The H1N1 influenza in pregnant women is more likely to develop complications and worsen more rapidly than when present within the general population
From April 15 to May 18, 2009, the admission of US pregnant women confirmed with H1N1 influenza pandemic was more than four fold compared with the general population . This suggested that the H1N1 influenza in pregnant women is more likely to develop complication and worsen more rapidly than general population. Pregnant women should pay more attention to influenza-like symptoms and consult health professionals immediately. The WHO recommends starting anti-viral no matter what the laboratory test result. Few physicians and pregnant women adhere to this suggestion, for the fear of potential side effects of anti-viral drugs on neonates. The early diagnosis and starting of anti-viral therapy appeared in only a minor proportion of the pregnant women when symptoms appeared. For those whose ignored the influenza-like symptoms, some developed severe hypoxia and resulted in rapid decline in respiratory function and other organ function. From Nov, 8 to Dec 14, there were 16 pregnant women and two postpartum admitted with severe H1N1 influenza in Shengjing hospital.
Shengjing hospital is the largest tertiary center in northeastern China. The department of obstetrics and gynecology is one of the features in this hospital. The department of obstetrics is the center of prenatal diagnosis and high risk pregnancy in Liaoning province. There are 105 beds in four obstetrical wards. In year 2008, there were 6338 women chose Shengjing hospital for delivery, which was the most among the tertiary center in China. This article is intended to highlight and explore the importance of early diagnosis and the appropriate use of anti-viral drugs in this high-risk population.
In the 18 pregnant women admitted in Shengjing hospital, except five went to the triage in Shengjing hospital within 48 hours of influenza-symptoms onset. The remaining 13 women were not in the early course of disease, either with a history of medicine taken by themselves or had been treated as severe pneumonia elsewhere. Those who took medicine were mostly anti-pyretic, yet the fever condition still persisted for several days. After several days of fever, some women presented to their local health providers. At that time, the symptoms, signs, and chest radiographic findings were similar between H1N1 influenza and pneumonia. These women didn’t received virology confirmation and were treated for severe pneumonia at their local hospital.
Various antimicrobial were used, but only two of the 13 womens temperatures returned to normal levels. Severe hypoxemia followed by respiratory failure, acute lung injury, and eventually adult respiratory distress syndrome. The lower lobe of both lungs were consolidation and opacities with massive infiltrative lesion. The two radiographic findings were common when admission. The baseline PaO2 to FiO2 ratio of nine women in second or third trimester on admission were below 300, suggestive of acute lung injury (ALI). Among the nine women, eight of them were even below 200, indicating acute respiratory distress syndrome (ARDS). After a careful assessment of the maternal respiratory status and fetal status, we performed cesarean on the nine women to improve maternal respiratory function.
Seven women were mechanically ventilated soon after admission. Antiviral therapy was given by the emergency physician immediately and thereafter. Nasopharyngeal swabs were also collected for confirmation using reverse-transcriptase-polymerase-chain-reaction by Chinese CDC certified lab. They were isolated from normal hospitalized patients in the ICU of the Infectious Disease Department in Shengjing hospital. In the subsequent therapy, 16 women recovered and discharged, and two died. No apparent oseltamivir-resistant cases were found in the pregnant women.
There were several setbacks including:
1. The unwillingness of admission in early course of disease
Probable fear of the side effect to neonate from the new anti-viral drug oseltamivir. Although lack of large trial in pregnancy women, there is no apparent negative influence of its use . On the other hand, they didn’t recognize the raised possibility of neural tube defect (NTD), cerebral palsy, and schizophrenia, which accompanied with hyperthermia in all periods of gestation . The only way to minimize the risk of the malformation above is to reduce the time of exposure to hyperthermia and shorter the duration of viraemia. Since anti-pyretic alone is insufficient in stopping fever, pregnancy women should consult medical professionals and consider to start anti-viral therapy immediately.
2. Physicians lack of awareness of H1N1 influenza when encountering influenza-like symptoms
According to the weekly surveillance report from Chinese Center for Disease Control and Prevention, over 87.5% of influenza-like symptoms were actually cause by novel H1N1 influenza virus between Dec, 7 and Dec, 13. Physicians should stay alert when pregnant women come with symptoms like fever, sore throat, cough, dyspnea…etc, and take action of both nasopharyngeal swab collection and give anti-viral drugs immediately, especially those with underlying medical condition. The effect of early anti-viral drug therapy is prominent .
3. Radiology and the harm to neonates
Due to the severe hypoxia and potential fetal distress, we considered to terminate pregnancy if acute respiratory distress syndrome occurred. We advised pregnant women in third trimester who was suspected of H1N1 influenza to have a chest computer tomography scan when admission. The aim of the scan was to assess the area of consolidation ,and determine when and how to terminate pregnancy if the respiratory function rapidly deteriorated. However, many women refused to have the scan because of the worry about the radiation and the latent neonatal teratogenesis or carcinogenesis. In the recommended termination of pregnancy after radiation exposure, the so-called “Danish rule” were advisable termination for a fetal dose of over 10 rads . The reference dose value of one routine chest CT is approximately 3 rads . Even in the most sensitive early period, one routine chest CT with well shielded abdomen need no termination of pregnancy.
H1N1 influenza in the general population is usually mild. There are several physiological changes during pregnancy, including cardiovascular and immunological that predispose H1N1 influenza in pregnant women to severe infection. If the patient or health care provider ignores the importance of early diagnosis and use of anti-viral drugs, poor outcomes like emergency cesarean or intra utero fetus death may occur. The bad prognosis may not be directly from influenza, but the complication accompanied with. Referring to a study between 1974 and 1993 in women, there were 356 women whose study event was associated with death; 164 deaths occurred during non-influenza season, 104 during peri-influenza season, and 88 during influenza season. No pregnant women died from cardiopulmonary causes during influenza season . Among the 18 pregnant women with confirmed H1N1 influenza infection, the condition of those in second or third pregnancy were more unstable than the women in first trimester. Since the resolution power of chest computer tomography scan is superior than chest plain film, the information of computer tomography is very useful in assessing the respiratory function. We advised pregnant women in their second or third trimester with influenza-like symptoms to have a regular computer tomography when admitted. Regard to well abdominal shield, the neonatal radiation exposure is under the dose required termination of pregnancy.
Mao Ming-Huan is a fourth year medical student at China Medical University
*Chong Qiao is an Obstetrician at Shenjing hospital
*Specially thank to Qiao C for her fully support and careful revision of this report as corresponding author.
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