Brief Answer: EXPLAINED BELOW Detailed Answer: Hello Thanks for writing to us with your health concern. With just one day's gap between the two encounters, it is IMPOSSIBLE to differentiate the father without DNA testing. Ultrasound dates have an inherent error margin of upto a week. Just one day difference can never be pinpointed. Please get DNA testing done, that is the only way you will be reassured. All the best. Please feel free to discuss further.

---

Brief Answer: EXPLAINED BELOW Detailed Answer: You do not have to wait until the birth at all. They would need a sample from your ex and the baby's cells, that would prove that he is the father or not. If he is not, obviously the other guy is, so you do not need samples from him right now. A non-invasive prenatal paternity test is the most accurate non-invasive way to establish paternity before the baby is born. The process is state-of-the-art, combining the latest technology and proprietary methods of preserving and analyzing the baby’s DNA found naturally in the mother’s bloodstream. This test requires only a simple blood collection from the mother and alleged father and can be performed any time after the 8th week of pregnancy. The test is 99.9% accurate. Invasive testing includes amniocentesis or CVS. Amniocentesis is performed in the second trimester, anywhere from the 14th-20th weeks of pregnancy. During this procedure, the doctor uses ultrasound to guide a thin needle into your uterus, through your abdomen. The needle draws out a small amount of amniotic fluid, which is tested. Risks include a small chance of harming the baby and miscarriage. Other side effects may include cramping, leaking of amniotic fluid, and vaginal bleeding. Chorionic Villus Sampling (CVS) consists of a thin needle or tube which a doctor inserts from the vagina, through the cervix, guided by an ultrasound, to obtain chorionic villi. Chorionic villi are little finger-like pieces of tissue attached to the wall of the uterus. The chorionic villi and the fetus come from the same fertilized egg, and have the same genetic makeup. This testing can be done earlier in pregnancy from the 10th-13th weeks. The non invasive test is better for you, as you would have the results earlier. All the best.

---