Prenatal care - what is, first, second and third trimester

Prenatal care - what is, first, second and third trimester

What is Prenatal Care and Definition

Prenatal Care - Routine and preventive health care provided during PREGNANCY to safeguard the health and well-being of the woman and the FETUS. In the United States routine prenatal care consists of regular visits to the health-care provider (family practitioner, obstetrician, or nurse midwife), URINE and BLOOD tests, BLOOD PRESSURE checks, and additional diagnostic procedures as needed such as ULTRASOUND, AMNIOCENTESIS, or CHORIONIC VILLI SAMPLING (CVS). The schedule of visits varies according to the trimester of pregnancy and any specific concerns about the pregnancy.

Ideally, prenatal care begins before CONCEPTION with a focus on nutritious EATING HABITS, healthy weight, appropriate management of any health conditions (such as DIABETES, HYPERTHYROIDISM, and HYPERTENSION), and abstinence from cigarette smoking, ALCOHOL consumption, and substance abuse. The prospective father should share this focus, as the health of both parents contributes to FERTILITY and fetal health. Also ideally, a woman who is planning pregnancy already receives routine medical examinations, including PELVIC EXAMINATION and PAP TEST, according to the recommendations appropriate for her age, sexual activity, and health history. Lifestyle habits to maintain the health of the woman and the fetus remain significant for the duration of pregnancy.

Health experts strongly encourage all women of childbearing age, regardless of their intentions toward pregnancy, to take a folic acid supplement. Folic acid, also called folate, significantly reduces the risk for serious BIRTH DEFECTS called NEURAL TUBE DEFECTS. However, the neural tube (the rudimentary CENTRAL NERVOUS SYSTEM) develops very early, well before a woman suspects she might be pregnant. Taking 400 micrograms (mcg) of folic acid supplement daily provides protection even when pregnancy is unexpected (as is the case with half of pregnancies that occur in the United States) and provides nutritional benefit for the woman. Oral contraceptives (birth control pills) deplete folic acid.

Prenatal Care: First Trimester

Routine prenatal care visits occur monthly during the first trimester, which extends through the 12th week of pregnancy. The first prenatal visit is more extensive than subsequent visits because the health-care provider conducts a comprehensive medical examination, including pelvic exam, and collects detailed information about the woman’s health history, including any previous pregnancies, SEXUALLY TRANSMITTED DISEASES (STDS), childhood diseases, and immunizations. At the first prenatal visit the health-care provider also establishes a baseline of vital data such as height, weight, blood pressure, and size of the pelvic opening and the UTERUS. Routine blood tests done on the first prenatal visit commonly check BLOOD TYPE including Rh factor, ANEMIA, and antibodies for MUMPS, MEASLES, CHICKENPOX, HEPATITIS B, RUBELLA, and SYPHILIS. The provider may also recommend a blood test for HIV/AIDS and screening of both parents for cystic fibrosis if not yet done.

Another priority on the first prenatal visit is estimation of the anticipated due date for birth, which is important to assess whether the pregnancy and fetal growth are progressing as they should. Adding seven days and subtracting three months from the date the last menstrual period started gives the approximate due date, which the provider compares to findings from the pelvic examination to assess the age of the fetus.

At each subsequent prenatal visit during the first trimester the health-care provider tests a urine sample for GLUCOSE and protein, obtains weight and blood pressure, and measures the growth of the uterus. Pelvic exams are not usually necessary. If there are concerns about GENETIC DISORDERS or CHROMOSOMAL DISORDERS the provider may offer CVS (chorionic villi sampling) between the 10th and 12th weeks. At the last visit of the first trimester the health-care provider is often able to detect the fetal heartbeat using Doppler ultrasound.

Prenatal Care: Second Trimester

Routine prenatal visits continue monthly during the second trimester, the 13th through the 26th weeks of pregnancy. The growth of the uterus is more apparent and measurements of it more precise, allowing the health-care provider to refine the prospective due date. Weight, blood pressure, and urine sample for glucose and protein remain staples of prenatal visits in the second trimester.

Around the 18th week the health-care provider offers a set of screening blood tests, the triple screen or the quad screen. These tests measure certain hormones and proteins in the woman’s blood that may suggest neural tube defects such as SPINA BIFIDA and chromosomal disorders such as DOWN SYNDROME. The results of these tests are specific to the gestational age so the provider will be as certain as possible about the due date before conducting them.

It is important for the woman, her partner, and the provider to discuss the implications of positive results from screening tests, and for the woman and her partner to consider what actions they might take. The provider typically recommends amniocentesis to further evaluate positive triple screen or quad screen results. The provider may recommend abdominal ultrasound around the 20th week if the due date is questionable or if there is reason to suspect abnormalities in fetal development. At the end of the second trimester the provider typically requests a glucose challenge test to check for GESTATIONAL DIABETES as well as blood tests to check for anemia.

Triple Screen
beta human chorionic gonadotropin (beta-HCG)
unconjugated estriol (uE3)
Quad Screen
pregnancy-associated plasma protein A (PAPP-A)

Prenatal Care: Third Trimester

Routine prenatal care visits shift to every two weeks between 28 and 36 weeks and weekly from 36 weeks until delivery. The health-care provider continues to check weight, urine, and blood pressure. Early in the third trimester the provider discusses the potential for delivery by CESAREAN SECTION if the fetus is in a breech position or there are other circumstances that might increase the risk to the fetus or the woman with a vaginal delivery.

At the 34th or 35th week the provider cultures swabbed samples from the VAGINA and rectum for group B streptococcus (GBS) BACTERIA, which some women harbor without harm to themselves but that can cause life-threatening INFECTION in the newborn. Women who test positive for GBS receive ANTIBIOTIC MEDICATIONS when they go into labor. The provider also monitors the status of GENITAL HERPEs, when this STD is present, to be prepared for cesarean section should an outbreak occur near the anticipated time of delivery.


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