Is it necessary to routinely monitor HCG and progesterone levels in early pregnancy? How to calculate the expected date of delivery?

Author: Chen Qian, Chief Physician, Peking University First Hospital

Reviewer: Bai Wenpei, Chief Physician, Beijing Century Altar Hospital, Capital Medical University

After finding out that you are pregnant through an early pregnancy test, I think everyone will go to the hospital for a check-up. Some people say that if the early pregnancy test has already detected the pregnancy, why do we still need to have a blood test and do an ultrasound?

The early pregnancy test strip actually checks the human chorionic gonadotropin, or HCG. It is only a qualitative test. If one bar deepens and the other bar does not deepen obviously, you still need to recheck and go to the hospital to have a blood test for HCG.

Generally, at 6-7 weeks of pregnancy, an ultrasound is done to see whether the fertilized egg has successfully reached the uterus to rule out the possibility of ectopic pregnancy. It can also be done to see whether it is a single or twin baby, whether there is a fetal heartbeat or embryo, and to see if the little life is safe.

If the doctor says that the HCG and progesterone values ​​are good, there is a fetal heartbeat and embryonic bud, and the baby is healthy, then your heart will finally be at ease and you will feel happy. At this time, you will start to calculate the approximate month when the baby will be born, and whether it will be summer or winter.

However, some mothers’ early pregnancy examination results are not very ideal, such as low progesterone levels, unsatisfactory HCG doubling, etc. They are very worried. What should they do?

1. Does low progesterone levels in early pregnancy mean that the baby is not good?

After pregnancy, everyone is very concerned about the progesterone value.

Progesterone is to maintain pregnancy. In the first three months of pregnancy, progesterone is mainly derived from the corpus luteum formed locally after ovulation in the ovary. The corpus luteum secretes progesterone, which has a protective effect on early pregnancy and can also stimulate the embryonic trophoblast cells to secrete blood HCG. At 10-11 weeks of pregnancy, the corpus luteum atrophies and becomes the corpus albicans. The maintenance of late pregnancy mainly depends on the placenta, which also has the function of secretion and can secrete progesterone.

Figure 1 Original copyright image, no permission to reprint

Does low progesterone mean that the baby is not developing well?

It cannot be generalized and needs to be evaluated dynamically. Studies have found that progesterone is not released continuously or at a uniform rate throughout the day. It is released in a fluctuating and pulsed manner. If the time of blood drawing coincides with the peak of progesterone secretion, then the progesterone value may be high. If the time of blood drawing coincides with the low peak of progesterone secretion, then the progesterone value detected will be low, so it is not very accurate. So should progesterone testing be performed routinely?

The role of progesterone is to maintain pregnancy, but routine progesterone testing is not recommended. People who really need progesterone supplementation are those with luteal insufficiency and a clear medical history. For those with luteal insufficiency, the menstrual cycle must be very short, or there are clear symptoms of threatened abortion, and then routine progesterone testing or progesterone supplementation may be necessary.

2. It is not good for the blood HCG value to double. Could it be an ectopic pregnancy?

The HCG value begins to increase after pregnancy, reaches a peak around 8-10 weeks of pregnancy, then begins to gradually decline, and then remains at a relatively low level during pregnancy.

Personally, I don’t know whether the HCG value reaches its peak at 8 weeks, 10 weeks, or 11 weeks, but generally speaking, HCG shows a continuous upward trend before 8 weeks of pregnancy, and the value usually doubles every other day. At least the increase can reach 65% or more, which means that the possibility of intrauterine pregnancy is relatively high.

If the menstruation is not particularly regular, or there is vaginal bleeding in early pregnancy, and there has been a history of spontaneous abortion or fetal growth retardation, paying attention to the changes in HCG at this time may be helpful for differential diagnosis, such as identification of ectopic pregnancy or early embryonic development.

If, as the gestational age increases, ultrasound reveals a gestational sac, fetal heartbeat and fetal bud in the uterus, the value of HCG monitoring and evaluation will be weakened, so HCG testing should not be performed routinely.

3. How to calculate the expected date of delivery?

Assisted reproductive technology can determine the exact time of conception, so that the due date can be calculated relatively accurately. Women who conceive naturally do not actually know when they conceived, so the due date is relatively more difficult to determine. Women who conceive naturally can use the following algorithms to roughly estimate the due date.

First, the 40-week algorithm. The 40-week algorithm is the most common method currently. It is based on the female menstrual cycle, starting from the first day of the last menstrual period, with the first day of the last menstrual period as day 0, 7 days as 1 week, and 4 weeks as the second month of pregnancy. According to this calculation, 40 weeks, that is, 280 days from the first day of the last menstrual period, is the scheduled delivery date.

The specific calculation method is as follows:

If the first day of the last menstrual period is between April and December, the expected delivery month = the month of the last menstrual period - 3; the expected delivery day = the day of the last menstrual period + 7.

For example, if the first day of the last menstrual period is November 5, 2018, the expected delivery month is 11-3=8, and the expected delivery day is 5+7=12, then the expected date of delivery is August 12, 2019.

Figure 2 Original copyright image, no permission to reprint

If the first day of the last menstrual period is between January and March, the expected delivery month = the month of the last menstrual period + 9; the expected delivery day = the day of the last menstrual period + 7.

For example, if the first day of the last menstrual period is February 8, 2017, the expected delivery month is 2+9=11, and the expected delivery day is 8+7=15, then the expected date of delivery is November 15, 2017.

Figure 3 Original copyright image, no permission to reprint

Second, ultrasound examination. If the pregnant woman's menstrual cycle is irregular, or she forgets the first day of her last menstrual period, she can choose to do an early ultrasound examination at this time to accurately determine the actual gestational age of the pregnant woman based on the length of the head and arm and the size of the fetal bud.

After discovering that you are pregnant, you should go to the hospital for a check-up in time to ensure that the baby is healthy. If the progesterone level is low or the HCG value does not double, don't worry too much. The doctor will judge whether it is normal or whether treatment is needed based on the specific situation and medical history. If the examination shows that the baby is fine, then you can calculate when the baby will come and prepare to be a mother.