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CSU 4/2008: BIRTH SPACING/ MORE ON MALE CIRCUMCISION

Friday, 25th of January 2008

CSU 4/2008: BIRTH SPACING/MORE ON MALE  CIRCUMCISION
 
 
 1) BIRTH SPACING
 
 Readers of these updates will be familiar with the benefits of birth
 spacing, especially in terms of child mortality reduction (to refresh your
 recollection, consult Rachel Royce's review article on the subject from the
 Journal of the American Medical Association), text at the foot of this updae.
 
 
 2) MORE ON MALE CIRCUMCISION
 
 Thanks to Daniel Halperin, of Harvard University, for forwarding this item
 on male circumcision and HIV prevention.
 
 If 2007 had seen the unveiling of an HIV/AIDS vaccine with 60 percent
 proven efficacy, how many governments would not have introduced it by now?
 To the knowledge of this writer, 3 out of 46 AFRO states have thus far
 prepared policies in favor of male circumcision.
 
 http://blogs.law.harvard.edu/politicshiv/2008/01/13/the-most-persuasive-article-on-male-circumcision/
 
 Good reading.
 
 BD

 

Birth Spacing—The Long and Short of It

Rachel A. Royce, PhD, MPH

JAMA. 2006;295:1837-1838.

Worldwide, more than 4 million children die in the first 4 weeks of life, and 28% of these deaths are thought to be due directly to preterm birth.^1-2 Reducing child mortality by 2015 is one of 8 goals in the United Nations Millennium Declaration, adopted by more than 180 nations.³ Birth spacing is mentioned in the strategies set out to achieve the goals but its potential seems underemphasized.

In this issue of JAMA, Conde-Agudelo and colleagues⁴ report the results of a systematic review and meta-analysis of observational studies investigating the association between interpregnancy interval and untoward perinatal health events that are entwined with neonatal mortality.

The authors amassed an impressive amount of cross-cultural evidence to firmly establish the J-shaped relationship between risk of adverse reproductive outcomes and interpregnancy intervals that are either short or long. A total of 67 studies including more than 11 million pregnancies met the strict inclusion criteria for the review. Twenty studies were from the United States, and the remaining 47 were from 61 countries, including research from Latin America, Asia, Africa, Europe, and Australia. As shown in the Figure in the article, the meta-regression curves for preterm birth, low birth weight, and small for gestational age showed lowest risks between approximately 20 and 60 months after delivery of the previous child and those for fetal death and early neonatal death showed lowest risks between approximately 20 and 40 months after delivery.

Twenty-six of the studies fulfilled more rigorous criteria that were required for the meta-analyses, with the number of studies providing data for the individual outcomes ranging from 4 for early neonatal death to 16 for preterm birth. These criteria included using interpregnancy interval instead of birth interval, using at least 4 cut points for intervals, and reporting odds ratios or relative risks or the data to calculate them. Smaller groups of studies were used to compute pooled unadjusted and adjusted estimates of the associations between interpregnancy interval and risks for preterm birth, low birth weight, and small for gestational age. For intervals less than 6 months, the pooled unadjusted odds ratios for these outcomes were 1.77 (1.40 adjusted) for preterm birth, 2.12 (1.61 adjusted) for low birth weight, and 1.39 (1.26 adjusted) for small for gestational age. The results of the meta-analyses provide estimates of risk for the entire range of intervals of birth spacing.

Reservations about the validity of these pooled estimates arise from the troubling amount of heterogeneity that was present. Although the authors attempted to account for some of the potential sources of heterogeneity, one important source was not adequately explored—the country where each study was conducted. The authors looked at economic development status but not at individual countries because several of the studies were multinational. However, only 4 of the 26 included studies involved multiple countries in the same study. For these studies, an indicator for multiple countries could have been used along with country indicators.

Breastfeeding is an important example of a potential confounder that differs greatly by country. Exclusive breastfeeding for the first 6 months of life delays the mother's resumption of menstruation.⁵ Estimates of exclusive breastfeeding in the first 6 months vary dramatically by ethnic group and by country. For example, in the United States, by 6 months of age only 8% of infants are breastfed exclusively, and that practice is about half as common in non-Hispanic blacks.⁶ In Africa, Asia, and Latin America and the Caribbean, Lauer et al⁷ estimated proportions of exclusive breastfeeding in infants younger than 6 months of age at 24.9%, 44.9%, and 30.8%, respectively. Even within regions of continents, much variation exists. For example, the proportion of women in Western and Eastern Africa who exclusively breastfeed for 6 months varies from 6.1% to 41.4%.⁷

Although listed as an important confounder, breastfeeding does not appear to have been controlled for in the studies used in the meta-analyses, probably because most of them were based on record review rather than interviews. These records do not contain enough or accurate information on breastfeeding. Another detail missing from the review is whether the studies' measurement of small for gestational age used appropriate race- sex-, and parity-specific growth curves.⁸

Several causal mechanisms have emerged to explain the risk associated with shorter intervals, including postpartum hormone imbalances, maternal stress, and, most plausibly, maternal nutritional depletion.⁹ Smits and Essed⁹ postulated that depletion of maternal stores of folate during and after pregnancy is responsible for adverse pregnancy outcomes, especially for women who breastfeed or begin their reproductive years with a deficit of folate due to inadequate nutrition. As support for their theory, they cite the finding that neural tube defects are twice as common among children conceived within 6 months following a previous live birth compared with those conceived after 12 to 24 months. From this proposed mechanism flow several hypotheses testable in observational studies, as well as several possible interventions. For example, women who breastfeed and do not take folic acid supplements should be at increased risk. Folate supplementation during the interpregnancy interval should reduce the risk associated with short intervals. It might be beneficial for women who present for prenatal care after a short interpregnancy interval to take folate supplements.

What determines reduced birth spacing? Short interpregnancy intervals are for the most part probably unintended, as are half of all US pregnancies.¹⁰ Short interpregnancy intervals belong to a constellation of interrelated behaviors that ultimately are tied to a complex web of health and economic development. Extremes of the age distribution, marital status, ethnicity, menstrual irregularities, higher parity, and markers of lower socioeconomic status have been shown to be associated with short interpregnancy intervals.^11-12

Interventions that increase birth spacing could positively affect both maternal and child health. For example, improving the proportion of women who breastfeed exclusively for the first 6 months of their infant's life might lengthen the birth interval while providing better nutrition for the first infant and better health outcomes for both infants.¹³ The mother would reduce her risk for maternal death, puerperal endometritis, and anemia,¹⁴ especially if she replenished her folate stores. Also, women should have access to family planning methods to control the interval length.

The risks associated with long interpregnancy intervals are more difficult to explain. The association with untoward reproductive outcomes might be mediated through preeclampsia and eclampsia.^14-15 Risk of preeclampsia has been observed to increase significantly with interpregnancy interval, with an estimated odds ratio of 1.16 per additional year after pregnancy.¹⁵ Preeclampsia is a primary and significant cause of preterm delivery. Long intervals most likely are not chosen but may result from the end of a partnership, infertility, reproductive losses in the interval, health problems in mother or infant, or economic issues.

The implications of optimizing interpregnancy intervals are not limited to regions that account for a high proportion of neonatal deaths (Southeast Asia, 36%; Africa, 28%; Eastern Mediterranean, 15%; Western Pacific, 13%).² Conde-Agudelo et al¹⁶ estimated that 47 289 perinatal deaths (12.1% of all perinatal deaths) might be avoided in Latin America if the interpregnancy interval were shifted to 12 to 59 months. In high-income countries, increased birth spacing would also be beneficial. In North Carolina, for example, 11% of small-for-gestational-age births to white women and 21% of such births to black women could have been prevented by lengthening all 0- to 3-month interpregnancy intervals to at least 4 months.⁸ Clinicians should counsel all women to space pregnancies at least 12 months apart, if at all possible.

In 1999 Klebanoff¹⁷ noted the remarkable consistency in reporting the association of short interpregnancy intervals with increased risk of poor perinatal outcomes. Since then, additional findings have accrued on this topic. The meta-analyses by Conde-Agudelo et al in this issue of JAMA summarize these data and provide pooled effect measures. What is needed now is the translation of these solid research findings into practice and future studies to test hypotheses related to the effect of short and long intervals while adequately controlling for breastfeeding. More research is needed to determine whether folate supplementation should be recommended for women after delivery. Regarding the elevated risk associated with long interpregnancy intervals, more thought needs to go into generating plausible testable explanatory hypotheses. While longer intervals are likely to be beyond personal control, pregnancies occurring after an interval longer than 60 months may require more careful monitoring to avoid untoward outcomes.

AUTHOR INFORMATION

Corresponding Author: Rachel A. Royce, PhD, MPH, Research Triangle Institute International, PO Box 12194, Research Triangle Park, NC 27709-2194 (rroyce@rti.org ).

Financial Disclosures: None reported.

Editorials represent the opinions of the authors and JAMA and not those of the American Medical Association.

Author Affiliation: Research Triangle Institute International, Research Triangle Park, NC.

REFERENCES

1. World Health Organization. World Health Report 2005: make every mother and child count. Available at: http://www.who.int/whr/2005/whr2005_en.pdf. Accessed March 18, 2006.

2. Lawn JE, Cousens S, Zupan J, Lancet Neonatal Survival Steering Team. Why are 4 million newborn babies dying each year? Lancet. 2004;364:399-401. FULL TEXT | ISI | PUBMED

3. World Health Organization. WHO's contribution to achievement of the development goals of the United Nations Millennium Declaration. January 16, 2003. Available at: http://www.who.int/gb/ebwha/pdf_files/EB111/eeb1113c1.pdf. Accessed March 20, 2006.

4. Conde-Agudelo A, Rosas-Bermúdez A, Kafury-Goeta AC. Birth spacing and risk of adverse perinatal outcomes: a meta-analysis. JAMA. 2006;295:1809-1823. FREE FULL TEXT

5. Simondon KB, Delaunay V, Diallo A, Elguero E, Simondon F. Lactational amenorrhea is associated with child age at the time of introduction of complementary food: a prospective cohort study in rural Senegal, West Africa. Am J Clin Nutr. 2003;78:154-161. FREE FULL TEXT

6. Li R, Zhao Z, Mokdad A, Barker L, Grummer-Strawn L. Prevalence of breastfeeding in the United States: the 2001 National Immunization Survey. Pediatrics. 2003;111:1198-1201. FREE FULL TEXT

7. Lauer JA, Betrán AP, Victora CG, de Onís M, Barros AJD. Breastfeeding patterns and exposure to suboptimal breastfeeding among children in developing countries: review and analysis of nationally representative surveys. BMC Med. 2004;2:26. FULL TEXT | PUBMED

8. Shults RA, Arndt V, Olshan AF, Martin CF, Royce RA. Effects of short interpregnancy intervals on small-for-gestational age and preterm births. Epidemiology. 1999;10:250-254. FULL TEXT | ISI | PUBMED

9. Smits LJM, Essed GGM. Short interpregnancy intervals and unfavourable pregnancy outcome: role of folate depletion. Lancet. 2001;358:2074-2077. FULL TEXT | ISI | PUBMED

10. Henshaw SK. Unintended pregnancy in the United States. Fam Plann Perspect. 1998;30:24-29, 46. FULL TEXT | ISI | PUBMED

11. Gold R, Connell FA, Heagerty P, et al. Predicting time to subsequent pregnancy. Matern Child Health J. 2005;9:219-228. FULL TEXT | ISI | PUBMED

12. Kaharuza FM, Sabroe S, Basso O. Choice and chance: determinants of short interpregnancy intervals in Denmark. Acta Obstet Gynecol Scand. 2001;80:532-538. FULL TEXT | ISI | PUBMED

13. Rutstein SO. Effects of preceding birth intervals on neonatal, infant and under-five years mortality and nutritional status in developing countries: evidence from the demographic and health surveys. Int J Gynaecol Obstet. 2005;89(suppl 1):S7-S24. FULL TEXT | ISI | PUBMED

14. Conde-Agudelo A, Belizán JM. Maternal morbidity and mortality associated with interpregnancy interval: cross sectional study. BMJ. 2000;321:1255-1259. FREE FULL TEXT

15. Skjaerven R, Wilcox AJ, Lie RT. The interval between pregnancies and the risk of preeclampsia. N Engl J Med. 2002;346:33-38. FREE FULL TEXT

16. Conde-Agudelo A, Belizán JM, Norton MH, Rosas-Bermúdez A. Effect of the interpregnancy interval on perinatal outcomes in Latin America. Obstet Gynecol. 2005;106:359-366. FREE FULL TEXT

17. Klebanoff MA. The interval between pregnancies and the outcome of subsequent births. N Engl J Med. 1999;340:643-644. FREE FULL TEXT