Prior hormonal contraceptive use and preeclampsia in Angola: a hospital- based, individually matched case–control study
This hospital-based case-control study in Angola found that prior hormonal contraceptive use was associated with higher odds of preeclampsia, particularly for depot medroxyprogesterone acetate and recent discontinuation, though the authors caution that bias may explain part of this association and recommend prospective confirmation before altering counseling guidelines.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Pregnancy is a time of profound change for a woman's body, but for some, it brings a dangerous complication called preeclampsia. This condition causes blood pressure to rise sharply and can damage organs, posing serious risks to both mother and baby. While doctors know that factors like a woman's age, weight, and family history play a role, the origins of the disease are not fully understood. Scientists have long wondered if the choices a woman makes before becoming pregnant might influence her risk. Specifically, they have looked at hormonal contraceptives—medications like the pill or injections that prevent pregnancy by altering the body's chemistry. These drugs are known to affect blood pressure and metabolism while a woman is taking them, but it remains unclear whether those effects linger after she stops using them and becomes pregnant. In many parts of the world, particularly in sub-Saharan Africa, injectable contraceptives are the most common method used, yet there has been almost no research on whether using them in the past changes the odds of developing preeclampsia later.
To answer this question, a team of researchers in Angola conducted a detailed investigation at the main referral hospital in the province of Benguela. They focused on a specific group of women: those who had just been diagnosed with preeclampsia and a similar group of women who were pregnant but healthy. The study was designed to be very precise. For every woman with the condition, the researchers found two healthy women of the same age, with the same number of previous births, and at the same stage of pregnancy. This matching helped ensure that any differences found were likely due to the exposure being studied rather than other factors. The team then looked back at the medical history of all these women, asking them about their use of hormonal contraception before the current pregnancy. They did not just rely on memory; they cross-checked the women's stories against official family planning records whenever possible to confirm the details.
The results showed a clear pattern. Women who had used hormonal contraception before their pregnancy were more likely to develop preeclampsia than those who had never used it. Specifically, about one-third of the women with the condition had used these contraceptives, compared to less than one-fifth of the healthy women. When the researchers adjusted for other known risk factors like body weight and family history, the data suggested that prior use of hormonal contraception was associated with more than double the odds of developing the condition. The risk appeared highest for women who had used a specific type of injectable contraceptive called depot medroxyprogesterone acetate, often known by the brand name Depo-Provera, and for those who had stopped using the method less than three months before becoming pregnant.
However, the story is not as simple as a direct cause-and-effect relationship. The researchers were careful to test whether this link was real or if it was an illusion created by how the study was conducted. They found that the association became weaker when they looked only at women whose contraceptive use was confirmed by medical records rather than just their own memory. The link also faded when they excluded women who had been transferred to the hospital from other clinics, a group that might differ significantly from the general population. Furthermore, when they compared women who used hormonal methods to those who used non-hormonal methods, the difference was less clear. The study also found that the length of time a woman used the contraception did not seem to matter; the risk appeared similar whether she had used it for a short time or for many years.
Ultimately, the study suggests that there is an association between using hormonal contraception in the past and developing preeclampsia, but it cannot prove that the contraception causes the condition. The researchers suspect that factors such as how women access healthcare or why they choose certain birth control methods might explain part of the connection. Because the evidence is not definitive, the authors conclude that these findings should not change the advice doctors give to women about birth control. Hormonal contraceptives remain a vital tool for preventing unintended pregnancies, which saves lives. The researchers emphasize that more studies are needed, ideally following women from the moment they start using contraception through their pregnancies, to determine if there is a true causal link. For now, the data from Angola adds an important piece to the puzzle, highlighting a potential risk that requires further investigation rather than immediate alarm.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.