Pregnancy Timing and Ultrasound Accuracy in PCOS

Pregnancy issues

Hello Dr.
Tsao,
I would like to ask you some questions and provide you with the existing data for your confirmation regarding the dates.
I have been trying to conceive for nine years without success and have polycystic ovary syndrome (PCOS).
I unexpectedly became pregnant after having intercourse with another man, and I often wonder if that was the day.
I am also concerned that this situation might affect the health of the baby.
Therefore, I would appreciate your assessment.
My last menstrual period was on February 3rd, and my cycles are irregular, lasting 8-9 days.
I ovulated late, with the ovulation trigger shot administered on February 24th in the afternoon.
Intercourse occurred on the night of February 25th to the early morning of February 26th.
I took progesterone for 14 days from February 26th to March 11th.
Intercourse occurred again on March 12th, and I performed a home pregnancy test on March 16th, which showed two lines quite clearly.

On March 19th, at the first obstetrics and gynecology clinic, two doctors could not visualize the gestational sac and noted fluid in the uterus.
In the afternoon, I went to a second clinic where the doctor identified a 0.6 cm gestational sac.
On March 31st, an embryo and heartbeat were detected via transvaginal ultrasound.
On April 7th, the embryo measured 0.87 cm, and a heartbeat was heard (transvaginal ultrasound, showing 6 weeks and 6 days).
On April 10th, the measurement was 1.50 cm (ultrasound showing 7 weeks and 6 days).
On April 18th, the measurement was 2.30 cm, with a clear view of the baby's head and body (ultrasound showing 8 weeks and 6 days).
Since the ovulation trigger shot was given on February 24th, it is unlikely that I would not ovulate until March 12th.
Therefore, it seems improbable that conception could have occurred four days after intercourse on March 12th, and it is also unlikely that a transvaginal ultrasound could detect the gestational sac seven days later and the heartbeat nineteen days later.
Additionally, I would like to know if the ultrasound dating could be affected by late ovulation (as I administered the trigger shot three weeks after my last menstrual period).
Typically, two weeks are deducted from the estimated ovulation and conception date; should I deduct three weeks instead?
Dr.
Tsao, can these ultrasound data completely rule out March 12th as the date of conception? Thank you for your response, and I appreciate your help.

Bao'er, 30~39 year old female. Ask Date: 2018/04/30

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, theoretically, it can be completely ruled out that March 12 was the date of conception.
Wishing you good health.

Reply Date: 2018/04/30

More Info

Understanding pregnancy timing and the accuracy of ultrasound in the context of Polycystic Ovary Syndrome (PCOS) can be quite complex, especially when considering irregular menstrual cycles and the timing of ovulation. Based on the information you've provided, let's break down the timeline and clarify your concerns.

1. Menstrual Cycle and Ovulation: You mentioned that your last menstrual period (LMP) was on February 3rd, and you have irregular cycles, typically ovulating later than expected. In women with PCOS, ovulation can be unpredictable, which complicates the determination of the exact date of conception.
2. Triggering Ovulation: You indicated that you received an ovulation trigger shot on February 24th. This shot is designed to induce ovulation, typically occurring about 36 hours after administration. Therefore, ovulation would likely have occurred around February 25th to 26th.
3. Timing of Intercourse: You reported having intercourse on the night of February 25th and early February 26th, which aligns well with the expected ovulation window. Sperm can survive in the female reproductive tract for up to five days, so intercourse during this time frame could indeed lead to conception.

4. Pregnancy Testing and Ultrasound Findings: You conducted a urine pregnancy test on March 16th, which showed a positive result. This is approximately 20 days after your ovulation trigger shot and about 18 days after the likely conception date. The ultrasound findings you shared indicate that the embryo and heartbeat were detected on March 31st, which corresponds to approximately 6 weeks and 6 days of gestational age.

5. Gestational Age Calculation: In typical pregnancies, gestational age is calculated from the first day of the last menstrual period (LMP). However, in cases of irregular cycles or when ovulation is induced, adjustments may be necessary. Since you ovulated later than the standard cycle, it is reasonable to consider that your gestational age might need to be adjusted. Generally, if you ovulated later than the expected timeframe, you might subtract a week or two from the ultrasound measurements to account for the later ovulation.

6. Determining the Conception Date: Based on the timeline you provided, it is unlikely that conception occurred on March 12th, as this date is too far removed from your ovulation window. The ultrasound findings that show the presence of an embryo and heartbeat align more closely with the conception occurring around February 25th to 26th.

In summary, considering your irregular cycles, the timing of your ovulation trigger, and the ultrasound findings, it is highly probable that conception occurred shortly after your ovulation trigger shot, rather than on March 12th. The ultrasound data you provided supports this conclusion, and it is unlikely that you need to adjust the gestational age by three weeks.
If you have further concerns about the health of your pregnancy or the implications of PCOS, it is essential to maintain regular follow-ups with your healthcare provider. They can offer personalized advice and monitoring to ensure the best outcomes for you and your baby.

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