A nurse is caring for a newborn who is large for gestational age and is 12 hours old.
Which of the following laboratory tests should the nurse monitor based on the client's condition?

Choice A rationale

While seizures are a serious adverse effect of ergot alkaloids, they are primarily associated with the most severe form of ergotism, which is an overdose or prolonged exposure, or in clients with severe preeclampsia/eclampsia. Methylergonovine's more common and immediate adverse effect is its potent vasoconstrictive property, leading to elevated blood pressure.

Choice B rationale

Methylergonovine is an ergot alkaloid that acts as a potent vasoconstrictor and smooth muscle contractor, primarily on the uterus to treat postpartum hemorrhage and uterine atony. Its generalized vasoconstrictive effect, however, can lead to a significant elevation in blood pressure, making hypertension (blood pressure greater than 140/90 mmHg or an increase of 20 mmHg or more) a major and frequent adverse effect.

Choice C rationale

Methylergonovine's potent vasoconstrictive action typically causes an increase in peripheral vascular resistance, which often results in bradycardia (heart rate less than 60 beats/min) as a reflex response to the elevated blood pressure. Tachycardia (heart rate greater than 100 beats/min) is not a typical adverse effect of this medication.

Choice D rationale

Methylergonovine acts mainly on the smooth muscle of the uterus and blood vessels; it does not typically cause water retention. Water retention is more commonly associated with conditions like preeclampsia or medications such as glucocorticoids. The adverse effects of methylergonovine center around vasoconstriction and uterine cramping.

Vaginal bleeding

Bleeding occurs in placenta previa due to partial or total implantation of the placenta over the cervical os, leading to painless bright red bleeding from disrupted placental vessels. It also occurs in preterm labor when cervical effacement and dilation disrupt small cervical vessels, producing light bleeding or spotting. In abruptio placenta, bleeding is dark red and may be concealed or apparent, resulting from premature placental detachment and rupture of maternal vessels in the decidua basalis.

Uterine contractions

Regular uterine contractions every 2 to 3 minutes with cervical change are diagnostic of preterm labor, resulting from premature activation of uterine oxytocin receptors and prostaglandin release before 37 weeks. In abruptio placenta, contractions are often strong and sustained (hypertonic uterus) due to myometrial irritability from bleeding into the decidual layer. Placenta previa, however, typically presents with painless bleeding and a soft, relaxed uterus without contractions because the uterine muscle tone remains unaffected.

Cervical dilation

Cervical dilation indicates preterm labor, as biochemical changes in the cervix from increased prostaglandin and relaxin activity cause collagen breakdown and effacement before term. This process reflects uterine activation sequence initiation leading to potential preterm birth. In placenta previa, the cervix may remain closed despite bleeding because bleeding originates from placental implantation, not cervical change. Abruptio placenta rarely involves dilation unless labor progresses secondarily after placental separation, thus cervical dilation is not a key feature.

Abdominal tenderness

Abdominal tenderness is characteristic of abruptio placenta, caused by bleeding between the uterine wall and placenta leading to myometrial irritability, uterine rigidity, and ischemic pain. The trapped blood increases intrauterine pressure, stimulating pain receptors in the myometrium and stretching the uterine serosa. Placenta previa presents with a soft, nontender abdomen because bleeding is external and not associated with uterine muscle involvement. Preterm labor generally causes back discomfort or cramping, not localized abdominal tenderness.

Client report of low back pain

Low back pain is prominent in preterm labor, resulting from referred pain due to rhythmic uterine contractions transmitted through the lumbosacral plexus and pelvic nerves. It reflects early cervical change and uterine irritability. In abruptio placenta, the back pain may occur secondary to uteroplacental separation and posterior placental bleeding irritating the parietal peritoneum. Placenta previa typically lacks pain or back discomfort since bleeding occurs without uterine or peritoneal irritation.