involvement with the MNHR and complete follow-up visits
at home for women who did not traditionally access the formal health care services.

More subjects were LTFU before delivery than after delivery. This finding was consistent
in all sites except Argentina, which had an equal proportion. This means that only
basic maternal demographic data were available for the majority of subjects LTFU.
Some parallels exist between the results of our study and observational data on ANC
clinic attendance. In most countries, the percentage of mothers who attend at least
one ANC clinic is high but subsequent appointments are often not kept. Furthermore,
about 20% of women who attend ANC in sub-Saharan Africa and south Asia do not seek
skilled birth attendance 14]. This high rate of drop-out from the professional health care system, especially
at the point of delivery, is consistent with the findings of this community registry
study.

Maternal characteristics that increased risk of LTFU include: being pregnant at time
of enrollment rather than enrolling at or soon after delivery, younger age (20 years)
and having no formal education. Mothers who did not know their LMP were also at increased
risk of being LTFU. Unknown LMP may in some cases be associated with a pseudo pregnancy
which, although rare, results in study drop-out and may also make tracking based on
expected delivery more difficult 15]. Low birth weight and low socioeconomic status are also associated with an unknown
LMP, as well as poor pregnancy outcome. Therefore, disproportionate loss of subjects
with these characteristics are likely to bias the conclusions of a study such as this
in the direction of an underestimation of neonatal and/or maternal mortality. Women’s
education level has also been associated with antenatal care coverage in some studies
with having a higher education level increasing the likelihood of ANC attendance and
reducing the rate of LTFU 12]. Women from urban settings are also more likely to make more ANC visits compared
to women from rural settings. Women who presented late (20 weeks gestation) for ANC
were twice as likely to become lost prior to delivery compared to those who presented
earlier. Late presentation has been attributed to confusion over pregnancy status,
fear of HIV testing, transportation limitation, lack of perceived benefits and clinic
booking delays 16,17].

Other studies have found age to be associated with follow-up status where older patients
were more likely to return to the clinic compared to younger patients 8]. Young mothers who become pregnant while still living with parents are likely to
relocate during the study, either to get married and live with the husband, to go
back to school, or to seek employment in distant major towns. Older patients may have
more settled lifestyles making it easy for them to incorporate follow–up visits.

The neonatal and maternal outcomes for mothers LTFU after delivery and those who completed
follow up showed no significant difference in the initial follow up. From the findings
of this study, most children born to mothers LTFU after delivery were alive at the
perinatal visit (89.5%). This indicates that being LTFU was not associated with adverse
neonatal outcomes. This remained so even when comparison was made between sites with
relatively high and those with relatively low LTFU rates. Likewise, the maternal outcomes
did not differ significantly by the follow up status. It is however difficult to make
a definitive comment on the outcomes as the mothers who were LTFU before delivery
had no documented maternal or neonatal outcomes. Similarly those who were LTFU after
delivery had no day 42 outcomes.

This study has several limitations. Clearly, the major limitation is the fact that
for approximately 70% of women LTFU, no data beyond the most basic demographic indicators
were available. Information on how the circumstances and immediate outcome of delivery
were only available on the approximately 30% of subjects LTFU between delivery and
the final 42 day outcome. It is also not known how many out of those reported as LTFU
are still alive. However, it seems likely that since a maternal death is a relatively
rare event, even in low and middle income countries, neighbors and village elders
who were contacted would have reported any such deaths.

In conclusion, our data show that a community-based prospective birth registry can
be constructed and conducted in low and middle income countries with a very low LTFU
rate. Hence we are reasonably confident in the estimates of both maternal and perinatal/neonatal
mortality rates. However, we must caution that there could have been a selection bias
in the subjects lost to follow-up, resulting in an underestimation of mortality rates.
Several risk factors emerge for LTFU, such as low maternal age and lack of education.
Therefore, we recommend that special emphasis be made for subjects at risk, and tracking
of these subjects be intensified during the study. Ultimately, ensuring complete representation
in community-based studies such as the MNHR is needed to ensure generalizability of
study findings for public health research.