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Prenatal care: Second and third trimesters

Charles J Lockwood, MD, MHCM
Urania Magriples, MD
Section Editor
Vincenzo Berghella, MD
Deputy Editor
Vanessa A Barss, MD, FACOG


The goal of prenatal care is to ensure the birth of a healthy baby with minimal risk for the mother. Prenatal care is not a single intervention; instead, it represents a series of assessments and interventions over time that is variously applied by different practitioners. The "quality" of prenatal care and the effect of individual components on outcome are thus difficult to measure.

After the initial prenatal assessment and patient counseling, prenatal care is directed at ongoing evaluation of the health status of both mother and fetus, anticipation of problems, and intervention, if possible, to prevent or minimize morbidity. This topic will discuss prenatal care in the second and third trimesters. Prenatal issues related to the first visit and first trimester are reviewed separately. (See "Prenatal care: Initial assessment".)


Observational data suggest that prenatal care saves lives compared to no prenatal care [1] and show an association between the number of antenatal visits and/or early gestational age at the initiation of care and pregnancy outcomes, after controlling for confounding factors (eg, length of gestation) [2]. However, there are limited data as to what constitutes the optimal number and frequency of prenatal visits, or the optimal content of those visits.

In the United States, the typical intervals for prenatal visits for nulliparous women with uncomplicated pregnancies are every 4 weeks until 28 weeks of gestation, every 2 weeks from 28 to 36 weeks, and then weekly until delivery [3]. Parous women with uncomplicated medical and obstetrical histories can be seen less frequently. Women with problems are seen more frequently, depending on the nature of the problems. According to this schedule, an uncomplicated pregnancy where the first visit is at six weeks of gestation and the last visit is at 41 weeks will comprise 16 prenatal visits. While the above visit schedule is commonly followed, it requires significant effort and planning on the part of the patient without clear evidence of benefit.

In a cohort study of over 7200 women with low-risk pregnancies, there were no differences in neonatal intensive care unit admissions, five-minute Apgar score <7, neonatal demise, or small for gestational age infants among women who had more than 10 prenatal visits and those who had 10 or fewer prenatal visits [4]. While the women in the high utilization group were 33 percent more likely to undergo induction of labor and 50 percent more likely to have a cesarean delivery than the women in the low utilization group, there are insufficient data to conclude a causal relationship.

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Literature review current through: Oct 2017. | This topic last updated: Aug 17, 2017.
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