喫煙妊産婦におけるニコチンの胎児への影響 : 喫煙状況と臍帯血ならびに部分尿の検討

背景 わが国における成人女性の喫煙率は先進諸国に比べて低い。しかし,近年における大都市の生殖年齢にある女性の喫煙率や,妊娠期間中,喫煙を中止できない妊婦の喫煙率は増加傾向にある。この傾向は,喫煙が次世代の育成に大きな影響を与えるという観点から,周産期管理上見過ごせない問題となっている。妊娠中に禁煙できなかった妊産婦(以後,喫煙妊婦)から出生した子供の異常は胎児性タバコ症候群(fetal tobacco syndrome ;FTS)と呼称され,喫煙が胎児に与える影響やメカニズムが明らかにされている。また,喫煙あるいは受動喫煙下にあった妊婦7名が出産した新生児の尿中から,ニコチンが検出された報告はあるが,分娩直後の臍帯血と児の部分尿を採取し,妊婦の喫煙状況による胎児へのニコチンならびにコチニンの移行状況を検討した報告は見当たらない。目的 妊婦の禁煙指導ならびに健康教育の指標とするため,喫煙妊婦から出生した新生児の臍帯血ならびに尿中のニコチン濃度と,その代謝産物であるコチニン濃度を測定し,妊婦の喫煙状況によるタバコ成分の胎児への移行を検討し,禁煙指導の指標とした。方法 平成14年7月〜平成15年12月の間に満期で分娩した妊婦15名の承諾と協力を得て,分娩前の面接により喫煙歴,FTQ指数(Fagerstrom Tolerance Questionnaire : ニコチン依存度),妊娠中の喫煙状態などを調査し,ならびに分娩前後の呼気中CO濃度の測定を実施した。また,分娩直後の臍帯血と新生児の部分尿を採取し,各々のニコチンとコチニン濃度を測定した。さらに,分娩後には妊娠・分娩・産褥経過や出生時の新生児の様子を記録した。結果 1)喫煙妊婦は減煙行動をとるが肺喫煙の傾向を認め,胎児のニコチンとコチニン量は妊婦の喫煙状況が影響していた。2)ニコチンとコチニンは臍帯を通じて容易に胎児へ移行し,悪影響を与える可能性が示唆された。3)コチニンの高濃度群に,分娩や児の異常兆候を認める割合が高かった。4)1日15本以上の喫煙,ニコチン含有量が中位あるいは強い銘柄の喫煙,肺喫煙を時々あるいはいつもしている,という3つの喫煙行動が,産科異常・低体重児をもたらし易いことが示された。結論 これらの検討内容から,妊婦の健康教育の指標としてより具体的にEvidenceに基づいた保健指導が行えると考えられ,喫煙妊婦の禁煙には,行動変容につながる産前・産後の継続的な指導プログラムが必要であると考えられた。Background The percentage of women smokers of reproductive age and the percentage of women smokers who are unable to discontinue smoking during the pregnancy period are on the increase. This trend has become a problem that cannot be overlooked from the standpoint of perinatal man agement. Objective and Method As an indicator of health education for pregnant women, we examined the state of smoking by pregnant women and the passing along of tobacco components from expectant mothers to their embryos/fetuses by measuring the concentration of nicotine and the concentration of its metabolic product cotinine in the urine and umbilical blood of newborn infants born to expectant mothers who were unable to quit smoking during pregnancy. Results 1) Nearly all the pregnant smokers cut down on their smoking but it was observed that there was a tendency to inhale, and the state of inhaling, as well as number of cigarettes smoked, strength of the brand, and length of the cigarette also has effects on the volume of nicotine intake. 2) It is conjectured that both nicotine and cotinine are easily passed along to the embryo/fetus through the umbilical cord, and therefore it is possible that the embryo/fetus may be strongly affected by the nicotine. 3) From pregnancy to childbirth, pregnant women who smoke bear a high risk of developing obstetrical anomalies and deficient' development of the newborn infant and other anomalies, and especially in the high-concentration group, the ratio of signs of anomalies were observed to be very high. 4 ) It has been indicated that three smoking behaviors, i. e. smoking 15 or more cigarettes per day, smoking brands having a moderate or strong nicotine content, and sometimes or always inhaling the smoke into the lungs, are more likely to bring about an abnormal pregnancy and obstetric abnormalities, and are also likely to have a particularly strong effect on the fetus. Conclusion From the examined content, it is believed that evidence-based health guidance can be provided as a guide for the health education of expectant mothers. And, for pregnant smokers who either quit smoking or cut down on smoking, support and consideration from people around them, and understanding and cooperation especially by family members should be sought, and it is believed that non-stop counseling on non-smoking and the setting of step-by-step goals that will lead to behavior modification, both prior to and after childbirth, are necessary