An ounce of prevention: The evidence supporting periconception health care

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Applied Evidence

An ounce of prevention: The evidence supporting periconception health care

J Fam Pract. 2004 February;53(2):126-134

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References

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Other benefits of glycemic control

Major congenital malformations occur in 4% to 11% of infants of diabetic mothers compared with a background rate of 1.2% to 2.1%. Higher values of hemoglobin A_1c in the first trimester have been associated with these increased rates of congenital anomalies. However, it is not clear if the association is linear or if a threshold level of hemoglobin A_1c exists, above which the anomaly rate increases. Anomalies most commonly occur in the cardiovascular, skeletal, and central nervous systems before 8 weeks gestational age. Therefore, the critical time for preventing congenital anomalies is before conception.

Preconception care reduces anomalies overall

One meta-analysis of 16 studies provides evidence for the value of preconception care in reducing congenital anomalies due to diabetes mellitus.³³ The interventions included both inpatient and out-patient optimization of glucose control. The analysis reviews 8 prospective and 8 retrospective cohort studies with a total of 2651 offspring. The results of all 16 studies were consistent.

Hemoglobin A_1c values were significantly lower in the preconception care group. The overall rate for major congenital anomalies was 2.1% in the preconception group compared with 6.5% in the pregnancy care group (NNT=23) (LOE: 2a). The studies with the lowest anomaly rates had a pre-meal glucose target of <120 mg/dL, and participants injected insulin 4 times daily. A cost-benefit analysis based on a mathematical model of preconception diabetic care calculated that intensive preconception care for women with diabetes would save an average of $1720 per enrollee when adverse maternal and neonatal outcomes are taken into account.³⁴

Intensive preconception glycemic control helps prevent major congenital anomalies in children born to women with diabetes (SOR: B).

Epilepsy

Compared with healthy women, women with epilepsy have higher rates of infertility and miscarriage and higher rates of infants with congenital anomalies (4%–8%; mainly neural tube defects and heart defects).³⁵ Therefore, women with epilepsy (5.6/1000 among women aged 15 to 64³⁶) should receive special attention to preconception care. Adding to the urgency for counseling is the fact that medications for epilepsy can reduce the effectiveness of some forms of hormonal contraception.

Medications are the problem

A source of debate has been whether the increased rate of anomalies is due to epilepsy or the medications used to treat it. A cohort study compared 3 groups of pregnant women: those taking antiepileptic medications (some were taking these medications for other conditions, such as bipolar disorder), women with epilepsy who were not on medications, and a control group. The rate of major and minor malformations among infants of women taking antiepileptic medications was 20.6%, compared with 8.5% in the control group (LOE: 2b).³⁷ Women with epilepsy who were not on medications had a similar anomaly rate to the control group.

The medications primarily associated with congenital anomalies were valproic acid, carbamazepine, and phenytoin; polytherapy was associated with a higher anomaly rate. The data on newer antiepileptic medications (eg, gabapentin, lamotrigine, oxcarbazepine, tiagabine, topiramate, and vigabatrin) are insufficient to determine if anomaly rates are increased among fetuses exposed to them.³⁸ Because folic acid supplementation has been associated with lower rates of infants with neural tube defects, higher-dose folic acid supplementation (1–4 mg/d) has been recommended for women with epilepsy (LOE: 5).

Change treatment before conception

One cohort study has examined the effectiveness of preconception counseling for women with epilepsy.³⁹ The investigators compared women referred to a preconception epilepsy clinic with women who presented during pregnancy. In the preconception group, all women were placed on folic acid, two thirds were shifted to monotherapy prior to conception, and 6% were able to stop their epilepsy medications. The epilepsy clinic followed a protocol for confirming the diagnosis of epilepsy, determining if a woman was a candidate to discontinue medications, avoiding use of phenytoin and valproic acid, and switching as many women to monotherapy as possible.

The preconception care group had no major fetal malformations, compared with 18% in the pregnancy group (NNT=6) (LOE: 2b).

Applying the evidence

On the basis of this study, women with epilepsy who are considering pregnancy should be switched to monotherapy and potentially less teratogenic medications (when possible), and should receive at least 1 mg/d folic acid prior to conception (SOR: B).

Rubella

Immunization has reduced the occurrence of rubella in the US from 57,686 cases in 1969 (when vaccination was started) to 279 cases in 1999.⁴⁰ Cases of congenital rubella syndrome in the US have fallen to a low of 3 cases in 2001. However, rubella and congenital rubella syndrome are still fairly common in developing countries, many of which have no rubella vaccine program or have only recently started such programs.