In IVF (In Vitro Fertilization), how long after ovulation does the placenta start producing hormones in the absence of a functional corpus luteum?

Placental Hormone Production in IVF Pregnancies

In IVF pregnancies, the placenta begins producing sufficient progesterone to sustain pregnancy by approximately 6-8 weeks after conception (8-10 weeks gestational age), though this transition is often delayed compared to natural pregnancies, particularly when the corpus luteum is absent or suppressed. 1, 2

Timeline of Luteal-Placental Transition

Natural Pregnancy vs. IVF

• In spontaneous conceptions with a functional corpus luteum, the placenta gradually assumes progesterone production starting around 6-8 weeks post-conception, with the corpus luteum then regressing 1
• In IVF pregnancies, particularly those using GnRH agonist protocols that suppress corpus luteum function, the luteal-placental shift is significantly delayed 3
• Studies demonstrate that the luteal contribution to progesterone remains elevated throughout the first trimester in IVF pregnancies, obscuring the placental contribution for much longer than in natural pregnancies 3

Critical Early Pregnancy Period

• The corpus luteum provides essential progesterone support for the first 6-8 weeks of pregnancy before placental takeover 1
• In IVF cycles where normal hormones are suppressed, the corpus luteum does not produce adequate progesterone before the pregnancy test, necessitating exogenous supplementation 1
• A delay in implantation of approximately 1.3 days has been observed in pregnancies after GnRH agonist-HMG treatment compared to other stimulation protocols, related to temporarily defective corpus luteum function 4

Clinical Implications for Progesterone Support

Duration of Supplementation

• Progesterone supplementation is required in IVF cycles at least through the early pregnancy period until placental production is established 1, 2
• The inadequate corpus luteum function in assisted reproduction results from both GnRH analogue use (which prevents the LH surge) and aspiration of granulosa cells during oocyte retrieval 2
• Evidence suggests that in IVF pregnancies, serum progesterone levels remain significantly elevated up to 8 weeks post-conception even after discontinuing luteal support at 2 weeks, indicating sustained luteal contribution 3

Protocol-Specific Considerations

• In IVF protocols with hypothalamic-pituitary suppression (0 corpus luteum), progesterone supplementation is absolutely critical throughout early pregnancy 5
• Women in the 0 CL cohort show undetectable relaxin throughout pregnancy, including late gestation, indicating complete absence of corpus luteum function 5
• In ovarian stimulation protocols with multiple corpora lutea, progesterone, plasma renin activity, and aldosterone show transient surges at 5-6 gestational weeks 5

Important Caveats

Timing Variability

• The exact timing of adequate placental hormone production varies between individuals and IVF protocols 3, 5
• The luteal-placental shift is obscured in IVF pregnancies, making it difficult to determine precisely when the placenta assumes full hormonal control 3
• Measurement of the progesterone to 17-OHP ratio shows that in normal pregnancies this rises between 4-9 weeks, but does not change over the same period in IVF pregnancies, indicating delayed placental contribution 3

Clinical Practice Recommendations

• Most IVF protocols continue progesterone supplementation through at least 8-10 weeks gestational age to ensure adequate support during the transition period 1, 2
• Temporarily defective corpus luteum function is evidenced by measuring serum progesterone, estradiol, and 17-hydroxyprogesterone levels, which can be related to prolonged blockage of pituitary gonadotropic function after GnRH agonist use 4
• The maternal milieu of IVF pregnancy is not physiologic compared to spontaneous conception, with specific perturbations varying according to IVF protocol and corpus luteum status 5