FIRST TRIMESTER

What are the first symptoms of pregnancy?

Missing a period is usually the first signal of a new pregnancy, although women with irregular periods may not initially recognize a missed period as pregnancy. During this time, many women experience a need to urinate frequently, extreme fatigue, nausea and/or vomiting, and increased breast tenderness. All of these symptoms can be normal. Most over-the-counter pregnancy tests are sensitive 9-12 days after conception, and they are readily available at most drug stores. Performing these tests early helps to allay confusion and guesswork. A serum pregnancy test (performed in a provider’s office or laboratory facility) can detect pregnancy 8-11 days after conception.

How long after conception does the fertilized egg implant?

The fertilized conceptus enters the uterus as a 2- to 8-cell embryo and freely floats in the endometrial cavity about 90-150 hours, roughly 4-7 days after conception. Most embryos implant by the morula stage, when the embryo consists of many cells. This happens, on average, 6 days after conception. The new embryo then induces the lining changes of the endometrium, which is called decidualization. It then rapidly begins to develop the physiologic changes that establish maternal-placental exchange. Prior to this time, medications ingested by the mother typically do not affect a pregnancy.

What is the most accurate pregnancy test to use?

Serum beta–human chorionic gonadotropin (hCG) is the hormone produced by the syncytiotrophoblast beginning on the day of implantation, and it rises in both the maternal blood stream and the maternal urine fairly quickly. The serum hCG test is the most sensitive and specific, and the hormone can be detected in both blood and urine by about 8-9 days after conception. This test can be performed quantitatively or qualitatively. Urine pregnancy tests differ in their sensitivity and specificity, which are based on the hCG units set as the cutoff for a positive test result, usually 2-5 mIU/mL.

Urine pregnancy tests can produce positive results at the level of 20 mIU/mL, which is 2-3 days before most women expect the next menstrual period. The kits are very accurate and widely available. The test can be completed in about 3-5 minutes. The kits all use the same technique—recognition by an antibody of the beta subunit of hCG. Falsely high readings of the hCG hormone can occur in cases of hydatidiform molar pregnancy or other placental abnormalities. Also, test results can remain positive for pregnancy weeks after a pregnancy termination, miscarriage, or birth. On the other hand, false-negative test results can occur from incorrect test preparation, urine that is too dilute, or interference by several medications.

Serum pregnancy tests can be performed by a variety of methods. The enzyme-linked immunosorbent assay (ELISA) is the most popular in many clinical laboratories. This test is a determination of total beta-hCG levels. It is performed using a monoclonal antibody to bind to the hCG; a second antibody is added that also interacts with hCG and emits color when doing so. This form of ELISA is commonly called a “sandwich” of the sample hCG. Radioimmunoassay (RIA) is still used by some laboratories. This test adds radiolabeled anti-hCG antibody to nonlabeled hCG of the blood sample. The count is then essentially determined by the amount of displacement of the radiolabeled sample.

The hCG level doubles approximately every 2 days in early pregnancy. However, it should be noted that even increases of only 33% can be consistent with healthy pregnancies. These values increase until about 60-70 days and then decrease to very low levels by about 100-130 days and never decrease any further until the pregnancy is over.

Is cramping during pregnancy normal?

Early in pregnancy, uterine cramping can indicate normal changes of pregnancy initiated by hormonal changes; later in pregnancy, it can indicate a growing uterus. Cramping that is different from previous pregnancies, worsening cramping, or cramping associated with any vaginal bleeding may be a sign of ectopic pregnancy, threatened abortion, or missed abortion.

Other physical effects that are normal during pregnancy, and not necessarily signs of disease, include nausea, vomiting, increase in abdominal girth, changes in bowel habits, increased urinary frequency, palpitations or more rapid heartbeat, upheaving of the chest (particularly with breathing), heart murmurs, swelling of the ankles, and shortness of breath.

Why do pregnant women feel tired?

Fatigue in early pregnancy is very normal. Many changes are occurring as the new pregnancy develops, and women experience this as fatigue and an increased need for sleep. Lower blood pressure level, lower blood sugar levels, hormonal changes due to the soporific effects of progesterone, metabolic changes, and the physiologic anemia of pregnancy all contribute to fatigue. Women should check with their health care provider to determine if an additional work up, prenatal vitamin changes, and/or supplemental iron would be beneficial.

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