The First Trimester
The Normal Pregnancy:
Until the completion of the first 12 weeks of pregnancy, known as the first trimester, there are general medical considerations. This is also the time when miscarriage is most likely, and up to 20 percent of diagnosed pregnancies miscarry due to genetic mishaps at conception. Assuming all is well and in every way unsuspicious, you can expect your normal pregnancy to involve monthly visits that will continue usually until the end of your second trimester (24 weeks).
On your initial visit, a careful history will be obtained or updated. Prior records from your last doctor or from consultants (such as infertility specialists) who have been caring for you will be sent for. If there's a history of pre-existing conditions—hypertension, irritable bowel disease, diabetes, thyroid, etc.—this will mean you're out of the "normal" pregnancy group. The initial physical exam will be used to assess your general maternal health, and you should expect initial laboratory tests, vaginal cultures, and a check of the size of your uterus.
Routine cultures will be for chlamydia, gonorrhea, and perhaps group B strep, although the strep culture is usually done around 28 weeks. Expect a Pap smear, because no prenatal care is adequate without one.
The exam should indicate whether there is someone growing inside your uterus making it the size expected for the gestational age. An initial ultrasound might be done during the first trimester to document a normal-appearing fetus, establish agreement or disagreement with the patient's due date based on a last menstrual period, and to begin the actual bonding process. Except for a change in the due date, which is just arithmetic, any other ultrasound surprises (twins, for instance) will be your ticket out of the "normal" pregnancy group.
Many obstetricians feel comfortable getting two ultrasounds before 20 weeks, because the accuracy of the dating of the pregnancy falls off dramatically in later pregnancy. The first ultrasound is often obtained before 12 weeks. The second one, if done, will be obtained at least a month later so that an expected and appropriate interval-growth can be documented.
During the first trimester, each visit will record the blood pressure, weight, and urine values for sugar (glucose) and protein. Weight becomes important when following a patient with morning sickness. Actual weight loss, which will prompt weekly visits instead of monthly, can result from a severe version of morning sickness called hyperemesis gravidarum. Unless you have chronic hypertension or kidney disease, blood pressure problems or protein in the urine are more likely to be problems that occur in the third trimester.
Since the first trimester is the highest risk miscarriage zone, any bleeding will prompt ultrasounds more often, sometimes even weekly. You'll be out of the normal group for this as well, and you should then expect serial blood levels of the pregnancy hormone, hCG, to watch for ensuing miscarriage, ectopic pregnancy, or resolution toward a normal pregnancy. Fetal heart tones are often difficult to hear during the first trimester, so hearing the heartbeat will have to wait until the second trimester.
The High-Risk Pregnancy:
Problems that can make you high risk include in the first trimester include:
- Bleeding (threatened miscarriage)
- Chronic hypertension
- History of previous miscarriage, congenital abnormalities, stillbirth, or neonatal death
- Multiple gestation
- Medication exposure (either necessary medication for a pre-existing medical condition or exposure to medicines before a patient knew she was pregnant)
- Thyroid disease
- Alcohol or drug abuse
- Abnormal Pap smear
In summary, the first trimester is important for assessing any history that may prove prophetic for the rest of your pregnancy, watching the weight of the mother and the growth of the fetus, and being alert to miscarriage scares.