Placental weight and birthweight: the relations with number of daily cigarettes and smoking cessation in pregnancy. A population study.

Background: We studied associations of number of daily cigarettes in the first trimester with placental weight and birthweight in women who smoked throughout pregnancy, and in women who stopped smoking after the first trimester. Methods: We included all women with delivery of a singleton in Norway (n = 698 891) during 1999-2014, by using data from the Medical Birth Registry of Norway. We assessed dose-response associations by applying linear regression with restricted cubic splines. Results: In total, 12.6% smoked daily in the first trimester, and 3.7% stopped daily smoking. In women who smoked throughout pregnancy, placental weight and birthweight decreased by number of cigarettes; however, above 11-12 cigarettes we estimated no further decrease (Pnon-linearity < 0.001). Maximum decrease in placental weight in smokers compared with non-smokers was 18.2 g [95% confidence interval (CI): 16.6 to 19.7], and for birthweight the maximum decrease was 261.9 g (95% CI: 256.1 to 267.7). In women who stopped smoking, placental weight was higher than in non-smokers and increased by number of cigarettes to a maximum of 16.2 g (95% CI: 9.9 to 22.6). Birthweight was similar in women who stopped smoking and non-smokers, and we found no change by number of cigarettes (Pnon-linearity < 0.001). Conclusions: In women who smoked throughout pregnancy, placental weight and birthweight decreased non-linearly by number of cigarettes in the first trimester. In women who stopped smoking, placental weight was higher than in non-smokers and increased linearly by number of cigarettes; birthweight was almost similar to that of non-smokers.

Maternal human chorionic gonadotrophin concentrations in very early pregnancy and risk of hyperemesis gravidarum: A retrospective cohort study of 4372 pregnancies after in vitro fertilization.

OBJECTIVE: We investigated the association of human chorionic gonadotrophin (hCG) concentrations on a fixed day in very early pregnancy with development of hyperemesis gravidarum. STUDY DESIGN: This retrospective cohort study included 3107 singleton and 1265 twin pregnancies after in vitro fertilization treated at Department of Reproductive Medicine, Rikshospitalet, Oslo University Hospital, Norway in the period 1996-2013. Maternal serum hCG concentrations was measured on day 12 after embryo transfer. Information about development of hyperemesis gravidarum was obtained by individual linkage to the Medical Birth Registry of Norway. We studied hCG concentrations in very early pregnancy according to development of hyperemesis gravidarum, in singleton and twin pregnancies separately. We estimated the odds ratios for hyperemesis gravidarum with 95% confidence intervals according to quartiles of hCG concentrations. RESULTS: In twin pregnancies as compared to singleton pregnancies, we found higher mean maternal hCG concentrations (219 IU/L versus 130 IU/L, p<0.001 Student's t-test) and higher prevalence of hyperemesis gravidarum (2.7% versus 1.4%, p=0.002 chi-squared test). However, both in singleton and in twin pregnancies, we found no significant difference in mean hCG concentrations between women who developed hyperemesis gravidarum and women who did not (Singletons: 122 IU/L versus 130 IU/L, p=0.504. Twins: 234 IU/L versus 219 IU/L, p=0.417 Student's t-test). We found no significant differences in odds ratios for developing hyperemesis gravidarum according to quartiles of hCG concentrations. CONCLUSIONS: We found no association of maternal hCG concentrations on a fixed day in early pregnancy with development of hyperemesis gravidarum.

Placental weight in the first pregnancy and risk for preeclampsia in the second pregnancy: A population-based study of 186 859 women.

OBJECTIVE: To study whether placental weight in the first pregnancy is associated with preeclampsia in the second pregnancy. STUDY DESIGN: In this population-based study, we included all women with two consecutive singleton pregnancies reported to the Medical Birth Registry of Norway during 1999-2012 (n=186 859). Placental weight in the first pregnancy was calculated as z-scores, and the distribution was divided into five groups of equal size (quintiles). We estimated crude and adjusted odds ratios with 95% confidence intervals for preeclampsia in the second pregnancy according to quintiles of placental weight z-scores in the first pregnancy. The 3rd quintile was used as the reference group. RESULTS: Among women without preeclampsia in the first pregnancy, 1.4% (2507/177 149) developed preeclampsia in the second pregnancy. In these women, the risk for preeclampsia in the second pregnancy was associated with placental weight in the first pregnancy in both lowest (crude odds ratio (cOR) 1.30, 95% confidence interval (CI); 1.14-1.47) and highest quintile (cOR 1.20, 95% CI; 1.06-1.36). The risk associated with the highest quintile of placental weight was confined to term preeclampsia. Among women with preeclampsia in the first pregnancy, 15.7% (1522/9710) developed recurrent preeclampsia, and the risk for recurrent preeclampsia was associated with placental weight in lowest quintile in the first pregnancy (cOR 1.30, 95% CI; 1.10-1.55). Adjustment for interval between pregnancies, maternal diabetes, age, and smoking in the first pregnancy did not alter these estimates notably. CONCLUSION: Placental weight in the first pregnancy might help to identify women who could be at risk for developing preeclampsia in a second pregnancy.

Preeclampsia in pregnancies with and without diabetes: the associations with placental weight. A population study of 655 842 pregnancies.

INTRODUCTION: Women with diabetes are at increased risk of preeclampsia, and women with diabetes tend to deliver placentas and offspring that are large-for-gestational-age. We therefore studied placental weight in preeclamptic pregnancies according to maternal diabetes status. MATERIAL AND METHODS: Information on all singleton births from 1999 through 2010 (n = 655 842) were obtained from the Medical Birth Registry of Norway. We used z-scores of placental weight to adjust for differences in gestational age at birth between deliveries, and compared the distribution of placental weight z-scores, in deciles, in preeclamptic pregnancies with and without diabetes, and in non-preeclamptic pregnancies with and without diabetes. RESULTS: Overall, the prevalence of preeclampsia was higher in pregnancies with diabetes than in pregnancies without diabetes (9.9% vs. 3.6%). Among preeclamptic pregnancies, having a placental weight in the highest decile was nearly three times more frequent (28.8%) in pregnancies with diabetes than in pregnancies without diabetes (9.8%). In the lowest decile, preeclamptic pregnancies with diabetes were underrepresented (7.5%), and preeclamptic pregnancies without diabetes were overrepresented (13.6%). Among pregnancies with preterm delivery, the above patterns were more pronounced, with 30.1% of the placentas in in preeclamptic pregnancies with diabetes in the highest decile, and 19.5% of the placentas in preeclamptic pregnancies without diabetes in the lowest decile. CONCLUSIONS: These results suggest that women with diabetes who develop preeclampsia have a higher placental weight than other women with preeclampsia or non-preeclamptic women.