Now Can You—Correctly calculate the EDB?

Calculate the estimated date of birth using Naegele’s rule?

Lynne is a 28-year-old woman who comes to the clinic with a history of amenorrhea and a positive home pregnancy test.

Her last menstrual period began on August 26, 2014. She bled for the usual amount of time and reports that the amount of blood loss was normal. Assuming that Lynne had a 28-day cycle, use Naegele’s rule to calculate her estimated date of birth.

Important to remember: The month of August has 31 days.

• August 26 + 7 days = September 2
• (September) ninth month − 3 = sixth month (June)
• EDD/EDC/EDB = June 2

Correct calculation of the EDB is dependent on a reliable date of the LMP. Hormonal birth control methods such as combined oral contraceptive pills (OCP) and long-lasting progesterone injections can cause continued suppression of ovulation. Therefore, a discrepancy may exist between when the woman thought she ovulated and conceived and when these events actually occurred. Thus, the LMP may not be an accurate tool for estimating the due date.

Occasionally, pregnancy occurs in women who are taking oral contraceptives, usually as the result of a “pill failure” from forgotten pills or because of poor absorption that may result from various causes such as vomiting, diarrhea, or antibiotic use. Thus, contraceptive pill use may have unwittingly been continued during the early weeks of gestation. The nurse can assure the patient that prenatal hormone exposure associated with normal contraceptive use has not been shown to have any detrimental effects on the developing fetus (Nelson & Cwiak, 2011).

The Pregnancy Classification System

Another important task associated with the initial prenatal interview is to determine the patient’s gravidity and parity. Gravid is the state of being pregnant; a gravida is a pregnant woman. Gravidityrelates to the number of times that a woman has been pregnant, irrespective of the outcome. The term nulligravida is used to describe a woman who has never experienced a pregnancy. A primigravida is a woman pregnant for the first time, and a secundigravida is a woman pregnant for a second time. Although officially correct, this term is seldom used and instead the term multigravida is used in its place. A multigravida describes a woman who is pregnant for the third time (or more times). Parity refers to the number of pregnancies carried to a point of viability (generally accepted as 24 weeks of gestation), regardless of the outcome. For example, “para 1” indicates that one pregnancy reached the age of viability. A para 2 means that two pregnancies reached the age of viability. It is important to note that the term parity (or “para”) denotes the number of pregnancies, not the number of fetuses/babies, and does not reflect whether the fetuses/babies were born alive or stillborn. Some facilities use a digital system (i.e., GTPAL) for recording the number of pregnancies and their outcomes.

• G Gravida
• T Number of Term pregnancies
• P Number of Preterm deliveries
  

  Where Research and Practice Meet:

  Depo-Provera Use Before PregnancyBone mass can be adversely affected by the use of depot medroxyprogesterone acetate (Depo-Provera). The extent to which bone mass is lowered appears to be linked to the length of use (Bartz & Goldberg, 2011). Calcium has two main physiological functions: promoting skeletal growth and maintaining bone mass. Unfortunately, humans only absorb approximately 10% of the dietary calcium consumed. There are three periods in human life when calcium uptake is increased: during infancy, adolescence (growth spurt), and in the latter half of pregnancy. To counsel prenatal patients appropriately, nurses should understand the benefits associated with meeting the recommended intake of daily calcium and be knowledgeable about factors that increase absorption. Pregnancy is a time when maternal calcium absorption is increased. To take advantage of this physiological alteration, pregnant women should be encouraged to eat a well-balanced diet with adequate amounts of calcium, protein, and vitamin D and routinely participate in weight-bearing exercises (ACOG, 2011e).

• A Number of Abortions, both spontaneous and induced
• L Number of Living children

Pregnancy Testing

A detectable level of human chorionic gonadotropin (hCG) must be present in the urine or blood for a pregnancy test to be positive. hCG is produced by the syncytiotrophoblastic cells found in the outer layer of the trophoblast and secreted into the maternal plasma and then excreted in the urine. hCG levels peak between days 60 and 70 of pregnancy and then gradually decrease over approximately the next 40 days to reach a plateau that is maintained throughout the pregnancy. hCG can be detected in maternal blood as early as 1 day after implantation and in urine around day 26. The hCG molecule contains both an alpha subunit and a beta subunit. Because of the large number of commercial pregnancy tests available, women should be advised to use a home pregnancy test that is specific for the beta subunit of hCG because this marker prevents cross reactions with other hormones. The alpha subunit is very similar in molecular structure to luteinizing hormone (LH). Women with high LH levels (e.g., those experiencing perimenopause) who use a pregnancy test designed to detect the complete hCG molecule risk obtaining a false-positive result. If the over-the-counter pregnancy test used relies on urinary hCG, the patient should be advised to follow the manufacturer’s recommendations carefully to avoid an unreliable result. If a home pregnancy test is negative and the signs and symptoms of pregnancy persist, the test should be repeated in a week or the woman should see her health-care provider.

A “chemical pregnancy” is a term used to describe a situation that occurs when a home pregnancy test has confirmed the presence of hCG, but a late and often heavy menstrual period follows. In these instances, conception probably occurred but for some reason the pregnancy was unable to continue and develop into a viable embryo. The frequency of this occurrence is difficult to estimate accurately, but it is thought to affect approximately 30% to 50% of all pregnancies. Before the development of sophisticated methods for detecting an early pregnancy, most of these early and unfruitful fertilizations would have gone undiagnosed.

Optimizing Outcomes—Promoting a healthy beginning for the fetus

The first few weeks of gestation are of paramount importance to the developing fetus. During this time, the fetus is most susceptible to teratogenic substances such as alcohol, drugs, and environmental toxins. If a woman suspects that she may be pregnant despite a negative home pregnancy test, the nurse should advise her to avoid substances that could be potentially harmful to the developing fetus.

The diagnosis of a multiple gestation places the pregnancy into a “high risk” classification. An early diagnosis of a multiple gestation allows for the development of a care plan that includes more frequent visits for maternal–fetal surveillance. As with any pregnancy, early and ongoing prenatal care offers an opportunity for the timely recognition of complications (more often associated with multiple gestations) and the initiation of interventions to maintain the pregnancy as long as possible. The woman expecting a multiple birth also needs additional psychological support, practical advice, and education. She may experience more intense discomforts of pregnancy and need to deal with upsetting and extreme body changes. In addition, she also faces the financial challenges associated with a potentially complicated pregnancy, possible preterm birth, and the economic burden of providing for multiple newborns.

Now Can You—Discuss essential aspects of the current pregnancy?

• 1. Differentiate among the “presumptive,” “probable,” and “positive” signs of pregnancy?
• 2. Explain how to calculate the estimated date of birth using Naegele’s rule?
• 3. Describe the GTPAL pregnancy classification system?
• 4. Explain what women should be taught about home pregnancy testing?