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Maternal morbidity and mortality associated with interpregnancy interval: cross sectional study

BMJ 2000; 321 doi: (Published 18 November 2000) Cite this as: BMJ 2000;321:1255

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Other Important Considerations in Interpregnancy Interval

Editor--Conde-Agudelo et al1 have examined the effect of pregnancy
interval on maternal morbidity and mortality. Specifically they looked at
456,889 births over a twelve-year period as recorded in a database that
registers half a million births a year. We welcome their study; however,
their methodology raises some concerns.

Firstly, the study is not population based but rather hospital based and
therefore represents less than 2% of all births in the Latin American and
Caribbean region. As a result, they have probably excluded all isolated or
community births which tend to occur more frequently among vulnerable
mothers anyway. Therefore, how representative is their sample of the whole
population? This would threaten the generaliseability of their findings
both to the developed world and to the rest of Latin American and the

Secondly there is no detail about the CAVEAT’s that should be applied to
data from databases and surveillance systems. (C = completeness, A =
accurate, V = valid, E = evaluated, A = available, T = timely.)

Thirdly, the authors appear not to have considered socio-economic factors
other than maternal education and cohabitation of parents, which by
themselves may not be the most appropriate markers. Given the vastly
disparate cultural areas they covered, should a variable relating to
ethnic origin or religious persuasion also be included to be more
meaningful here and for use in other studies?

The authors explained an increased risk of eclampsia and pre-eclampsia
amongst women with an interpregnancy interval of five years or more by
suggesting that a protective effect from an earlier pregnancy wanes after
five years. However, more conventional theories of the pathogenesis of pre
-eclampsia suggest that maternal exposure to a paternal antigen is
responsible.2 3 These more conventional hypotheses suggests that second
pregnancies are less likely to result in pre-eclampsia if the first one
was event free. This paper does not contradict this hypothesis, since long
interpregnancy intervals may actually be associated with the acquisition
of new reproductive partners. The findings on long interpregnancy interval
would be of much greater interest had partner data been included.

Finally, the authors concluded by recommending family planning to increase
interpregnancy intervals and thus avoid the risks of short intervals.
While this is a valid suggestion the opportunity to compare short
interpregnancy interval risks with those of contraceptive is needed.

Competing interests:None declared.

Eithne Linnane, Specialist Registrar in Public Health Medicine,

Philip Watson, Specialist Registrar in Public Health Medicine,

Bro Taf Health Authority,
Temple of Peace and Health,
Cathays Park,

1 Conde-Agudelo A, Belizán JM. Maternal morbidity and mortality
associated with interpregnancy interval :cross sectional study. BMJ
2000;321:1255-1259.(18 November.)

2 Trupin LS,Simon LP,Eskenazi B. Change in paternity:a risk factor for
preeclampsia in multiparas. Epidemiology1996;7:240-4.

3 Dekker GA, Robillard PY, Hulsey TC. Immune maladaptation in the etiology
of preeclampsia: a review of corroborative epidemiologic studies.
Obstetrical and Gynaecological survey. 1998;53(6):377-82.

Competing interests: No competing interests

24 November 2000
Eithne Linnane
Specialist Registrar in Public Health Medicine
Bro Taf Health Authority, Temple of Peace Health, Cathays Park, Cardiff, CF13NW