to stop their preterm deliveries. However, most of the women (109/224) in the threatened PTL group (48.6%) had finally PTB even though the time inter- val between admission and delivery was longer. So presence of PSUC should be considered as a potent risk factor for PTB even if cervical dilatation has not yet occurred in the early stages. It was previously re- ported that contraction frequency is significantly greater in the women with preterm deliveries.7 There are published data showing that in addition to spontaneous PTB, 20% to 30% of PTB are consid- ered medically indicated to avoid or minimize mater- nal and/or fetal complications. Advances in maternal, fetal, and neonatal management have led to an in- creased willingness to deliver high-risk pregnancies preterm.8,9 During this study period, 6124 delivery occurred in this center. So the rate of PTB following spontaneous PTL was calculated to be 1.97%. It should be noticed that during this time period, other PTBs occurred in this center due to maternal or fetal indications which were not included in this study and this data shows only the spontaneous PTB rate and not the total. Considering the fact that 40-45% of PTBs follow spontaneous labor,4 the rate of total PTBs in this center can roughly be estimated to be about 5% during the time period. Multifetal pregnancies are at greater risks for pre- term deliveries and increasing the fetal numbers in- creases the risk.10 We classified the cases on the base of their fetal numbers and evaluated the groups sepa- rately. Following the cases to the time of delivery showed that finally PTB happened in 49% (98/200) of singletons, 95.23% (20/21) of twins and 100% (3/3) of triplets who presented with threatened PTL as shown in Figure 1. Occurrence of at least one previous spontaneous abortion was evaluated among the three groups which was 21.8%( 65/297) for singleton, 33% (9/27) for twin and 33% (1/3) for the triplet group. Suggesting that history of at least one previous spontaneous abor- tion can be considered as a risk factor for develop- ment of PTL in the subsequent pregnancies. However association of first trimester abortions and PTB is still controversial but there are systematic reviews show- ing that induced and spontaneous abortions were as- sociated with increased risk of PTB in subsequent pregnancies.11,12 The results of this study may support the hypothesis that pregnancy loss and PTB may have unique etiologies.13 We noticed a high percentage of women who re- ceived infertility treatments of 16.49%, 37% and Risk factors in preterm contractions 66.6% among singleton, twin and triplet pregnancies, respectively. A high number of preterm multiple ges- tations associated with assisted reproductive technol- ogies as an important contributor to preterm deliver- ies was documented. However, it is reported that even singleton pregnancies after IVF and infertility treat- ments are at increased risk of PTB.14,15 Our findings also suggested that women with infertility should be considered as a high risk population for PTL. We found that 8.75% (26/297) of women in the singleton group, 3.7% (1/27) in twin group and 33% (1/3) in triplet group had history of previous PTB. It is stated that a major risk factor for PTL is prior PTB.16 The recurrent, familial and racial nature of PTB has led to the suggestion that genetics may play a causal role.17 Although it had been suggested that the strongest risk factor for PTB is a maternal or fetal genetic predisposition toward PTB,18 but there were other factors which were more potently associated with PTL in this study. The other accompanying maternal risk factor was uterine abnormalities including; septate, bicornate and myomatous uterus as well as cervical incompe- tence. Uterine anomalies are proved to be risk factors for PTB.2 Cerclage for the treatment of incompetent cervix is the most frequent surgical intervention which was done during pregnancy in this study. Other accompanying maternal medical problems were car- diac and thyroid diseases followed by symptomatic renal stones, as showed in Table 1. This study showed that preterm ROM happened in 52 (17.5%) of singleton, 12 (44.4%) of twin and 2 (66.6%) of triplet pregnancies during their hospital course. Also thirty singleton (10.1%) and two twin (7.4%) cases suffered from a febrile illness. It is hy- pothesized that intrauterine infections trigger PTL by activation of immune system and inflammatory cyto- kines which stimulates the production of prostaglan- dins which stimulate uterine contractions and preterm rupture of membranes.4,19,20 It is reported that, in humans, as the number of fe- tuses per pregnancy increases, the percentage of male conspectuses decreases.21 However, in this study, 49% (98/200) of singleton neonates, 33.3% (14/42) of twins and 55.5% (5/9) of triplets were female. These results did not show any significant difference in the neonatal sex ratios in the three groups with PSUC. Logically the number of NICU admitted neonates and duration of their admissions increased with in- creasing the fetal numbers and decreasing the neonatal birth weights and gestational ages (Table 3). Increasing WWW.ircmj.com Vol 13 December 2011 881