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The timing and quality of prenatal care can influence an infant’s health
and survival. Early comprehensive care can promote healthier
pregnancies through early detection of risk factors, disease state
management, and encouragement of healthy behaviors.
Important physiologic changes occur in almost all maternal organs during
pregnancy to support the growth and development of the fetus.
Drug use during pregnancy presents a significant challenge to clinicians
because of the potential adverse effect on the embryo, fetus, and
newborn. A thorough assessment, including knowledge of the
teratogenic potential of the drug, the critical period of exposure, and
magnitude of risk, must be compared with the background risk.
Gastrointestinal (GI) disturbances such as nausea and vomiting and
gastric reflux that occur during pregnancy are common. Treatments
include intravenous (IV) hydration, pyridoxine (vitamin B6
antihistamines, and antiemetics for nausea and vomiting. Calcium
-receptor antagonists, and proton-pump inhibitors may be
used for common complaints from reflux.
Urinary tract infections can frequently occur during pregnancy and can
easily be treated with nitrofurantoin, cephalexin, or penicillin if cultures
Diabetes mellitus is the most common maternal medical complication
during pregnancy. Tight glycemic control can minimize neonatal and
fetal morbidity and mortality associated with diabetic embryopathy.
Women with pregnancy-associated hypertension can be grouped into the
following categories: chronic hypertension, preeclampsia–eclampsia,
preeclampsia superimposed on chronic hypertension, and gestational
The induction of labor involves the artificialstimulation of uterine
contractions that lead to labor and delivery.
Premature birth is the leading cause of neonatal mortality (infant death
<1 month of age). Tocolytic therapy to stop contractions, corticosteroids
for fetal lung maturity, and antibiotics for preterm premature rupture of
membranes can help to prolong the pregnancy.
Infectious complications, including bacterial vaginosis and urinary tract
infections, can lead to preterm labor. Chorioamnionitis, an infection of
the chorion and amnion usually diagnosed during labor with elevations in
temperature, should be treated with IV antibiotics until delivery. Human
immunodeficiency virus (HIV)-infected mothers should receive IV
zidovudine and continue their antiretroviral regimens during labor.
Obstetric postpartum hemorrhage is one of the top three causes of
maternal mortality in the United States. Pharmacologic therapy for
uterine atony includes oxytocin, methylergonovine, carboprost,
misoprostol, and dinoprostone.
Alloimmunization occurs when an Rh D-negative mother becomes
immunized after exposure to fetal erythrocytes that carry the D antigen.
(D) immune globulin should be given to all mothers who are Rh D
negative at 28 weeks’ gestation.
LACTATION AND DRUGS IN BREAST MILK
Breast milk is recognized as the optimalsource of nutrition for infants,
with documented benefits not only to infants but also to mothers,
families, and societies, and breast-feeding should be encouraged if
Most drugs are excreted in the breast milk. The pharmacologic and
adverse effects on the infant will be determined by the extent of oral
The relative infant dose (RID) can be calculated to estimate the infant’s
exposure based on volume of milk ingested.
Parity and gravida are terms used to describe a pregnant woman. Parity is the number
of deliveries after 20 weeks’ gestation. Parity is independent of the number of fetuses
delivered (live or stillborn, single fetus, or twins) or the method of delivery. Gravida
refers to the number of pregnancies a woman has had regardless of the outcome. For
example, a woman who is currently pregnant and has previously delivered one set of
twins and had two spontaneous abortions is described as a gravida 4, para 1 (G4,
The average pregnancy is approximately 40 weeks when calculated from the first day
of the LMP. Pregnancy is typically divided into three trimesters, approximately 13 to
1 The first trimester includes the critical period of organogenesis, the
time in which most of the vital organs are developing, which occurs between weeks
5 and 10. The time between the end of the 20th week of gestation and the end of the
28th day after birth is considered the perinatal period.
Depending on the gestational age at the time of delivery, the result can be an abortion,
preterm, term, or post-term birth. An abortion is a delivery before 20 weeks’
gestation. A term infant is a fetus delivered between 37 and 42 weeks’ gestation. A
preterm birth is one occurring between 20 and 37 weeks’ gestation, and a post-term
(postmaturity) birth occurs after the beginning of 42 weeks’ gestation. Parturition
refers to labor, and the puerperium is the 6 to 8 weeks after delivery.
QUESTION 1: S.C. is a 29-year-old, G1, P1 woman who is interested in becoming pregnant. Her past
Provide appropriate counseling to S.C. with regard to preconceptional care.
It is estimated that 3.9 million live births were registered in the United States in
2013, with an estimated 70.8% of women beginning prenatal care in the first
trimester. This can be contributed to several statewide initiatives to increase
education and access to prenatal care.
2 Although much improved, prenatal care is
still not easily accessible to all women. Early comprehensive care can promote
healthier pregnancies through early detection of risk factors, disease state
management, and encouragement of healthy behaviors, and will help to ensure normal
fetal organogenesis. Appropriate preconception counseling and treatment of women
with preexisting high-risk medical conditions, such as diabetes, hypertension, and
epilepsy, can greatly improve pregnancy outcomes. In 2013, the mortality rate in the
United States (from birth through the first year of life) for infants of mothers
beginning prenatal care in the first trimester was 5.96/1,000 live births.
S.C. should see her primary-care provider for regular physical examinations and
evaluation of her thyroid function before becoming pregnant. Her first prenatal visit
should generally occur by 8 weeks’ gestational age when she becomes pregnant.
Vitamins and Mineral Supplementation
CASE 49-1, QUESTION 2: S.C. asks you to recommend vitamin and mineral supplementation and to provide
guidance on when should she begin taking these vitamins and minerals.
A balanced diet that provides S.C. with multiple B vitamins, oil-soluble vitamins
(A, E, D, and K), folic acid, and minerals (iron, calcium, phosphorus, magnesium,
iodine, zinc) should be encouraged. S.C. should be started on a prenatal multivitamin
if she has not yet started taking one. Prenatal vitamins should be taken months before
conception to ensure that proper nutritional requirements are met during critical
periods of organogenesis and fetal growth.
Iron requirements increase during pregnancy because of maternal blood volume
expansion, fetal needs, placenta and cord needs, and blood loss at the time of
5 Maternal iron deficiency can cause anemia during infancy, spontaneous
abortion, premature delivery, and delivery of a low-birth-weight infant, and is
associated with low neonatal iron stores.
A woman needs about 18 to 21 mg of iron/day during pregnancy; the body
compensates by increasing iron absorption from the GI tract by about 15% to 50%.
in the United States does not meet these requirements because only about 6 mg of
iron is absorbed from 1,000 kcal of food. In addition, some women may already have
inadequate body stores of iron before pregnancy. For these reasons, the Centers for
Disease Control and Prevention recommends screening for iron deficiency in
pregnancy in addition to universal iron supplementation except when genetic
conditions such as hemochromatosis are present.
7 Prenatal vitamins usually contain
30 to 60 mg of elemental iron. Women with iron deficiency anemia should be given
60 to 120 mg of elemental iron daily. Iron deficiency anemia during pregnancy
generally is associated with a hemoglobin and hematocrit less than 11 mg/dL and less
than 33%, respectively, during the first and third trimesters or less than 10.5 mg/dL
and less than 32%, respectively, during the second trimester. The classic
morphologic changes observed in the erythrocytes in iron deficiency outside of
pregnancy, hypochromia, and microcytosis are not prominent in pregnant women.
Serum ferritin, however, is low, which has the highest sensitivity and specificity for
6 S.C.’s hemoglobin and hematocrit should be assessed
now and again at 26 to 28 weeks’ gestation. If her hemoglobin and hematocrit are
normal, the amount of iron in her prenatal vitamin should be sufficient.
Folic acid is essential in the synthesis of DNA and RNA. Pregnant women who take
0.4 to 0.8 mg of folic acid daily during the first trimester of pregnancy are
significantly less likely to have a child with neural tube defects (NTDs), such as
8,9 NTD can lead to stillbirth, neonatal death, or serious
disabilities. Approximately 4,000 pregnancies in the United States are affected by
NTDs develop within the first month of pregnancy at a time when many women are
In 1992, the US Public Health Service recommended
that all women with childbearing potential should consume 0.4 mg/day of folic acid
to reduce the risk of an NTD-affected pregnancy.
It may be difficult to meet the recommended daily allowance (RDA) for folic acid
prenatal vitamins contain 0.8 to 1 mg of folic acid.
Folic acid supplementation is especially important in women with a history of
infants born with NTD. Women who have had an NTD-affected pregnancy should
receive genetic counseling because they have a 2% to 3% risk of having another such
outcome. Women with previous NTD-affected pregnancies who plan another
pregnancy should take 4 mg/day of folic acid at least 1 month before conception and
through the first 3 months of pregnancy.
Women who require 4 mg/day of folic acid should be prescribed folic acid tablets
as an addition to combination prenatal multivitamins (which contain folic acid),
potentially teratogenic dose of vitamin A. High doses of folic acid do not prevent
NTD better than 0.4 mg/day in women without a previous history of NTD-affected
pregnancies and may complicate the diagnosis of a vitamin B12 deficiency.
S.C. should be counseled about the risks for NTD, and given she has no history of
NTD, she should receive adequate folic acid during the remainder of her pregnancy
from a daily prenatal vitamin.
Calcium is needed during pregnancy for adequate mineralization of the fetal skeleton
and teeth, especially during the third trimester when teeth are formed and skeletal
growth is greatest. The RDA for calcium during pregnancy is 1,000 mg/day for
women of 19 years and older, and 1,300 mg/day for teenagers younger than the age of
12 Large maternal stores can provide calcium if dietary intake is inadequate;
however, depleting maternal stores may put S.C. at risk for osteoporosis later in life.
Foods rich in calcium (e.g., milk, cheese, yogurt, legumes, nuts, dried fruits) or
calcium supplements can be used to meet the calcium RDA.
Commercially Available Home Pregnancy Tests
How do these home pregnancy tests work and how should S.C. be counseled?
Commercially available home pregnancy tests are enzyme immunoassays with
monoclonal or polyclonal antibodies that bind to hCG in the urine.
in the maternal circulation and urine approximately 8 to 10 days after conception.
Concentrations in the urine closely parallel those in the maternal blood. The hCG
serum concentrations increase rapidly, doubling every 2 days. Peak concentrations
are achieved at 60 to 70 days of pregnancy. Thereafter, hCG concentrations decline
and reach a low by approximately 120 days, at which point concentrations are
maintained for the remainder of the pregnancy.
hormone, thyroid-stimulating hormone); however, the β-subunit is specific to hCG.
Pregnancy tests specific for this β-subunit are useful diagnostic tests for confirming
1 They can provide accurate results within 1 to 2 weeks after ovulation.
Several kits are available. The tests can be performed privately and quickly and are
easily interpreted. The results are obtained rapidly—within 1 and 5 minutes—and
are highly accurate when performed at the start of the first missed menstrual period.
Although home pregnancy tests are reportedly 98% to 100% accurate when used
correctly, consumer studies have documented accuracy rates as low as 50% to 75%
if product directions are not precisely followed.
include a second test, which should be repeated at a specified time after the first
S.C. should purchase a product containing two tests and follow the instructions
carefully. If the first test result is negative, S.C. should repeat the test in 1 week if she
has not started menstruating. False-negative results occur when testing is done before
the first day of a missed period or if the urine is not at room temperature.
13 Falsenegative results can also occur with an ectopic (outside the uterus) pregnancy or in
women with ovarian cysts and in those receiving menotropins or chorionic
13 False-positive pregnancy test results are rare, but can occur with
serum testing if the woman has circulating heterophilic antibodies directed against
the animal-derived antigen use in pregnancy tests. These antibodies will not interfere
with urine assays, however, as they are not present in urine.
S.C.’s home pregnancy test is positive. Because she is pregnant she should be
counseled on the possible fetal effects of any medications or herbal products she may
be taking and advised to see her primary-care provider as soon as possible.
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