I was reading where the placenta completely takes over about 12-14 weeks. Some websites even say 13-16 weeks.  Why, then, do some practictioners have their patients stop progesterone at 8-10 weeks?  Is the idea that the placenta is already partially functioning by then?  I'm just wondering becasye my OB said to stop the progesterone at 12 weeks, but if in some cases the placenta isn't fully developed until 14-16 weeks, couldn't this still be risky?  I'm confused.                
                IF DX: DOR & Fragile X pre-mutation carrier
2011: FSH 13.3 & E 99; AMH 0.54 
2nd FSH 6.2 E 40's AFC: 8 
BFP from Clomid/IUI ~ Pre-e and IUGR during pregnancy ~ DS born 9/4/12 
Feb./March 2013: AMH less than 0.16 (undectable) and AFC = 4; 
BFP from supps ~ DS#2 due May 2014
May 2014 January Siggy Challenge:


               
        
Re: Placenta question and timing of stopping progesterone
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Trying for #1 since May 2010 l DX ~ Unexplained Infertility June 2011
IUI #1&2 = BFN; IUI #3 = BFP, m/c @ 6 weeks
November '11 ~ IVF#1 ~ ER 11/18 (29R, 17F) ~ 5dt of one beautiful blast on 11/23 = BFP!!
Beta #1 9dp5dt = 116, P4 = 28 ~ Beta #2 13dp5dt = 700 ~ Beta #3 20dp5dt = 9500, P4 = 26
1st u/s 12/27 - hb of 156!! EDD 8.10.12
   **TEAM GREEN!**
Sweet baby boy born 8.18.12
Trying for #2
FET #1 - October '13 - c/p l FET #2 - December '13 - cancelled
   l   FET #2.2 - 1.30.14 - BFN
~ More testing - hysteroscopy, endometrial biopsy & more b/w - all normal / negative~
Surprise BFP while waiting on FET #3 ~ beta #1 500; beta #2 1600; first u/s 4/3 - measuring 5w5d, no hb yet!; 2nd u/s 4/10 - hb 132, measuring 6w6d - EDD 11.29.14
    **TEAM GREEN!**
Beautiful baby girl born 11.24.14
Not anymore. I've graduated from my RE's office. My initial progesterone levels were so high that I was shocked they even left me on the progesterone. They just told me to keep taking them until 12 weeks. At the time, I had not looked up this info on the placenta and didn't think to inquire further. I asked my OB and she said I could probably go off at 10 weeks but to stay on them until 12 weeks just to play it safe.
I have not seen anyone on progesterone after 12-13 weeks, though...not on here and not on FF. And FF has alot of IF ladies. Thus, I am guessing that the placenta has sufficiently taken over by the point in pretty much all pregnancies to make the need for it moot??? Does anyone know?
2011: FSH 13.3 & E 99; AMH 0.54 2nd FSH 6.2 E 40's AFC: 8
BFP from Clomid/IUI ~ Pre-e and IUGR during pregnancy ~ DS born 9/4/12
Feb./March 2013: AMH less than 0.16 (undectable) and AFC = 4;
BFP from supps ~ DS#2 due May 2014
May 2014 January Siggy Challenge:
Thanks! This makes sense.
2011: FSH 13.3 & E 99; AMH 0.54 2nd FSH 6.2 E 40's AFC: 8
BFP from Clomid/IUI ~ Pre-e and IUGR during pregnancy ~ DS born 9/4/12
Feb./March 2013: AMH less than 0.16 (undectable) and AFC = 4;
BFP from supps ~ DS#2 due May 2014
May 2014 January Siggy Challenge:
I've heard that the placenta takes over at 10 weeks. I stopped my progesterone @ 11 weeks. Progesterone is given just in case us IF patients don't have a normal corpus luteum cyst (which supports the pregnancy until the placenta takes over). So, it is only given for precautionary reasons (except for those with true luteal phase defects).
My RE never checks a progesterone level b/c he supplements all patients, but I am sure that my P4 level was insanely high! I had 6 corpus lutem cysts (majority of eggs came from one side), one ovary measured 9 cm until the 2nd trimester PLUS I was using endometrin until 11 weeks.
Wedding Fall 2007 Off OCP's since 9/08-started with BBT charts Saw Ob/gyn May 2009 Blood work normal except single copy of MTHFR Clomid 50mg May 2009 Clomid 50mg + IUI June 2009 Femara 5mg + IUI July 2009 Normal HSG July 2009 Femara 5mg + ovidrel+IUI August 2009 Femara 5mg +ovidrel + IUI September 2009 November 2009-normal lap December 2009-met with RE December/January-Injectible med cycle with IUI-Abnormal sperm morpology found-only 0-1% normal All Head defects. Jan/Feb 2010 1st IVF with ICSI-5 week chemical pregnancy
Feb 2010-male infertility doc says DH's anatomy and blood work are normal so nothing he can do. 
FET July 2010-BFP! Twin m/c @ 5.5 wks 
Dec/Jan 2011 IVF #2 Only 4 eggs retrieved-Ganirelix dose messed up BFFN
Feb/March 2011 IVF #3 ER 3/9 9 eggs, 7 fertilized, ET 3/14, No frosties. BFN
IVF #4 ER 8/22 9R,7F ET 8/25-3 embies, 1 frostie! Beta 9/2= 54, 9/6=274, 9/8=625, 9/12=2953, 9/16 greater than 10,000. B/G TWINS born April 2012 @ 36wks & 1 day! 
July 2014-going back for the frozen embryo! ET 7/28, heartbeat seen at 6wks1day with SCH. Miscarriage confirmed at 6wks4days