hormones

I have been thinking a lot about hormones since we began TTC. Estrogen and Progesterone play important roles in preparing the uterus for implantation and fetal development. We have begun using the fern test to track estrogen in my cycles, and using bbt charting to track progesterone. A little digging produces the following

The figure on the left is from the study in [1]. It shows estrogen and progesterone concentrations as a function of the number of days from LH peak for women who conceive and for those who do not. The filled circles are averages for 26 conception cycles, and the open circles are averages from 27 non-conception cycles. Since the LH peak occurs 24-36 hours before the egg is released, day 1 is O-day, not day 0. From this data one can see that both estrogen and progesterone start to fall, on average, after about 7 dpo, unless conception takes place.

What is also interesting about the figure from [1] is that the difference in progesterone levels between conception and non-conception cycles is noticeable from 2-3 dpo. This may indicate that a higher concentration of progesterone helps implantation to take place, rather than that fertilisation has signalled for progesterone to be produced.


One can also consider what happens for a single individual. The figure on the right is from the study in [2]. It shows estrogen and progesterone levels for 3 cycles of one woman, who conceived in her third cycle. The thick grey bands represent days of menstruation and the dotted lines ovulation. The ticks represent days of intercourse. E1G is a metabolite of estrogen, and PdG is a metabolite of progesterone. What we can learn from this is that both estrogen and progesterone concentrations show significant fluctuations day by day, but in the conception cycle they both show a marked increase after about 1 week past ovulation compared to the non-conception cycles.

In the first cycle of the figure from [2] it appears that a chemical pregnancy has taken place, given the low concentration of hCG in weeks 5-6. It may be that estrogen and/or progesterone concentrations were not high enough to produce an endometrium lining which can sustain the fetus, or that the fertilised egg in this cycle was simply not viable at the time of implantation. In either case, the authors speak of "cycle viability", referring to the ability for a given ovulatory cycle to result in pregnancy. They find the proportion of viable cycles to be on average around 0.37.

What I have gathered from this information is that, with regard to the fern test, my estrogen will peak 1-2 days before O-day. In addition, both estrogen and progesterone should on average keep rising after around 7 dpo in the case of successful conception, and fall in the case of non-conception.


[1] Elizabeth A Lenton, Rafida Sulaiman, O Sobowale, and ID Cooke, The human menstrual cycle: plasma concentrations of prolactin, lh, fsh, oestradiol and progesterone in conceiving and non-conceiving women, Journal of reproduction and fertility 65 (1982), no. 1, 131–139.
www.ncbi.nlm.nih.gov/pubmed/6804627

[2] Allen J Wilcox, Clarice R Weinberg, and Donna D Baird, Timing of sexual intercourse in relation to ovulationeffects on the probability of conception, survival of the pregnancy, and sex of the baby, New England Journal of Medicine 333 (1995), no. 23, 1517–1521.
www.nejm.org/doi/full/10.1056/nejm199512073332301