Division of Obstetrics and Gynecology, Akershus University Hospital, Lørenskog, Norway; Institute of Clinical Medicine, University of Oslo, Norway.
Department of Community Dentistry, University of Oslo, Norway.
Placenta. 2023 Dec;144:38-44. doi: 10.1016/j.placenta.2023.11.003. Epub 2023 Nov 7.
We studied changes in placental weight from the first to the second delivery according to length of the inter-pregnancy interval.
We followed all women in Norway from their first to their second successive singleton pregnancy during the years 1999-2019, a total of 271 184 women. We used data from the Medical Birth Registry of Norway and studied changes in placental weight (in grams (g)) according to the length of the inter-pregnancy. Adjustments were made for year and maternal age at first delivery, changes in the prevalence of maternal diseases (hypertension and diabetes), and a new father to the second pregnancy.
Mean placental weight increased from 655 g at the first delivery to 680 g at the second. The adjusted increase in placental weight was highest at inter-pregnancy intervals <6 months; 38.2 g (95 % CI 33.0g-43.4 g) versus 23.2 g (95 % CI 18.8g-27.7 g) at inter-pregnancy interval 6-17 months. At inter-pregnancy intervals ≥18 months, placental weight remained higher than at the first delivery, but was non-different from inter-pregnancy intervals 6-17 months. Also, after additional adjustment for daily smoking and body mass index in sub-samples, we found the highest increase in placental weight at the shortest inter-pregnancy interval. We estimated no difference in gestational age at delivery or placental to birthweight ratio according to inter-pregnancy interval.
Placental weight increased from the first to the second pregnancy, and the increase was most pronounced at short inter-pregnancy intervals. The biological causes and implications of such findings remain to be studied.
我们根据两次妊娠间隔的长短研究了胎盘重量从第一次到第二次分娩的变化。
我们对 1999 年至 2019 年期间挪威所有连续单胎妊娠的妇女进行了随访，共有 271184 名妇女。我们使用了挪威医学出生登记处的数据，并根据两次妊娠的间隔时间研究了胎盘重量（以克(g)为单位）的变化。调整了年份和首次分娩时的母亲年龄、母亲疾病（高血压和糖尿病）的流行率变化以及第二次妊娠的新父亲。
胎盘重量从第一次分娩时的 655g 增加到第二次分娩时的 680g。在妊娠间隔<6 个月时，胎盘重量的调整后增加最高，为 38.2g（95%CI 33.0g-43.4g），而妊娠间隔为 6-17 个月时为 23.2g（95%CI 18.8g-27.7g）。在妊娠间隔≥18 个月时，胎盘重量仍高于第一次分娩，但与妊娠间隔为 6-17 个月时无差异。此外，在亚组中对每日吸烟和体重指数进行额外调整后，我们发现最短的妊娠间隔时胎盘重量增加最大。我们估计根据妊娠间隔，分娩时的胎龄或胎盘与出生体重比没有差异。
胎盘重量从第一次妊娠增加到第二次妊娠，且在最短的妊娠间隔内增加最明显。这些发现的生物学原因和意义仍有待研究。
