Do more injections to prevent premature ovulation mean a lower chance of pregnancy in IVF? An observational study of 3,764 women found no clear adverse association between total GnRH antagonist dose and pregnancy outcomes.
The researchers compared implantation, pregnancy and miscarriage outcomes across doses. Their findings support tailoring ovarian stimulation to each patient's response, rather than judging treatment by the number of injections alone.
For women preparing for IVF, ovarian stimulation and ovulation-suppressing injections can be familiar but burdensome parts of treatment. When follicles grow more slowly than expected and additional antagonist injections are needed, some patients worry that their chances of pregnancy may be affected.
Researchers at the Center for Reproductive Medicine, Xiangya Hospital, Central South University in China analyzed treatment outcomes in 3,764 women who received gonadotropin-releasing hormone antagonists and found no clear negative association between total dose and pregnancy outcomes.
The study was published in Reproduction & Fertility on October 15, 2026.
Why are ovulation-suppressing injections used in IVF?
IVF stimulates the ovaries to obtain multiple eggs. Ovulation before follicles have grown sufficiently can disrupt egg retrieval: eggs must be collected with a needle before they are released. GnRH antagonists help prevent premature ovulation.
Common agents include cetrorelix and ganirelix. They suppress the sudden surge of luteinizing hormone from the pituitary gland that could trigger ovulation before egg retrieval.
Some earlier studies raised the possibility that these drugs might affect endometrial receptivity—the ability of the uterine lining to accept an arriving embryo.
Whether longer treatment or a higher cumulative dose could adversely affect implantation and pregnancy has therefore been a clinical concern.
No clear worsening of pregnancy outcomes with higher total doses
The researchers examined total antagonist dose and pregnancy outcomes in 3,764 women who underwent antagonist-based ovarian stimulation followed by embryo transfer.
Participants were grouped by the total dose used during stimulation, and outcomes including implantation, pregnancy and miscarriage were compared.
There was no clear trend toward poorer pregnancy outcomes as total dose increased. Women receiving relatively higher doses did not show a consistent reduction in their chance of pregnancy.
Receiving several antagonist injections alone therefore does not establish that implantation or pregnancy has been adversely affected.
This does not mean pregnancy rates were identical at every dose. The key finding was the absence of a statistically clear adverse association between total drug exposure and pregnancy outcomes.
Ovarian response matters more than injection count alone
The study highlights the importance of individualized ovarian stimulation.
Women undergoing IVF differ in age, ovarian reserve, hormone levels and follicular growth. Even with the same stimulation drug, follicles can grow at different rates, affecting the duration and total dose of antagonist treatment.
Some women need antagonist treatment for only a short period; others may require it for longer depending on follicular development.
More injections may therefore reflect ovarian response and the treatment schedule. Injection count alone cannot determine whether stimulation was appropriate or predict the likelihood of pregnancy.
Clinicians need to consider ultrasound findings, hormone levels and follicular growth together when deciding when to start antagonist treatment and how long to continue it.
The findings provide evidence relevant to adjusting antagonist use to an individual's ovarian response.
The findings do not mean doses can be increased without limits
The results should not be read as permission to increase antagonist doses freely.
This was an observational study of the relationship between total dose and pregnancy outcomes. It did not establish a causal conclusion that higher doses have no effect on those outcomes.
Timing and duration matter. Because treatment depends on follicular growth and hormonal changes, patients should not independently change the number of injections or the dose.
IVF success is influenced by age, ovarian function, egg quality, embryo development and the endometrial environment. Total antagonist dose should be assessed within that wider treatment context.
The researchers interpreted their findings as supporting treatment strategies that adjust GnRH antagonist use to individual ovarian response.
The important issue is therefore not simply how many injections were given, but whether the medication was used at appropriate times for the patient's response, allowing treatment to proceed through egg retrieval and embryo transfer.
Source: Fen Tian, Bin Xu, Yanping Li, Jing Zhao and colleagues, Center for Reproductive Medicine, Xiangya Hospital, Central South University. “Association between the total dosage of gonadotropin-releasing hormone antagonist during controlled ovarian stimulation and pregnancy outcomes.” Reproduction & Fertility, October 15, 2026. Observational analysis of IVF data from 3,764 women. DOI: 10.1530/RAF-26-0049. PMID: 42886833.
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