Multiple gestations are associated with increased risk of pregnancy loss, preterm delivery (PTD), preterm premature rupture of membrane (PPROM) and perinatal morbidity and mortality. PTD before 32 weeks in twins is associated with higher neonatal rate of cerebral palsy, likely related to prematurity related neurological complications like high-grade intraventricular hemorrhage and periventricular leucomalacia. This issue of the Journal of Perinatal Medicine presents interesting questions on commons clinical issues related to twin pregnancies such as PTD and PPROM. This issue also sheds light on the innovative use of four-dimensional (4D) sonography on fetal movement in twins, and on the correlation of hormone levels in twins from artificial reproductive techniques. These interesting observations opens arena for new research questions, which would help advance the science and knowledge in evaluation and management of multiple gestations.
O’Brien et al.  studied association of histological chorioamnionitis and magnesium sulfate treatment in singleton and dichorionic twin pregnancies with PPROM. Fifty-seven pregnancies were studied. The inclusion criteria were pregnancies with PPROM, singleton and dichorionic pregnancies with one intact sac, admitted to the hospital before 34 weeks’ gestation. The primary outcome was histological chorioamnionitis. Interestingly, after controlling for demographic variables, placental histological chorioamnionitis was associated with antenatal exposure of magnesium sulfate in singleton gestation with PPROM before 34 weeks, compared to dichorionic twins with ruptured sac of presenting twin (41% vs. 19%, χ2=6.46; P=0.01). The authors reported no statistical differences between singletons and twins in terms of other perinatal variables and outcomes such as antenatal corticosteroids, antibiotics use, latency period, gestational age at delivery, birth weight and Apgar score <7. The study is limited by the retrospective study design and small sample size. The literature reports higher prevalence of histological chorioamnionitis in preterm PROM and this study also suggests association and not causation. It would be interesting to study the same question in control subjects without PPROM and also compare perinatal outcomes in PPROM with clinical and histological chorioamnionitis. The authors raise interesting questions to study the effect of antenatal magnesium sulfate in PPROM subjects in terms of dosing, duration and gestational age at exposure (before and after 28 weeks). This study highlights important observations and opens the door for further research to identify perinatal variables that could affect the biological actions of magnesium sulfate for neuroprotection in pregnancy.
Park et al.  studied the outcomes of physical examination-indicated cerclage in twin pregnancies with acute cervical insufficiency compared to singleton pregnancies. The inclusion criteria included singleton and twin pregnancies with acute cervical insufficiency with intact membranes, who underwent physical-examination indicated cerclage between 16 and 23 weeks. Perioperative antibiotics were used. Tocolytics were not routinely used. The primary outcomes, spontaneous PTD before 34 weeks of gestation was similar in twin and singleton pregnancies [twins, 56% (9/16) vs. singleton, 53% (37/70), P=NS >0.999]. Other outcomes including rate of PTD before 28 weeks, interval from cerclage to delivery and neonatal outcomes were similar in both groups. Multivariate analysis showed that a lower gestational age at cerclage placement and a larger size of visible membranes (more than 4 cm) were independently associated with a higher risk of PTD before 28 weeks of gestation; however, a twin gestation and prior PTD were not risk factors for PTD less than 28 weeks and less than 34 weeks. This is an important study suggesting no increased risk of physical examination indicated cerclage in multiple gestations compared to singletons with acute cervical insufficiency.
AboEllail et al.  evaluated the frequency of fetal movements in singleton and twin fetuses at 12–19 weeks of gestation, and to assess fetal behavioral differences between singleton and twin fetuses using 4D ultrasound. This unique study found that the twin fetal behavioral pattern was similar to singleton fetuses at 14–19 weeks of gestation, however, the frequencies of all eight movements in singleton fetuses were significantly higher than those in twin fetuses at 14–19 weeks, which is likely due to limited space in-utero in twins. The authors suggested further studies to understand the affect of decreased fetal movements with advancing gestational age in twin pregnancies on the fetal and neonatal development and maturation. Developing literature on evaluation of fetal behavior using 4D sonography is an exciting new tool for evaluation of functional neurological assessment before and after birth.
Povoa et al.  prospectively evaluated β-human chorionic gonadotropin (hCG) and estradiol levels during the first trimester of 47 dichorionic twin pregnancies and 50 singletons from assisted reproduction technique (ART) (with fresh embryo transfers) that eventually resulted in live birth. The authors report significantly higher levels of β-hCG and estradiol in twins compared to singletons. This study points towards lower rate of pregnancy loss in twins resulting from ART compared to singletons due to higher number of feto-placental units. The authors rightly suggest further studies to establish the cause-effect relationship of hormonal levels and pregnancy outcomes in twin gestations from ART. It would be interesting to study hormone levels and clinical outcomes of dichorionic and monochorionic twins from ART (fresh vs. frozen embryo transfer).
1. O’Brien JM, Santolaya JL, Palomares K, Blitzer D, Santolaya-Forgas J. Association of histological chorioamnionitis and magnesium sulfate treatment in singleton and dichorionic twin pregnancies with preterm premature rupture of membranes: preliminary observations. J Perinat Med. 2018;46:839–44.10.1515/jpm-2017-0043Search in Google Scholar PubMed
2. Park JY, Cho S-h, Jeon SJ, Kook SY, Park H, Oh KJ, et al. Outcomes of physical examination-indicated cerclage in twin pregnancies with acute cervical insufficiency compared to singleton pregnancies. J Perinat Med. 2018;46:845–52.10.1515/jpm-2017-0218Search in Google Scholar PubMed
3. AboEllail MAM, Kanenishi K, Mori N, Noguchi J, Marumo G, Hata T. Ultrasound study of fetal movements in singleton and twin pregnancies at 12–19 weeks. J Perinat Med. 2018;46:832–8.10.1515/jpm-2017-0158Search in Google Scholar PubMed
4. Póvoa A, Xavier P, Matias A, Blickstein I. First trimester β-hCG and estradiol levels in singleton and twin pregnancies after assisted reproduction. J Perinat Med. 2018;46:853–6.10.1515/jpm-2017-0132Search in Google Scholar PubMed
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