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. 2019 Jan;144(1):9-15.
doi: 10.1002/ijgo.12686. Epub 2018 Oct 19.

Quantifying bias between reported last menstrual period and ultrasonography estimates of gestational age in Lusaka, Zambia

Joan T Price  1   2 , Jennifer Winston  1 , Bellington Vwalika  2   3 , Stephen R Cole  4 , Marie C D Stoner  4 , Mwansa K Lubeya  2 , Andrew Kumwenda  2 , Jeffrey S A Stringer  1
Affiliations

Quantifying bias between reported last menstrual period and ultrasonography estimates of gestational age in Lusaka, Zambia

Joan T Price et al. Int J Gynaecol Obstet. 2019 Jan.

Abstract

Objective: To quantify differences in assessing preterm delivery when calculating gestational age from last menstrual period (LMP) versus ultrasonography biometry.

Methods: The Zambian Preterm Birth Prevention Study is an ongoing prospective cohort study that commenced enrolment in August 2015 at Women and Newborn Hospital of University Teaching Hospital in Lusaka, Zambia. Women at less than 20 weeks of pregnancy who were enrolled between August 17, 2015, and August 31, 2017, and underwent ultrasonography examination were included in the present analysis. The primary outcome was the difference between ultrasonography- and LMP-based estimated gestational age. Associations between baseline predictors and outcomes were assessed using simple regression. The proportion of preterm deliveries using LMP- and ultrasonography-derived gestational dating was calculated using Kaplan-Meier analysis.

Results: The analysis included 942 women. The discrepancy between estimating gestational age using ultrasonography and LMP increased with greater gestational age at presentation and among patients with no history of preterm delivery. In a Kaplan-Meier analysis of 692 deliveries, 140 (20.2%, 95% confidence interval [CI] 17.7-23.0) and 79 (11.4%, 95% CI 9.6-13.6) deliveries were classified as preterm by LMP and ultrasonography estimates, respectively.

Conclusion: Taking ultrasonography as a standard, a bias was observed in LMP-based gestational age estimates, which increased with advancing gestation at presentation. This resulted in misclassification of term deliveries as preterm.

Keywords: Gestational age; Gestational age estimation; Last menstrual period; Preterm birth; Ultrasonography; Zambia.

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Conflict of interest statement

Conflicts of Interest:

The authors have no conflicts of interest.

Figures

Figure 1
Figure 1
Cohort populations used for analyses. Abbreviations: LMP, last menstrual period; ZAPPS, Zambian Prematurity Prevention Study.
Figure 2
Figure 2
Discrepancy between ultrasonography- and LMP-based EGA by ultrasonography-based gestational age at presentation (n=1785). Abbreviations: EGA, estimate gestational age; LMP, last menstrual period.
Figure 3
Figure 3
Kaplan–Meier estimates of gestational age at delivery by ultrasonography and by LMP. Abbreviations: EGA, estimated gestational age; LMP, last menstrual period.
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References

    1. Blencowe H, Cousens S, Oestergaard MZ, et al. National, regional, and worldwide estimates of preterm birth rates in the year 2010 with time trends since 1990 for selected countries: a systematic analysis and implications. The Lancet. 2012;379(9832):2162–2172. - PubMed
    1. Smid MC, Stringer EM, Stringer JS. A Worldwide Epidemic: The Problem and Challenges of Preterm Birth in Low- and Middle-Income Countries. Am J Perinatol. 2016;33(3):276–289. - PubMed
    1. Zash R, Souda S, Chen JY, et al. Reassuring Birth Outcomes With Tenofovir/Emtricitabine/Efavirenz Used for Prevention of Mother-to-Child Transmission of HIV in Botswana. J Acquir Immune Defic Syndr. 2016;71(4):428–436. - PMC - PubMed
    1. Chen JY, Ribaudo HJ, Souda S, et al. Highly active antiretroviral therapy and adverse birth outcomes among HIV-infected women in Botswana. J Infect Dis. 2012;206(11):1695–1705. - PMC - PubMed
    1. Li N, Sando MM, Spiegelman D, et al. Antiretroviral Therapy in Relation to Birth Outcomes among HIV-infected Women: A Cohort Study. J Infect Dis. 2016;213(7):1057–1064. - PubMed

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