Timing of Initiation of Antiretroviral Therapy and Risk of Preterm Birth in Studies of HIV-infected Pregnant Women: The Role of Selection Bias

Antiretroviral Therapy Use Was Not Associated with Stillbirth or Preterm Birth in an Analysis of U.S. Medicaid Pregnancies to Persons with HIV

Background

Using a U.S. based, nationally representative sample, this study compares stillbirth and preterm birth outcomes between women living with HIV (WWH) who did and did not use antiretroviral therapy (ART) during pregnancy, additionally assessing ART duration and regimen type.

Methods

Using 2001 to 2012 Medicaid Analytic eXtract (MAX) data from the 14 states with the highest prevalence of HIV. We estimated two, propensity score matched, multivariate logistic regression models for both outcomes of stillbirth and preterm birth: (1) any ART use and (2) the number of months on ART during pregnancy for ART users, adjusting for patient-level covariates.

Results

Only 34.6% of pregnancies among WWH had a history of ART use and among those, the proportions of stillbirth and preterm birth were 0.9% and 7.9%, respectively. Any ART use was not significantly associated with either outcome of stillbirth (marginal effects [MEs]: 0.06%, 95% confidence interval [CI]: -0.17 to 0.28) or preterm birth (ME: -0.12%, 95% CI: -0.79 to 0.55). For ART users, duration of ART was not significantly associated with either outcome. Black race was a strong independent predictor in both models (stillbirth: 0.80% and 0.84%, preterm birth: 4.19% and 3.76%). Neither protease inhibitor (PI) nor boosted PI regimens were more strongly associated with stillbirth or preterm birth than nucleoside reverse transcriptase inhibitor-based regimens.

Conclusion

ART use during pregnancy was low during this period. Our findings suggest that ART use and ART regimen are not associated, positively or negatively, with stillbirth or preterm birth for mothers with Medicaid. Additionally, our findings highlight a persisting need to address disparities in these outcomes for Black women.

Adverse pregnancy outcomes associated with antiretroviral therapy initiated before pregnancy and during pregnancy: a retrospective study in Hubei province, China

Background

Antiretroviral therapy (ART) initiation before pregnancy was reported to have an increased risk of adverse pregnancy outcomes (APOs) than ART initiation during pregnancy. However, the risks of APOs associated with different ART regimens initiated before or during pregnancy remain unknown.

Methods

Pregnant women living with HIV (PWLHIV) from Hubei Province, China, were retrospectively enrolled between January 1, 2004, and December 31, 2021. The trends of ART initiation time and application of different ART regimens were evaluated over time, separately. Using no ART exposure before and during pregnancy as control, the risks of APOs associated with protease inhibitor (PI) based regimens and non-nucleoside reverse transcriptase inhibitors (NNRTIs) based regimens initiated before pregnancy were analyzed; and the risks of APOs associated with PI-based regimens, NNRTIs based regimens and zidovudine (AZT) monotherapy initiated during pregnancy were analyzed. APOs, including low birthweight (LBW), stillbirth, preterm birth (PTB) and early miscarriage, were reviewed.

Results

Among 781 PWLHIV including 1,010 pregnancies, 522 pregnancies (51.7%) were exposed to ART before or during pregnancy. Of them, the proportion of ART initiation before pregnancy per year increased from around 20% in the early period to more than 60% after 2019. Efavirenz (EFV)-nucleoside reverse transcriptase inhibitors (NRTIs) (32.2%), LPV/r-NRTIs (31.2%), and nevirapine (NVP)-NRTIs (27.4%) were the most commonly used regimens, and the proportion of LPV/r-NRTIs used per year has increased to around 50.0% in recent years. LPV/r-NRTIs was associated with higher risks of LBW whether initiated before pregnancy [adjusted OR (aOR) = 2.59, 95%CI 1.04-6.45, p = 0.041] or during pregnancy (aOR = 2.19, 95%CI 1.03-4.67, p = 0.041), compared with no exposure to ART before and during pregnancy. However, no matter initiated before or during pregnancy, LPV/r-NRTIs had no significantly increased risks of stillbirth, PTB and early miscarriage, and EFV /NVP-NRTIs and AZT monotherapy had no significantly increased risks of LBW, stillbirth, PTB and early miscarriage when compared with no exposure to ART before and during pregnancy.

Conclusion

Our data suggests that LPV/r-NRTIs has been widely used among PWLHIV in recent years. However, the potential risk of LBW should be continuously monitored among PWLHIV whether LPV/r-NRTIs is initiated before or during pregnancy.

Timing of Antiretroviral Therapy: Initiation and Birth Outcomes Among Pregnant Women With Human Immunodeficiency Virus in Tanzania

BACKGROUND

Combination antiretroviral therapy (cART) initiation during pregnancy reduces the risk of perinatal human immunodeficiency virus (HIV) transmission; however, studies have suggested that there may be unintended adverse consequences on birth outcomes for selected cART regimens.

METHODS

We analyzed adverse birth outcomes among a prospective cohort of 1307 pregnant women with HIV in Dar es Salaam who initiated cART during the first or second trimester of a singleton pregnancy. Our primary analysis compared birth outcomes by gestational age at cART initiation among these women initiating cART in pregnancy.

RESULTS

Among women who initiated cART in pregnancy, there was no relationship of gestational age at cART initiation with the risk of fetal death or stillbirth. However, women who initiated cART before 20 weeks of gestation compared with after 20 weeks had increased risk of preterm birth (risk ratio [RR], 1.30; 95% confidence interval [CI], 1.03-1.67) but decreased risk of small-for-gestational age birth (RR, 0.71; 95% CI, .55-.93).

CONCLUSIONS

With increasing use of cART preconception and early in pregnancy, clinicians should be aware of the benefits and potential risks of cART regimens to optimize birth outcomes.

Preterm Birth in Women With HIV: The Role of the Placenta

Maternal HIV infection is associated with an increased risk of preterm birth (PTB). However, the mechanisms underlying this increased risk in women with HIV remain poorly understood. In this regard, it is well-established that labor is an inflammatory process and premature activation of the pro-inflammatory signals (associated with labor) can result in preterm labor which can subsequently lead to PTB. HIV infection is known to cause severe immune dysregulation within its host characterized by altered immune profiles, chronic inflammation and eventually, the progressive failure of the immune system. The human placenta comprises different immune cell subsets, some of which play an important role during pregnancy including participating in the inflammatory processes that accompany labor. It is therefore plausible that HIV/antiretroviral therapy (ART)-associated immune dysregulation within the placental microenvironment may underlie the increased risk of PTB reported in women with HIV. Here, we review evidence from studies that point toward the placental origin of spontaneous PTB and discuss possible ways maternal HIV infection and/or ART could increase this risk. We focus on key cellular players in the maternal decidua including natural killer cells, CD4+ T cells including CD4+ regulatory T cells, CD8+ T cells as well as macrophages.

Methodological Considerations for Preterm Birth Research

Complications from preterm birth are a leading cause of infant mortality, with long-term implications for morbidity and quality of life of preterm infants. There are many important risk factors for preterm births however in this article, we focus on the maternal infection etiological pathway, given its significance in low-to-middle income countries. In high preterm birth settings such as sub-Saharan Africa, maternal HIV infection and antiretroviral therapy (ART) use have been associated with an increased risk of preterm births. Consequently, we highlight methodological considerations related to selection and measurement bias in preterm birth research. We further illustrate the potential impact of these biases in studies investigating the relationship between HIV/ART and preterm births. We also briefly discuss issues related to population-level estimations based on routinely collected clinical or civil registration data. We conclude by emphasizing the importance of strengthening of antenatal care services to improve quality of population data as well as optimizing current and future study designs, by taking into account the important methodological considerations described in this article.

Perinatal outcomes in women living with HIV-1 and receiving antiretroviral therapy-a systematic review and meta-analysis

INTRODUCTION

Antiretroviral therapy-naïve pregnant women living with HIV are at an increased risk for adverse pregnancy outcomes. It remains controversial whether this risk persists with antiretroviral therapy. We conducted a systematic review and meta-analysis to evaluate whether pregnant women living with HIV and receiving antiretroviral therapy antenatally, are at an increased risk of adverse outcomes compared with HIV-negative controls.

MATERIAL AND METHODS

We searched MEDLINE, Embase, International Pharmaceutical Abstracts, EBM Reviews, PubMed (non-MEDLINE records), EBSCO CINAHL Complete, Clarivate Web of Science, African Index Medicus, LILACS and Google Scholar for all observational studies comparing pregnant women living with HIV on antiretroviral therapy with HIV-negative controls from 1 January 1994 to 10 August 2021 with no language or geographic restrictions. Perinatal outcomes included preterm birth (PTB), low birthweight, small-for-gestational age and preeclampsia. Using a random-effects model we pooled raw data to generate odds ratio (OR) with 95% confidence intervals (CI) for each outcome. Sub-analyses for high and low resource countries and time of antiretroviral therapy initiation were performed. This systematic review and meta-analysis is registered with PROSPERO, number CRD42020182722.

RESULTS

Of the 7900 citations identified, 27 were eligible for analysis (12 636 pregnant women living with HIV on antiretroviral therapy and 7 812 115 HIV-negative controls). ORs (95% CI) of PTB (1.88 [1.63-2.17]), small-for-gestational age (1.60 [1.18-2.17]) and low birthweight (2.15 [1.58-2.92]) were significantly higher in pregnant women living with HIV than in HIV-negative women, while the risk of preeclampsia (0.86 [0.57-1.30]) was comparable. The risk of PTB and low birthweight was higher in both high resource and low resource countries, while the risk of small-for-gestational age was higher only in the former. Preconceptional antiretroviral therapy was associated with a higher risk of PTB compared with antenatal initiation.

CONCLUSIONS

Pregnant women living with HIV on antiretroviral therapy have an increased risk of PTB, low birthweight and small-for-gestational age in high resource countries, as well as PTB and low birthweight in low income countries compared with HIV-negative controls.

Neurological development of children who are HIV-exposed and uninfected

Widespread use of antiretroviral drugs for pregnant/breastfeeding females with human immunodeficiency virus (HIV) has led to declining vertical transmission. Despite being HIV-uninfected, the increasing number of children who are HIV-exposed and uninfected (CHEU) often present with developmental alterations. We review seminal and recent evidence on the neurological development of CHEU and associations with early life HIV/antiretroviral exposure. Our conceptual model highlights the numerous exposures and universal risk factors for CHEU developmental disorders. Early studies suggest a significant association between HIV exposure and neurological abnormalities, varying according to the burden of HIV-specific exposures and other risk factors. More recent observations from the modern era are inconsistent, although some studies suggest specific antiretrovirals may adversely affect neurological development of CHEU. As the CHEU population continues to grow, alongside simultaneous increases in types and combinations of antiretrovirals used in pregnancy, long-term monitoring of CHEU is necessary for understanding the effects of HIV/antiretroviral exposure on CHEU developmental outcomes. What this paper adds Evidence on the neurological development of children who are human immunodeficiency virus (HIV)-exposed and uninfected (CHEU) is synthesized. Comparisons are made to children who are HIV-unexposed, across treatment eras and settings, and by antiretroviral drug regimens and drug classes. CHEU exposures are complex and include HIV-specific and universal risk factors which may affect development during the early years of life.

Adverse Pregnancy Outcomes Among HIV-positive Women in the Era of Universal Antiretroviral Therapy Remain Elevated Compared With HIV-negative Women

BACKGROUND

Without treatment, HIV infection in pregnant women is associated with adverse pregnancy outcomes. We compared adverse pregnancy outcomes among HIV-positive women on antiretroviral therapy (ART) and HIV-negative women who enrolled for antenatal care in selected health facilities in Maseru district, Lesotho.

METHODS

We enrolled a cohort of HIV-positive and HIV-negative women at their first antenatal visit and followed them through delivery. Study data on miscarriage, stillbirth, preterm birth, low birth weight and birth defects were collected through participant interviews and medical record abstraction. We used the Rao-Scott χ2 test and the t test to assess differences in characteristics and outcomes between HIV-positive and HIV-negative women and generalized estimating equations for multivariable analysis.

RESULTS

A total of 614 HIV-positive and 390 HIV-negative pregnant women were enrolled in the study with delivery information on 571 (93.1%) and 352 (90.3%) respectively. In the delivery cohort, the median age at enrolment was 28 years for HIV-positive women and 23 years for HIV-negative women with median gestational ages of 20 and 21 weeks, respectively. A total of 149 singleton pregnancies had documented adverse pregnancy outcomes; 33 (9.6%) HIV-negative pregnancies and 116 (20.6%) HIV-positive pregnancies. Compared with their HIV-negative counterparts, HIV-positive women were more likely to experience an adverse pregnancy outcome, adjusted odds ratio (AOR) 2.6 [95% confidence interval (CI): 1.71-3.97]; an intrauterine death (miscarriage or stillbirth), AOR 2.64 [95% CI: 1.25-5.49]; or a low birth weight delivery, AOR 1.89 [95% CI: 1.16-3.09].

CONCLUSION

Adverse pregnancy outcomes remained 2-3 times higher among HIV-positive women compared with HIV-negative women despite universal ART.

Quantifying the influence of bias in reproductive and perinatal epidemiology through simulation

PURPOSE

The application of simulated data in epidemiological studies enables the illustration and quantification of the magnitude of various types of bias commonly found in observational studies. This was a review of the application of simulation methods to the quantification of bias in reproductive and perinatal epidemiology and an assessment of value gained.

METHODS

A search of published studies available in English was conducted in August 2020 using PubMed, Medline, Embase, CINAHL, and Scopus. A gray literature search of Google and Google Scholar, and a hand search using the reference lists of included studies was undertaken.

RESULTS

Thirty-nine papers were included in this study, covering information (n = 14), selection (n = 14), confounding (n = 9), protection (n = 1), and attenuation bias (n = 1). The methods of simulating data and reporting of results varied, with more recent studies including causal diagrams. Few studies included code for replication.

CONCLUSIONS

Although there has been an increasing application of simulation in reproductive and perinatal epidemiology since 2015, overall this remains an underexplored area. Further efforts are required to increase knowledge of how the application of simulation can quantify the influence of bias, including improved design, analysis and reporting. This will improve causal interpretation in reproductive and perinatal studies.

Maternal HIV Infection and Spontaneous Versus Provider-Initiated Preterm Birth in an Urban Zambian Cohort

OBJECTIVE

We investigated the effect of maternal HIV and its treatment on spontaneous and provider-initiated preterm birth (PTB) in an urban African cohort.

METHODS

The Zambian Preterm Birth Prevention Study enrolled pregnant women at their first antenatal visit in Lusaka. Participants underwent ultrasound, laboratory testing, and clinical phenotyping of delivery outcomes. Key exposures were maternal HIV serostatus and timing of antiretroviral therapy initiation. We defined the primary outcome, PTB, as delivery between 16 and 37 weeks' gestational age, and differentiated spontaneous from provider-initiated parturition.

RESULTS

Of 1450 pregnant women enrolled, 350 (24%) had HIV. About 1216 (84%) were retained at delivery, 3 of whom delivered <16 weeks. Of 181 (15%) preterm deliveries, 120 (66%) were spontaneous, 56 (31%) were provider-initiated, and 5 (3%) were unclassified. In standardized analyses using inverse probability weighting, maternal HIV increased the risk of spontaneous PTB [RR 1.68; 95% confidence interval (CI): 1.12 to 2.52], but this effect was mitigated on overall PTB [risk ratio (RR) 1.31; 95% CI: 0.92 to 1.86] owing to a protective effect against provider-initiated PTB. HIV reduced the risk of preeclampsia (RR 0.32; 95% CI: 0.11 to 0.91), which strongly predicted provider-initiated PTB (RR 17.92; 95% CI: 8.13 to 39.53). The timing of antiretroviral therapy start did not affect the relationship between HIV and PTB.

CONCLUSION

The risk of HIV on spontaneous PTB seems to be opposed by a protective effect of HIV on provider-initiated PTB. These findings support an inflammatory mechanism underlying HIV-related PTB and suggest that published estimates of PTB risk overall underestimate the risk of spontaneous PTB.

Differential impact of antiretroviral therapy initiated before or during pregnancy on placenta pathology in HIV-positive women

OBJECTIVE

To examine the association between timing of antiretroviral treatment (ART) initiation in HIV-infected women and placental histopathology.

DESIGN

A nested substudy in a larger cohort of HIV-infected women which examined the association between ART status and birth outcomes.

METHODS

Placentas (n = 130) were examined for histopathology from two ART groups: stable (n = 53), who initiated ART before conception and initiating (n = 77), who started ART during pregnancy [median (interquartile range) 15 weeks gestation (11-18)]. Using binomial regression we quantified associations between ART initiation timing with placental histopathology and pregnancy outcomes.

RESULTS

One-third of all placentas were less than 10th percentile weight-for-gestation and there was no significant difference between ART groups. Placental diameter, thickness, cord insertion position and foetal-placental weight ratio were also similar by group. However, placentas from the stable group showed increased maternal vascular malperfusion (MVM) (39.6 vs. 19.4%), and decreased weight (392 vs. 422 g, P = 0.09). MVM risk was twice as high [risk ratios 2.03 (95% confidence interval: 1.16-3.57); P = 0.01] in the stable group; the increased risk remaining significant when adjusting for maternal age [risk ratios 2.04 (95% confidence interval: 1.12-3.72); P = 0.02]. Furthermore, MVM was significantly associated with preterm delivery and low birth weight (P = 0.002 and <0.0001, respectively).

CONCLUSION

Preconception initiation of ART was associated with an increased MVM risk, and may contribute to placental dysfunction. The association between MVM with preterm delivery and low birth weight suggests that a placenta-mediated mechanism likely links the putative association between long-term use of ART and adverse birth outcomes.

Maternal HIV, antiretroviral timing, and spontaneous preterm birth in an urban Zambian cohort: the role of local and systemic inflammation

OBJECTIVE

To assess plasma and vaginal inflammation in three antenatal groups (HIV-uninfected women, HIV-infected women entering care on preconceptional ART, and HIV-infected women not on preconceptional ART) and whether these measures are associated with spontaneous preterm birth (sPTB).

DESIGN

Case--control study nested within a pregnancy cohort in Lusaka, Zambia.

METHODS

We analyzed 11 pro-inflammatory and two anti-inflammatory markers in 207 women with paired plasma and vaginal specimens collected between 16 and 20 gestational weeks. Among 51 HIV-infected women, we repeated the assays in 24-34-week samples. We used confirmatory factor analysis to create inflammation scores and compared them among the three groups.

RESULTS

At baseline, HIV-infected women not on ART had higher vaginal pro-inflammatory scores than HIV-uninfected women [mean 0.37 (95% CI -0.06 to 0.80) vs. -0.02 (-0.32 to 0.27), P = 0.02]. In repeat testing, women not on preconceptional ART had an increase in vaginal inflammation between the baseline and 24-34-week visits compared with those continuing preconceptional ART [mean 0.62 (95% CI -0.80 to 4.20) vs. -0.07 (-2.78 to 2.11), P = 0.04]. In multivariate analyses, baseline vaginal inflammation predicted sPTB (aOR 1.5; 95% CI 1.0-2.3; P = 0.02). Plasma inflammation did not differ by HIV or ART exposure and was not associated with sPTB.

CONCLUSION

Women not receiving ART at entry into pregnancy care had more vaginal inflammation than women entering on treatment. They also experienced an increase in vaginal inflammation between the two sampling timepoints, possibly as a consequence of ART initiation. Vaginal (but not systemic) inflammation was associated with sPTB and offers a potential mechanistic insight into this important adverse birth outcome.

Use of Antiretroviral Therapy During Pregnancy and Adverse Birth Outcomes Among Women Living With HIV-1 in Low- and Middle-Income Countries: A Systematic Review

BACKGROUND

Worldwide, nearly 18 million women of reproductive age are living with HIV-1. Although increased access to antiretroviral therapy (ART) during pregnancy has significantly reduced HIV-1 mother-to-child transmission (MTCT), a similarly robust reduction in preterm birth (PTB) and low birthweight (LBW) among infants born to women living with HIV has not been observed. This study was designed to identify associations between classes of ART regimens and risk of PTB or LBW.

SETTING

Low- and middle-income countries.

METHODS

We conducted a systematic review of randomized and observational studies that assessed the effect of ART regimen on the risk of PTB (≤37 completed weeks of gestation) or LBW (<2500 g at birth) among pregnant women in low- and middle-income countries living with HIV-1. We searched Medline, COCHRANE, Web of Science, SCOPUS, and CPCI-S for included studies.

RESULTS

When compared to monotherapy, both nonnucleoside reverse transcriptase inhibitor- and protease inhibitor-based regimens had a consistent, harmful association with LBW. There is mixed evidence suggesting both potential harm and potential benefit for most other regimens on risk of LBW and PTB, and the harmful or protective effects of certain regimens varies depending on the drug backbone.

CONCLUSIONS

Although the benefits of ART during pregnancy for prevention of MTCT are undisputed, this systematic review indicates that ART regimens vary substantially in their association with LBW and PTB. Although challenging, optimization of ART regimens could simultaneously promote maternal health, prevent MTCT, and also minimize risks of PTB and LBW.

Birth outcomes following antiretroviral exposure during pregnancy: Initial results from a pregnancy exposure registry in South Africa

Background

In 2013, a pregnancy exposure registry and birth defects surveillance (PER/BDS) system was initiated in eThekwini District, KwaZulu-Natal (KZN), to assess the impact of antiretroviral treatment (ART) on birth outcomes.

Objectives

At the end of the first year, we assessed the risk of major congenital malformations (CM) and other adverse birth outcomes (ABOs) detected at birth, in children born to women exposed to ART during pregnancy.

Method

Data were collected from women who delivered at Prince Mshiyeni Memorial Hospital, Durban, from 07 October 2013 to 06 October 2014, using medicine exposure histories and birth outcomes from maternal interviews, clinical records and neonatal surface examination. Singleton births exposed to only one ART regimen were included in bivariable analysis for CM risk and multivariate risk analysis for ABO risk.

Results

Data were collected from 10 417 women with 10 517 birth outcomes (4013 [38.5%] HIV-infected). Congenital malformations rates in births exposed to Efavirenz during the first trimester (T1) (RR 0.87 [95% CI 0.12–6.4; p = 0.895]) were similar to births not exposed to ART during T1. However, T1 exposure to Nevirapine was associated with the increased risk of CM (RR 9.28 [95% CI 2.3–37.9; p = 0.002]) when compared to the same group. Other ABOs were more frequent in the combination of HIV/ART-exposed births compared to HIV-unexposed births (29.9% vs. 26.0%, adjusted RR 1.23 [1.14–1.31; p < 0.001]).

Conclusion

No association between T1 use of EFV-based ART regimens and CM was observed. Associations between T1 NVP-based ART regimen and CM need further investigation. HIV- and ART-exposed infants had more ABOs compared to HIV-unexposed infants.

HIV serostatus, viral load, and midtrimester cervical length in a Zambian prenatal cohort

OBJECTIVE

To evaluate whether maternal HIV serostatus and plasma viral load (VL) are associated with midtrimester cervical length (CL).

METHODS

The Zambian Preterm Birth Prevention Study (ZAPPS) is an ongoing prospective cohort that began enrolling in Lusaka in August 2015. Pregnant women undergo ultrasound to determine gestational age and return for CL measurement at 16-28 weeks. We evaluated crude and adjusted associations between dichotomous indicators and short cervix (≤2.5 cm) via logistic regression, and between VL and CL as a continuous variable via linear regression.

RESULTS

This analysis includes 1171 women enrolled between August 2015 and September 2017. Of 294 (25.1%) HIV-positive women, 275 (93.5%) had viral load performed close to CL measurement; of these, 148 (53.8%) had undetectable virus. Median CL was 3.6 cm (IQR 3.5-4.0) and was similar in HIV-infected (3.7 cm, IQR 3.5-4.0) versus uninfected (3.6 cm, IQR 3.5-4.0) participants (P=0.273). The odds of short CL were similar by HIV serostatus (OR 0.64; P=0.298) and detectable VL among those infected (OR 2.37, P=0.323). We observed no association between log VL and CL via linear regression (-0.12 cm; P=0.732).

CONCLUSION

We found no evidence of association between HIV infection and short CL.

Nucleoside reverse transcriptase inhibitor backbones and pregnancy outcomes

OBJECTIVES

The aim of this study was to investigate whether specific nucleoside reverse transcriptase inhibitor (NRTI) backbones are associated with risk of adverse pregnancy outcomes among pregnant women starting antiretroviral therapy (ART).

DESIGN

Seven observational studies across eight European countries of pregnancies in HIV-positive women.

METHODS

Individual-level data were pooled on singleton pregnancies conceived off-ART in which a single combination ART regimen was initiated at least 2 weeks before delivery, and ending in a live birth in 2008-2014. Preterm delivery (PTD) was defined as less than 37 gestational weeks and small-for-gestational-age (SGA) as less than 10th percentile according to INTERGROWTH standards. Poisson regression models were fitted to investigate associations between NRTI backbones and PTD/SGA.

RESULTS

Out of 7193 pregnancies, 45% (3207) were in UK/Ireland, 44% (3134) in Ukraine. 10% (722/7193) of deliveries were preterm and 11.1% (785/7089) of newborns SGA. The most common NRTI backbones were zidovudine (ZDV)-lamivudine (3TC) (71%), tenofovir (TDF)-XTC (16%) and abacavir (ABC)-3TC (10%) with TDF-containing backbone use increasing over time. Overall, 77% of regimens contained ritonavir-boosted lopinavir (LPV/r). There was no association between NRTI backbone and PTD in main adjusted analyses [adjusted prevalence ratios (aPRs) 0.97 (95% confidence interval, 95% CI 0.73-1.28] for ABC-3TC and aPR 1.06 (95% CI 0.83-1.35) for TDF-XTC, both vs. ZDV-3TC) or in 4720 pregnancies on LPV/r [aPR 1.03 (95% CI 0.74-1.43) for ABC-3TC and aPR 1.16 [0.85-1.57] for TDF-XTC, both vs. ZDV-3TC]. Infants exposed to ABC-3TC or TDF-XTC in utero were less likely to be SGA than those exposed to ZDV-3TC [aPR 0.72 (95% CI 0.53-0.97) and aPR 0.70 (95% CI 0.53-0.93), respectively].

CONCLUSION

Results support the safety of TDF-XTC backbones initiated in pregnancy with respect to gestation length and birthweight.

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

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.