2005 Pregnancy Watch
July 9
Mei gave birth to a cub at 3:41 a.m. today. 
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July 5
The decline in Mei Xiang's urinary progestins continues. The first chart below is her ongoing hormone profile; the second chart shows her urinary progestins profile from this year aligned to similar profiles from the past three years. These comparisons provide perspective on the trajectory of the decline and some idea of the expected time when concentrations may reach baseline—probably within the next week or so.
July 3
Our latest hormone data suggest that Mei Xiang's urinary progestins are declining. Based on trends from past years, we are probably entering the final days of this year's reproductive cycle. A best guess is that we will reach baseline within the next ten days.
June 29
Six urine samples were sent to our lab (three were replicates) and one was overly dilute, leaving two good samples to analyze (June 25 and June 28). Mei Xiang's progestin levels remain elevated near peak concentrations, and despite a dip in the last sample assayed, it's premature to determine whether this represents to the beginning of the decline to baseline that typically lasts ten days or so. As of today, it has been 36 days since the secondary rise began; the secondary rise typically lasts 40-50 days. With samples collected over the next few days, we hope we can pinpoint when hormone concentrations are likely to decline to baseline coincident with a birth or the end of pseudopregnancy.
June 24
Mei Xiang's urinary progestins continue to be elevated, as expected, and our estimates on timing for the end of pseudopregnancy or pregnancy remain unchanged.
June 18
Mei Xiang's urinary progestins continue to increase, providing further evidence that she has begun the anticipated secondary rise in post-ovulatory progestin concentrations. From the current profile we are now confident that the secondary rise, which has a duration of 40 to 50 days in the giant panda, began on approximately May 25. If this year is like previous years, we expect urinary progestins to decline, coincident with the birth of a cub—if pregnancy resulted from the artificial insemination—or the end of another pseudopregnancy.
These data cannot be used to diagnose pregnancy, but weekly updates may be of assistance to the veterinary and animal management staff in making the appropriate preparations for a birth, should Mei Xiang be pregnant.
June 9
Mei Xiang's urinary progestin levels in the samples collected over the past week continue to show an increasing trend in concentration. As of today it has been 89 days since the artificial insemination (AI), and with the new data we are estimating that the anticipated secondary rise in progestins began on May 25, roughly 73 after the AI. While it is always best to evaluate data as they unfold, we can make some estimates that may aid animal management and veterinary staff in preparing for a potential birth. The secondary rise typically lasts between 40 and 50 days. A decline in urinary progestins to baseline will signal the end of another pseudopregnancy or will mark the birth of a cub, should Mei Xiang be pregnant. We will continue to provide data in the weeks to come, so be sure to stay tuned.
June 2
For the second week in a row, Mei Xiang's urinary progestin levels have
continued to increase. We suspect that this is the onset of the long-awaited secondary rise, but our confidence in this conclusion will increase as we gather more data in the next one to two weeks. We expect the secondary rise in progestins to last 40-50 days before hormone levels decline coincident with birth or the end of a pseudopregnancy.
May 26
The progestin and estrogen levels for Mei Xiang over the past week have pretty much remained the same with the exception of one lone progestin point yesterday. The onset of the secondary rise in progestins is characterized by a marked increase in progestin concentrations over the levels seen in the primary rise, and while intriguing, it's a bit premature to conclude that this lone spike in hormone excretion means we've reached that point yet. Stay tuned!
May 18
Once again there have been no significant changes in the concentrations of Mei Xiang's urinary estrogen and progestin levels over the past two weeks. To date, hormone patterns are within normal limits. We still have not detected the expected secondary rise in progestins that will signal the onset of pseudopregnancy or true pregnancy (the fetal development stage), both of which last 40-50 days.
May 5
It has been 55 days since Mei Xiang's artificial insemination. During this period her urinary estrogen and progestin levels have remained almost unchanged. We do not expect the hormone concentrations to change significantly for another few weeks. Once we see an increase in progestin values, we can begin the countdown to the end of pregnancy or pseudopregnancy.
April 28
The concentrations of Mei Xiang's hormones have not changed appreciably during the past week. Progestin levels—our key indicator for pregnancy/pseudopregnancy—have not yet increased to what we refer to as the secondary rise. Once the secondary rise commences, we will be 40 to 50 days from the end of this year's reproductive cycle. We will keep you posted.
April 20
There were no significant changes in Mei Xiang's urinary estrogen and progestin excretion over the past week. Hormone concentrations have remained in the same range since the insemination on March 11. However, we are closer to the period when we should see an increase in progestin activity, which would designate the beginning of the secondary rise, a period that lasts 40 to 50 days.
April 14
Mei Xiang's reproductive hormones continue to stay the course. As of today, it has been 34 days since the insemination, and the presumptive time of ovulation. We do not expect to see any changes in progestin concentrations for another few weeks. Stay tuned.
April 6
The urinary estrogen and progestin levels are still on track with results from the past. The secondary rise will be evident when there is a large increase in urinary progestins (blue line). The duration of the secondary rise is about 40-50 days. If Mei Xiang is pregnant, we would expect to see a birth at the end of the secondary rise. However, secondary rises are exactly the same in pregnant and nonpregnant giant pandas, which currently makes pregnancy detection with these measures virtually impossible. We hope that ultrasound examinations conducted this year during the secondary rise interval—when fetal development occurs during a true pregnancy—will help provide clues as to whether Mei Xiang is pregnant.
March 30
Mei Xiang's urinary hormones are on track with results from the past several years (see the green line). It will likely be several more weeks before we see the expected secondary rise in progesterone metabolites.
March 23
Following Mei Xiang's estrus two weeks ago, urinary estrogen and progesterone metabolites excretion has proceeded in a similar pattern to the average of the previous three years. Estrogen values have returned to the levels they were at prior to the breeding season, while progestins rose to levels slightly above her baseline range. These data provide further evidence that Mei Xiang has entered the luteal phase of her reproductive cycle—an interval that we refer to as the primary rise in urinary progesterone metabolites. We expect to eventually detect a secondary rise in urinary progesterone metabolites that will signal that the end of pregnancy or pseudopregnancy is imminent within the subsequent four to six weeks. If Mei Xiang is pregnant, this interval corresponds to the period of fetal development, and would indicate when our veterinary team might be able to detect a pregnancy using ultrasonography.
March 21
Changes to Mei Xiang's vaginal cells were similar to those in 2004 and correspond to her hormone profile as expected, based on last year's activity. This means that today's hindsight tells us that Zoo scientists correctly anticipated Mei Xiang's estrus earlier this month and timed her artificial insemination quite well.
March 18
Although urine specimens for this week were not received, substantive changes in Mei Xiang's hormones are not expected for a little while. Looking back to give us some perspective, her previous pseudopregnancies lasted 158, 147, and 156 days in 2002, 2003, and 2004, respectively. These numbers are based on the interval from the peak in urinary estrogen until progesterone metabolites declined to baseline following the secondary rise that characterizes pregnant and pseudopregnant giant pandas. Zoo scientists are hesitant to make predictions about a possible pregnancy. When they consider Mei Xiang's past, they anticipate an end to a true or pseudopregnancy to occur between August 5 and 15. Ongoing hormone monitoring will help fine-tune these estimates.
March 11
Zoo scientists have been monitoring Mei Xiang's hormone levels and were surprised when her estrogen levels suddenly rose precipitously the first weekend of March, indicating that ovulation and peak estrus would occur very soon. Estrogens continued to rise, and Mei showed clear behavioral signs of impending estrus, such as pacing and increased scent marking. When estrogens began to decline on March 10, Zoo scientists determined that ovulation had occurred. This was early, but not outside the realm of normal. See the hormone chart below.
Mei Xiang and Tian Tian were brought together and separated in a series of mating encounters on March 10. After staff determined that there had been no successful natural mating, they decided to perform artificial insemination under anesthesia on March 11.
With only a two- or three-day window in which a panda can become pregnant each year, timing was critical. Scientists said that the timing of the artificial insemination relative to ovulation was nearly ideal. The pandas may continue to mate naturally until the end of Mei Xiang's estrus period. Zoo staff are hopeful pregnancy will occur, and await the birth of a baby in three to six months. Because pandas experience pseudopregnancy, only a panda birth or the passage of six months without a birth will provide the answer. Mei Xiang's hormones and behavior will continue to be monitored.
