As many of you may recall, we ran a series on issues pertaining to maternal overweight/obesity here on Science & Sensibility not too long ago. Throughout the series, we looked at the common complications associated with maternal obesity - and questioned which of those complications were iatrogenic as opposed to purely caused by maternal overweight. Likewise, several of us participating in that series questioned the validity of the Body Mass Index scale - and how generalizable it is to the vast population.

In the current issue of the American Journal of Obstetrics & Gynecology a study has been published by Lorie Harper, MD et al.[1] that also looks at issues pertaining to maternal weight gain - but with a focus on teen pregnancy and complications that tend to evolve out of less-than-adequate weight gain: Adolescent pregnancy and gestational weight gain: do the Institute of Medicine recommendations apply?

The study raises an important question: are maternal weight gain recommendations adequate for teen pregnancy?

I have to admit, there are some concerns with this study in terms of its generalizability to the larger population: while decent in size (n=76,682) and conducted over a sixteen-year period (1989-2005), this population-based, retrospective cohort study was based on birth, fetal and infant death certificate data from the state of Missouri (as opposed to a multi-state study). Maternal weight gain was self-reported (as opposed to documented by clinical staff upon hospital admission) and obtained for study purposes from birth certificates. Noted characteristics of the study population included age, race, smoking status, chronic hypertension, diabetes mellitus, weight gain and Medicaid recipient status. Despite identifying whether or not study participants were in receipt of Medicaid, no analysis was provided for placing this information in context with the greater Missourian population, nor the United States population as a whole. And yet, I can only assume study authors included Medicaid enrollment due to the implications contained therein regarding socioeconomic status and its inferred correlation with overall health and well-being of study participants.

The overriding theme of this study is the concern about inadequate weight gain during adolescent pregnancy, and the morbidities and mortalities associated. From the study:

'In 2006, the rate of low birthweight (<2500g) in infants of teenagers was as high as 13.4%, compared with 8.3% for the entire population. [emphasis, mine] Although the reason for the increased rate of low birthweight infants among adolescent mothers in unclear, it is well-known that maternal weight gain is correlated to infant birthweight, either because gestational weight gain is associated causally with fetal growth or because the same determinants of gestational weight gain (diet and exercise) also impact fetal growth.'

Outcomes of interest for this study included small-for-gestational-age (SGA), large-for-gestational-age (LGA)* preterm delivery, infant death, preeclampsia and cesarean delivery. Study participants were broken into three groups:

• Less than IOM weight gain guideline
• Within IOM weight gain guideline
• More than IOM weight gain guideline.

The hallmark finding of this study? 'For every BMI category, the odds of having a SGA baby decreased as gestational weight gain increased.' Likewise, preterm delivery and infant death were more frequent among mothers with poor weight gain (irrespective of BMI category).

A question is raised early in the article, in regards to categorizing teenage girls using adult BMI charting. One can easily imagine how a young teenager - say a fourteen- year-old who is yet to reach physical maturity - would end up classified as 'underweight' on an adult BMI chart while still being considered 'normal weight' on an age-specific BMI chart. The study authors conclude, however, that because of the general concern for fetal morbidities and mortality associated with teen mother inadequate weight gain, that using the adult BMI chart can only serve to encourage beneficial, greater amounts of weight gain during the course of pregnancy. (Later, in the commentary, study authors note that because 'adolescents who gain within the IOM recommendations for the BMI category have 14-19% incidence of SGA infants,' that revisiting - and likely increasing - the weight gain guidelines for the adolescent population would be a good idea.)

Aside from this particular study (and those which it references) we must realize that caring for adolescents during pregnancy requires great care and consideration. From social factors to physiologic differences, teen pregnancy - even while on the decline - warrants tender care from all aspects of the maternity care and birth education/support arenas.

How have you tailored your professional efforts to better care for pregnant teens?

Posted by: Kimmelin Hull, PA, LCCE

[1] Harper LM, Chang JJ, Macones GA. Adolescent pregnancy and gestational weight gain: do the Institute of Medicine recommendations apply? Am J Obstet Gynecol 2011; 205:140.e1-8

*United States population served as reference for fetal growth
**For statistics on teen pregnancy in the US, go here and here. For information on Medicaid-sponsored family planning programming, go here.

To read a Roiters update on teen pregnancy stats, go here (and scroll down to the very bottom of the page).

Published: August 09, 2011

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