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Methods of gestational age assessment influence the observed association between antiretroviral therapy exposure, preterm delivery and small-for-gestational-age infants: a prospective study in Cape Town, South Africa

Methods of gestational age assessment influence the observed association between antiretroviral therapy exposure, preterm delivery and small-for-gestational-age infants: a prospective study in Cape Town, South Africa
Methods of gestational age assessment influence the observed association between antiretroviral therapy exposure, preterm delivery and small-for-gestational-age infants: a prospective study in Cape Town, South Africa
Purpose: Heterogeneous findings exist on antiretroviral treatment (ART) use in pregnancy and preterm delivery (PTD) or infants born small-for-gestational age (SGA). Whether reported differences may be explained by methods used to ascertain gestational age(GA) has not been explored. Methods: We enrolled consecutive pregnant women attending a large primary care antenatal clinic in South Africa. Public-sector midwives assessed GA by last menstrual period (LMP) and symphysis-fundal height (SFH). Separately, if clinical GA was <24weeks, ultrasound (US) was performed by a research sonographer blinded to midwife assessments. In analysis, the impact of measurement error on the association between HIV/ART status and birth outcome by GA method was assessed, and factors associated with clinical GA under- or over-estimation identified. Results: In 1787 women included overall, estimated PTD incidence was 36% by LMP, 17% by SFH and 11% by US. PTD risk was higher for HIV-infected than HIV-uninfected women using US-GA (adjusted odds ratio (aOR) 1.95; 95% CI 1.10-3.46); for LMP/SFH-GA the associations were smaller and not significant. These findings persisted after adjustment for age, parity, height and previous PTD. PTD risk did not vary by timing of ART initiation (before or during pregnancy) for any method. Elevated BMI and older age were associated with decreased risk of under-estimation by both LMP and SFH; HIV status and obesity were associated with increased risk of over-estimation by SFH. There were no differences in SGA incidence across GA methods. Conclusions: Findings for an association between HIV/ART and birth outcomes are substantially influenced by GA assessment method. With growing public health interest in this association, future research efforts should seek to standardize optimal measures of gestation.
1047-2797
Malaba, Thokozile R.
f191c932-7697-43cf-b4f7-c64e7b307fa9
Newell, Marie-Louise
c6ff99dd-c23b-4fef-a846-a221fe2522b3
Madlala, Hlengiwe
81e70a9f-bda3-4f79-b9e7-ca5e5a11d395
Perez, Alexander
764a109e-56ec-425a-92f3-f056f69069f2
Gray, Clive
d960bd69-9548-4bff-8f4f-e814ad485b49
Myer, Landon
ead875bb-dcfa-43e3-b34a-4cbc45f545c1
Malaba, Thokozile R.
f191c932-7697-43cf-b4f7-c64e7b307fa9
Newell, Marie-Louise
c6ff99dd-c23b-4fef-a846-a221fe2522b3
Madlala, Hlengiwe
81e70a9f-bda3-4f79-b9e7-ca5e5a11d395
Perez, Alexander
764a109e-56ec-425a-92f3-f056f69069f2
Gray, Clive
d960bd69-9548-4bff-8f4f-e814ad485b49
Myer, Landon
ead875bb-dcfa-43e3-b34a-4cbc45f545c1

Malaba, Thokozile R., Newell, Marie-Louise, Madlala, Hlengiwe, Perez, Alexander, Gray, Clive and Myer, Landon (2018) Methods of gestational age assessment influence the observed association between antiretroviral therapy exposure, preterm delivery and small-for-gestational-age infants: a prospective study in Cape Town, South Africa. Annals of Epidemiology. (doi:10.1016/j.annepidem.2018.08.011).

Record type: Article

Abstract

Purpose: Heterogeneous findings exist on antiretroviral treatment (ART) use in pregnancy and preterm delivery (PTD) or infants born small-for-gestational age (SGA). Whether reported differences may be explained by methods used to ascertain gestational age(GA) has not been explored. Methods: We enrolled consecutive pregnant women attending a large primary care antenatal clinic in South Africa. Public-sector midwives assessed GA by last menstrual period (LMP) and symphysis-fundal height (SFH). Separately, if clinical GA was <24weeks, ultrasound (US) was performed by a research sonographer blinded to midwife assessments. In analysis, the impact of measurement error on the association between HIV/ART status and birth outcome by GA method was assessed, and factors associated with clinical GA under- or over-estimation identified. Results: In 1787 women included overall, estimated PTD incidence was 36% by LMP, 17% by SFH and 11% by US. PTD risk was higher for HIV-infected than HIV-uninfected women using US-GA (adjusted odds ratio (aOR) 1.95; 95% CI 1.10-3.46); for LMP/SFH-GA the associations were smaller and not significant. These findings persisted after adjustment for age, parity, height and previous PTD. PTD risk did not vary by timing of ART initiation (before or during pregnancy) for any method. Elevated BMI and older age were associated with decreased risk of under-estimation by both LMP and SFH; HIV status and obesity were associated with increased risk of over-estimation by SFH. There were no differences in SGA incidence across GA methods. Conclusions: Findings for an association between HIV/ART and birth outcomes are substantially influenced by GA assessment method. With growing public health interest in this association, future research efforts should seek to standardize optimal measures of gestation.

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Accepted/In Press date: 23 August 2018
e-pub ahead of print date: 29 August 2018

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Local EPrints ID: 424391
URI: http://eprints.soton.ac.uk/id/eprint/424391
ISSN: 1047-2797
PURE UUID: f9cc1c26-65e6-475f-bd8b-9bca629970aa
ORCID for Marie-Louise Newell: ORCID iD orcid.org/0000-0002-1074-7699

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Date deposited: 05 Oct 2018 11:36
Last modified: 16 Mar 2024 07:03

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Contributors

Author: Thokozile R. Malaba
Author: Hlengiwe Madlala
Author: Alexander Perez
Author: Clive Gray
Author: Landon Myer

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