Biochemical Pregnancy and IVF

Reviewed by: Katherine Moran, MD MBA

What is biochemical pregnancy in IVF?

  • Biochemical pregnancy is also known as “chemical pregnancy”, or “pre-clinical embryo loss.” [1]

  • After embryo transfer, if implantation occurs, the developing embryo begins to secrete human chorionic gonadotropin (β-hCG); more β-hCG gets released once the embryo begins to implant. If enough β-hCG is produced, it can be detected by a blood test. Biochemical pregnancy for IVF is after the initial positive blood test, there’s a rapid fall in urinary or serum β-hCG concentration, and lack of substantial delay in onset of the next menstrual period. [1][2]

  • If imaging is available to help with the diagnosis, another way to think about this is having an increased β-hCG production without later ultrasound evidence of a gestational sac (~6-7 weeks). [3]

  • Ultimately a biochemical pregnancy is an early miscarriage before a gestational sac can even be seen on ultrasound (which is around the 5th week of gestation). [1]

What is the incidence of biochemical pregnancy in IVF?

  • The incidence of biochemical pregnancy for fresh and frozen embryo transfer cycles combined was 13.8% of all pregnancies. [4]

  • The incidence of biochemical pregnancy is similar between frozen and fresh embryo transfers. [4]

  • The rate of biochemical pregnancies for IVF is similar to that of the fertile population not requiring IVF. [4]

Why does biochemical pregnancy occur?

The exact mechanism of why biochemical pregnancy occurs is largely unknown, however, there was an article published in 2018 that looked into recurrent biochemical pregnancies and maternal factors. [5]

  • Maternal age: biochemical pregnancy rates were significantly higher in women 35 or older compared to less than 35 (28.1% vs. 14.9% respectively) [5]

  • BMI: patients with class III obesity (BMI > 40 kg/m2) had the highest overall rates of biochemical pregnancy with up to 68% lower odds of having a live birth compared to patients with a BMI < 30 kg/m2. [5][6]

  • Anti-phospholipid syndrome (APLAS): APLAS is an autoimmune condition associated with higher rates of biochemical pregnancy and miscarriage. Diagnosis is made by checking auto-antibodies against anti-cardiolipin, beta-3-glycoprotein and lupus anticoagulant. Women who are diagnosed with this condition are often treated with aspirin and a blood thinner (Lovenox or heparin). [5]

What symptoms will you have with a biochemical pregnancy?

  • Typically, you will not have any symptoms of early pregnancy (such as breast tenderness, fatigue, or nausea), but your period may be a few days late and it can be heavier with more cramping than usual.

What does it mean for the future pregnancies and live birth rates?

  • While a biochemical pregnancy is a heart-breaking thing to go through, your overall prognosis for successful pregnancy is high. Studies have demonstrated that having a positive β-hCG means that the embryo implantation process did start, and this means that the prognosis for a healthy pregnancy in the future is better than for someone with a negative β-hCG. [7]

Last Reviewed: September 21, 2023