What are the recommended serum progesterone (Progesterone) levels after Frozen Embryo Transfer (FET) day 15 in a twin pregnancy?

Serum Progesterone Levels After FET Day 15 in Twin Pregnancies

There are no specific recommended serum progesterone levels established for day 15 post-frozen embryo transfer (FET) in twin pregnancies, as current guidelines do not specify target progesterone levels for twin gestations following assisted reproductive technology. 1, 2

Progesterone Supplementation in FET Cycles

General Recommendations for FET

• For FET cycles, progesterone supplementation begins on the day of endometrial transformation in artificial cycles 1
• The Chinese experts' consensus guideline recommends continuing luteal support for 1-3 weeks after pregnancy is confirmed by ultrasound in natural or ovarian stimulation cycles 1
• In artificial cycles, estrogen and progesterone should be continued at original doses for 3-4 weeks, with gradual reduction to complete discontinuation within 2 weeks 1

Progesterone Monitoring in FET

• While some studies have investigated progesterone levels on the day of embryo transfer, there is limited evidence regarding optimal levels at day 15 post-FET, particularly for twin pregnancies
• Research suggests that serum progesterone levels ≥10 ng/mL on the day of embryo transfer may be adequate for pregnancy maintenance 3, 4
• One study found that progesterone levels <5 ng/mL on the day of transfer were associated with lower live birth rates 4

Multiple Gestations and Progesterone

Lack of Evidence for Multiple Gestations

• Current guidelines from the Society for Maternal-Fetal Medicine (SMFM) indicate there is no evidence of effectiveness for progesterone supplementation in multiple gestations for preventing preterm birth 1, 2
• Multiple studies have shown that neither 17-alpha-hydroxyprogesterone caproate (17P) nor vaginal progesterone has demonstrated benefit in twin or triplet pregnancies 1

Clinical Management Considerations

• No specific progesterone level targets have been established for twin pregnancies at day 15 post-FET
• Recent research suggests that higher serum progesterone levels (>40 ng/mL) do not negatively impact live birth rates in FET cycles 5, 6
• One study found that extremely high progesterone levels (>32.5 ng/mL) on the day of embryo transfer might be associated with lower live birth rates 7, but more recent evidence contradicts this finding 5, 6

Practical Approach

• Monitor for adequate progesterone levels (generally ≥10 ng/mL) during the luteal phase and early pregnancy
• For patients with low progesterone levels (<10 ng/mL), rescue progesterone supplementation may be considered 3
• Continue progesterone supplementation according to clinic protocol after confirmation of pregnancy (typically 3-10 weeks)
• Be aware that twin pregnancies may have different progesterone requirements than singleton pregnancies, though specific target levels are not established

Important Caveats

• The metabolism of progesterone varies substantially between individuals receiving identical doses 2
• After 8-10 weeks of pregnancy, the placenta produces sufficient progesterone to maintain pregnancy, making supplementation less relevant 2
• Twin pregnancies may have different progesterone dynamics compared to singleton pregnancies, but specific guidelines are lacking