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Notes: The nuclear hyperfine structure of OD and Ar⋅OD in their A 2Σ+ electronic states has been studied by quantum beat spectroscopy. The very cold transient species were produced in a supersonic expansion using a pulsed discharge nozzle. Coherent excitation of hyperfine (hf) states, arising from one fine structure (OD) or rotational (Ar⋅OD) level, created quantum beats on the fluorescence decay. The beat frequencies, which correspond to energy separations between hf levels, could be measured to ±75 kHz. The splitting of the hf levels into their Zeeman components was investigated in a weak magnetic field. A fit of the zero field and Zeeman data yielded the relevant constants for the nuclear magnetic and electric quadrupole hyperfine interactions as well as the pertinent g-factors in each species. In the case of OD, the hf parameters agree well with those reported previously but are more accurately defined. For Ar⋅OD the previously unknown hyperfine and spin-rotation parameters of the A 2Σ+ state were determined. A comparison of the hf parameters in the two systems allowed assessment of the effect of van der Waals complex formation on the electron distribution. Thus complexation is found to reduce the unpaired electron density on the deuteron by 7% which is indicative of significant chemical bonding between the Ar atom and the OD moiety in the A 2Σ+ state of Ar⋅OD. For both systems, the g-factors gS and gl obtained suggest an admixture of other, possibly quartet, electronic states into the A 2Σ+ state. © 1996 American Institute of Physics.

Notes: The dynamics of pyrimidine in three vibronic levels of the S1 (1B1) state with excess energies of 1100–1300 cm−1 above the 00 level has been studied by time resolved spectroscopy. The fluorescence decays from 40 to 50 single rovibronic levels in each vibronic band were measured and were found to be biexponential due to coupling with background triplet states. Analysis of the decays yielded the amplitude ratio of the fast (coherent) and slow (incoherent) component of the fluorescence intensity, A+/A−, and the lifetime of the slow component, being τ ≈700–900 ns. Both data show a clear dependence on the S1 rotational quantum number J. The A+/A− ratio, which reflects the number of coupled states, takes the form of a linear dependence on (2J+1) implying full rovibronic state mixing in the background 3B1 state. More states were found to be coupled than could be accounted for by the calculated background state density, suggesting further state mixing, possible mechanisms for which are discussed. The lifetime results were found to converge to limiting values at high J, the lifetime of the 3B1 state at the given energy. A small but significant difference (∼10%) in the lifetimes of the asymmetry doublets with Kc=1 was observed. Finally, a comparison of the rotational state dependent dynamics in pyrimidine with those in propynal and butynal is presented, pointing to a role for nuclear hyperfine interactions in dynamics. © 1995 American Institute of Physics.

Notes: Abstract Conceptions involving aging gametes are of relevance to natural family planning (NFP) because women using NFP to avoid pregnancy abstain from intercourse during the fertile time of the cycle. To help verify the safety of pregnancies occurring among NFP practitioners, our group has, since 1986, conducted a large cohort study involving six experienced NFP centers. Timing of conception was determined from NFP charts, in which women recorded days on which intercourse occurred. The number of days from the most probable conception intercourse to probable day of ovulation was first determined, and used as an estimate of the time gametes remained in the genital tract before fertilization. Several studies have already been completed, cohort as well as case-control in nature. 1. Spontaneous abortions. Three hundred and sixty-one conceptions occurred during the optimal time (day -1 or 0 relative to ovulation), and of these 33 resulted in spontaneous abortion (9.1%). Five hundred and seven conceptions occurred at non-optimal times during the cycle, and of these 55 resulted in spontaneous abortions (10.9%). These differences were not statistically significant (relative risk 1.19, 95% CI, 0.79-1.80) [1]. 2. Anomalies. Among 780 singleton births in 868 cohort pregnancies, 24 infants had major anomalies (3.1%) as of the present analysis [2]. This frequency is comparable to the general population. To further assess anomalies we employed a case-control approach. All consecutive births (live and stillborn) weighing 500 g or more taking place in 18 participating South American hospitals were examined for minor and major congential anomalies. Mothers of malformed and control infants did not differ with respect to the reported frequency of NFP use, which overall was 6.3% of the 10 642 mothers interviewed (5277 having a malformed infant; 5371 controls). Of 262 discordant pairs, there were 28 or 10.69% mothers within the Down syndrome case group vs. 16/262 or 6.11% among matched controls [3,4]. The odds ratio was 1.84; 95% CI, 0.99-3.96; however, even this non-significant difference narrowed substantially when adjusted for maternal age (OR, 1.78; 95% CI, 0.84-3.75); parity (OR, 1.68; 95% CI, 0.87-3.24); maternal educational level (OR, 1.71; 95% CI, 0.86-3.44); or all three together (OR, 1.74; 95% CI, 0.83-3.64). Conclusions. Our findings should be reassuring to natural family planning users. The overall rate of spontaneous abortion was not increased in NFP users who became pregnant, nor to date was the rate of anomalies. Any contribution to Down syndrome or abortion due to aging gametes would have to be small.

Notes: Abstract Objective: Various birth defects and untoward perinatal outcomes have been claimed to be associated with pregnancies conceived by gametes aged in vivo before fertilization. Thus, these outcomes were systematically assessed in pregnancies occurring in natural family planning (NFP) users. Our international multicenter cohort study of NFP pregnancies (n = 877) is by far the largest systematic study designed to assess pregnancy outcome and is of sufficient power to allow us to address the concern of low birth weight (〈 2500 g) and preterm delivery (〈 37 weeks gestation). Study design: In addition to gathering baseline medical data, evaluation was performed at 16 weeks, 32 weeks and at term. Data were collected in a systematic cohort fashion, verified by the five collaborating international recruiting centers, and analyzed by investigators in the US. Most recruiting center principal investigators are obstetrician-gynecologists and, if not, have integral relationships with such specialists. Standard criteria could thus be applied within and among centers. In our cohort, birth weight was recorded accurately at delivery. Almost all of the deliveries occurred in hospitals; thus, data should be quite reliable. Neonatal examination for anomalies was usually conducted immediately after delivery, when birth weight was recorded. Results: Analysis of risk factors for low birth weight and pretern delivery showed that this population had a low risk profile. Low birth weight infants (〈 2500 g) and preterm deliveries were increased among women with a history of either prior low birth weight or preeclampsia in the index pregnancy. However, mean birth weight was unaffected by the timing of conception vis à vis ovulation or pregnancy history. Mean birh weight for the 877 singleton NFP pregnancies was 3349.6 g. The risk of preterm delivery was increased among older women who drank alcohol, but there were no significant effects of timing of conception vis à vis ovulation on preterm delivery. Results held when analysis was stratified according to whether NFP was being used for contraception or to achieve pregnancy. Conclusions: Our data do not appear to show striking differences between 877 NFP pregnancies and the general obstetric population. The timing of conception vis à vis ovulation does not exert significant effects on the birth weight or preterm delivery of resulting pregnancies, a reassuring finding for NFP users.

Notes: Abstract A multicenter cohort study was designed to assess pregnancy outcome among natural family planning (NFP) users, and provide the opportunity to address complications in NFP users by planning status and by timing of conception with respect to day of ovulation. There were 877 singleton births in this sample. Complications evaluated were abnormal vaginal bleeding, urinary tract infection, vaginal infection, hypertension of pregnancy, proteinuria, glycosuria, and anemia. There was no significant difference in the mean age, number of prenatal visits or birth weight among optimally and non-optimally timed pregnancies or for planned and unplanned pregnancies. There were higher incidences of "parity 2 or more" and current smokers in the non-optimally timed pregnancies and lower incidences of prior pregnancy loss and "currently employed" in the non-optimally timed pregnancies. There was little difference in pregnancy complications with respect to pregnancy timing, with the exception of a significant increased risk of vaginal bleeding late in pregnancy among non-optimally timed conceptions (11.5%) compared to optimally timed pregnancies (5.2%, RR = 2.2, 95% CI 1.3-3.7). More differences were observed in pregnancy complication rates by planning status. Unplanned pregnancies were associated with significantly more late pregnancy bleeding, vaginal infections, proteinuria, glycosuria and medication use than planned pregnancies. Unplanned pregnancies had lower incidences of maternal anemia. Complications of pregnancy were low in this NFP population, irrespective of planned versus unplanned status. Women with planned pregnancies had even fewer complications during pregnancy than women with unplanned conceptions, suggesting that women using NFP to plan their reproduction may be at particularly low risk.