High prevalence of adverse drug reactions among oral contraceptive pill users in Western India: a prospective observational study

Oral contraceptive (OC) pills are among the most widely prescribed hormonal preparations globally, yet prospective adverse drug reaction (ADR) surveillance data from the Indian subcontinent remain sparse. This prospective observational study aimed to estimate the prevalence, spectrum, and temporal pattern of ADRs among OC pill users at a tertiary care gynecology outpatient department and affiliated private clinics in Pune, Western India. A total of 201 women aged 18–60 years prescribed OC pills for contraceptive or non-contraceptive indications were enrolled; 130 were new initiators and 71 were existing users. Participants were followed for 3 months, with ADRs documented at three pre-specified time points anchored to the date of OC pill initiation. Of 201 participants, 179 (89.05%; 95% Wilson confidence interval: 83.98%–92.66%) experienced at least one ADR, with a mean of 1.87 ± 1.06 ADRs per participant. Nausea was the most frequently reported ADR (62.69%), followed by weight gain (25.87%), breast pain (24.88%), vomiting (22.39%), and headache (19.90%). A notable 87.06% of participants used OC pills for non-contraceptive therapeutic purposes, with polycystic ovary syndrome as the predominant indication (36.82%). Among new initiators, a distinct biphasic temporal pattern was observed: early-onset gastrointestinal ADRs—particularly nausea and vomiting—resolved completely by the third month, while weight gain emerged as a persistent late-onset effect. On multivariable analysis, reported weight gain was independently associated with baseline overweight/obese status rather than with polycystic ovary syndrome or OC pill formulation. Serious ADRs were rare, with no thromboembolic events recorded. These findings demonstrate a high ADR burden among OC pill users in an Indian clinical setting, predominantly driven by transient gastrointestinal symptoms, and highlight the importance of anticipatory counseling on the biphasic ADR trajectory, and prospective pharmacovigilance in guiding individualized prescribing.