In women with HIV-1 infection, immune function declines through the natural course of HIV-1 disease. Pregnancy is common among HIV-1–infected women, and the interaction between HIV-1 and pregnancy has been a topic of biological and behavioral investigation.1,2 During pregnancy, changes to the maternal immune system, including decreased levels of circulating CD4 lymphocytes, are normal.3 It is important to understand how these natural changes may be impacted by HIV-1 infection and whether any deleterious effects are sustained postpartum.
Studies examining the long-term impacts of pregnancy on HIV-1 disease progression before the initiation of antiretroviral therapy (ART) have used different methods and come to inconsistent conclusions.4–7 A meta-analysis of 8 studies concluded that there may be a moderate increase in the risk of an AIDS-defining illness during pregnancy, especially in developing countries.5 A more recent study used a prediction model to estimate that, although HIV-1–infected ART-naive women who became pregnant generally had higher CD4 counts than women who did not become pregnant (ie, a “healthy woman” effect), the rate of CD4 count decline was greater after pregnancy, and this more rapid rate was predicted to be sustained in the years following pregnancy.8 Studies of women using ART, however, have not seen any indication of accelerated progression to death or AIDS stemming from pregnancy.9 For women who have not initiated ART before or during pregnancy, it remains unknown whether pregnancy results in sustained declines in immune function (measured through CD4 count) and increases in virologic replication (measured by plasma HIV-1 RNA concentrations), which would have effects after pregnancy.
Given high fertility rates among some populations of HIV-1–infected women, particularly in high prevalence settings such as sub-Saharan Africa, understanding the effects of pregnancy on HIV-1 disease progression is a public health priority.1,10 In a large cohort of women from southern and eastern Africa with chronic HIV-1 infection, we evaluated the effect of pregnancy on CD4 counts and plasma HIV-1 RNA concentrations and whether any changes in these markers were sustained in the first year after pregnancy.
Between 2004 and 2008, we conducted a randomized clinical trial of acyclovir to prevent HIV-1 transmission from 3408 individuals dually infected with HIV-1 and herpes simplex virus type 2 to their HIV-1–uninfected sexual partners (the Partners in Prevention HSV/HIV Transmission Study).11 Participants were enrolled at 14 sites in 7 countries (Botswana, Kenya, Rwanda, South Africa, Tanzania, Uganda, and Zambia) in southern and eastern Africa. At enrollment, HIV-1–infected participants were aged at least 18 years, sexually active with their study partner, not pregnant, not using ART, without AIDS-defining conditions, and had a CD4 count ≥ 250 cells/mm3. HIV-1–infected members of these HIV-1 serodiscordant partnerships were randomized 1:1 to receive acyclovir (400 mg orally twice daily) or matching placebo and followed up monthly for up to 24 months. In the final study analysis, acyclovir did not reduce the risk of HIV-1 transmission but it did result in a 0.25 log10 copies per milliliter [95% confidence interval (CI): 0.22 to 0.29; P < 0.001] decrease in plasma HIV-1 RNA concentrations and a modest decline in the rate of HIV-1 disease progression for the HIV-1–infected partners.12,13
For this analysis, HIV-1–infected women (2269 of the 3408 HIV-1–infected participants in the trial) were included. Participants attended monthly clinic visits for study drug provision and HIV-1 care services, including individual and couples risk reduction counseling, free condoms, and treatment of sexually transmitted infections. Women who became eligible for ART use according to national guidelines at the time were referred to nearby clinics to receive treatment. Data on ART use and clinical symptoms were collected using interviewer-administered questionnaires. Women who became pregnant during follow-up had study drug (acyclovir or placebo) withheld during pregnancy.
CD4 counts were measured every 6 months using FacsCount or FacsCalibur instrumentation (BD Biosciences, San Jose, CA), and plasma HIV-1 RNA concentrations were measured quarterly during the first year of follow-up and every 6 months thereafter using the COBAS TaqMan real-time HIV-1 RNA assay, version 1.0 (Roche Diagnostics, Indianapolis, IN) with 240 copies per milliliter being the lower limit of quantification. Of all CD4 count measurements conducted, 7412 (77.1%) were from women who did not become pregnant during the study, 225 (2.4%) were from the first trimester of pregnancy, 200 (2.1%) from the second trimester, 108 (1.1%) from the third trimester, and 546 (6.8%) were from postpartum period.
Measurement of Pregnancy
Urine pregnancy tests were performed at enrollment and during quarterly study visits. Date of last menstrual period (LMP), estimated date of delivery, and pregnancy outcome were collected with standardized questionnaires. We defined the start of pregnancy as the date of LMP and the end of pregnancy as the date of delivery or pregnancy loss. Complete data on LMP and date of delivery were available for 96% pregnancies observed during the study; for the remaining pregnancies, we estimated start and end dates using the reported duration of the pregnancy (based on maternal history) and either the LMP or date of delivery.
We used linear mixed effects models with a random intercept and a compound symmetry correlation structure to estimate the average difference in CD4 count and plasma HIV-1 RNA levels during several time periods: pregnancy, postpartum (the time following pregnancy), nonpregnant periods (all follow-up time for women who did not become pregnant and the time before the first pregnancy for women who became pregnant), and the time before the first pregnancy for women who became pregnant (the “prenatal” period). We performed analyses first for all women in the study and compared CD4 and plasma HIV-1 RNA levels among pregnant versus nonpregnant and postpartum periods and postpartum and nonpregnant periods. We then repeated the analyses restricted only to women who experienced pregnancy during the study (thus comparing prenatal, pregnant, and postpartum periods among these women). All models accounted for time on study. For women who had multiple pregnancies, the time between pregnancies was considered postpartum time since second pregnancies occurred a median of 5.8 months after the first pregnancy ended.
Follow-up time was censored in all analyses when women initiated multidrug ART (3.1% of study time); we did not censor for single- or dual-drug ART use that was associated only with pregnancy (eg, single-dose nevirapine use) because it is unlikely that limited duration ART would have substantial impact on subsequent CD4 counts or plasma HIV-1 RNA levels. We determined a priori that full multivariate models would be adjusted for the enrollment CD4 count or plasma HIV-1 RNA concentration. Additional adjustment accounted for treatment arm (acyclovir or placebo) and study drug dispensing (any or none), to account for the effect of acyclovir on reductions in plasma HIV-1 RNA concentration, increases in CD4 count, and that study drug was discontinued during pregnancy. Using the same statistical modeling methods, we conducted separate sensitivity analyses to account for early pregnancy losses (by excluding pregnancies that terminated at <20 weeks) and multiple pregnancies in a single woman (by including only these pregnancies) that may have a different impact on disease progression. SAS 9.3 (Cary, NC) was used for all analyses.
For the 2269 women enrolled, the median age was 30 years [interquartile range (IQR)], 25.3–34.8 years; Table 1). Most women were married with a median of 2 children and 8 years of education. In the month before enrollment, women reported a median of 4 (IQR, 2–8) sex acts with their study partner and 28.7% women reported having unprotected sex. The median CD4 count was 483 (IQR, 355–663) cells/mm3, 472 (IQR, 348–655) cells/mm3 among women who did not go on to have a pregnancy, and 507 (IQR, 378–689) cells/mm3 among women who later became pregnant. The median plasma HIV-1 RNA concentration was 3.9 (IQR, 3.2–4.5) log10 copies per milliliter.
Pregnancy During Follow-Up
During follow-up for this analysis, 476 (21.0%) women became pregnant (29 women had more than 1 pregnancy), and the pregnancy incidence rate was 15.4 per 100 person years (505 pregnancies/3270 years); 7.2% of total follow-up time was during pregnant periods and 6.8% was during postpartum periods. Women who became pregnant contributed a median of 7.2 (IQR, 4.0–13.0) months of time during the prenatal period, 7.1 (IQR, 3.1–9.0) months pregnant, and 7.9 (IQR, 4.0–11.9) months “postpartum,” between the end of pregnancy and study exit. Two hundred nineteen (43.4%) pregnancies ended in a live birth, 144 (28.5%) pregnancies ended in a pregnancy loss, 3 (0.60%) were ectopic pregnancies, 133 (26.3%) were ongoing at the time of study completion, and the outcome was unknown for 6 (1.2%) pregnancies. Of pregnancies that ended in a pregnancy loss, 114 (79.2%) ended before reaching 20 weeks gestation. ART was used during 177 of 219 (80.8%) pregnancies that resulted in a live birth, including single- and dual-drug regimens during delivery for 102 of 219 (46.6%) pregnancies and multidrug ART during the pregnancy for 75 of 219 (34.3%) pregnancies.
Effect of Pregnancy on CD4 Counts and Plasma HIV-1 RNA Concentrations
In the fully adjusted model, CD4 counts were lower during pregnant than nonpregnant periods (average difference in CD4 count: 56 cells/mm3, 95% CI: 39 to 73) and postpartum periods (average difference in CD4 count: 70 cells/mm3, 95% CI: 53 to 88; Table 2). The average CD4 count was similar, however, during postpartum periods and nonpregnant periods (P = 0.1). HIV-1 RNA concentration did not statistically differ between pregnant and nonpregnant periods (P = 0.9) nor pregnant and postpartum periods (P = 0.3). Before full adjustment, we observed a moderately higher level of plasma HIV-1 RNA concentration during pregnancy relative to the postpartum period (average difference in plasma HIV-1 RNA concentration = 0.07, 95% CI: 0.01 to 0.03). This difference was no longer present, however, after adjusting for randomization arm and pill dispensing suggesting that the unadjusted association was a result of the effect of acyclovir to reduce plasma HIV-1 levels.12
When limited to the subgroup of women who became pregnant, CD4 counts were lower during pregnancy than during prenatal periods (adjusted average difference in CD4 count = 51 cells/mm3, 95% CI: 30 to 72) or postpartum periods (adjusted average difference in CD4 count = 70 cells/mm3, 95% CI: 51 to 90). Consistent with the results for the cohort as a whole, there was no difference in CD4 counts between prenatal and postpartum periods (P = 0.1). Plasma HIV-1 RNA concentration levels were similar across comparisons of pregnant and prenatal (P = 0.7), pregnant and postpartum (P = 0.7), and prenatal and postpartum (P = 0.9) periods.
To account for early pregnancy losses that may have a different impact on disease progression than full-term pregnancies, we conducted a sensitivity analysis that excluded pregnancies that were <20 weeks duration by censoring follow-up time at the beginning of a pregnancy that ended in an early loss (9.3% of pregnant and 5.7% of postpartum follow-up). The results from this were not different from the primary results. In a separate sensitivity analysis, we limited the data set to 29 women who experienced multiple pregnancies during the study and saw similar changes to CD4 count but no sustained change in postpartum periods and no change in HIV-1 RNA concentration (data not shown).
In this prospective study of African women with chronic HIV-1 infection, we found that CD4 counts were lower during pregnancy than during prenatal and nonpregnant periods but these lower CD4 counts were not sustained in the postpartum period. Thus, a drop in CD4 count that is commonly experienced by HIV-1–infected women during pregnancy does not seem to result in sustained immunologic effects during the first year after pregnancy. Our results are consistent with the process of hemodilution during pregnancy and a return to previous immune function levels following the end of pregnancy.3 These findings suggest that pregnancy does not result in subsequent accelerated HIV-1 disease progression by affecting immune function or by increasing HIV-1 levels, as minor changes were not sustained postpartum.
Our study is limited by the length of time women were followed up postpartum. Furthermore, investigation is required to understand whether the immunologic rebound that we observed is maintained in the years after the pregnancy, as was demonstrated in a recent prediction model.4 An additional consideration is whether breastfeeding periods have a different level of influence on immune function or viral levels; we did not record the duration of breastfeeding in this study. This question is difficult to study because women who become pregnant are different than women who do not become pregnant, and thus traditional survival analysis with time-limited follow-up data may suffer from selection bias. We conducted sensitivity analyses to restrict our data to “healthy pregnancies” and then to look at women with multiple pregnancies, with similar results. We chose to use a linear mixed model to examine the difference in disease progression markers, in lieu of defining a threshold endpoint, which can suffer from survival bias if exposure groups are defined based on a future experience (ie, pregnancy).14
Pregnancy is common among women living with HIV-1, especially after ART initiation, which often brings restored health and fertility desire.15–17 Although there seems to be little risk of pregnancy accelerating a woman’s HIV-1 disease progression, becoming pregnant indicates a lack of condom use before pregnancy and potential risk of HIV-1 transmission to an uninfected male partner. In addition, pregnant periods are often accompanied by less frequent condom use.1,18 Unintended pregnancy is often associated with increased morbidity and mortality and a priority for programs to prevent mother-to-child HIV-1 transmission.19 Integrated reproductive health programs that proactively engage couples to consider their fertility intentions and use effective contraception until fertility is desired, plan future pregnancies, and incorporate HIV-1 prevention are of public health importance.20 Planning allows couples to use low technology harm reduction strategies to reduce the risk of HIV-1 transmission to the uninfected male partner—strategies include unprotected sex timed to peak fertility days, self-insemination, ART, PrEP use, male circumcision, and treatment of sexually transmitted infections—and use ART to prevent vertical transmission.21,22 Couples have indicated a desire for knowledge and discussions about these options with health care workers and willingness to use them.23
In 2012, the World Health Organization recommended that national prevention of mother-to-child transmission (PMTCT) programs consider multidrug ART initiation during pregnancy followed by lifelong use for HIV-1–infected women to achieve HIV-1 viral suppression, prevent maternal to child HIV-1 transmission, and maintain their health during pregnancy and thereafter (ie, Options B or B+).24 PMTCT guidelines, including the duration and complexity of ART prophylaxis regimens, have evolved rapidly since the first WHO guidelines were published in 2000.25 Twenty percent of pregnancies in our study did not have ART prophylaxis during the pregnancy or at delivery, which likely reflects programmatic challenges and the gradual implementation of ART in PMTCT programs during 2004–2008 when our data were collected.25 ART use during and after pregnancy is a critical public health strategy to reduce vertical HIV-1 transmission and to provide clinical benefits to the mother, but resources, health system factors, and personal factors provide challenges for universal implementation and retention in ART programs.26,27 In addition, many women decline ART initiation when it is first recommended or experience system delays when trying to start.
Our data support the conclusion that, even before ART initiation, CD4 declines during pregnancy are modest and short term for women with HIV-1 infection. As PMTCT guidelines evolve to increase coverage of ART in pregnant women, more emphasis and strategies are needed to improve ART initiation and continuation rates among women who become pregnant to ensure their maximum health status and favorable birth outcomes.
The authors thank the couples who participated in this study and the teams at the study sites and at the University of Washington for study on data and sample collection and management.
Partners in Prevention HSV/HIV Transmission Study Team: University of Washington Coordinating Center and Central Laboratories, Seattle, WA: Connie Celum (Principal Investigator), Anna Wald (Protocol Co-Chair), Jairam Lingappa (Medical Director), Jared M. Baeten, Mary Campbell, Lawrence Corey, Robert W. Coombs, James P. Hughes, Amalia Magaret, M. Juliana McElrath, Rhoda Morrow, James I. Mullins.
Study sites and site principal investigators: Cape Town, South Africa (University of Cape Town): David Coetzee; Eldoret, Kenya (Moi University, Indiana University): Kenneth Fife, Edwin Were; Gaborone, Botswana (Botswana Harvard Partnership): Max Essex, Joseph Makhema; Kampala, Uganda (Infectious Disease Institute, Makerere University): Elly Katabira, Allan Ronald; Kigali, Rwanda (Rwanda Zambia HIV Research Group, and Emory University): Susan Allen, Kayitesi Kayitenkore, Etienne Karita; Kisumu, Kenya (Kenya Medical Research Institute, University of California San Francisco): Elizabeth Bukusi, Craig Cohen; Kitwe, Zambia (Rwanda Zambia HIV Research Group, and Emory University): Susan Allen, William Kanweka; Lusaka, Zambia (Rwanda Zambia HIV Research Group, and Emory University): Susan Allen, Bellington Vwalika; Moshi, Tanzania (Kilimanjaro Christian Medical College, Harvard University): Saidi Kapiga, Rachel Manongi; Nairobi, Kenya (University of Nairobi, University of Washington): Carey Farquhar, Grace John-Stewart, James Kiarie; Ndola, Zambia (Rwanda Zambia HIV Research Group, and Emory University): Susan Allen, Mubiana Inambao; Orange Farm, South Africa (Reproductive Health Research Unit, University of the Witwatersrand): Sinead Delany-Moretlwe, Helen Rees; Soweto, South Africa (Perinatal HIV Research Unit, University of the Witwatersrand): Guy de Bruyn, Glenda Gray, James McIntyre; Thika, Kenya (University of Nairobi, University of Washington): Nelly Rwamba Mugo.
Data management was provided by DF/Net Research, Inc. (Seattle, WA) and site laboratory oversight was provided by Contract Lab Services (University of the Witwatersrand, Johannesburg, South Africa).
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