Comparing Low-dose vs conventional-dose ovarian stimulation for IVF

This review compared mild-dose ovarian stimulation (OS) for in vitro fertilization (IVF) to standard higher dose OS. It found that mild OS has fewer side effects and similar birth rates.

The first stage of the infertility treatment IVF is to stimulate the ovaries. The most common type of medication used is gonadotropin hormones, which are similar to the follicle-stimulating hormone (FSH) that is produced during a natural menstrual cycle. The high doses of gonadotropins used during OS can lead to the collection of multiple oocytes (eggs). However, there is debate among researchers whether these high doses lead to better pregnancy rates compared to milder doses. Mild dose IVF may lead to fewer but higher quality oocytes. 

Additionally, gonadotropins can cause side effects including ovarian hyperstimulation syndrome (OHSS). This occurs when the ovaries respond too strongly to treatment. Symptoms of OHSS include bloating and pain, and it can have serious complications. Mild dose OS can reduce OHSS and other side effects, making it easier on the body.

Not all patients respond to OS in the same way. People who produce few oocytes after gonadotropin treatment are said to have a poor response. In contrast, high responders have a higher risk of OHSS.

It is not clear whether mild dose OS has similar pregnancy outcomes to the conventional OS. It is also not clear whether this depends on whether the patient has a poor, normal, or high ovarian response.

This review included 31 studies of women undergoing IVF. Participants were randomly assigned to either mild dose (< 150 IU) or conventional dose (>150 IU) of gonadotropins. 

For patients with a poor ovarian response (POR), pregnancy rates were examined in 12 studies with 2211 patients. There was no difference in pregnancy rates based on ultrasound between conventional- and mild-dose OS. No difference was found between birth rates. The risk of OHSS was similar with both doses for patients with POR.

For patients with a normal ovarian response, seven studies were evaluated. There was no clear difference in the pregnancy rate between mild and conventional-dose OS. Also, no difference was found in birth rates. The risk of OHSS was significantly lower using mild-dose OS (74% lower risk) for patients with normal ovarian response.

Patients with high ovarian response had a similar birth rate between the two treatments, and a significantly lower risk of OHSS using mild-dose IVF (53% lower).

This review found similar birth rates and a lower risk of OHSS between conventional and mild-dose OS in women undergoing IVF. 

The studies analyzed had different protocols. The definition of poor, normal, and high responders was different among studies. This might have influenced the results.