Factors Affecting In Vitro Fertilisation (IVF) Success Rates

Age

A woman's age has the most impact on IVF success. With age, both egg quantity and quality decline, reducing success rates.

“Age is the most important factor in determining when it comes to successful fertility treatments like IVF,” said Dr Yeong.

“Women below the age of 35 have a 26.6 percent chance of becoming pregnant through IVF. Those above 40 have only a 6.7 percent chance[1],” he added.

Further illustrating this point, a 2022 study found that the clinical pregnancy rate for women under 30 who'd undergone an embryo transfer was 69.4%, whereas, for women ages 40 to 43, that figure declined to 9.4%[2].

That said, age isn’t the only factor at play when it comes to success in IVF, which is defined as a live birth. Here’s a look at what else may play a role in IVF success.

Ovarian Reserves

During IVF, the ovaries are stimulated to yield multiple eggs, retrieved, fertilized in a lab, and then implanted back into the uterus, aiming for a successful pregnancy and birth.

But there is a finite number of eggs that your fertility doctor can work with.

A woman is born with all the eggs she will ever have; this supply doesn't replenish throughout her life. Fertility begins to decline around age 32, with a woman starting with about 1,000,000 eggs at birth, halving by puberty, and dropping to around 200,000 by her twenties. The decline accelerates with age, particularly in the thirties and forties, albeit at varying rates for each woman. The anti-Mullerian hormone (AMH) test is recommended to gauge fertility health status accurately. AMH, secreted by developing egg sacs, provides insight into egg count, with results unaffected by menstrual cycle timing.

Irregular menstrual cycles may signal hormonal imbalances or conditions like PCOS, warranting further evaluation. Those with conception difficulties or conditions like endometriosis should consider ovarian reserve testing.

While a lower ovarian reserve may present hurdles, it doesn't eliminate the chance of natural conception. Fertility hinges not only on egg quantity but also on quality. Even with a diminished reserve, viable, healthy eggs can lead to successful fertilisation and pregnancy.

Weight

Weight does determine the success of IVF treatments. Women who are underweight may have irregular menstrual cycles or even stop ovulating altogether. It can make it difficult to retrieve an adequate number of eggs during IVF procedures, reducing the chances of successful fertilisation and embryo implantation.

However, excess weight, particularly if you have a high BMI, can also decrease the chances of successful IVF outcomes[3].

Obesity is associated with hormonal imbalances, such as insulin resistance and elevated levels of certain hormones like leptin, which can disrupt ovulation and affect egg quality. Additionally, obesity is linked to a higher risk of conditions such as polycystic ovary syndrome (PCOS), which can further complicate fertility treatments.

“If we come across patients who are overweight, we normally advise that you try to lose at least five to ten percent of their current body weight to induce natural ovulation. That may be sufficient to help them achieve a pregnancy without anything at all,” Dr Yeong explained.

Lifestyle and Diet

Beyond age, egg supply, and weight, other factors influencing the success of IVF treatments are lifestyle and dietary choices.

“Studies have shown that consumption of coffee and tea with caffeine has to be moderated. It’s not to say to stop coffee completely but limit to not more than two cups of coffee and not more than three or four cups of tea a day,” Dr Yeong advised.

“There is clear evidence that smoking does impact the changes of pregnancy. Women who smoke tend to take a longer time to get pregnant, and even the number of eggs that we retrieve from them during IVF tends to be falling below our expectations," he added.

Regarding alcohol, Dr Yeong said that occasional social drinking is generally deemed acceptable, but heavy alcohol intake can compromise fertility outcomes. Therefore, it's advisable to limit alcohol consumption during IVF cycles. 

In summary, both partners should stop smoking, have a healthy BMI, minimise alcohol and caffeine intake, exercise regularly, and have a balanced diet. Women should also take 500mg of folic acid daily for at least three months before conception. 

Overall, prioritizing a healthy lifestyle and diet for both partners is essential to the IVF success rate. It includes maintaining a healthy body mass index (BMI), minimising alcohol and caffeine intake, engaging in regular physical activity, and following a balanced diet rich in essential nutrients. 

Additionally, women are advised to supplement with 500mg of folic acid daily for at least three months before attempting conception, as it can contribute to a healthy pregnancy outcome. 

When to See a Doctor

Ready to start a family now or in the future?

Generally, it’s recommended to see a doctor if you’ve been trying for a year and have not gotten pregnant (this guidance drops to six months for those over 35). Your doctor will order a fertility assessment to measure hormone levels and ovarian reserves for women and a semen analysis for men.

For a woman, a pelvic ultrasound may follow to check the condition of the endometrium (the lining of the womb) and diagnose any polyps or fibroids.

These assessments help identify underlying issues and guide personalized fertility treatment plans, improving the chances of successful conception and achieving your dream of parenthood.

[1] https://www.moh.gov.sg/news-highlights/details/response-to-adjournment-motion-on-providing-more-help-for-those-undergoing-ivf

[2] Adebayo FO, Ameh N, Adesiyun AG, Ekele BA, Wada I. Correlation of female age with the outcome of IVF in a low-resource setting. Int J Gynaecol Obstet. 2023 Apr;161(1):283-288. doi: 10.1002/ijgo.14545. Epub 2022 Nov 15. PMID: 36330818.

[3] Sermondade N, Huberlant S, Bourhis-Lefebvre V, Arbo E, Gallot V, Colombani M, Fréour T. Female obesity is negatively associated with live birth rate following IVF: a systematic review and meta-analysis. Hum Reprod Update. 2019 Jul 1;25(4):439-451. doi: 10.1093/humupd/dmz011. PMID: 30941397.