Independent Risk Factor For Preterm Birth Research Articles

Risk of Preterm Delivery in Very Advanced Maternal Age Parturients Utilizing In Vitro Fertilization.

Among patients ≥45 years, the birth rate in the United States continues to increase. As fertility declines with age, this cohort often utilizes assisted reproductive technology, specifically in vitro fertilization (IVF). While both advancing maternal age and IVF are independently associated with adverse maternal outcomes, data regarding their additive effect are scant. This article aims to determine if patients who conceive via IVF are at increased risk for preterm birth (PTB) compared to patients with non-IVF pregnancies in a very advanced maternal age (vAMA) cohort (≥45 years). Retrospective cohort study of all pregnant patients ≥45 years old who delivered at a single institution (2014-2021). Those with incomplete delivery/neonatal records or multiples beyond twins were excluded. We compared individuals who conceived via IVF to those who conceived without IVF. The primary outcome was preterm delivery <37 weeks gestation. Secondary outcomes included other adverse perinatal outcomes. Using multivariable logistic regression, we adjusted for multiple gestation as well as confounders found to be significantly different in the univariable analysis and other known risk factors for PTB. In our study cohort of 420 vAMA patients, individuals who underwent IVF were more likely to be older, privately insured, nulliparous, and with a twin gestation. The PTB rate in vAMA patients who underwent IVF was 24.4 compared to 8.4% in patients who did not use IVF (p < 0.001). After adjusting for confounders, IVF was an independent risk factor for PTB <37 weeks in vAMA patients (adjusted odds ratio {aOR] = 4.3, 95% confidence interval [CI]: 1.7-10.4, p = 0.001). In vitro fertilization was also associated with a composite of adverse maternal outcomes (hypertensive disorder of pregnancy, postpartum hemorrhage, blood transfusion, and unplanned hysterectomy) (aOR = 1.7, 95% CI: [1.1-2.9], p = 0.03). In the vAMA population, conception via IVF is associated with an increased risk of PTB <37 weeks. · This study examines IVF as an independent risk factor for PTB in patients ≥45 years at delivery, which has not been specifically addressed in prior studies.. · In vAMA patients, use of IVF is associated with an increased risk of PTB <37 weeks. These patients also have higher rates of cesarean delivery. Neonates from IVF pregnancies are more likely to be very low birth weight or low birth weight.. · Bodies of research exist for both advanced maternal age and assisted reproductive technology, there is a paucity of data specifically in parturients of vAMA who conceive via IVF..

Estimating the individual singleton preterm birth risk: nomogram establishment and independent validation.

To establish and independently validate nomograms for predicting singleton preterm birth (PTB) risk based on a large sample size comprising data from two independent datasets. This cohort study used data from 50 states and the District of Columbia in the National Vital Statistics System (NVSS) database between January 2016 and December 2020. Multivariate logistic regression analysis was used to confirm the independent risk factors for PTB. Statistically significant variables were incorporated into the logistic regression models to establish PTB prediction nomograms. The models were developed using the United States (US)-derived data and were independently validated using data from US Territories. A total of 16,294,529 mother-newborn pairs from the US were included in the training set, and 54,708 mother-newborn pairs from the US Territories were included in the validation set. In all, 4 nomograms were built: 1 to predict PTB probability, and another 3 to predict moderately and late PTB probability, very PTB probability, and extremely PTB probability, respectively. Hypertensive eclampsia and infertility treatment were found to be the top 2 contributors to PTB. We developed and validated nomograms to predict the individualized probability of PTB, which could be useful to physicians for improved early identification of PTB and in making individualized clinical decisions.

Association between preterm birth and low birth weight and maternal chronic periodontitis: A hospital-based case-control study.

Periodontal diseases (PDs) are one of the most common chronic diseases affecting overall oral functions, and their association with adverse pregnancy outcomes (APOs) has been an area of interest since the late 90s. The present hospital-based case-control study aimed to find any association between maternal chronic periodontitis (CP) and preterm birth (PTB) and low birth weight (LBW) by comparing the periodontal parameters in patients with normal birth, PTB and LBW. The participants of the study were females that had delivered a live baby (n = 1,200). They were classified as either cases or controls. The cases were defined as PTB if the delivery was before 37 weeks of gestation, and as LBW if the infant weighed <2,500 g. The others were controls. The intraoral examination, which included recording the periodontal status, was conducted within 3 days of delivery. Detailed medical history and demographic data were recorded for the determination of the confounding factors. The multivariable dependence of PTB and LBW on both the categorical and continuous data was analyzed using a multivariate logistic regression analysis. Adjusted odds ratios (AORs) with a 95% confidence interval (CI) for the risk of PTB and LBW were calculated. A strong association with PTB was found for a high plaque index (PI) score (AOR = 1.61; p < 0.001; 95% CI: 1.26-2.07) and a mean pocket probing depth (PPD) ≥4 mm (AOR: 4.32; p < 0.001; 95% CI: 3.09-6.02). A strong association with LBW was found for a high PI score (AOR = 2.02; p < 0.001; 95% CI: 1.43-2.83) and a mean PPD ≥4 mm (AOR: 8.70; p < 0.001; 95% CI: 6.01-12.59). A high PI score and a mean PPD ≥4 mm were independent risk factors for PTB and LBW. The presence of deep pockets and inadequate plaque control in pregnant females increased the risk of APOs.

Association of Sleep Quality and Duration With Preterm Birth: The Qazvin Maternal and Neonatal Metabolic Study (QMNMS)

Background: Preterm birth (PB) is a worldwide gestational problem. Poor sleep quality and short duration have been reported as possible predisposing factors of PB in some studies. Objective: This study was conducted to investigate the roles of sleep quality/duration in the occurrence of PB. Methods: This longitudinal study was performed on pregnant women with gestational age ≤14 weeks. The sleep quality was evaluated using the Pittsburgh sleep quality index (PSQI) at the first visit and women were followed until delivery. A total of 76 women with preterm and 441 women with term delivery were compared regarding the sleep quality components, sleep duration, and long or short sleep duration. The multivariate logistic regression was performed to examine the independent association of sleep quality/duration with PB. Findings: Data from 517 participants were analyzed. PB occurred in 14.7% of participants. No significant difference of 7 items of sleep quality was observed between preterm and non-preterm groups (P&gt;0.05 for each comparison). The total PSQI score in the preterm group was significantly higher (poorer quality) compared to the non-preterm group (5.6±2.1 vs 5.3±2.4, P=0.076). In multivariate logistic regression, each unit of worsening PSQI was independently associated with a 20% higher risk of PB occurrence. Sleep duration was not associated with PB either in unadjusted or adjusted models. Conclusion: No relationship was observed between poor sleep quality (defined as PSQI&gt;5) and PB; however, based on our results, poorer sleep quality (as a continuous variable) can be an independent risk factor for PB.

Association between Maternal Serum 25-Hydroxyvitamin D Concentrations and the Risk of Preterm Birth in Central Sudan: A Case-Control Study.

There are few published studies on the association between vitamin D concentrations and preterm birth (PB) in sub-Saharan Africa. The current study aimed to assess the association between 25-hydroxyvitamin D (25[OH)] D) levels and PB. A matched case–control study (60 women in each arm) was conducted in Medani maternity hospital in central Sudan. The cases were women with spontaneous PB, and healthy women with term deliveries were the controls. The clinical/medical and obstetric history was gathered using a questionnaire. The enzyme-linked immunosorbent assay was used to measure the serum 25(OH)D levels. Women with PB had significantly lower median (interquartile range) 25(OH)D concentrations compared with the controls (18.4 (7.3) ng/mL vs. 20.2 (16.5) ng/mL, p = 0.001). Forty-two (70.0%) women with PB and 29 (48.3%) women in the control group had vitamin D deficiency (25(OH)D level ≤ 20 ng/mL). The results of the multivariable logistic regression showed that the 25(OH)D concentrations were negatively associated with PB (adjusted odds ratio (aOR) = 0.92, 95% confidence interval (CI) = 0.87–0.97). Vitamin D-deficient pregnant women were at a higher risk of PB (aOR = 2.69, 95% CI = 1.17–6.23). Low 25(OH)D concentrations were found at the time the variable was determined in women with spontaneous PB and were an independent risk factor for PB.

Elevated Anti-Müllerian Hormone Is an Independent Risk Factor for Preterm Birth Among Patients With Overweight Polycystic Ovary Syndrome.

ObjectiveTo explore whether elevated anti-Müllerian hormone (AMH) levels affect the rate of preterm birth (PTB) among PCOS patients with different BMIs.MethodsIn this retrospective cohort study, patients with PCOS who had undergone IVF/ICSI from January 2017 to December 2019 were included for potential evaluation. A total of 2368 singleton live births from PCOS patients were included. According to the BMI, all the PCOS patients were divided into two groups: BMI<24 kg/m2 and BMI≥24 kg/m2. In total, 1339 PCOS patients with a BMI<24 kg/m2 were grouped according to their serum AMH levels: ① <2.71 ng/ml (n=333), ② 2.71-4.08 ng/ml (n=330), ③ 4.09-6.45 ng/ml (n=351), and ④ >6.45 ng/ml (n=325). Additionally, 1029 cycles of patients with a BMI≥24 kg/m2 were grouped according to the serum AMH level: ① <2.71 ng/ml (n=255), ② 2.71-4.08 ng/ml (n=267), ③ 4.09-6.45 ng/ml (n=239), and ④ >6.45 ng/ml (n=268), with <2.71 ng/ml being considered the reference group. The grouping was based mainly on the interquartile range of serum AMH levels. The primary outcome of the study was PTB. The secondary outcomes were low birth weight (LBW), small for gestational age (SGA), macrosomia and large for gestational age (LGA).ResultsRegarding PCOS patients with a BMI<24 kg/m2, compared with the PTB rate of the AMH <2.71 ng/ml group, the PTB rates of the different groups were not significantly different (AMH 2.71-4.08, AOR (95% CI)=1.01 (0.52-2.00), P=0.99; AMH 4.09-6.45, AOR (95% CI)=0.93 (0.45-1.91), P=0.85; AMH>6.45, AOR (95% CI)=0.78 (0.35-1.73), P=0.54). Regarding PCOS patients with a BMI ≥24 kg/m2, compared with the PTB rate of the AMH <2.71 ng/ml group, the PTB rate of the AMH>6.45 ng/ml group was significantly higher (OR=2.47; 95% CI=1.34-4.55). After multiple logistic regression analysis, the risk of PTB in the AMH>6.45 ng/ml group was 2.1 times that in the AMH<2.71 ng/ml group (AOR=2.1, 95% CI=1.01-4.37, P=0.04). However, no statistically significant difference was found in the rate of SGA, LBW, macrosomia or LGA among patients in the different serum AMH groups.ConclusionFor PCOS patients, a BMI≥24 kg/m2 plus serum AMH>6.45 ng/ml (75th percentile) is an independent risk factor for PTB.

Study on the correlation between vaginal bleeding in first trimester and preterm birth: A birth cohort study in Lanzhou, China.

To investigate the correlation between first trimester vaginal bleeding and preterm birth (PB), and to offer suggestions on the perinatal health care and preterm birth prevention. A birth cohort study was conducted on 10 179 pregnant women. Unconditional logistic regression model was used to evaluate the associations between vaginal bleeding and preterm birth in sub-preterm groups. Of the 10 179 pregnant women included, a total of 1001 women suffered from vaginal bleeding during the first trimester, of which 119 suffered from PB. Any vaginal bleeding increased the risk of PB. Severe bleeding was a high-risk factor of PB, associated with 4.8-fold risk of very PB, 2.7-fold risk of spontaneous PB without PROM (premature rupture of membrane) and 4.6-fold risk of medical induced PB. Bleeding prolonged more than 1 week increased 66% risk of PB and 36% risk of PB on initial episode happened in 5-12 weeks of gestation age, especially in moderate PB, in medical-induced PB and in spontaneous PB with PPROM (preterm premature rupture of membrane which is one cause of PB). Mild bleeding or bleeding within 1 week or initial episode happened within 4 weeks of gestation age possibly had no influence on PB. Vaginal bleeding in the first-trimester was an independent risk factor for PB. The severity, duration and initial time of vaginal bleeding had different effects on different subtypes of PB.

Preterm Birth in Assisted Reproductive Technology: An Analysis of More Than 20,000 Singleton Newborns.

BackgroundSeveral studies have shown that newborns conceived through the ART procedures were associated with an increased incidence of preterm delivery compared to those conceived spontaneously regardless of the type of ART procedure. The aim of the study was to explore risk factors for preterm birth (PTB) in assisted reproductive technology.MethodIn this single center retrospective cohort study, a total of 23,111 singleton newborns from January 2010 to December 2018 were included. The primary outcome in this study was preterm birth, defined as live birth before 37 weeks’ gestation.ResultIn the 23,111 pregnancies, the incidence of PTB was 7.13%. In multivariate logistic regression analysis model, BMI was an independent predictor for PTB (OR = 1.05, 95% CI: 1.03–1.07; P = 0.00 in IVF/ICSI cycles; OR = 1.08, 95% CI: 1.03–1.12; P = 0.00 in IUI cycles). Also, another independent predictor in ART was male newborns (OR = 1.27, 95% CI: 1.14–1.41; P = 0.00 in IVF/ICSI cycles; OR = 1.60, 95% CI: 1.17–2.18; P = 0.00 in IUI cycles). In IVF/ICSI cycles, PTB was significantly higher in patients with advanced age (9.56% in ≥ 38 years old), and in patients with a history of cesarean section (10.39%). In addition, Blastocyst transfer, and frozen thawed transfer were also risk factor for PTB as compared with cleavage transfer, and fresh transfer, respectively. Moreover, in frozen thawed transfer cycles, stimulated protocol (estrogen-progesterone) increased PTB as compared with natural protocol (OR = 1.33, 95% CI: 1.12–1.59; P = 0.00). This situation was similar in IUI cycles as stimulated protocol also increased PTB when compared with natural protocol (OR = 1.72, 95% CI: 1.19–2.48; P = 0.00).ConclusionBody mass index (BMI), delivery with male newborn, as well as stimulated protocols, were independent risk factors for PTB in both IVF/ICSI and IUI treatment cycles. In IVF/ICSI cycles, independent risk factors also included maternal, history of cesarean section, frozen thawed transfer, and blastocyst transfer.

The Effect of Maternal Age at the First Childbirth on Gestational Age and Birth Weight: The Japan Environment and Children's Study (JECS).

BackgroundIn Japan, mean maternal age at first childbirth is increasing. The aim of this study was to investigate whether maternal age at the first childbirth is a risk factor for preterm birth (PTB), low birth weight (LBW), and small for gestational age (SGA).MethodsWe used the results of Japan Environment and Children’s Study (JECS) who gave birth in 2011–2014. Cases of primiparous singleton pregnancies where the subject was ≥20 years and delivered after 22 weeks were included. All subjects were categorized into five groups according to maternal age: 20–24, 25–29, 30–34, 35–39, and ≥40 years. Adjusted odds ratios (aORs) for PTB (before 37 and 34 weeks), LBW (<2,500 g and <1,500 g), and SGA were calculated using a logistic regression model, with the 20–24-year age group as reference.ResultsWe analyzed 38,412 singleton primiparous pregnancies. The aORs of all outcomes increased in parallel with each maternal age group >30 years. The aORs of PTB before 37 and 34 weeks, LBW <2,500 g, LBW <1,500 g, and SGA in the 30–34-year age group were 1.39 (95% confidence interval [CI], 1.16–1.67), 2.23 (95% CI, 1.45–3.41), 1.34 (95% CI, 1.18–1.53), 2.30 (95% CI, 1.35–3.94), and 1.24 (95% CI, 1.05–1.46), respectively.ConclusionThe present study showed that higher maternal age (>30 years) at the first childbirth was an independent risk factor for PTB, LBW, and SGA.

Identifying Maternal Constraints on Fetal Growth and Subsequent Perinatal Outcomes Using a Multiple Embryo Implantation Model.

IntroductionAlthough the majority of singleton births after in vitro fertilization (IVF) are uncomplicated, studies have suggested that IVF pregnancies may be independently associated with low birth weight (LBW), preterm birth (PTB), and perinatal mortality. These outcomes complicate multiple gestations as expected, but have also been reported in singletons. A multiple embryo implantation model allows for assessment of the early in utero environment, and therefore, assessment of any maternal constraints on developing fetuses. We question whether adverse perinatal outcomes associated with assisted reproductive techniques (ART) occur as a result of maternal physiologic adaptations.Patients and MethodsThis is a retrospective, single center study of ART cycles, specifically intracytoplasmic sperm injection (ICSI) cycles during a 16-year period. For each positive pregnancy test 9–11 days after embryo transfer, an ultrasonogram was performed at 7 weeks of gestation to record the number of implanted fetal poles with cardiac activity. Controlled ovarian stimulation (COS), hCG trigger, oocyte retrieval and sperm injection were performed as per our standard protocols. First trimester implantation sites that resulted in live births were defined as “true” to distinguish them from those that spontaneously reduced called “virtual.” Birth outcomes analyzed included birth weight and gestational age at delivery.ResultsA total of 17,415 cycles were analyzed. The average maternal age was 36.9 (±5.0) years. An overall fertilization rate of 73.4% generated approximately 48,708 good quality cleavage-stage embryos. In most patients (92.8%), an average of 3 embryos were transferred. The clinical pregnancy rate was 39.2% (n = 6,281). The overall occurrence of multiple gestations was 38.2% (n = 2,608) consisting of 2,038 twin, 511 triplet, and 59 quadruplet pregnancies. Of these multiple gestations, 18.6% of twin, 54.2% of triplet and 76.3% of quadruplet gestations spontaneously reduced. Failure of the implanted embryo to progress was not related to maternal age. Singleton newborns resulting from multiple implantation sites had lower birth weights (P<0.01) and shorter gestational ages (P<0.01) than those from a single implanted embryo. The number of embryos transferred did not affect the gestational length of singleton newborns. Although the birth weights of singletons from multiple implantation sites (virtual singletons) were lower than true singletons, the birth weight of virtual singletons were comparable to the birth weights of true twin, triplet, and quadruplet live births. Multiple logistic regression revealed that virtual singletons were an independent risk factor for PTB (odds ratio: 4.55, 95% CI 2.23–9.29) and LBW (odds ratio: 3.61, 95% CI 1.78–7.32), even after controlling for the number of oocytes, stimulation protocol type, sperm source, total gonadotropins administered, age, embryo quality, and day of embryo transfer.ConclusionsOur study highlights that embryonic implantation sites during early gestation set the growth profile of each embryo, dictating later growth patterns. Specifically, spontaneous reduction of an embryo after multiple embryo implantations can confer greater perinatal risk in the form of LBW and PTB to the surviving fetus. Our findings suggest that maternal constraints or physiologic adaptations maybe one of the mechanisms mediating adverse perinatal outcomes when multiple embryo implantation occurs.

Risk Factors for Preterm Birth and Low Birth Weight Among Pregnant Indian Women: A Hospital-based Prospective Study

Objectives:The present study was undertaken to study the maternal risk factors for preterm birth (PTB) and low birth weight (LBW) with a special emphasis on assessing the proportions of maternal genitourinary and periodontal infections among Indian women and their association with adverse pregnancy outcomes.Methods:A hospital-based prospective study comprising 790 pregnant women visiting the obstetrics clinic for a routine antenatal check-up was undertaken. Once recruited, all study participants underwent clinical and microbiological investigations for genitourinary infections followed by a dental check-up for the presence of periodontitis. The study participants were followed up until their delivery to record the pregnancy outcomes. Infectious and non-infectious risk factors for PTB and LBW were assessed using univariate and multivariate Cox regression analysis. Independent risk factors for PTB and LBW were reported in terms of adjusted relative risk (ARR) with the 95% confidence interval (CI).Results:Rates of PTB and LBW in the study population were 7.6% and 11.4%, respectively. Previous preterm delivery (ARR, 5.37; 95% CI, 1.5 to 19.1), periodontitis (ARR, 2.39; 95% CI, 1.1 to 4.9), Oligohydramnios (ARR, 5.23; 95% CI, 2.4 to 11.5), presence of Nugent’s intermediate vaginal flora (ARR, 2.75; 95% CI, 1.4 to 5.1), gestational diabetes mellitus (ARR, 2.91; 95% CI, 1.0 to 8.3), and maternal height <1.50 m (ARR, 2.21; 95% CI, 1.1 to 4.1) were risk factors for PTB, while periodontitis (ARR, 3.38; 95% CI, 1.6 to 6.9), gestational hypertension (ARR, 3.70; 95% CI, 1.3 to 10.8), maternal height <1.50 m (ARR, 2.66; 95% CI, 1.3 to 5.1) and genital infection during later stages of pregnancy (ARR, 2.79; 95% CI, 1.2 to 6.1) were independent risk factors for LBW.Conclusions:Our study findings underscore the need to consider screening for potential genitourinary and periodontal infections during routine antenatal care in developing countries.

307: The association between cervical dysplasia, a short cervix, and preterm birth

307: The association between cervical dysplasia, a short cervix, and preterm birth

Amniotic fluid “sludge” is an independent risk factor for preterm delivery

Objective: To determine the prevalence and the clinical significance of amniotic fluid “sludge” (AFS) in asymptomatic patients at low and high risk for spontaneous preterm delivery.Method: A prospective cohort study was conducted on 195 singleton pregnancies at low or high risk for preterm birth (PTB) between the 16th and 26th weeks. Cervical length (CL) <25 mm and the presence of AFS were evaluated. The risk for preterm delivery before 28, 32, 35 and 37 weeks were determined according to the presence of AFS, CL < 25 mm and history of high risk for PTB. Stepwise logistic regression was performed to compare variables.Results: AFS was an independent risk factor for PTB < 35 weeks (OR: 3.08, 95% CI: 1.13–8.34, p = 0.027) but not for PTB < 28, 32 and 37 weeks. CL < 25 mm was an independent risk factor for PTB < 28, 32 and 35 but not for PTB < 37 weeks. High risk for PTB was not found as an independent risk factor for PTB.Conclusion: AFS is an independent risk factor for PTB before 35 weeks.

Asthma in Children in Relation to Pre-term Birth and Fetal Growth Restriction

To assess the impact of parental asthma on risk of pre-term birth (PTB) and intrauterine growth restriction, and their subsequent association with childhood asthma. Three sequential cross-sectional surveys were conducted in 1993 (3,746), 1998 (1,964) and 2006 (1,074) in the same 15 schools among 5-11 year old children in Merseyside using the same respiratory health questionnaire completed by parents (sample size in brackets). Between 1993 and 2006, prevalence of PTB varied between 12.4 and 15.2 %, and of small for gestational age (SGA or growth restricted) babies between 2.1 and 4.6 %, and maternal asthma prevalence between 8.1 and 13.4 %. For the combined surveys mothers with asthma were more likely to have a PTB than non-asthmatic mothers (OR 1.39, 95 % CI 1.10-1.95, p < 0.001), and in the 2006 survey were more likely to have an SGA baby. 40.9 % of PTBs of asthmatic mothers developed doctor diagnosed asthma compared to 34.3 % for term babies (adjusted OR 1.65, 1.34-2.04, p < 0.001). The corresponding estimates for the symptom triad of cough, wheeze and breathlessness were 19.4 and 17.6 % (adjusted OR 1.78, 0.79-3.98). Conversely SGA babies were less likely to develop doctor diagnosed asthma (adjusted OR 0.49, 0.27-0.90, p < 0.021), or the symptom triad of cough, wheeze and breathlessness (adjusted OR 0.22, 0.05-0.97, p < 0.043), whether or not the mother was asthmatic. Maternal asthma is an independent risk factor for PTB which predisposes to childhood asthma. Intrauterine growth restriction was protective against childhood asthma.

The contribution of maternal race/ethnicity and fetal sex to prematurity in twins

The contribution of male fetal sex to twin preterm birth (PTB) rates was evaluated in the United States. The 2002 National Center for Health Statistics Natality database was analyzed for fetal sex and twin gestations based on birth sex for MM and FF pairs (M, male; F, female). Multivariable Cox proportional hazards regression was applied to estimate the hazard ratio for PTB with adjustments for known risks. Thirty-three thousand nine hundred twenty-six pairs were analyzed. PTBs between 20-36 completed weeks occurred in 59.1% MM pairs and 57.5% FF pairs. MM sex was an independent risk factor for PTB. This effect was greatest for deliveries between 20-29 weeks (hazard ratio, 1.224; 95% CI, 1.113-1.346). The effect was most pronounced in non-Hispanic white MM pairs. In the United States, MM pairs are at greater risk for PTB. Race and ethnicity modulate sex effects. Further studies are needed to understand potential mechanisms.

Pre‐term delivery and periodontal disease: a case–control study from Croatia

The aim of this report was to assess the strength and influence of periodontitis as a possible risk factor for pre-term birth (PTB) in a cohort of 81 primiparous Croatian mothers aged 18-39 years. PTB cases (n = 17; mean age 25 +/- 2.9 years; age range 20-33 years) were defined as spontaneous delivery after less than 37 completed weeks of gestation that were followed by spontaneous labour or spontaneous rupture of membranes. Controls (full-time births) were normal births at or after 37 weeks of gestation (n = 64; mean age 25 +/- 2.9 years; age range 19-39 years). Information on known risk factors and obstetric factors included the current pregnancy history, maternal age at delivery, pre-natal care, nutritional status, tobacco use, alcohol use, genitourinary infections, vaginosis, gestational age, and birth weight. Full-mouth periodontal examination was performed on all mothers within 2 days of delivery. PTB cases had significantly worse periodontal status than controls (p = 0.008). Multivariate logistic regression model, after controlling for other risk factors, demonstrated that periodontal disease is a significant independent risk factor for PTB, with an adjusted odds ratio of 8.13 for the PTB group (95% confidence interval 2.73-45.9). Periodontal disease represents a strong, independent, and clinically significant risk factor for PTB in the studied cohort. There are strong indicators that periodontal therapy should form a part of preventive prenatal care in Croatia.