Coffee and Smoking as Risk Factors of Twin Pregnancies: The Danish National Birth Cohort

Abstract

Twinning rates have changed substantially over time for reasons that are only partly known. In this study we studied smoking, coffee and alcohol intake, and their possible interaction with obesity as potential determinants of twinning rates using data from the Danish National Birth Cohort between 1996 and 2002. We identified 82,985 pregnancies: 81,954 singleton and 1031 twins. For the twins we had data to classify 121 as monozygotic, 189 dizygotic (same sex), 313 dizygotic (opposite sex) but, 408 were of the same sex but with unknown zygosity. All mothers were interviewed about their prepregnancy weight and height, coffee and alcohol intake, smoking habits, and potential confounding factors at early stages of pregnancy. We identified smoking (> 10 cigarettes/day) as a possible determinant of twinning, particularly for dizygotic twinning rates (same sex) and furthermore corroborated that obesity and the mother's age are strong correlates of twinning. Others have found coffee intake to increase twinning rates but that is not seen in these data.

Body composition, smoking, and spontaneous dizygotic twinning

“…This study replicates previous findings on height, BMI, and smoking in relation to DZ twinning (1,7,10,15,16,18,20,21). Our study further extends these findings by taking into account possible influences of socioeconomic status, which was operationalized as educational attainment.…”

“…Maternal Age, Gravidity, and Educational Attainment Maternal age at time of the twin pregnancy was obtained by subtracting the birth date of twins from the birth date of the mother and was recoded into the same four categories as reported in by Basso et al (15); 25 or younger (17)(18)(19)(20)(21)(22)(23)(24)(25), 26-30, 31-35, 36 or older (36)(37)(38)(39)(40)(41)(42)(43)(44)(45).…”

“…Such an association was not found for MZ twinning. With respect to smoking, significantly higher multiple birth rates have been reported for mothers who smoke (17)(18)(19)(20), although this association is not always significant (21).…”

Twinning across the Developing World

“…The number of twin pregnancies increases substantially with maternal age, until age 38, and then decreases again [1], [3], [11], [12]. Other factors associated with twinning are parity (the number of pregnancies experienced by the mother before the twin pregnancy) [1], [12], [13], maternal height [13]–[15], smoking [16], [17], oral contraceptive use [12], [18] and race/ethnicity [1], [6], [19], [20]. There is also a substantial hereditary component, which runs through the female line [21], [22].…”

Risk of Gestational Diabetes Due to Maternal and Partner Smoking

“…Pregnant women are among the most vulnerable to exposure to atmospheric environmental pollution, which has been linked to alterations in fetal development [ 6 , 7 ]. Previous studies have reported that tobacco smoking during pregnancy is associated with increased risks of a number of short and long term health complications for both mother and child [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. Passive EET is associated with numerous harmful effects [ 2 ] however; passive EET during pregnancy has not been extensively studied [ 11 , 18 , 19 ].…”